TRICHOGRAMMA TECHNICAL BULLETIN RINCON-VITOVA INSECTARIES, INC. SUPPLIERS OF BENEFICIAL INSECTS SINCE 1960 P. O. BOX 95, OAK VIEW, CA. 93022 (805) 643-5407 FAX 805-643-6267 OUTSIDE CA 800-248-2847 BENEFITS OF BIOCONTROL Biological control with beneficial insects makes dollars and sense, even in chemically sprayed fields. Growers using Rincon-Vitova's Trichogramma and other beneficials (all natural, none genetically engineered) to augment indigenous natural enemies can expect to improve profits by reducing or eliminating pesticide use. In many cases, crop yield and quality improve as previously unrecognized adverse pesticide effects on plant physiology disappear. Resistance problems, and outbreaks of secondary pests like spider mites, whiteflies and leafminers are avoided when biological control is integrated into pest defense systems. Residue problems, costs of sprays, scheduling sprays around irrigations and when workers are not present, health and safety liability risks, even insurance costs, may be reduced when beneficial insects assume more pest management chores. Even gaining a few weeks delay in the onset of spray programs with early releases of Rincon-Vitova's beneficials can produce dramatic monetary gains, eliminating weeks of costly pesticide inputs. As if this were not enough, there are also public relations and marketing benefits from using this "green", environmentally-friendly alternative to conventional chemical control. Trichogramma and other Rincon-Vitova beneficials belong on your crop production team. TRICHOGRAMMA - MICRO MARVELS Trichogramma are pale yellow micro-wasps (1/100 inch long) that destroy the eggs of over 200 pest moth species (cutworms, fruitworms, leaf worms, leafrollers, loopers, armyworms, borers etc.), preventing ravenous worms (caterpillars) from hatching out and devouring crops. Trichogramma stop caterpillars in almost every imaginable row and field crop, cotton, vegetables, vines, fruit, nut, forest and street trees, ornamentals and interiors, wherever worms (caterpillars) are a problem. These tiny pest-fighting farm animals are the world's most widely used commercially produced beneficial insects. Smaller than a pinhead and dwarfed in size by pest eggs little larger than sand grains, Trichogramma are micro-engineering marvels, with microscopic "stingers" drilling through moth eggs to deposit their own eggs. From one to three Trichogramma eggs are laid inside most moth eggs, though up to 50 eggs may be laid inside relatively large moth eggs. Trichogramma determine the size of moth eggs, and hence how many of their own eggs to lay, by timing their walks across moth egg surfaces. Trichogramma larvae eat out the insides of pest eggs, pupate, and cut an exit hole in the pest eggshell just big enough for winged adults to squeeze through. Male Trichogramma emerge first, wait for females to emerge, and immediately mate. The life cycle from egg to adult is typically completed in 7 to 10 days (longer in cooler weather). This short life cycle allows as many as 30 generations per season, with rapid increases in Trichogramma populations. Thus, we recommend starting Trichogramma releases as early in the season as possible, building up large Trichogramma populations ahead of major pest invasions. Trichogramma wasps attack only insect eggs, and do not harm people, plants, pets or livestock. MANY SPECIES & BIOTYPES Rincon-Vitova Insectaries began raising Trichogramma in 1960, and currently rears several different Trichogramma species and strains (biotypes) adapted to a variety of crops and caterpillar (worm) pests. A phone call will help us match your pest problems with the right Trichogramma species or biotype. In many cases, our staff entomologists recommend combining Trichogramma with other beneficials, such as Rincon-Vitova's green lacewings, excellent general predators that further strengthen the natural enemy complex. Trichogramma pretiosum is our all purpose species, recommended for field, row and vegetable crops, as well as vineyards and selected tree crops. It is a warm weather species. Trichogramma platneri, a western U.S. native, is recommended for western tree crops. The avocado strain of T. platneri has garnered rave reviews on avocados. We also rear a codling moth strain of T. platneri (breeding stock collected in northern California) for west coast apple, pear and walnut growers. Trichogramma minutum is best for trees in eastern states, where it is native and overwinters in moth eggs. T. minutum has proven useful against spruce budworm on Canadian forest trees, codling moth in eastern orchards, and has parasitized up to 90% of corn earworm eggs in the southeastern U.S. T. minutum is most active from early morning to evening, taking a break during the hottest (above 90o F), driest midafternoon hours, when it seeks the shady undersides of leaves. Optimum temperature for T. minutum is 65-85o F). All tiers of trees are colonized effectively. Trichogrammatoidea bactrae, recently imported from Australia to fight pink bollworm in cotton, has a wide host range. Besides fighting pinkie