Pre-Bloom Insecticide Options

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Photo of apple treesPrebloom is an important time for preventive management of several key insect and mite pests that can cause problems down the road. Among these are San Jose scale, European red mite, and rosy apple aphid. Oil applications at green tip are highly effective at suppressing overwintering scales and and ERM eggs, and can help to suppress populations later in the season. However, additional insecticide use is often necessary for season-long control of scale and sometimes mites. Below is a summary of the insecticide options from tight cluster to pink..

Lorsban 4E applied with oil has long been used for scale, but for resistance management purposes it is good rotate different insecticide strategies annually. In addition, some orchards treated with Lorsban pre-bloom have experienced scale problems in recent years. For these reasons, other insecticide options should be considered.

The two most effective scale products are Esteem and Centaur, which are both insect growth regulators, but have different modes of action. The window of application is fairly wide with both of these products ranging from green tip to first cover. Applications before bloom are targeting overwintering immatures and recently developed adult scales, while applications after bloom target first generation crawlers that emerge shortly after first cover (see figure below).

Movento is another insecticide that will control scale, but it should be applied  between petal fall and first cover, when sufficient leaf tissue is present for this systemic insecticide to be taken up. It must be applied with a spreading and penetrating adjuvant for effective leaf uptake. Because of the systemic activity of this product, it will also control woolly apple aphid, a pest of sporadic occurrence.

Graph of San Jose scale population trends

Rosy Apple Aphid is another insect that can be controlled with insecticides applied at either the pink or petal fall stage. Nymphs begin to hatch at pink, and they remain susceptible to exposure of insecticide applications through petal fall. RAA-induced leaf curl begins at first or second cover, after which they become difficult to control. Most neonicotinoids are effective against RAA, but be sure that blooms have fallen from trees and bees are not in the orchard when spraying.

(Click on table below for full size.)Table of early season insecticide options