From sals@rain.orgThu Mar 2 00:09:38 1995 Date: Wed, 1 Mar 1995 18:35:56 -0800 From: sal schettino To: sanet-mg@ces.ncsu.edu Subject: Bio-Control Matters This is long so I will cut it but think its important:To: Deke >From: JOEL GROSSMAN, 937 6th St. #5, Santa Monica, CA 90403; 310/394-1233 The Biological Pest Control Transition Experience at NaturFarm authors = E.J. Dietrick, John Phillips, Joel Grossman After a year of fallowing land farmed conventionally with pesticides by a previous owner, NaturFarm adopted a sustainable organic pest control approach relying on natural biological control organisms to keep pests from destroying crops. Some cultural measures, such as cultivating ant nests and growing pest break strips, were adopted to enhance the natural biological pest control. However, widely-used organic pesticide substitutes like soaps, oils, Bacillus thuringiensis [BT] and botanicals were not part of the NaturFarm pest control paradigm because natural biological control organisms are the most sustainable form of pest control. This almost exclusive reliance on natural biological control organisms to provide sustainable organic pest control is rarely, if ever, attempted anymore. However, there have been times and places in California history where natural biological control organisms have provided all the pest control needed in major agroecosystems such as citrus, cotton and alfalfa. NaturFarm's pest control adviser on this biological control transition project, E.J. Dietrick, personally worked in these unsprayed agroecosystems teeming with natural biological control organisms while a researcher at the University of California and later in private practice with Rincon-Vitova Insectaries, Inc. Indeed, E.J. Dietrick's vision and practical knowledge of natural biological pest control, gained from several decades of firsthand experience and research, guided NaturFarm in this pioneering and innovative transition towards natural biological control of vegetable pests that are routinely sprayed with pesticides by most other farmers around the world. The pest break strips at the heart of the NaturFarm transition to natural biological control are a specialized form of strip cropping. Pest break strips are designed both to trap pests away from the vegetable crops and to act as insectary crops for growing beneficial insects providing biological control of pests in the market crop of vegetables. The pest break strips at NaturFarm go beyond traditional strip crop design in another important way. NaturFarm uses special management practices known as strip cutting or strip harvesting to maximize the numbers of pests trapped and the quantities of natural enemies grown in the pest break strips. The strip cutting concept is rather simple. Only half the alfalfa or other cover crop is cut at any one time. At strip cutting time, half the alfalfa or other cover crop is flowering and ready to be cut, while the other half is young and lush. The young, lush uncut strips of alfalfa and other cover crops serve a dual role: first protecting the market crops by acting as trap crops catching pests moving out of the just-cut strips, but perhaps more importantly as insectary crops growing beneficial insects. Strip cutting for biological pest control was devised in 1956 by Evert I. Schlinger and Everett J. Dietrick as part of the University of California's statewide `war' against the spotted alfalfa aphid, a pest then causing $12 million per year in damage to alfalfa. Tiny wasps imported from the aphid's foreign homeland provided excellent biological control until the entire alfalfa field was cut and harvested. After the entire alfalfa stand was cut, the beneficials starved to death or flew away. Then in the absence of their natural enemies, the few remaining aphids exploded in numbers with the regrowth of the hay. The strip cutting concept was devised to keep beneficial insects in the fields as a defensive army of sorts, preventing population explosions of aphids and other pests from occurring in the new crop growth. Another major benefit of strip cutting further developed by other University of California researchers [Stern, van den Bosch & Leigh, 1964] is that the uncut portion of alfalfa acts as a trap crop for pests like Lygus bugs, preventing damage to cotton, strawberries and other nearby crops. Continuously cutting the pest break strip before seed set also prevents the alfalfa or legume cover crop from becoming too favorable a habitat for seed feeders like Lygus bugs and certain leafhoppers. If the entire pest break strip is cut and there is not nearby uncut alfalfa [the preferred Lygus host crop], then Lygus and other pests typically migrate into nearby market crops. "Strip cutting works best and is started most easily on the first cutting. In the spring when days are short, alfalfa is slow to go into bloom," write Stern et al. (1967) in one of the definitive University of California how-to publications on the subject. "At this season, the correct time for cutting can be determined from the new buds at the base of the plant. The first set of strips should be cut when 25 percent of the new shoots are 1/2 to 3/4 inches high. About 10 days later, the second or alternate set of strips should be cut. This will set up a harvesting differential for the second cutting." A 12- to 14-day cutting differential is important because adult Lygus, particularly females, begin moving out of maturing hay when alfalfa reaches three-fourths maturity. "If the alfalfa in the adjoining strips is 6 to 8 inches tall, these females will drift into these plots and remain there. Shorter hay is not as attractive to these drifting Lygus. At cutting time, when the alternate strips have about 10 inches or more regrowth, all of the Lygus are driven from the cut strips to this young succulent hay." In essence, strip cutting subdivides the alfalfa or cover crops into at least two sets of crops always at different levels of maturity and on staggered cutting schedules. The staggered cutting schedule enhances agroecosystem biodiversity by providing plants of different ages or maturities, in much the same way that a forest is more diverse with different ages and species of trees. The diversity added to the agro-ecosystem by strip cutting alfalfa and cover crops provides stability, preventing wild insect population explosions and crashes. This freedom from pest outbreaks is a consequence of the pest break strips creating a more permanent habitat for the beneficial species providing biological pest control. [perhaps a place to insert diagrams of strip cutting schemes, like those from University of California publications] Unfortunately, the necessity of providing permanent habitat for beneficial insects, spiders and mites is usually neglected in the design of both conventional and organic cropping systems. Besides a lack of appreciation of