in cotton, T. bactrae has potential against tomato pinworm, potato tuber moth, Oriental fruit moth, navel orangeworm, peach twig borer, diamondback moth and other pests. From time to time, and on special demand, Rincon-Vitova Insectaries offers other Trichogramma species and biotypes to customers on account. RELEASE BASICS Rincon-Vitova recommends beginning Trichogramma releases as early in the season as possible to allow for a Malthusian (geometric) Trichogramma population explosion before peak pest moth egg-laying. The basic idea is creating a defensive army of Trichogramma positioned to attack eggs deposited by hordes of invading pest moths. Periodic releases of Trichogramma insure the presence of overlapping generations of mated females ready to attack eggs of any moths flying into fields or orchards. Trichogramma are shipped (as pupae ready to emerge as adults) inside parasitized grain moth eggs, usually glued to perforated cards. There are approximately 120,000 Trichogramma per card. Each card can be broken into 30 squares with 4,000 parasites per square inch -- this permits even distribution of Trichogramma in fields and orchards. Loose eggs can be divided into paper cups; there are approximately 20,000 eggs in a cubic centimeter. Trichogramma wasps emerge from cards in two to five days, depending on temperature, which should ideally be 80o to 90o F. Emergence can be delayed by holding parasitized moth eggs at cooler temperatures (not less than 40o F). Emerging wasps are usually seen in the morning. Keep Trichogramma cards in the shade, out of the hot sun, or you'll have cooked insects, rather than live pest fighters. To maximize pest fighting time in fields and orchards, don't delay release after adult wasps emerge from grain moth eggs. (Graphic of lifecycle) To increase Trichogramma mating prior to release, incubate parasitized moth eggs in a gallon jar, paper bag, paper wedge cup or other closed container. This can be done by cutting cards (along perforations) into 30 squares, and placing squares in a paper wedge cup according to the diagram. Fold the mouth of the cup closed (folding over twice), and fold back the two corners like dog ears. (Graphic of cutting cards and folding cups) Anytime after Trichogramma adults begin emerging and swarming, cups can be set out. Cups can be opened and placed in plants, or punctured with a knife, creating an exit hole on each side while protecting remaining unhatched eggs from predators and moisture. Punctured cups can be broadcast on and around plants or vines, set in branches or stapled to leaves. Large incubation containers can be opened at randomly spaced rows or trees; allow containers to remain open longer at pest "hot spots," so more parasites emerge where pests are concentrated. Since Trichogramma wasps attack freshly deposited moth eggs, the time to release Trichogramma is when moths are in flight and laying eggs. Begin releases as early in the season as field and row crops provide shade for the parasites, e.g. when tomatoes are 12-28 inches high. It is better to start releases early than too late, as Trichogramma populations have the potential to grow geometrically each 7-10 days, and a long headstart on pests is more likely to tip the ecological balance in favor of biological control. MONITORING Information gleaned from monitoring progress of biological control in the field can be used to raise economic treatment thresholds above published levels, and reduce spray bills. Large armies of beneficial insects permit crops to withstand higher pest populations without economic damage. Most published economic treatment thresholds are based upon numbers of pests on plants sprayed with pesticides to eliminate natural enemies. Hence, economic treatment thresholds can be adjusted upwards to account for natural enemies on farms using biological control. Careful monitoring is also important because not all parts of fields get pests at the same time. It is often possible to identify pest "hot spots" that can be targeted for treatment with larger numbers of beneficials or spot-treated with least toxic, low residual materials. While 98% pest kills may be necessary in heavily sprayed fields devoid of natural enemies, softer materials knocking off 50-75% of pest populations may suffice in fields teeming with natural enemies. Natural enemies can mop up pests remaining after the top is knocked off pest populations by selective, least toxic pest controls. The goal is establishing an ecological balance with pests at tolerably low levels, not eradication. Low pest populations and innocuous alternate prey are necessary to feed biological control organisms. Without prey, predators and parasites starve. Hence, a few minor pest situations must develop and be tolerated, in order to obtain and maintain a buffering natural enemy complex that subsequently controls major pest problems. The ideal monitoring tool is a vacuum insect net, as it provides the most complete sample of relative amounts and ratios of pests and beneficials. We recommend working with PCAs and IPM practitioners