BIOLOGICAL CONTROL SOLUTIONS FOR WALNUT PESTS Safe Ways to Say No Nuts to Walnut Pests PRESENTED BY 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 Biological control with beneficial insects makes dollars and sense. No orchard, even one that is chemically sprayed, can afford to be without biological control. Growers transitioning from toxic pesticides towards greater reliance upon biological control by natural enemies typically report fattening up bottom lines during the first two years with 50-75% pest control cost savings. Difficulty achieving satisfactory pesticide spray coverage is incentive enough to experiment with biological control agents that seek out pests with the precision of laser-guided missles. Costs of sprays, the hassle of scheduling sprays when workers are not present, managing residue and resistance problems, particularly the resistant codling moth, can be avoided with greater reliance upon biological pest control solutions. Improved plant vigor and health may also be noted when pesticide stresses on plant physiology are removed. Public and worker liability risks, even insurance costs, may be reduced. Besides safety and profit benefits, adding biological control with natural enemies as a pest control input can also provide valuable public relations and marketing benefits as a "green", environmentally-friendly alternative to conventional chemical control. BIOLOGICAL CONTROL IN ORCHARD AGRO-ECOSYSTEMS Releasing Rincon-Vitova's beneficial insects into walnut agro-ecosystems is part of a sound profitable strategy for achieving biological control and minimizing crop damage. Rincon-Vitova's natural enemies help police pest populations and stabilize orchard ecosystems, bringing predator and prey (pest) into better ecological balance. Walnut trees provide a favorable environment for a wide variety of organisms, including several hundred insect and mite species, most of which are beneficial -- e.g. pollinators increase fruit set, antagonists suppress pests via niche competition, scavengers turn debris into vital soil humus and are part of the food chain, an alternative food source for beneficials when pests are absent. In orchards where pesticides have not killed off the predators and parasites, most potential pests go unnoticed, as they are so effectively squelched by resident beneficials. Of the several hundred arthropod species residing in walnut orchards, only three (e.g. codling moth) are key pests directly attacking the fruit. These key pests are attacked by a wide array of general feeding predators and parasites. Rincon-Vitova's insectary-grown beneficial insects (all natural, none genetically engineered) supplement indigenous orchard biological control organisms and shift the ecological balance towards sustainable biological pest control by natural enemies. FARMING WITH BENEFICIALS Maximizing the diversity and distribution of selected plant species -- e.g. planting covercrops or tolerating certain weed species between trees at critical times instead of herbiciding or discing the orchard floor completely clean -- is a farming technique useful for increasing orchard biological control. The strategy behind cover cropping vis-a-vis pest control is increasing resident insect and arachnid micro-wildlife, thereby expanding the food chain and supporting a larger army of beneficial pest-fighting arthropods. Thus, after cleaning up walnut aphids in the trees, brigades of predators and parasites can find shelter and sustenance on cover crops, and be available to fight future infestations in the trees. The best cover cropping strategy may vary from area to area, and is best selected in consulation with pest control advisers and other sources knowledgeable about integrated pest management (IPM) techniques like habitat diversity and refuge management. Rincon-Vitova's philosophy is that orchard cover crops and cultural practices must be designed to grow beneficial organisms in ecological environments that closely emulate the natural systems in which they evolved. At Rincon-Vitova, we enthusiastically recommend consideration of legume green manure cover crops. Besides injecting nitrogen into the soil and promoting formation of nourishing soil humus, legumes and mixtures of legumes, grasses and weeds can be managed to reduce orchard pest problems. For example, by periodically alternately cutting every other border of leguminous cover crops, weeds can be kept from going to seed, while at the same time encouraging composting organisms. Composting organisms become part of the food chain, nourishing biological control organisms ranging from beneficial arthropods to predatory nematodes and fungi that aid in the biocontrol of soil and foliar insects and diseases, such as the walnut blight caused by Xanthomonas campestris. Rincon-Vitova's insectary-grown beneficial insects (all natural, none genetically engineered) are intended to be part of a larger orchard integrated pest management (IPM) strategy, augmenting naturally occurring populations of predators and parasites. Our beneficial insects are not intended to be used as pesticides, and 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 toxicchemicals that brought on the current environmental crisis and consumer distrust of agriculture -- beneficial insects are part of the solution, not the problem. Rincon-Vitova's beneficial insects are not designed to be magic bullets applied like pesticides for instant pest