As concerns increase over changes in pesticide regulations, farmworker safety, surface and groundwater contamination and escalating costs and uncertainties associated with chemical controls, walnut growers need effective and cost-efficient ways to produce walnuts with minimal use of pesticides. This study compared the effectiveness of Biologically Integrated Orchard Systems (BIOS) with conventionally managed walnut orchards in the northern San Joaquin Valley from 1999 to 2001. We found no significant differences between BIOS and conventional blocks in nut quality or yields. Codling moth was effectively controlled by pheromone disruption and alternative pest-control methods. Mating disruption, by itself, appears to provide good control of codling moth in many orchards. However, it is still more expensive for growers than conventional pest-control methods.
Standardization of pest monitoring practices and materials to maximize sensitivity to pest populations in the field is a foundation of effective integrated pest management (IPM). In response to changes in the availability of commercial bait material for navel orangeworm (NOW) egg traps, we evaluated potential alternative bait materials for use in monitoring this key pest of almonds, pistachios, walnuts and figs. Navel orangeworm egg traps baited with uninfested nutmeats were as effective as almond meal plus 10% crude almond oil, whereas traps baited with freeze-killed, navel orangeworm–infested nutmeats were less effective. The use of nut mummies (culled during winter orchard sanitation) as trap bait may not produce consistent results since the level of navel orangeworm infestation of these nuts is typically unknown. Three seasons of field tests showed that egg traps baited with almond meal plus 3% or 10% crude almond oil received similar numbers of navel orangeworm eggs, and these traps were equally effective for at least 10 weeks.
Conventional almond growers in Merced and Stanislaus counties who use organophosphate, carb-amate and pyrethroid insecticides were compared with participants in the Biologically Integrated Orchard Systems (BIOS) program, who do not use these broad-spectrum insecticides. The results demonstrated consistent but not significantly lower infestation by navel orangeworm and peach twig borer for growers who used broad-spectrum sprays. Infestation by ants resulted in the most consistent difference between the two management practices, with significantly less damage when broad-spectrum sprays were used. The differences in overall pest damage were relatively minor, but the variation was greatest among those not using broad-spectrum sprays. Winter survival of the navel orangeworm parasitoid, Goniozus legneri, and parasitism by this beneficial insect were low in all orchards, sprayed or unsprayed. Winter removal of unharvested almonds to fewer than two per tree reduced navel orangeworm infestations in both treatments. Although many of the almond growers not using organo-phosphate, carbamate or pyrethroid sprays had less damage than some who used these materials, the greater range of damage experienced by these growers may explain why more almond growers prefer to use them annually to combat insect pests.
Slow-release pheromone tech-nology can successfully control oriental fruit moth and peach twig borer while eliminating in-season insecticide sprays in cling peaches. In conjunction with a demon-stration program, we compared mating disruption for these two pests with standard grower pest-control methods in the Sacramento and San Joaquin valleys, and monitored for pest damage, yield and grower costs. While the mating-disruption program was effective in controlling the targeted pests, costs were higher and growers preferred a partial disruption program that included some supplemental late-season insecticide sprays. Subsequently, we developed monitoring methods to determine the need for supple-mental sprays. This partial mating-disruption program still costs about $60 more per acre than a standard spray program. Predicting efficacy and determining the need for supplement sprays is also more difficult with the partial program than with the pheromone-based control program.
A comprehensive survey of full-time almond growers in the three primary almond-producing regions of California showed that growers rely substantially on pest control advisers (PCAs) for pest management decision-making. Independent PCAs communicated more frequently with growers than PCAs who are employed by agricultural product suppliers. Growers who use independent PCAs tend to feel more knowledgeable about integrated pest management (IPM) and report the use of more complex pest-monitoring techniques and control practices. The use of insecticide sprays, however, is independent of the type of PCA employed, and the percentage of growers using them has declined substantially since a 1985 survey.