the benefits of ecosystem diversity, many farmers eschew strip cropping because of the extra work involved. Fueling up a spray rig is such a simpler solution, that even organic vegetable farmers usually succumb because it seems easier and is better known and understood than managing ecological complexity to achieve biological control. Also, prior to this CEC/NaturFarm/Rincon-Vitova Insectaries project, vegetable farmers had no prior case history documenting the energy and cost savings of the pest break strip approach and sustainable biological control. The mental paradigm of most vegetable farmers, whether organic or conventional, is that managing noncrop vegetation strips is an extra chore in their already overworked and stressful lives. For instance, seed may need to be purchased and additional planting operations undertaken to establish special strips. Pest break strips must also be monitored just like any other crop. Strip cutting requires extra management inputs so that mowing gets done ahead of scheduled irrigations. Sometimes the irrigation needs of watering up the pest break strip regrowth conflict with the irrigation, equipment logistics or harvesting needs of neighboring vegetable crops. In short, adding on the pest break strip cropping system sometimes seems like a headache to those doing the farming, an unwanted burden superimposed onto an already hectic overly long day, despite knowledge of the cost savings and benefits. In other words, managing pest break strips adds complexity to the farm operation, challenging the farmer's resources, as well as adding beneficial biodiversity and sustainable biological control to the agro-ecosystem. Even at NaturFarm, the demands of the pest break strip crops were a difficult burden to superimpose upon an already management-intensive cropping system of 30 different vegetable crops. Even though the increasing computerization of farms might ease scheduling tasks and smooth equipment utilization logistics, the humans running vegetable farms are still a key component in making the system work. The human component -- complete with the stresses, strains, perceptions, reactions and motivations -- of integrating biological control and pest break strips into an energy-efficient sustainable agricultural system still needs more research attention if the NaturFarm transition model is to be more widely implemented. In contrast, the extra energy-intensive spray rig runs required for pest control in the absence of the biological control benefits of pest break strips are so deeply ingrained that they are accepted as routine, a normal everyday part of modern farm life that often goes unquestioned. One result of this mindset in which spraying is the accepted and expected everday norm is that pest break vegetation strips are the rare exception, rather than the rule on vegetable farms. Lacking the permanent natural enemy habitat and agro-ecosystem stabilizing biological control benefits of pest break strips, both conventional and organic vegetable farms are heavily sprayed for pest control purposes with either conventional pesticides or organic substitutes like soaps, BT, pyrethrum and rotenone. NaturFarm's goal with pest break strips is breaking this deeply ingrained, energy-intensive habit of constantly spraying both conventional and organically-grown vegetables to control insect pests. But the pest break strips at NaturFarm are more than just a paradigm shift away from spraying. The pest break strips are also about habitat creation. Just as it is essential to maintain wetland habitats for migratory birds, it is necessary to create on-farm habitats for beneficial arthropod wildlife in order to reap the benefits of biological control. Pest break strips are, in essence, island-like wildlife refuges for natural enemies of agricultural pests. Functionally, managed natural enemy habitats like strip-cut pest break strips are essential transition inputs, providing the sustainable biological control missing from most conventional and organic vegetable cropping systems. Thus, pest break strips are vital if vegetable farms are to be successful in transitioning towards an energy-efficient agriculture in which sustainable biological control of insect pests replaces the energy-intensive pesticide spray habit. Pest break strips are more than just theory on NaturFarm's diversified vegetable farm, where sustainable biological control is operative and even organic sprays are never used. Indeed, NaturFarm has documented substantial energy and dollar savings compared to conventional farms by substituting pest break strips and beneficial insects for pesticide sprays. Whereas conventional farms spend 26% of their dollar budget and 24% of their energy budget on non-weed pest control, NaturFarm spends only 1% of its energy budget and 4% of its dollar budget on non-weed pests. Thus, provision of natural enemy habitats like pest break strips to grow natural biological control organisms is the necessary next step in pest control if organic vegetable production is to become truly sustainable and energy efficient, rather than a mere carbon copy of the pesticide spray model substituting "organic" substances in the spray tank. [might be a good place for the energy & cost pie charts on pp. 12-13 of the 1992 CEC NaturFarm Conversion report] As a pest control paradigm shift, the strip cut alfalfa borders and rows of insectary cover crops among the 30 or so vegetable varieties grown on the 70-acre NaturFarm are a bold leap beyond the less sustainable organic spray, pesticide substitution phase characterizing much of organic vegetable production today. Even NaturFarm's pest control adviser commented that on other organic farms he would have recommended sprays like soap and BT to combat high levels of pests that NaturFarm elected to tolerate. Instead, NaturFarm chose to risk and tolerate some short-term crop loss to further the longer-term objective of establishing sustainable biological control. In the face of a severe flea beetle infestation the first season, NaturFarm even elected to stop growing daikon radishes and switch to less susceptible crops for a season or two, until fall, so that long-lived Collops and Staphylinid beetle natural enemies would have more time to exert biological control on the soil life stages of flea beetles and worrisomely high populations of cucumber beetles [known as corn rootworms in the soil stage]. The beneficial beetles finally brought the flea beetles under biological control by the end of the first season, and daikons have been grown successfully ever since without any pest problems or sprays. Fortunately, NaturFarm was well-capitalized and had investors committed so strongly to sustainable biological control that they were willing to take short-term crop losses, if necessary, in the interests of the longer-term goal of establishing a reservoir of