control. Successful sustainable biological control is an ecological process, and inoculative releases of Rincon-Vitova's beneficials into the orchard ecosystem to augment existing natural controls is but one component of a larger sustainable ecological farming system that may take three to five years to establish. Farming ecologically with Rincon's biological control inputs gets easier the second and third year, as a reservoir of natural biological control organisms becomes established. After the initial first year biocontrol inoculation, which is best planned out with an IPM specialist who can monitor progress and advise on release dates etc., smaller annual maintenance releases of predators and parasites may subsequently suffice to get a headstart on pests and compensate for biocontrol losses to weather, orchard sprays, pesticide drift etc. Besides helping integrate sustainable biological control into your farming system, an IPM practitioner can provide guidance on least toxic, low residual sprays and reduced dosages of conventional pesticides that minimize disruption of biological control. Continued attention is advised to nurture biological control organisms from year to year and detect new pest invasions. Careful monitoring and sampling of the progress of biological controls is important because not all walnut trees or parts of groves 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 spray materials. Knowledge inputs -- e.g. publications like the IPM Practitioner (BIRC, P.O. Box 7414, Berkeley, CA 94707) and the University of California's Integrated Pest Management for Walnuts manual -- and staying on Rincon-Vitova's customer list are also recommended to keep you up to date on the latest advances in managing pest natural enemies. To be most effective and sustainable, biological pest control is best designed into an area. Alfalfa is the beneficial insect nurse crop for many agroecosystems. Spraying "insectary" crops like alfalfa is a guaranteed recipe for major pest infestations in all area crops; the media seems to have missed this message in the recent sweetpotato/poinsettia whitefly scourge. Slight modifications in the way one farms can emulate more natural systems, and encourage beneficial insect armies to attack walnut pests. For example, planting cover crop or alfalfa refugia (safe havens that are never sprayed) mimics the natural movement of beneficials from crop to crop. Biological control is maximized when alternate crops act as field insectaries, growing large populations of pest-fighting predators and parasites. Refuges of alfalfa and other legumes attract large numbers of aphids, mites, and worms (none of which attack walnuts) that nourish general predators which can move into the trees to eat walnut pests. A form of intercropping known as strip cropping (e.g. strips of cover crops between at least some tree rows) and maintaining small fields of unsprayed alfalfa are ecological farming practices Rincon-Vitova recommends to create on-farm insectaries, growing your own free supply of hungry predators and parasites to devour pests. General predators that feed on a wide variety of prey eat early season pests in unsprayed alfalfa and cover crops. Several generations later their offspring form the basis of biological controls that enter the canopy of new spring growth occurring in walnut trees. Alternate strip harvesting of alfalfa and cover crop beneficial insect refuges (safe havens that are never sprayed) keeps the plants attractive to arthropod food sources that nourish beneficials throughout the season. As the season advances, begin mowing alternate strips when cover crops or alfalfa begin to bloom; cut half and let this start to grow back before mowing the alternate strips. Avoid broad spectrum pesticides at all costs in early season for maximum production of predators and parasites. This "battle of the bugs" in adjacent crops takes place without damage to the walnuts. USING RINCON-VITOVA'S BIOLOGICAL CONTROL INPUTS Maintaining biological control in walnuts is an ongoing process involving introduction and conservation of natural enemies and careful monitoring. Periodic maintenance release of insectary-grown beneficials timed to focus on developing pest hotspots aids in season-long biocontrol. Conservation of natural enemies is facilitated by phasing out hard pesticides interfering with biological control. Repeated spraying of hard-to-kill resistant pests devastates beneficials, and in the longrun creates even more pests. Where walnut's beneficials are destroyed by spray programs or starved away by lack of alternate prey, releases of Rincon-Vitova's green lacewings and other beneficials helps restore the natural checks and balances found in unsprayed ecosystems. Early season release of insectary-grown beneficials is the backbone of reestablishing biological control. It is like restocking the fish pond when one starts releasing Rincon's beneficials to rescue such natural-enemy-depleted farms from the pesticide treadmill. Rincon-Vitova Insectaries tries to make the transition from pesticides to ecologically-based biological control as smooth as possible by continually collecting new strains of beneficials from heavily sprayed agroecosystems. Though we do not specifically test natural enemies for ability to withstand chemical sprays, we believe that some of our insects, particularly our green lacewings, great all-around predators, have been successful