Dormant Season Spray Strategies
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Monitoring
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If orchard has history of worm damage, it is not recommended to skip the dormant spray. However, if no dormant spray is applied, monitor for peach twig borer larvae associated with blooms or emerging shoots, as well as twig strikes resulting from feeding by the emerging larvae. If larvae are observed associated with blooms or emerging shoots, Bacillus thuringiensis (Bt) can be applied during bloom. Once strikes are observed, it is probably too late for bloom time Bt sprays to be effective.
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Dormant Diazinon and Oil Spray
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Diazinon combined with dormant oil during the dormant season.
Diazinon applications are frequently alternated with non-OP pesticides to prevent resistance from developing to either diazinon or non-OP pesticides.
Information is being developed on earlier timing of winter OP applications when less rainfall is likely or when the rainfall is more likely to be absorbed into the soil rather than runoff.
Reduced rates: additional data is needed to demonstrate effects at varying pest (aphid) densities.
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No Dormant Treatment or Dormant Oil Only Treatment
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Dormant insecticide spray is not applied or an oil only treatment is made.
Skipping dormant insecticide sprays has been successful in almonds when pest pressure is low or non-existent.
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Alternate Year Dormant OP Pesticide With Yearly Oil Spray
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Use dormant OP every other year but use dormant oil on an annual basis.
In years with no dormant OP used the following may be necessary:
Additional in-season treatments for peach twig borer.
Additional in-season treatments for mites are possible following in-season applications of carbaryl, esfenvalerate and permethrin.
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Dormant Spray (Non-OP Pesticides) and Oil
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Pyrethroids (permethrin and esfenvalerate) and carbamates (carbaryl) for peach twig borer in the delayed-dormant or dormant season.
Residues of the pyrethroid insecticides permethrin and esfenvalerate persist on bark and may impact naturally occurring predator mites for extended periods of time after dormant season and in-season applications.
Mite outbreaks caused by use of pyrethroids may require additional miticide treatments over and above those normally applied.
While pyrethroids remain effective for controlling peach twig borers in most areas, greatly increased tolerance by peach twig borer to pyrethroids has been identified in the Sacramento Valley, raising the possibility of resistance.
In general, insects become resistant to pyrethroids more rapidly than other classes of pesticides.
Some registered products are not widely used in the dormant season because of possible effects on non-target organisms or because of label restrictions. For example, carbaryl cannot be used in orchards where honeybees are present and endosulfan use is restricted near water or wetlands.
Non-OP pesticides can affect non-target organisms in water and the potential for offsite movement from runoff has not been well studied.
If a non-OP pesticide is applied as a dormant spray, precautions such as on-site practices (following sections) should be taken to prevent movement into surface waters.
Laboratory exposures indicate that fish and invertebrates are particularly sensitive to pyrethroids. Pyrethroid persistence may mean that they will be transported off site. If so, they may be bioavailable to fish in water or to invertebrates in sediment. Sediment toxicity may result after pyrethroids are transported into water bodies.
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Spinosad and Oil as Dormant Spray
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Spinosad (Success Naturalyte insect control) is a low-risk pesticide for control of peach twig borer.
Peach twig borer shoot strikes should be monitored in each generation as well as nuts for the presence or indication of larvae. If monitoring indicates that any of the pest species require additional control measures, they can be applied in-season.
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Bloomtime Sprays of Bacillus thuringiensis (Bt) For Peach Twig Borer
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Treatments of Bt at bloom to control over-wintering peach twig borer larvae.
Peach twig borer shoot strikes should be monitored in each generation, as well as nuts for the presence or indication of larvae. If monitoring indicates that any of the pest species require additional control measures, treatments can be applied in-season.
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Pheromone Mating Disruption for Peach Twig Borer
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Mating disruption relies on releasing pheromones through dispensers distributed throughout an orchard or applied as a spray.
It has been shown to be effective against peach twig borer in almond orchards (although some details of application and effective rates of specific products are incomplete). It is most effective in orchards with low moth populations that are not close to other untreated peach twig borer hosts or almond orchards. Efficacy is reduced by small orchard size, uneven terrain, reduced pheromone application rates, applying too low in the tree, improper timing, and high insect pressure. Pheromone mating disruption cannot be considered a stand-alone system. It is selective for the target pest so monitoring for other orchard pests as well as peach twig borer is necessary.
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