natural enemies for a more permanent and energy efficient form of natural biological pest control. Before embarking on this transition, NaturFarm's investors understood the risks and possible short-term losses that could result during the time needed for the pest break strips and natural enemies to establish a longer term presence. But the long-lasting and sustainable benefits of the pest break strips and biological control were perceived as being worth much more than any initial crop loss that might have to be tolerated in establishing an agro-ecosystem with sustainable biological control by natural enemies. There is no cheaper and more affordable army of pest-fighting beneficial arthropods than that found in strip-cut alfalfa, which is why NaturFarm made this the first choice for pest break strips. The millions of beneficials living in an acre of unsprayed strip-cut alfalfa are a ravenous army capable of destroying several million pests per day. Indeed, on a per acre basis, the number and diversity of natural enemies in strip cut alfalfa is so staggeringly high that it could not be purchased from commercial insectaries, though it can be grown for free! There are over a thousand species of insects interacting in complex ecological food webs in alfalfa. Describing and modeling the complexity of the alfalfa ecosystem, particularly when the insect diversity is further increased by intermixed crimson clover, ryegrass and various weeds, exceeds available taxonomic and entomological resources. But NaturFarm's pest control adviser, E.J. Dietrick, judged from his experience that the alfalfa pest break border strips at NaturFarm provided beneficial insect benefits similar to those that he and colleagues reported earlier from unsprayed strip-cut alfalfa fields in southern California [Schlinger & Dietrick, 1960]. When strip cut, each acre of alfalfa has 400% more natural enemies than when the whole stand is cut or harvested at the same time. The young tender alfalfa is an excellent insectary for growing beneficial arthropods, providing biological control organisms an abundant food source of small soft-bodied insects that thrive in the strip-cut regrowth. Alfalfa plants also yield 15% more, an extra ton of hay per acre, when managed by strip cutting. When the cut alfalfa is sheet composted rather than removed from the field, an expanded food chain of decomposing organisms feeds an even more diverse and abundant fauna of beneficial arthropods. The strip-cut alfalfa food chain produces over 1 million predatory spiders per acre, which is 1,000% more than without strip cutting. Each acre of strip cut alfalfa also contains 287,000 of the parasitic wasps providing biological control of aphids, caterpillars and other pests; this is 400% more than without strip cutting. Big-eyed bugs, good general predators of small caterpillars, mites and other pests, number 401,000 per acre in strip cut alfalfa, double the number occurring without strip cutting. Lady beetle adults number over 200,000 per acre in the strip cut alfalfa habitat, versus under 50,000 without strip cutting. There are 232,000 lady beetle larvae per acre after strip cutting, 2,000% more than the 11,000 without strip cutting [Schlinger & Dietrick, 1960]. Thus, strip cutting alfalfa pest break strips assures a more abundant supply of beneficial insects than could be produced under a more static management regimen. In contrast to strip cutting, when a whole field is harvested it is an ecological catastrophe for the beneficial insects, as they lose their food supply and are made homeless. The winged pests look for lush green nearby market crops to infest, while most of the beneficials either starve or disperse too far away to be available to combat new pest outbreaks. Strip-cut pest break strips remedy this situation by providing an alternative or trap crop for the pests, as well as simultaneously being a natural enemy refuge near the vegetable crops. As managed wildlife habitats for beneficial arthropods, pest break strips might be likened to military bases where beneficial arthropods are stationed and kept on alert to combat pest infestations as they arise. In other words, the reservoir of natural enemies in pest break strips stabilizes the vegetable agro-ecosystem by providing an army of beneficials lying in wait to ambush invading pests and prevent pest outbreaks. As a necessary component of an energy efficient agricultural system, pest break strips provide the habitat continuity that guarantees the presence of the natural enemies needed to provide biological pest control and idle the pesticide spray rigs. If conventional and organic agriculture are to kick the spray habit and become energy efficient with sustainable biological control, then strip cut alfalfa and other pest break strip crops will need to become integral components of the farm landscape. Economics, as much as anything else in past decades, helped make unsprayed strip-cut alfalfa a regional reservoir of natural enemies protecting nearby crops, including cotton and lettuce, in southern California. This changed only when alfalfa hay became economical to spray with insecticides and herbicides, which reduced biodiversity by killing the grassy weeds and diverse arthropod fauna. When alfalfa and other crops producing beneficial arthropods for a regional agro-ecosystem are sprayed and natural enemies destroyed, there may be quite dramatic and costly consequences. For example, the decline of cotton growing from an over 100,000 acre industry to a few thousand acres in California's Imperial Valley in recent years coincided with the pesticide-induced loss of alfalfa's natural enemies and their replacement by massive migrations of secondary pests like whiteflies. Imperial Valley vegetables like lettuce, broccoli and cabbage similarly suffer now from the whitefly migrations that have replaced the natural enemy influx from alfalfa. NaturFarm is using pest break strips in an attempt to re-create on a one farm microcosm level the sustainable biological control benefits onced provided region-wide in southern California's desert valleys by unsprayed and strip-cut alfalfa. But turning the theory that worked area-wide in the inland desert valleys of California into a success at NaturFarms' coastal valley location has proven a tough challenge. First of all, establishing an alfalfa stand proved unexpectedly difficult, as gophers undermined the alfalfa. Since other alfalfa fields exist in the vicinity, this was not expected. In the inland desert valleys, where alfalfa is grown in whole fields and flood irrigated, an irrigator with a shovel or a dog can destroy many gophers as they emerge from their flooded tunnels. Indeed, many gophers were flushed out by a period of unusually heavy rains at NaturFarm. But the NaturFarm uses sprinkler irrigation, which does not routinely flood out gophers. In any