in transition situations due in part to this hardiness and ability to withstand some chemical residues. General predators such as green lacewings and lady beetles are released to insure timely presence when aphid prey are in the cover crop. Ideally, releases are started early when the first pests enter the field. These early releases are forced into the trees when walnut aphids appear. The same beneficials control spider mites after aphids come under biological control. Later season worm control is an additional benefit of letting small early season populations of beneficials expand their numbers in a pesticide-free environment. If it is necessary to knock runaway pest populations down to levels that small populations of newly-introduced beneficials can easily mop up, use least-toxic, low-residual spray materials. The goal of spraying (selective use of least toxic pesticides) is lowering pest populations to tolerable levels, not pest eradication. Low pest populations and innocuous alternate prey are necessary to feed biological control organisms. Without prey, predators are scarce. Hence, it is essential that a few minor pest situations develop, in order to obtain and maintain a buffering natural enemy complex within the walnut ecosystem, and control major pest problems as they develop. A natural enemy complex of several dozen species building up over time may be necessary for sustained biological control of key caterpillar pests, such as the codling moth. An advantage of releasing Trichogramma reared in Rincon-Vitova's insectary is that this pinhead-sized parasite kills codling moth in the egg stage before it can damage fruit or nuts. Trichogramma is one of Rincon's specialities. Releases work best in conjunction with natural enemy conservation measures such as avoiding harsh sprays toxic to indigenous beneficials and growing cover crops with nectar to nourish wasps attacking codling moth larvae and pupae. Rincon started out rearing Trichogramma for cotton growers in 1960, and has since reared several Trichogramma species adapted to a wide variety of crops and pests. One of our most popular strategies is initially releasing large numbers of Trichogramma and green lacewings to colonize groves, then following up with a series of smaller releases to ensure long-term establishment. We currently recommend purchase of Trichogramma platneri for release in west coast orchards against codling moth and a wide variety of fruit and leaf worms, including navel orangeworm, redhumped caterpillar, fall webworm, Oriental fruit moth and twig borers. Trichogramma minutum is the species of choice for the east coast. Releasing the wrong species can have adverse consequences, which are explained in a special bulletin. We can explain this further over the phone when discussing your order. Customers on accounts are informed through periodic mailings of new beneficial species, some of which are so scarce that only very small quantities can initially be provided for inoculation. In addition, where demand is sufficient, we can on special request collect or obtain rarer natural enemies not normally available commercially. Technical bulletins are available for all the beneficials that we sell. 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. / Trichogramma's Role in Codling Moth Biocontrol&& Jan Dietrick Bassari, Rincon-Vitova Insectaries, Inc. & Joel Grossman&& In the 1920's, Professor 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," a key pest of apples, pears and walnuts. 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, Flanders touted ecological farming methods, such as cover crops and plants with nectar and alternate insect hosts for codling moth natural enemies to feed on, as the way 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."&& In other words, Flanders recognized early on that biological control organisms were not magic elixirs or pesticidal magic bullets to be used in ecological ignorance. Rather, biological control organisms need to be incorporated into ecological systems. This means changing farming systems to more closely resemble the plant diversity of backyard gardens. Biological control of codling moth works when diverse plants act as field insectaries, growing large populations of pest-fighting predators and parasites that migrate into orchard trees.&& As adults, =Trichogramma feed on insect eggs, nectar, pollen and honeydew. =Trichogramma and most other parasites live several times longer and destroy many more pests when supplied with nectar. Good sources of nectar, pollen, and insect foods include borders or strips of alfalfa, sorghum, sunflower, corn, cover crops, flowering herbs and certain weeds, like red-root pigweed, =Amaranthus retroflexus, which increases =Trichogramma parasitism of pest eggs. These refugia (safe havens that are never sprayed) are breeding grounds for natural enemies that migrate into crops to provide biological pest control. [See =IPMP 11(8):5]&& [BOX A] Which =Trichogramma For You?&& Recent taxonomic studies by Pinto et al. (in press) lead us to believe that biological control practitioners using =Trichogramma are entering an exciting and at times confusing period. Pinto et al.'s reevaluation of =Trichogramma species and biotypes clouds interpretation of past studies, as there is now uncertainty as to which =Trichogramma species or biotypes researchers have actually studied and field tested. The difficulty in distinguishing =Trichogramma platneri from =T. minutum has far-reaching implications for biological control of codling moth.