Washington State University Cooperative Extension

Areawide IPM Update

The Newsletter of Pheromone-based Orchard Pest Management

Vol. 3, No. 4   April 1, 1998

Inside this issue:

Web links:

...Ted Alway's Areawide IPM page

...USDA Yakima Areawide IPM page (with CAMP site descriptions)

...WSU-TFREC Entomology home page

...Index to Areawide IPM Update newsletters

Cooperating agencies: Washington State University, Oregon State University, University of California, U.S. Department of Agriculture, and Chelan County.

Cooperative Extension programs and employment are available to all without discrimination.


Kaolin particles: a new product for orchard pest control

Kaolin particles are a natural product derived from kaolin clay that is being investigated as a pest control material. Research with "kaolin particle films" has shown some promising and often surprising results for the control of both tree fruit diseases and arthropod pests. Tom Unruh, entomologist with the USDA-ARS lab in the Yakima Valley, has even been heard to say that this product, with regard to certain tree fruit pests, can "kick caudal segment!"

Research with this product began in 1992 by Mike Glenn, Gary Puterka and colleagues at the USDA-ARS lab in Kearneysville, West Virginia. Based on the idea that plant diseases need wet leaves for infection to occur, they sought to waterproof the plant by coating it with a dust of clay particles treated to make them water-repellent, or hydrophobic. Disease damage was reduced significantly by this treatment and, surprisingly, so was damage by several insect pests. Glenn and Puterka developed in 1996 a kaolin formulation that could be suspended in water, allowing applications with conventional spray equipment. In 1997, research was expanded to other sites, including studies conducted on apples and pears by Tom Unruh and Alan Knight of the USDA-ARS lab in the Yakima Valley. Their research used both treated (hydrophobic) and untreated (hydrophilic) kaolin particle formulations; apparently, the hydrophobic treatment is not needed for insect control. They applied the kaolin using both hand guns and speed sprayers, generally at a rate of 25 pounds/100 gallons with the trees sprayed to drip.

In their work they found dramatic effects on several arthropod pests. The kaolin particles apparently kill nothing. Rather, they act as a repellent barrier, one that encourages insects to leave or not settle down, and to deposit few or no eggs on the treated surfaces. Pear psylla adults avoided trees treated with kaolin and laid few eggs on them. There was a 5 to 10-fold reduction in psylla egg numbers compared with an untreated control, following several early season kaolin applications, and they observed an over 95% reduction in psylla nymphs one month after the applications began. White apple leafhoppers, both nymphs and adults, "bailed out" following kaolin applications, leaving the treated trees for parts unknown. Thrips, apple rust mite and predatory mites were lower in kaolin treated plots. This effect on mites may be a concern with integrated mite management on apples, but could fit better with the management of rust and spider mites on pears. Some suppression of green apple aphid was seen. However, use of kaolin in one study apparently reduced parasitism of leafminers, resulting in higher leafminer populations in the treated trees.

Codling moth control results with kaolin were less dramatic. Repeated applications reduced codling moth damage from 30 to 90% in several trials when compared with the untreated controls, but was still not commercially acceptable. Moths laid few eggs on treated surfaces, when given a choice. Leafroller moths also avoided depositing eggs on kaolin-treated leaves, and delayed dormant applications reduced significantly the number of emerging overwintered larvae that established feeding sites.

The horticultural effects of kaolin applications on apple and pear trees are also surprising and intriguing. Mike Glenn has shown that photosynthesis rates are increased during the heat of the day on treated trees. This is due to the lower tree canopy temperatures resulting from the whitish particles reflecting the infrared component of the sunlight. Studies in the Yakima Valley and West Virginia have shown increases in fruit size and yield in treated blocks for both apples and pears. Studies have also shown improved red color (on Gala and Red Delicious), smoother fruit finish and even higher fruit firmness! The kaolin residue cleaned off fairly well from most of the fruit on commercial packing lines but some remained in the stem and calyx end cavities.