event, flood irrigation is not compatible with the permanent raised bed planting system established for vegetable growing. What was learned here was that strips of alfalfa interplanted or grown as field borders are a different cropping system than alfalfa grown in whole fields. Natural gopher biological controls like raptors were not a factor in the first year of nature farming, a result predictable from ecological theory and classical predator-prey models. Namely, the gopher pests have to erupt to high levels before predators can be expected to move in and supply control. Though gopher tunnels were explosively destroyed, the alfalfa border strips never recovered enough to produce the strong stands associated with whole alfalfa fields. Needless to say, with the 20-20 vision of hindsight, NaturFarm would have benefitted by starting the alfalfa pest break strips a year ahead of planting the vegetables, as the problems of stand establishment could have been worked out in advance of the first year's plantings of market crops of vegetables. The failure to predict the gopher problem and get a year's headstart in establishing the pest break strips meant that the natural enemy habitat did not reach its full potential in time to provide maximum biological control of the first spring's planting of vegetables. More research is needed into how to best integrate alfalfa and other pest break strips into vegetable agro-ecosystems for sustainable biological control. One option worth considering is interplanting small fields of furrow-irrigated alfalfa, which could be strip harvested for a commercial hay crop, around the vegetable farm. These pest break fields have the potential to ease gopher problems and management logistics, while still producing many of the same benefits as pest break strips. The right combination of pest break strips and/or small pest break fields of alfalfa needed to produce the desired benefits of trapping cropping and growing beneficial arthropods on vegetable farms has never been investigated. A Sense of Place Other human factors were also at work, such as the lack of sense of place that comes from years of working the land at one location. Being new to this farm location and unable to anticipate what the natural cycles of climate and the surrounding land would bring added an extra dimension of challenge to this transition farming experience, not that anyone could have predicted the weather and adequately prepared for its pest consequences on NaturFarm's first year. Specifically, the first year of cropping happened to be one of California's extreme drought years, which had enomorous pest consequences, especially when combined with the difficulty in establishing the pest break strips. Drought years in California usually exacerbate a farmer's pest problems, as the surrounding wild vegetation dries up early, forcing insects to migrate. The lush green of irrigated farms acts almost like a magnet, attracting migrating insects from the the dying hillside vegetation in this part of California. In a more normal rainfall year, insects inhabiting the surrounding landscape would not have migrated in such large numbers to NaturFarm's first spring vegetable plantings. But being an extremely attractive [to hungry insects] island of lush green plants in a drying landscape, NaturFarm was like a beacon luring in insects migrating from dry hillsides and nearby drying lima bean fields early that first spring. Thus, the first spring transition vegetable crop at NaturFarm was challenged by unusually heavy numbers of cucumber beetles, Diabrotica species, and flea beetles coming off drying wild mustards, wild gourds, jimson weed, nightshade and other farms with drying crops. The combination of unusually heavy insect migrations and pest break strips weakened by gophers threatened to overwhelm NaturFarm's vegetable crops with flea beetles and cucumber beetles that first spring. Most organic and conventional farmers would have reached into their arsenal of sprays. But NaturFarm remained true to its paradigm of not spraying, even when its pest control adviser expressed some doubts about getting by without any pest damage in the face of heavy flea beetle attacks on daikons, cabbage aphids on cole crops like cabbage and broccoli, and cucumber beetle populations so heavy that they threatened to spill out of the pest break strips and overwhelm the farm. Basically, NaturFarm gambled that some initial crop loss to the daikons, cabbage and broccoli would prove an acceptable price for attainment of the longer-term goal of establishing sustainable biological control of pests. The underlying premise, based on E.J. Dietrick's decades of firsthand field experiences in similar situations, was that unusually high insect populations are a common phenomena at the beginning of abrupt transitions from conventional to organic farming. When freed from a pesticide population control regimen, pests initially enjoy a Malthusian geometric population growth spurt in the absence of natural enemies, which are scarce from having been sprayed into near oblivion. As might be predicted from ecological theory, natural enemies find these high concentrations of pests, but usually not until after there is some plant damage. Thus, without spraying or some type of pest control actions during the early phases of the transition, some crop damage like the flea beetle destruction of the daikons and cabbage aphid injury to the cabbage and broccoli, is to be expected. For a period of time early in transitions, Dietrick has also routinely observed that high populations of beneficial insects can co-exist with high pest populations, making for extraordinarily high total insect populations. Thus, even though biological control may be occurring when total insect population levels are high, the pest populations may still be so high that some damage and insect-contamination of crops is almost inevitable when there is no spraying or other pest control action early in the transition experience. Even high populations of beneficial insects like lady beetles remaining after destroying aphid infestations are an unacceptable contaminant on a harvested broccoli crop. Eventually, usually towards the end of the first year, and almost always by the second or third year, a permanent lowering of total insect populations occurs. Also, the ratio of good bugs to bad bugs improves after the early stages of a transition, an outcome expected from ecological theory and empirical evidence of predator-prey ratios. At least this has been the general rule over several decades of Dietrick's experience implementing biological control for the University of California and private client farmers in California, Arizona, Mexico, Central America and elsewhere. NaturFarm's first year transition experience was no exception, only overlayed onto the expected high total insect populations