skilled in biological control, and monitoring moth flights and egg laying (e.g. with pheromone traps, scouting, D-Vac, sweep net sampling, degree-day calculations), as well as natural enemy and pest population parameters. Trichogramma parasitism of moth eggs can be monitored by placing cards of fresh moth eggs in fields or sampling pest eggs on plants. Techniques like two-minute timed egg searches are used in some IPM programs to monitor eggs of pests like the cotton bollworm and tomato fruitworm. Fresh moth eggs are usually white or a pale shade of yellow or orange. It is easy to recognize moth eggs parasitized by Trichogramma, as the color darkens to black. The ratio of black (contains pupating Trichogramma) to white (unparasitized) eggs is a measure of Trichogramma parasitism. Field egg counts underestimate Trichogramma parasitism, as it takes 48 hours for freshly parasitized moth eggs to turn black (holding eggs for 48 hours overcomes this problem). Pest egg identification can be quickly learned from a trip into fields with farmer advisers, IPM consultants, researchers et al. RELEASE RATE CONTROVERSY The question of how many Trichogramma to release is controversial, and complicated by numerous variables like pest density, release dates (early vs late season), single vs. multiple releases, indigenous natural enemy populations, cultural practices, pesticides, pruning, alternate hosts, weather (e.g. rain and low temperatures reduce T. minutum parasitism of codling moth on the east coast), etc. Factors like type and growth stage of the crop also need to be considered in setting release rates. Numbers of Trichogramma to release also depend upon whether releases are intended to bridge a temporary lag before indigenous parasites come into effect, are used in combination with other measures, such as predator releases (e.g. green lacewings) or BT treatments, or are intended to recolonize fields where biological control is lacking because of pesticide drift or other interference. More Trichogramma are needed in heavily sprayed agro-ecosystems, than in ecologically farmed areas where minimal pesticide use allows natural enemies to live, multiply and migrate from crop to crop. The natural movement of beneficials complicates scientific field tests, as Trichogramma freely migrate (usually drifting downwind) and colonize adjacent control (no release) plots. Frequently, Trichogramma destroy 60-70% of pest eggs in control plots adjacent to release plots, in effect turning agro-ecosystems into one big Trichogramma release plot. Other times, pesticide drift from adjacent control plots kill Trichogramma in release plots, effectively eliminating all biological control in the agroecosystem. In either case, faulty experimental design leads to meaningless conclusions as to release rates, and underestimates the value of Trichogramma. Studies minimizing these common methodological errors show that caterpillar (moth) egg parasitism on crops as diverse as cabbage, tomatoes, bell peppers, collards and soybeans can be increased from 0-20% in no release plots to 50-85% or more with Trichogramma releases. Trichogramma alone can parasitize 80-96% of Heliothis (cotton bollworm, tobacco budworm, tomato fruitworm), alfalfa caterpillar, cabbage worm and other pest eggs (Lindgren, 1969). There are no computer programs or cookbook formulas taking all variables into account and telling exactly how many Trichogramma to release in a particular field or orchard. USDA models theorize that 12,000 to 50,000 Trichogramma per acre should be released for each generation of caterpillar pest in order to achieve the 80% egg parasitization levels necessary to keep worms below economic levels (Ridgway et al., 1981). Augmenting the indigenous natural enemy complex with early releases of Trichogramma and other Rincon-Vitova beneficials is the real secret to sustainable biological pest control. Many release rate experiments spray pesticides to kill off indigenous natural enemies, then release Trichogramma. Though killing off the natural enemy complex isolates Trichogramma for scientific study, the release rate information -- very high release rates are needed when the natural enemy complex is murdered, and quick pest kills are needed -- is mainly applicable to heavily sprayed fields using Trichogramma like a quick kill pesticide. Rincon-Vitova's Trichogramma are not intended to be used like pesticides for quick pest kills in fields where natural enemies have been slaughtered by pesticides. Rather, Rincon-Vitova intends that its beneficials (all natural, none genetically engineered) be integrated into IPM programs and sustainable ecological farming systems to augment and strengthen the indigenous natural enemey complex, creating an agro-ecosystem where predator and prey (pest) are in better balance. Since our beneficial insects are not intended to be used as pesticides, we oppose government regulatory agency expenditures of taxpayer monies (e.g. Cal-EPA) to regulate these tiny pest-eating farm animals as toxic chemical pesticides subject to the same costly regulatory