This material is a proprietary product of the Engelhard Corporation of New Jersey. It will be formulated for application with standard orchard spray equipment. The very fine particles are not abrasive and will not damage nozzles. There have been concerns with the material plugging sprayer screens and with kaolin deposits building up in spray tanks; these are being addressed and the with the latest formulation should not be a problem. Material handling will be a concern for some, with the high amounts of the material that may need to be handled with applications of up to 50 pounds/acre or more. Thorough coverage of trees is critical for this material to work well, and repeated applications will need to be made following rain, overhead irrigation or to maintain coverage of new growth in the spring.

Kaolin particle films certainly show promise for providing additional control of pests like pear psylla and white apple leafhopper, with limited effect upon their natural enemies. Their unique mode of action may fit particularly well with the development of softer, less-disruptive pest control programs. Research trials will be ongoing in Yakima, West Virginia and many other locations in 1998, working with improved kaolin formulations and aiming to further define the best timings and rates for a number of orchard pests. This product will not be available commercially this year, as Engelhard plans to further perfect the product before sales begin, but grower trials will be expanded in many locations.

Monitoring leafrollers with pheromone traps

Leafrollers are among the more difficult orchard pests to monitor accurately. Larvae are small and green and are generally concentrated in the upper portions of the tree canopy, making them difficult to find. They are usually not distributed evenly across a block, requiring extra effort to detect the scattered infestations. Too often larval populations are identified after the damage to fruit has been done.

Pheromone traps could provide a very useful tool to detect and assess leafroller populations, much as they do with codling moth. To this point, however, this has rarely been the case. The lures available for monitoring obliquebanded (OBLR) and pandemis (PLR) leafrollers are very attractive and useful for determining the beginning of adult flights. They can be too attractive, capturing up to several hundred moths per week, making trap maintenance difficult and expensive. In addition, the number of moths caught does not necessarily correlate with the number of leafroller larvae in the block being monitored. High catches can occur in blocks where larvae are at very low levels, probably the result of males being drawn in from distant sources. Conversely, low catch in traps does not always indicate that there is no risk to fruit from leafroller larvae in that block.

The standard lures for OBLR and PLR contain at least 1 mg of pheromone loaded in a red rubber septa.

Investigations have been conducted in to the use of low-load lures by Larry Gut and Jay Brunner. Septa loaded with 10% of the standard dose of PLR pheromone or 5% of the OBLR dose were shown to still be attractive to male moths but caught substantially fewer moths. They found that catches of PLR in low-load traps were higher in blocks with higher leafroller activity, and that there was good correlation of catches of moths from the overwintering generation and fruit injury at harvest. The 1997 results with OBLR were not as consistent, complicated, in part, by a contaminant in the OBLR pheromone used. Maintenance of these low-load traps was easier and less expensive, as catching fewer moths resulted in fewer trap bottom replacements. The low-load lures lasted as long in the field as the standard lures, about six weeks. These lures will be tested more extensively in commercial orchards in 1998.

Different trap types for leafrollers were investigated by Gut and Brunner in 1997. Three trap types were compared for PLR: triangular (Delta trap, Scenturion, Inc.), diamond (Pherocon IIB, TrÈcÈ, Inc.), and pentagonal (Intercept A, IPM Concepts, Inc.). For OBLR, two other types were added to the previous three: wing (Pherocon 1C, TrÈcÈ, Inc.) and bucket (Multipher). The Multipher is a non-sticky trap in which moths are attracted in with the pheromone lure and killed with an insecticide from a knockdown strip.

For PLR, the delta trap was the most effective, catching nearly twice the number of moths as the Pherocon IIB or the Intercept A. For OBLR, the delta was again superior to the other two, but the standard Pherocon 1C and the Multipher both caught equivalent numbers.