was an unexpectedly heavy insect migration onto the farm due to the severe drought affecting the surrounding non-irrigated landscape. Indeed, total insect populations were 10-fold greater the first transition year than in the second year of the transition at NaturFarm. Thus, NaturFarm was exposed to unusually heavy insect pressures when the abrupt transition from conventional to sustainable organic farming began. Though these high total insect populations early in the transition may be unavoidable, maybe even desirable for a sustainable long-term outcome, the 20-20 vision of hindsight would have dictated preparing for unusually heavy drought-year insect migrations by establishing stronger pest break strips covering more acres. Ideally, at least 10% of the farmed area would be in pest break strips planted ahead of the main crop as trap crops to stop such a heavy pest onslaught. The type of experiment needed to determine the ideal size of pest break strips for heavy pest years is difficult, because it might have to be repeated for several years until another drought year of similar pest magnitude comes along. But 10% of the area to trap heavy pest populations is the figure experimentally determined in several other cropping systems. NaturFarm had planned to have 10% of its vegetable cropping area in pest break strips. But difficulties establishing the alfalfa pest break strips during the first year made the effective trap crop area less than optimum. [perhaps a good place to insert a diagram of the layout of the pest break strips, showing a 35 ft pest break strip every 350 ft = 10% of area, and mentioning in caption] In order to stop pests from moving out of the trap crop and into the market crop, trap crops are traditionally either destroyed along with the pests, sprayed or treated with some sort of cultural control like barriers to prevent pest migrations. Treating only the 10% trap crop area to destroy pests reduces pesticide sprays, energy inputs or other pest control actions by 90%, as compared to treating the entire cropping area. However, since the pest break strips at NaturFarm are designed to double as insectary crops and grow beneficial insects, the usual crop destruction and spray management options for trap crops were out. Heavy cucumber beetle populations migrating into the pest break strips from the drying hillsides and threatening to spill over into the market crops were particularly worrisome that first spring of the transition. The question that might be asked here is why the pest break strips did so well at trapping cucumber beetles, but not cabbage aphids or flea beetles, which caused considerable crop damage. The simple answer is that the cabbage aphids attacking the cole crops and the flea beetle species attacking the daikons are what is known as specialist pests, attacking mainly members of the Cruciferae plant family, which includes daikon radishes, cabbages and broccoli. Unlike the adult cucumber beetles, which are attracted to a variety of blossoms, these cole crop specialist pests do not have much affinity for the alfalfa, strawberry clover or pasture grasses growing in the pest break strips, much less the squash, strawberry or lettuce crops. A more complex pest break strip system could have brought the cabbage aphids under quicker biological control. Though, as a practical matter, what with the difficulties establishing the alfalfa pest break strips and other demands upon the farmer making an abrupt transition in a new setting, planting a special insectary blend to protect the first spring cole crops was not even attempted. Thus, the first spring planting of cole crops functioned like a pest break strip in what scientists would call the space-time continuum. In other words, NaturFarm's first spring planting of cole crops ended up functioning as a sacrificial trap crop for specialist pests like the cabbage aphid, as well as being an insectary crop producing cabbage aphid natural enemies for biological control of subsequent [in the time continuum] NaturFarm cole crops. Thus, cabbage aphids came under biological control when their natural enemies became more abundant after that first spring attack. Indeed, cabbage aphids remained under biological control for several subsequent cole crops, thanks to the descendants of the natural enemies of that first destructive spring of the transition. Only later did ant interference disrupt the biological control. The ants harvest honeydew from the aphids, and like good shepherds chase away the natural enemies attacking their aphid dairies. In order for biological control of aphids to function again, the ants require periodic management. A culture control, cultivating ant trails and nests, disrupts the ants enough to allow natural enemies to restore biological control to the cole crops. Of course, NaturFarm would have preferred that its first spring planting of cole crops be sold as a market crop, not become a de facto pest break strip. But this would have required advance planning, and added a layer of complexity for the already hard-pressed farmer, who would have had to plant a special cole crop pest break strip in addition to the alfalfa pest break strip. If the initial cole crop loss is to be avoided at the beginning of a transition to a no-spray sustainable organic vegetable agro-ecosystem, then special cole crop pest break strips are needed to compensate for the time lag between pest outbreaks and the onset of biological control. In classical predator-prey ecological theory, the time lag for onset of biological control exists because the prey [cabbage aphid] population peak reaches crop damaging levels before natural enemy [predators, parasites, pathogens] populations increase enough to dampen the infestation. In other words, pests are necessary to grow natural enemy populations; and if the pests are not to damage the initial cole crop plantings, then the pests needed to nourish natural enemies have to be grown in special cole crop pest break strips ahead of the market cole crop. Indeed, establishing cole crop pest break strips far enough in time in advance of the market crop would also help grow Collops beetle, Staphylinid beetle and other natural enemies for biological control of flea beetles, cucumber beetles and other pests. [if available, might not be a bad place to insert diagrams or illustrations of the pests & natural enemies mentioned; e.g. cole crop roots attacked by larval flea beetle, which is attacked by Collops & Staphylinid beetle larvae, while adult flea beetle is munching shot-holes in leaves.] Since cole crops are so heavily sprayed, with many pests resistant to pesticides, much more research is needed on integrating cole crop pest break strips into vegetable agro-ecosystems. Only one experimental paradigm, a strip farming experiment in Tennessee in the 1930s, even exists for using cole crop