&& "It is important for biological control practitioners to understand that the names =T. minutum and =T. platneri are applied somewhat arbitrarily," write Pinto et al. (in press). "The extent to which reproductive and allozymic variation in these nominal species correlates with variation in life history traits important to biological control is unknown. It should be emphasized that these two taxa cannot yet be distinguished morphologically, claims to the contrary notwithstanding. Consequently, documenting the success of introductions in areas already inhabited by the complex will be difficult, especially if identifications are based on morphology alone. Also, because of a degree of reproductive compatibility among forms, introduced material may hybridize with native populations. Unless the advantage of using one population over another is clearly established, the movement and release of =minutum or =platneri to any area already harboring natural populations of the complex is biologically questionable."&& In other words, what is sold as =T. minutum for release in the eastern U.S. mates with what we call =T. platneri in west coast orchards (i.e. =minutum and =platneri may actually be biotypes of the same species, not separate species). Unfortunately, the hybrid formed when =T. minutum mates with =T. platneri in west coast orchards dies out, as the progeny are mostly male (females are needed to attack codling moth eggs, and produce the next generation of =Trichogramma).&& We believe that the most appropriate =Trichogramma biotypes for release into orchards for codling moth biocontrol are =Trichogramma native or indigenous to the orchard area. It is best to collect codling moth egg masses at the end of the season, and use =Trichogramma emerging at that time as breeding stock for releases to be made the next season. In an ideal world, growers would cooperate with local insectaries in rearing and then releasing progeny of locally collected =Trichogramma; and universities, the USDA and grower groups would fund research to better understand what is happening in the field, and improve implementation of biological control.&& Rincon-Vitova collects its =T. platneri on the west coast (northern California), and =T. minutum is derived from the east coast. For states in the middle of the country, where taxonomic surveys of =Trichogramma species are sketchy, which =Trichogramma to use is an educated best guess. The best available information, Pinto et al. (in press), points toward =T. minutum being best against codling moth east of the Rocky Mountains, and =T. platneri best for codling moth biocontrol west of the Rockies.&& One last caveat derived from Pinto et al. (in press), ask the insectary where their =Trichogramma breeding stock is from. Buy =Trichogramma for codling moth biocontrol only if the insectary breeding stock is from your side of the Rocky Mountains, as this is probably more important than the sometimes misleading species labels, =T. minutum and =T. platneri. [END BOX A]&& Release Rates & Techniques&& Though we take =Trichogramma species identifications with a grain of salt [See Box A], the older studies still provide good guidance on releasing =Trichogramma for codling moth biological control. Soviet studies summarized by Zhilyaeva et. al. (1981) reveal that =T. minutum parasitism of codling moth is highest in the trees in which =Trichogramma are actually released. According to the Soviets, there is some downwind drift of =Trichogramma, but most =Trichogramma remain on the crown of the tree where originally released.&& Thus, in order to get =Trichogramma working against codling moth in every orchard tree, Zhilyaeva et. al. (1981) recommend: "=Trichogramma should be released in the morning hours in the lower tiers of the crown of EACH fruit-bearing tree." One release of 2,000 =Trichogramma per tree resulted in 6-28% parasitism of codling moth eggs. "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%." Achieving 70-96% =Trichogramma parasitism of codling moth eggs required releasing 10,000 to 20,000 =Trichogramma per tree.&& Soviet studies (Zhilyaeva et al., 1981), like those of Flanders (1930) in California, found that parasitism of codling moth eggs is low (10%) 10 days after =Trichogramma release. It is only when =Trichogramma have reproduced and multiplied in orchards that codling moth egg parasitism climbs to 30-40%, a few weeks later. After several weeks of reproducing in orchards, =Trichogramma can eventually parasitize 70-90% of codling moth eggs. Thus, =Trichogramma releases need to begin early in the season, preferably with other alternate hosts (i.e. other butterfly or moth eggs) on weeds, wildflowers, cover crops etc. allowing =Trichogramma and other natural enemies to reproduce and produce large populations capable of controlling later season codling moth invasions.&& To get codling moth missed by =Trichogramma, an integrated pest management (IPM) approach is needed. Monitoring is combined with least toxic control methods, such as granulosis virus and pheromone mating disruption [See Box B], and encouragement of other natural enemies.