policing policies as the toxic chemicals that brought on the current environmental crisis and consumer distrust of agriculture -- Trichogramma are part of the solution, not the problem. Indigenous natural enemies growing wildly in fields and migrating freely within the agro-ecosystem are nature's greatest source of free pest control -- Rincon-Vitova's Trichogramma augment this natural control. Over 50% moth (caterpillar) egg parasitism is not uncommon. Indigenous predators like pirate bugs, big-eyed bugs, damsel bugs, Staphylinid rove beetles, Carabid ground beetles, Collops beetles, lady beetles and spiders can add an additional 45% moth egg destruction. Thus, total natural enemy destruction of moth eggs before caterpillars hatch out can easily exceed 95%. Few pesticides can match the 95+ percent pest egg destruction potential of the natural enemy complex -- indeed, pests are prolific egg layers to insure that a few individuals survive to perpetuate the species in this tough bug-eats-bug natural environment. ROW & FIELD CROPS One of our most popular strategies is initially releasing small numbers of beneficials to colonize young plants, and following up with a series of weekly releases to insure long-term establishment of pest-destroying natural enemies. Ideally, releases of beneficials are started as early in the season as possible, when the first pests enter fields. Monitoring fields to synchronize parasite releases with pest life stages maximizes results. Ridgway (1981) reported the following commercial suggestion for cotton, which can be modified for corn and other crops: "Control of Heliothis on cotton. For light infestations of Heliothis eggs, 10,000 Trichogramma per acre per week should be released beginning when squares are one-half grown and continuing through the fruiting season, or for about eight to ten weeks. For heavy infestations of Heliothis eggs, a minimum of 30,000 Trichogramma per acre should be released biweekly, or more frequently if necessary, thoughout the fruiting season." Weekly augmentative releases of Rincon-Vitova's Trichogramma and lacewings have been successful against cotton pests in Central America for over three decades. Trichogramma in cotton in California, Texas and other U.S. areas have been killed in recent decades by pesticides directed against boll weevil and pink bollworm. Rincon's recent decision to begin commercial production of Trichogrammatoidea bactrae to fight pinkie, along with recent IPM advances like pheromone mating disruption, are steps toward reinvigorating biological control in cotton. Rincon-Vitova's Trichogramma pretiosum is still recommended to fight bollworm and cotton leaf worms. When Trichogramma augment a strong natural enemy complex, 98% of moth eggs may be destroyed. Fifty to 80 percent parasitism of eggs of key pests like Heliothis or Helicoverpa (i.e. tobacco budworm, cotton bollworm, tomato fruitworm, corn earworm) have been reported with release rates of 25,000 to 100,000 Trichogramma per acre when there are 25,000 Heliothis eggs per acre. High rates of egg parasitism are almost always followed by drastic reductions in worm (caterpillar) populations. Another commercial suggestion reported by Ridgway (1981): "Control of cabbage loopers on cabbage. For light infestations early in the season, 25,000 Trichogramma should be released twice a week. For medium and heavy infestations, 50,000 and 100,000 Trichogramma, respectively, should be released twice each week." In cabbages, combining Trichogramma (an egg parasite) releases with larval and pupal parasites and predators (e.g. green lacewings) that get what egg parasites miss is the best strategy. A southern California cabbage field survey (Oatman, 1966) found 10 different parasite species attacking each caterpillar pest, with parasites destroying up to 90% of cabbage caterpillars in unsprayed fields. Reports from former Soviet republics indicate that 20,000 Trichogramma per acre, or roughly 1 parasite per 20 pest eggs, produce 90-100 percent parasitization of cabbage worm eggs. Rincon-Vitova is not currently producing the cool weather Trichogramma biotypes needed to achieve 90% parasitism of cabbage worm eggs on cool season cole crops. In processing tomatoes, Ridgway (1981) cited 8 seasons of work by Oatman et al. at the University of California, Riverside, that "showed that biological control of the three key pests (tomato fruitworm, cabbage looper, tomato hornworm) on early plantings could be achieved by releasing a total of 200,000 to 300,000 parasites per acre. They further suggested that, for maximum success, releases should be made twice weekly from June through August, or until harvest." USDA studies (Agric. Res., April 1981) recommend 50,000 to 70,000 Trichogramma per acre per release over the growing season for tomatoes. Rincon-Vitova's experience is that prevention or control of low to moderate tomato fruitworm infestations can be achieved with 100,000 to 300,000 Trichogramma per acre, provided releases are started early in the season (when infestations are low) and pesticide interference is