pest break strips to prevent cabbage aphid damage [Marcovitch, 1935]. In these early experiments, strips of turnips, a good cabbage aphid host, planted a month ahead of market crops acted as insectary plants, providing aphid natural enemies to nearby market crops. The turnips were partially destroyed by aphid infestations by late spring or early summer, but predators like lady beetles and parasites like Lysiphlebus testaceipes controlled aphids in the nearby later-planted market crops for most of the rest of the season. The NaturFarm experience was similar, only the planned market crops of cabbage and broccoli the first spring of the transition played the insectary crop role of turnips. More research is needed to determine whether other Cruciferae family plants like the wild mustards [probably relatives of the mustard seed industry crop plants farmed nearby in bygone decades] and wild radishes growing in the vicinity of Naturfarm might also be harnessed as cole crop pest break strips in interplanted rows or around field perimeters. Integrating these locally adapted weedy crucifers [e.g. wild radish and wild mustards] into the agro-ecosystem might also help produce needed energy-savings in weed control, as these Brassica species are known for their allelopathic inhibition of other vegetation. Under a plastic tarp like those used for solarization, residues of Brassicas such as cabbage and mustards are as effective as soil fumigants against soil pathogens and plant-parasitic nematodes. Hence, the potential to rotate locally-adapted Brassicas into the strip cropping scheme for control of multiple types of pests and increased energy savings needs to be further investigated. NaturFarm has so far only scratched the tip of the iceberg, as far as the potential of pest break strips to save energy and pest control costs. With such encouraging initial savings in energy and insect pest control costs compared to conventional farming, NaturFarm feels strongly that the concept of pest break strips needs to be further developed and extended to control a wider range of pests, save energy on other farm operations, and increase the overall sustainablity of farming. Many potential species, from legumes like peas to grasses and native plants like marigolds await testing in vegetable agro-ecosystems for insect, nematode, weed and pathogen control. Pest break strip cropping schemes can become even more varied to meet gaps in pest control. For example, strips of peas planted by Marcovitch [1935] in September grew pea aphids and their natural enemies, providing biological control of aphids on turnips and several other crops for several weeks into the fall. Future research should followup some of these many leads, and determine the best and easiest to use pest break strip cropping schemes for the long-term sustainability of vegetable agro-ecosystems. Research is also needed to fine-tune the planting times of pest break strips in relation to market crops for maximum biological control efficacy. The 1935 Tennessee experiments indicate that timing of plantings is critical -- the insectary crops had to be planted enough in advance, a month in spring, of the main crop for sufficient natural enemies to be available to nearby market crops. Perhaps by simply adjusting pest break strip species and planting times, transition farms like NaturFarm could get through the first season with no sprays, no crop loss and the same energy and pest control savings. Future research will have to address these and many other issues, including irrigation effects on pest management, if the transition to energy-efficient, sustainable no-spray organic vegetable farming is to be made easier to follow and more painless. In most cole crop production areas in California and worldwide, caterpillar pests like the imported cabbageworm, cabbage looper and diamondback moth are a problem, and sprayed with everything from microbials like Bacillus thuringiensis [BT] to synthetic pesticides. Pesticide resistance has turned diamondback moth into a major problem in the Asian Pacific Rim countries. Inexplicably, cole crop caterpillar pests like diamondback moth, imported cabbageworm and cabbage looper never became a problem at NaturFarm. NaturFarm's diverse natural enemy complex, which contained many generalist predators, including large beetles capable of eating caterpillars, may have played a role in keeping caterpillar pests like cabbage looper, imported cabbageworm and diamondback moth from reaching pest status. However, another caterpillar pest, the corn earworm, did become a problem on sweet corn despite an abundance of its primary generalist predator, the minute pirate bug. Hence, there may have been factors other than direct biological control by natural enemies at work suppressing cole crop caterpillars but not corn earworms. For example, NaturFarm injected very low levels of the microbial inoculant EM in overhead irrigation waters sprinkled on crops. EM has never been directly tested or evaluated with respect to its potential direct or indirect control effects on pests. So, an EM role in suppressing insects like the caterpillars attacking cole crops cannot be entirely dismissed without further research. In fact, there is reason to suspect that the very low incidence of plant disease problems at NaturFarm might be related to EM. Microbes like those in EM are known to produce antibiotics, which can stop other microbes, including some plant pathogens. Also, microbes that do not harm plants have been known to occupy niches favorable to plant pathogens, thereby excluding colonization of the plant by the pathogen. In a phenomena roughly analagous to immunity, microbes can also be a factor in induced resistance of crop plants to pests. Microbes can also be antagonistic to pathogens in a manner analagous to the biological control of insects by predators and parasites. Indeed, recent scientific research indicates that the microbial products in compost teas sprayed on plants can stop plant diseases like downy mildew, powdery mildew and leaf blight [Weltzien, 1989]. Vegetable crops are known to be attacked by a wide range of plant diseases, and fungicide use is the rule on many conventional vegetable farms. Yet, surprisingly, NaturFarm's only plant pathogen problem of consequence was a blue mold on spinach believed to be downy mildew race 3. Like most California coastal areas, powdery and downy mildew occurred on cucurbits like squash, though were not severe enough to impact production. Whether this low level of disease incidience was coincidental, due to natural biological controls moving from the pest break strips with insects, or related to EM, cover crop, fertility or other practices associated with the NaturFarm farming system is unknown. It would take a complicated research design to determine what is happening at NaturFarm with respect to the