&& A survey by Zlatanova (1987) in the former Soviet Union identified 20 different natural enemy species attacking codling moth larvae and pupae, including the braconid parasite, =Ascogaster quadridentata, which is also found parasitizing codling moth eggs and larvae in the U.S. In Sweden, Subinprasert (1987) noted that 50-78% of codling moth larvae and pupae overwintering on tree trunks are killed by natural enemies, particularly tachinid flies like =Elodia morio, ichneumonid wasps like =Pristomerus vulnerator, and braconid wasps like =Ascogaster quadridentata; fungi like =Beauveria bassiana and =Paecilomyces farinosus, and birds also take their toll on codling moth.&& Releasing insectary-reared =Trichogramma while simultaneously nurturing the many other codling moth natural enemies in an ecological orchard system (e.g. one with cover crops and alternate food sources for natural enemies) is the way to achieve biological control of codling moth. Sustainable biological control is best viewed as a three to five year long-term goal, as it takes time for natural enemy populations to buildup, especially after having been devastated by pesticides.&& [BOX B] ESA Emphasizes Pheromone Mating Disruption&& [NOTE: Sheila said that ESA Conference Highlight on codling moth pheromone mating disruption could go into box with this article.]&& Codling moth IPM was updated at the 1991 ESA Annual Meeting in Reno, Nevada. In lab studies, J.E. Cossentine (Agric. Canada Res. Stn., Summerland, B.C., Canada V0H 1Z0) found that in addition to codling moth, =Cydia pomonella, both fruit tree and oblique banded leafrollers were susceptible to codling moth granulosis virus (CpGV). [See =IPMP 12(9):10 for a recent report on CpGV for codling moth control in Canada] Hence, this alternative codling moth control, which is compatible with =Trichogramma, may be more useful than previously realized, if multiple pests can be controlled.&& J.F. Howell (USDA-ARS, 3706 W. Nob Hill Blvd., Yakima, WA 98902) presented a USDA-ARS/Biocontrol Ltd. film with a jazzy musical score updating codling moth pheromone mating disruption [See =IPMP 11(11/12):12 for successful use in Switzerland]. Codling moth females begin pheromone release at sundown, and male moths scan up and down in a zigzag pattern, becoming confused and unable to locate females (hence, not mating) in orchards utilizing mating disruption. Ten acre orchard blocks in Yakima, WA, had one pheromone dispenser (with 60 days constant output) per tree (more on border trees) for two generations of codling moth. In June 1987, there was a 67-71% reduction in codling moth; by July, codling moth was reduced over 80%. There was 77% less fruit damage in pears in July. First generation control was inadequate for commercial growers, but control of the second generation was sufficient.&& Codling moth pheromone mating disruption is now providing 90% control in treatment plots, with 1/2 to 2 percent damage in untreated plots an indication of lasting control. From first to second generation, codling moth can go from 1 to 50 larvae per tree, whereas there is less than 1 codling moth larvae per tree in treatment blocks (with $1 million in fruit in a 40-acre test block, good grower relations were needed in this work). Good control continued into the third year, with less than 10 codling moth larvae per tree.&& Though there were immigrant codling moths, few moved into the mating disruption block. There were 1,097 larvae per acre in the pheromone treated block, versus many thousands per acre in other blocks. Infestation in the treatment block was limited to the edges. Though pheromone mating disruption has been said to only work on low moth populations, this work showed decreasing codling moth populations over a period of years even where codling moth populations were initially high.&& In an overview talk on pheromone mating disruption, R.E. Rice (Kearney Agric. Cent., Univ. California, Parlier, CA 93648) noted that there was commercial registration of codling moth pheromone mating disruption in apples and pears with EPA on the national level, but that the technology was not legal in California (Cal-EPA wants additional data). Rice also pointed out that there can be problems from very erratic pheromone release from dispensers. A problem using pheromone mating disruption against codling moth in the Netherlands is that orchards need to be retreated with a second application of pheromones, as dispensers have only a 60 day field life (200 mg of pheromone per 25 mm2). In Italy, dispensers hold 350 mg of pheromone; but this is also probably not enough for season long codling moth control.&& [end Box B]&& References&& Flanders, Stanley E. 1930 (June). Mass Production of Egg Parasites of the Genus Trichogramma. =Hilgardia 4(6):465-501.&& Pinto, J.D. et al. (in press). Taxonomy of the =Trichogramma minutum complex (Hymenoptera: Trichogrammatidae): Allozymic variation and its relationship to reproductive and geographic data. =Annals of the Entomological Society of America. Subinprasert. S. 1987. Natural enemies and their impact on overwintering codling moth populations (Laspeyresia pomonella L.) (Lep., Tortricidae) in South Sweden. =Journal of Applied Entomology 103(1):46-55.&& Zhilyaeva, V.M. et al. 1981. Influence of behavior of =Trichogramma on its parasitism of eggs of the codling moth in the crown of apple trees. In: Pristavko, V.P., ed. =Insect Behavior as a Basis for Developing Control Measures Against Pests of Field Crops and Forests. Amerind, New Delhi. pp. 52-55.&& Zlatanova, A.A. 1987. The codling moth. =Zashchita Rastenii 11:54. (Russian; English abstract).&& / BIOLOGICAL