avoided. Trichogramma pretiosum releases of 15,000 wasps per acre twice weekly over 10 weeks in the summer successfully control fruitworms, loopers and hornworms. Another approach is aiming for a ratio of 1 parasite per 10-20 pest eggs to boost parasitization into the 90-100% range. This requires working closely with IPM practitioners, monitoring fields, and timing releases (with pest egg laying). Reports from former Soviet republics claim that releases of 6-8,000 Trichogramma per acre produce 68% cutworm parasitism on wheat and sugar beets. Extra releases and higher numbers of Trichogramma are released if cutworm eggs are more numerous than usual -- up to 3 releases of 12,500 Trichogramma per acre are used when there are 30 cutworm eggs per square meter, with the aim being a 1:10 ratio of parasites to pest eggs. Sunflowers were a key to integrating biological control into a failing pesticide spray program at a 10,000 acre processing tomato and canteloupe cooperative in the Dominican Republic, where a thousand farmers, each with an 8-10 acre tomato field, were buying Trichogramma and lacewings from Rincon-Vitova to end suffering caused by sweetpotato whitefly, as well as caterpillars and other pests. Two plantings of sunflowers 60 and 30 days prior to tomatoes acted as field insectaries, producing natural enemies that moved over to tomatoes with the early sweetpotato whitefly invasion and provided control. Pesticide spraying, which had been continuous, was reduced to spot treatments, allowing Rincon-Vitova's Trichogramma (very sensitive to insecticides) and lacewings to provide tomato fruitworm control (Grossman, 1990). Similar programs with borders or interplants of insectary crops like corn and alfalfa have been successful in southern California (e.g. corn to protect processing tomatoes), Mexico and elsewhere. Establishing biological control in neighboring crops, particularly those preceding the target crop, is an effective agro-ecosystem approach that takes advantage of the natural migration of beneficials to adjacent and downwind fields. Alfalfa is the best of the insectary crops, though unsprayed sorghum, corn, grains, oil seed Brassicas, vegetables and cover crops are also valuable. Growing beneficials in the field is the best way to introduce biological control, and turn heavily sprayed crop systems into rarely sprayed crop agro-ecosystems. AVOCADOS Combined with conservation of indigenous natural enemies, early season inoculation of orchards with Rincon-Vitova's T. platneri provides an alternative to pesticides for control of omnivorous loopers and Western leafrollers. In field tests, T. platneri has produced 60% parasitism of omnivorous looper eggs and 80% parasitism of Western leafroller eggs. "These rates of parasitism should be obtained by releasing 200,000-250,000 parasites per acre for the year," wrote University of California IPM specialist Dr. Phil Phillips (1984). "This total amount released per acre should be divided into at least four release sites per acre and releases at each location should be made over a period of 6 to 8 weeks following the peak of the spring flight. This can be accomplished starting in early to mid-March with releases every other week of approximately 12,500 parasites per each of the 4 release sites per acre over the 6-8 week release period through early May...Releases of parasites after the flight peaks occurring in June-July and September-October may also prove beneficial, but probably not as effective as releases in the spring. Not only have the pest populations increased considerably by these later season flights, but the daytime temperatures have increased to a point more deleterious to the insectary-reared parasites." CODLING MOTH In the 1920s, Prof Harry Smith of the University of California, Riverside, urged Stanley Flanders to develop techniques for mass-rearing Trichogramma because it was "the most adaptable egg parasite with which to attempt the biological control of the codling moth." In 1927, Flanders released insectary-reared Trichogramma in orchards, and wrote that the "increase in parasitism from less than 1 percent to 50 percent occurred in a period of three weeks." Mass rearing of Trichogramma promptly spread to the Soviet Union, and then around the world before coming back to the U.S. As early as 1930 (Hilgardia, v.4,n.16), Flanders touted ecological farming methods to maximize Trichogramma's pest-fighting power: "Clean cultivation, by reducing the number and variety of the food plants of the hosts of Trichogramma, acts as a check on the natural abundance of the latter. In southern California there is a noticeable difference between the degree of parasitism of the codling moth in orchards and on fruit trees in dooryard situations where food plants of moths are present throughout the year. Properly managed cover crops may aid parasitism under orchard conditions...Trichogramma may be of value in maintaining pest populations below the economic zero." As adults, Trichogramma feed on insect eggs, nectar, pollen and honeydew. Texas experiments show that Trichogramma