A few people have inquired about the differences between spray product choices for worm control during Hull Split and/or “May” Spray. I thought I would highlight some of the thoughts that the UC has developed over the years regarding this decision. Some of this may be redundant, but hopefully some new points will be brought to the table. Which product is best?Determining which product is the best treatment option for your orchard depends on budget, pest pressure, timing, and familiarity. Pyrethroid products are effective in knocking down adult moths and killing larvae that come in contact with the product. Persistence of the product within the field is not as long as the reduced risk products (about 2-5 days less), but they are useful for later hullsplit applications – around 2-5% for optimal timing. The downside with pyrethroids is the assumed mite flare up, knock down of orchard beneficial insects, and water run-off issues. A miticide should be tank mixed with the hull-split application if applying a pyrethroid. “Reduced risk” products (i.e. Entrust, Success, Delegate, Intrepid, Belt, etc.) target the eggs and larvae of the moths. They do not knock down adult populations as well as pyrethroids, but control developing larvae more effectively and selectively. These products tend to persist within the orchard a little longer, providing longer control and thus can be applied earlier than pyrethroid products (when blanks split). They have a minimal effect on beneficials, allowing the natural predators to help control mite populations, usually preventing a mite flare up, thus not requiring the tank mixing of a miticide. These products are very effective but resistance to the mode of action may occur – so chemical class rotation is important if products are sprayed more than once per season. Water impacts appear to be minimal. Currently, a pyrethroid treatment is cheaper
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