the leaves show one stage or another of the pest. The guidelines are available on- line atwww2.ipm.ucanr.edu/agriculture/ avocado/Persea-mite. “You look at new leaves in areas of the orchard that had persea mites or thrips last year,” Headrick said, “but for the av- ocadobrownmites, theplace to look is on the tips of the leaves.” For the omnivorous leafroller, look for leaves that are flat and tied together, he advised. “As you get into June, look for six-spot- ted spider mites on the underside of the leaves,” Headrick said. “Mites defoliate. There’s not really a threshold—it’s what’s worked for you in the past.” The question of what to do once action is warranted depends on a farmer’s pest control philosophy, he said. “You have to decide where you are in terms of a biological or chemical ap- proach,”Headrick said. “Natural enemies do their best workwhen the pest popula- tions are low.” Even growers who lean toward letting biology handle the pest question may soon look at usingnew technology touni- formly distribute biocontrols throughout the orchard, he said. “We might someday look at drones to get good coverage with predatorymites,” Headrick said. “Almond growers are al- ready using them.” ( Bo b J o hn s o n i s a r e p o r t e r i n Sacramento. He may be contacted at bjohn11135@gmail.com.)
Avocado growers can slow pests by monitoring them A biological-control expert says weekly monitoring of pests in avocado groves can provide farmers with the information they need to make informed decisions on control options.
ByBob Johnson Because there are few established thresholds for applications to control avocado pests, the issue can involve remembering the point at which expe- rience shows populations threaten the bottom line in a grove. Even the decision of how much time to devote to monitoring, and where, comes down to experience, advises a university entomologist. “You balance accuracy and time,” said DavidHeadrick, aprofessor of entomolo- gy at Cal Poly San Luis Obispo. “We know that time ismoney, but youwant to know what’s out there. Monitoring saves you money.” Headrickwrote “TheBiologicalControl Companion: AGuide toEnvironmentally Appropriate Pest Management.” He made his remarks about monitor- ing and managing avocado pests during the Zooming to Healthier Trees and Soils webinar, cosponsored inmid-April by the CaliforniaAvocadoSociety, theCalifornia Avocado Commission and University of California Cooperative Extension. “The key things are not being sur- prised, knowing what’s out there and making informed decisions,” Headrick said. “If you can see howmany pests you can have without affecting the bottom line, that’s your threshold.” The place to start looking for mites, thrips and other pests is in areas of the orchard where they have caused trouble in recent years. “Start with areas that had pests in the past, and then you’re going to want to add a few trees,” Headrick advised. “For the persea mite and avocado thrips, al- ways look first on a dirt roadside on the upwind sides; the pests and natural ene- mies come in on the wind.” By monitoring these pests weekly, a farmer can learn not just whether they arepresent, but whether they are increas- ing in numbers or decreasing because beneficial insects are at work. “You’re looking at population trends,
because that’s what’s going to drive your decisions,” Headrick said. “For persea mites, look for spotting on the underside of the leaves that becomes yellowing on the top side.” If mite populations become extreme, they can cause defoliation that exposes the fruit to direct sun. UC Pest Management Guidelines ad- vise monitoring persea mites regularly and releasing predatorymites when half
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