extraordinarily low incidence of plant disease on the 30 vegetable crops. Usually, overhead irrigation plays a role in plant disease and arthropod pest management. Sometimes, overhead sprinkler irrigation stimulates germination of the spores of plant pathogens like those causing downy mildew and powdery mildew. Other times, overhead irrigation timing is such that the plant pathogen spores do not germinate in greater than usual quantities. In fact, overhead irrigation sometimes reduces powdery mildew by washing off spores. Overhead irrigation also washes off arthropod pests as diverse as aphids, spider mites, thrips and caterpillars. Wingless pests washed off plants by rainfall or overhead irrigation have a more difficult time surviving and returning than do winged predators and parasites. Predatory mites survive because they float in water, whereas pestiferous spider mites drown. Irrigation, rain, fog, dew and other water sources can also create damp microclimates favorable to epidemics of entomogenous fungi, an occurrence observed when indigenous biocontrol fungi destroyed aphids living deep in the wet understroy of the pest break strips. In fact, there is also good reason to suspect that the irrigation process itself, in this case overhead sprinklers, could also be one of the reasons for the surprising absence of cole crop caterpillar pests. In fact, in Hawaii, daily overhead irrigation was shown to control diamondback moth; however, the crop was watercress, an aquatic plant that could withstand moisture without fear of disease. But more recently in the Midwest, daily overhead irrigation of head cabbage growing in a well-drained soil was shown to reduce diamondback moths up to 90%, with no plant disease problems. The key to attaining such a high level of control is timing overhead irrigations for the evening hours, as this disrupts the calling, mating and dispersal of diamondback moth, a nocturnal pest [McHugh, 1993]. NaturFarm did not set up controlled test plots to investigate the effects of its overhead sprinkler irrigations on cole crop caterpillar pests like diamondback moth. So, there is no way to know what percent of the pest control effect can be ascribed to biological control and what percent ascribed to irrigation. There is also evidence that overhead irrigations timed for the hottest part of the day also reduce numbers of adult flea beetles, as these pests like it hot and dry. It might almost require a computer system to keep track of and schedule irrigations for pest control purposes so that fungal biocontrol agents are triggered against aphids, diamondback moths disrupted on cole crops by evening sprinklings and flea beetles deterred from daikons by overhead watering during the hottest part of the day. Factors like water conservation and energy use have never been determined for a system of this sort integrating irrigation and pest management. Future research into integrated pest management [IPM] systems might consider designing in and taking advantage of the potential pest control synergisms between irrigation and biological control by natural enemies. Thus, an overhead sprinkler irrigation system like NaturFarm's could potentially be fine-tuned to wash off pests, disrupt pest mating and optimize biological control in crops and pest break strips while delivering the optimum daily dose of water to crops. However, integrating irrigation into cropping systems as a form of pest control may not be simple, as evidenced by the irrigation scheduling difficulties encountered with the pest break strips. Vegetable farms might require a computer system with software combining the interactivity of expert systems with scheduling and forecasting [e.g. crop irrigation needs, expected pest problems] abilities; though this might be technically achievable, such a system has yet to be invented for vegetable farms. Designing a vegetable cropping system harmonizing the pest control advantages of irrigation and pest break strips with crop needs and farmer abilities and equipment limitations would be an innovative future research direction. Another reason for learning how to better integrate the irrigation and maintenance of pest break strips into vegetable cropping systems is that the pest break strips may be the only year-round habitat available on vegetable farms for colonizing new natural enemies. Some pests became problems because when inadvertently imported from their foreign lands of origin, their natural enemies were left behind. In the absence of predation and parasitism by natural enemies from the native ecosystems of pest origin, pest populations can quickly explode to damaging levels. These damaging pest population explosions are also seen when natural enemies are missing for other reasons, such as pesticide spray mortality. Classical biological control remedies the absence of natural enemies from the pests native homeland, though the introduced natural enemies have to be protected from eco-catastrophes like pesticide spray drift. In classical biological control, natural enemies from the pest's homeland are collected, quarantined and evaluated, usually by the USDA, universities or state agencies. Natural enemies passing the test criteria and surviving the rigors of rearing are released in an attempt to establish a natural ecological balance similar to that keeping the pest rare in its native homeland. Not all classical biological control releases of natural enemies provide permanent pest control. Natural enemies imported for classical biological control programs are not always those best suited to the pest or climate of the new agro-ecosystem. Nevertheless, successful classical biological control programs more than pay for any R&D expenses and failures, often saving millions of dollars per year in pest control costs and reducing pesticide use dramatically. At NaturFarm, the year-round habitat provided by pest break strips afforded an opportunity for classical biological control not commonly found in vegetable agro-ecosystems. Most vegetable farms lack the year-round habitat provided by pest break strips, and are therefore inherently unsuitable for classical biological control. In contrast to less sustainable vegetable farms lacking pest break strips, NaturFarm was able to implement classical biological control, augmenting the indigenous natural enemy complex with exotic natural enemies capable of controlling tough potential pests like the diamondback moth and Lygus bug. A Braconid parasite, Peristenus digoneutis, imported from Europe by the USDA and impossible to raise in commercial quantities at the insectary, was released into the pest break strips to reproduce naturally and increase destruction of Lygus bug nymphs. The starter culture of two dozen mated female P. digoneutis were placed into an improvised field insectary, a tent-like nylon organdy cage slipped over a section of