The susceptibility of aphid natural enemies to orchard insecticides

T. S. Price and E. H. Beers, WSU-Tree Fruit Research and Extension Center, Wenatchee

As a secondary pest, aphids receive sporadic attention. Occasionally, aphid outbreaks can lead to sooty mold damage and potentially cause down graded fruit. For the most part, aphids are controlled with insecticides, although in recent years natural enemies have played a greater role. Predators such as lady beetles and lacewings help to suppress aphid populations throughout the growing season. A sudden loss of natural enemies can lead to a resurgence of the aphid population which can increase the need for more chemical control measures. How then can we best use chemical control measures (both those directed at aphids and at other pests) to preserve the aphid predators naturally occurring in our orchards?

For the past four years, research sponsored by the Washington State Tree Fruit Research Commission has been conducted at WSU's Tree Fruit Research & Extension Center in Wenatchee to find answers to this question. This study looked at the direct toxicity to lady beetles and lacewings of many of the commonly used insecticides, as well as currently unregistered products. Colonies of three lady beetle species (the convergent lady beetle, the multicolored Asian lady beetle, and the transverse lady beetle), and two lacewing species (Chrysopa nigricornis, and Chrysoplera carnea) were maintained in a greenhouse. The transverse, convergent, and C. nigricornis colonies were reared from individuals collected in local orchards. The multicolored Asian lady beetle colony was a laboratory colony that was graciously donated by the late Dr. Ken Hagen, an entomologist from UC Berkley. This lady beetle species has been introduced into Washington State and is currently found throughout central Washington. The C. carnea larvae were generously supplied by Rincon Vitova.

The larvae of each species were exposed in the laboratory to field rates of the insecticides. They were then monitored for 96 hours, and mortality rates recorded. In order to simplify our reporting system, we divided the percentage mortality into three categories; low (less than 30%), moderate (30-70%), and high (greater than 70%).

Lady beetles: The three lady beetle species we tested did not all react the same to the various insecticides. While the multicolored Asian lady beetle was highly susceptible to the broad spectrum organophosphates (such as Guthion, Lorsban, and Imidan), the transverse lady beetle showed a moderate to low susceptibility. The transverse lady beetle had mortality rates that were consistently lower for all of the chemicals when compared to the other species tested. Thiodan, Provado (8 fl oz/acre) and Vydate were moderately toxic to all three lady beetle species, whereas Aphistar, Sterling, Pirimor, M-Pede, Neemix, and oil caused little or no lady beetle mortality.

Lacewing Results: The most dramatic find of this research was the response (or lack thereof) of lacewings to insecticides used in orchards. The lacewings are by far the less susceptible of the two groups of predators we tested. In fact, it was rather difficult to kill the lacewing larvae. Very little differences in mortality rates were found between the laboratory species and the field collected species. Provado (2, 4, and 8 fl oz/acre), Aphistar, Sterling, Pirimor, Thiodan, Orchex, M-pede, Spinosad, Guthion, Lorsban 50W, Lorsban 4EC, Imidan, Penncap-M, Vydate, Sevin, Neemix, Comply, Confirm (Tebufenozide), Agri-Mek, Carzol, Asana, Diazinon, Vendex, Bt-Dipel, and Omite all caused little or no mortality. Dimethoate was the only product causing signifcant mortality, about 76%. This bioassay is currently being re-run since this mortality rate with Dimethoate is significantly higher than with all the other products tested.

We hope that this information will give growers and consultants another tool to help make decisions regarding orchard pesticide applications, and to fine-tune IPM programs in terms of better maintenance of aphid predators. The Washington tree fruit industry has a long history of judicious use of materials to preserve the predatory mite, Typhlodromus occidentalis, based on many years of field and laboratory experience which identified high-risk, disruptive materials. We now have the same information to bring to bear on the aphid problem.

Ted Alway, Editor
Phone: (509) 664-5540
Fax: (509) 664-5561
e-mail: alway@coopext.cahe.wsu.edu

Partial Funding provided by: Washington State Tree Fruit Research Commission, U.S. Department of Agriculture-Agricultural Research Service.

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