Biocontrol Solutions for
PO Box 1555, Ventura, CA 93002
800-248-2847 * 805-643-5407 * fax 805-643-6267
Safe Ways to Say No Nuts to Walnut Pests
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 as much as 50-75% pest control cost savings.
Difficulty achieving satisfactory pesticide spray coverage in large trees is one reason to experiment with biological control agents that seek out pests with the precision of laser-guided missiles. Costs and employee safety and liability concerns with sprays are other reasons. Managing resistance problems that evolve over a few seasons with chemical pesticides and may also evolve with Bt treatments 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. 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 pecan 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.
Pecan 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.
The key pests of pecans are attacked by a wide array of general feeding predators and parasites, including various species of lacewing, lady beetles, assassin bugs, spined soldier bugs, syrphid flies and trichogramma. 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 yellow aphids and black pecan 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 consultation 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 should be designed to grow beneficial organisms in ecological environments that emulate natural systems.
USDA entomologist Louis Tedders has found that a mix of annuals like hairy vetch and crimson clover performed well to build up aphid predators, die out in summer to avoid competing for moisture and regrow in the fall after harvest. Dr. Robert Bugg of the Sustainable Agriculture Research and Education Program at UC Davis recommends lana vetch, hairy vetch and cereal rye oats in California pecans. Others find any native or seeded cover that provides a succession of bloom will help avoid treating for aphids early in the season and foster early reproduction of parasites of hickory shuckworm and pecan nut casebearer.
At Rincon-Vitova, we 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 scab infection.
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 head start 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 long run 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 specialties. 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.