alfalfa in the pest break strip infested with Lygus. The idea behind this type of classical biological control is permanent establishment of the new natural enemy in equilibrium with populations of Lygus that become permanently lower than would otherwise be the case. Clasical biological control does not seek to eradicate the pest, as this would risk starvation of the natural enemy. Rather, the goal is reducing the pest to tolerably low levels. Besides release of P. digoneutis against Lygus bugs, an egg parasite was released to attack diamondback moth in cole crops. The diamondback moth egg parasite, Trichogrammatoidea bactrae, was collected as part of a University of California, Riverside, expedition to Australia for pink bollworm natural enemies. T. bactrae is a good candidate for establishment as a classical biological control because it attacks a wide array of moths in the family Gelechiidae, which includes many pest species. Also, T. bactrae can be produced commercially in the insectary. NaturFarm also "seeded" the pest break strips and vegetable rows with well-known insectary-grown natural enemies like green lacewings, predators attacking soft-bodied insects ranging from aphids and tomato russett mites to corn earworms and cabbage loopers. The beneficial insect releases, designed to augment or supplement indigenous biological control organisms, also included Trichogramma egg parasites that stop moth and butterfly eggs from hatching into pests like damaging cabbage caterpillars and tomato fruitworms. These natural enemy releases can be thought of like vitamin supplements, helping ensure that the agro-ecosystem has the biological control "nutrients" needed to fight off pest infestations. The supply of indigenous natural enemies found on NaturFarm included classical biological organisms introduced by the University of California many decades ago, a lasting reminder to knowledgable entomologists that the few thousand dollars spent on biological control many years ago are still working and paying millions of dollars in pest control dividends around the state every year. The most immediate source of the thousand or so species of natural enemies colonizing the pest break strips at NaturFarm was probably a nearby unsprayed alfalfa field. Had there not been quick natural colonization of the pest break strips by natural enemies from a nearby unsprayed alfalfa field, natural enemies could have been vacuumed harvested from a slightly more remote source in the same county and transported to NaturFarm for release. The same D-vac and Cycle Vac vacuum insect harvesting equipment used to sample fields as part of monitoring arthropod populations can be used to harvest "crops" of pests to study or beneficial insects to transport. With over one thousand arthropod species interacting in California alfalfa fields, practical population monitoring for everyday pest management requires using a rougher index, a ratio of good bugs to bad bugs, to monitor the progress of biological control on a more macro level. Since the D-vac and Cycle Vac collect huge numbers of insects, well-above the numbers needed for sampling and monitoring purposes, the excess not put into alcohol for preservation and possible future dissecting microscope identification to the species level can be utilized as a "crop." This huge excess D-vac or Cycle Vac harvested "crop" of living insects can be sorted via a series of screens of varying mesh size. For example, parasites tend to be very small, sometimes pin-head species like Trichogramma, and pass through the smaller screens. Larger insects like cucumber beetle adults remain behind. Indeed, this principle of insect separation after vacuum harvesting, which did not require energy expenditures beyond planned sampling needs, proved to be an excellent tool for managing the pest break strips as a cucumber beetle trap crop. Instead of spraying or plowing under the trap crop to destroy the cucumber beetle adults, the pests were vacuumed up and the beneficials returned unharmed to the pest break strip. The idea of vacuuming up pests and returning the beneficials to the field to improve the "good bug to bad bug ratio" is an innovation in vegetable farming. Since the invention of the D-Vac in the 1950s, E.J. Dietrick has sold over 1,500 D-Vac vacuuming units, mostly for scientific sampling purposes. Variations on the D-Vac concept, like Tractor Vacs, have been around for decades, mostly used by University of California researchers to harvest insects from alfalfa fields. Only recently have commercial quantities of tractor-drawn vacuum devices been sold to suck up everything from Colorado potato beetles on potatoes to Lygus bugs on strawberries and caterpillars on lettuce. However, there is a big underlying difference in the way that NaturFarm uses vacuuming to harvest insects. First of all, NaturFarm vacuums only the pest break strip area, when needed, or less than 10% of the acreage, not whole fields. Other vegetable farms tend to vacuum their whole acreage, which may have a different effect on the agro-ecosystem, much like the big differences in numbers of natural enemies between strip-cut alfalfa and cutting the whole field all at once; but more research is needed, as these ecological changes have not been measured. Also, other vegetable farms do not screen their insect harvests and return the beneficials to the field -- so their paradigm is more like the pesticide era philosophy that "the only good bug is a dead bug." In contrast, NaturFarm integrates vacuuming as a selective [good bugs are returned to the pest break strips] cultural control tool that raises the good bug to bad bug ratio, and promotes the longer-term goal of sustainable biological control. NaturFarm was fortunate that E.J. Dietrick's bag of biocontrol tricks included this innovative strategy of harvesting excess cucumber beetles from the pest break strips without disrupting development of biological controls. Since cucumber beetles also have a soil larval stage, much like flea beetles, and can damage crop roots, biological control of the soil stage of the pest could have better complemented the above-ground adult life stage vacuuming. Mulching around the susceptible crops would provide habitat for more natural enemies, as well as another food source from the food chain involved in mulch decomposition. As it was, the adult stage of the cucumber beetle was eventually lightly parasitized by a Tachinid fly, while the soil stages were attacked by larval Collops and Staphylinid beetles. The end result was as would be predicted from classical ecological predator-prey theory: namely, the Collops beetles, Staphylinid beetles and other natural enemies brought the flea beetles and cucumber beetle pests under sustainable biological control, and crops like daikon can now be grown without fear of crop destruction. To be continued...