pretiosum and many other parasites live several times longer and destroy many more pests when supplied with nectar. Hence, borders or strips of alfalfa, sorghum, sunflower, corn, cover crops, flowering herbs and certain weeds, like red-root pigweed (Amaranthus retroflexus), increase Trichogramma parasitism of pest eggs. These refugia (safe havens that are never sprayed) mimic the natural movement of beneficials from crop to crop. Biological control of pests is maximized when plants act as field insectaries, growing large populations of pest-fighting predators and parasites that migrate into orchard trees and surrounding crops. Soviet studies reveal that Trichogramma minutum parasitism of codling moth is highest in release trees. Though there is some T. minutum movement with the prevailing wind, downwind from the release point, the parasite tends to remain on the crown of the tree where released, leading to the recommendation that "Trichogramma should be released in the morning hours in the lower tiers of the crown of EACH fruit-bearing tree." In single release Soviet studies, there was 6-28% parasitism with 2,000 Trichogramma per tree. "With 500 and 1,000 eggs of codling moth per tree and a ratio of parasites to host of 10:1 and 5:1 the rate of parasitism was 30 to 39%. A decrease in number of eggs to 200 increased the parasite ratio (25:1) but parasitism declined to 17%. This is attributable to the fact that if the number of host eggs is low it is difficult for the parasite to locate them. In polyphagous Trichogramma, which are characterized by a low searching ability, searching activity increases once the first host eggs are located." Achievement of 70 to 96 percent Trichogramma parasitism of codling moth eggs required releasing either 10,000 or 20,000 Trichogramma per tree. Studies in the various climatic zones of the Soviet Union also "revealed that when the pest population is low the release of fewer Trichogramma, done once in the first days of oviposition, yield a low rate of parasitism -- a little more than 10%. Only with the appearance of the progeny of the released Trichogramma, i.e., 10 to 20 days later, does the rate of parasitism rise to 30 to 40%, gradually increasing to 70 to 90%" (Zhilyaeva et. al., in Pristavko ed. 1981). Hence, growers should not treat either Trichogramma minutum (species for east coast release) or Trichogramma platneri (species for west coast release) as "magic bullets" or pesticides. Trichogramma need to be integrated into a larger natural enemy complex, and provided alternate hosts that favor a buildup of predator and parasite populations in multi-year integrated pest management programs where pesticide use is phased out. ECOLOGICAL FARMING ENHANCES BIOCONTROL IN ALL CROPS Best results are seen 3 to 5 years after the start of beneficial insect releases. The first year of transition from pesticides to greater reliance upon biological control is the most difficult. Each year of ecological farming, the background level of indigenous predators and parasites helping Rincon-Vitova's insectary-reared beneficials increases. Many farmers shake their heads in disbelief when looking back at their past chemical pest control practices, which seem wastefully expensive and barbaric in comparison to relying on natural enemies. Pesticide interference and drift is a major cause of biological control failure. We recommend Croft's book (see references at end) to those making the transition from pesticides to biological control, as it covers selective pesticide use concepts (e.g. lower doses, spraying only borders, alternate rows, selected parts of the plant canopy etc.) that conserve biological control organisms. A quality control specialist works to insure that the best possible product is sent out. Nevertheless, sometimes shipments of fragile insects can arrive injured or otherwise not meet expectations. As we stand behind all product shipped, please feel free to contact us should you ever feel that there is a problem or that a replacement may be necessary. SELECTED REFERENCES Croft, Brian A. 1990. Arthropod Biological Control Agents and Pesticides. NY:Wiley. Grossman, J. 1990 (Dec.). Compatibility of Pesticides and Biocontrols. Agrichemical Age 34(11):20+ Lindgren, P.D. 1969. "Approaches to the Management of Heliothis Spp. in Cotton with Trichogramma Spp." Tall Timbers Conf. n. 1. Oatman, E.R. 1966. An ecological study of cabbage looper and imported cabbageworm populations on cruciferous crops in southern California. J. Econ. Entomol. 59(3):1134-9. Paristavko, V.P. ed. 1981. Insect Behavior as a Basis for Developing Control Measures Against Pests of Field Crops and Forests. New Delhi: Amerind Publ. Co. Phillips, P.A. 1984. "Avocado Worms - What Do We Do About Them?" Assoc. Applied Insect Ecol. Newsletter 4(2):1. Ridgway, R.L. et al. 1981. "Trichogramma and Its Utilization for Crop Protection in the U.S.A." in Coulson, J.R. ed. Proceedings of the Joint American-Soviet Conference on Use of Beneficial Organisms in the Control of Crop Pests. College Park, MD: Entomological Society of America. /