The San Jose scale (SJS) is an established and tenacious pest of tree fruit. Trees attacked include apple, peach, and pear. The SJS may have up to 3 generations per year, depending upon the locality and the length of the growing season. This season we are seeing the 3rd generation in Highland with the likelihood of its development up through the northern Hudson Valley.
The 2nd generation adults emerged on 2nd of September with peak emergence on the 15th. We use a 400DD from the male flight (biofix) to calculate emergence using 51F baseline. In orchard blocks where SJS is established, nymphs are likely to emerge slowly over the remaining course of harvest as temperatures decline.
The emerging crawlers are bright yellow and quite mobile. After exiting from beneath the female’s cover, the crawlers walk or are air-borne to new sites of infestation on the bark, fruit, and leaves. Within 24 hours of emergence the crawlers settle, tuck in their legs and antennae, and insert their mouthparts into the tree or fruit. Red halos from newly established 3nd generation nymphs have been observed.
First instar nymphs secrete a white waxy covering or “white-cap”. The final phase of the first instar or “black-cap” stage develops concentric rings of darkened wax. Presently we are seeing the onset of fruit injury. Where SJS has been and issue of the past two year, scouting will be essential to determine if additional management is required for this late generation.
A number of choices are available for SJS management. Centaur 0.7WDG acts to inhibit the synthesis of chitin (Class 16) working as an insect growth regulator (IGR). Esteem 35WP, also an IGR, functions as a juvenile hormone mimic, inhibiting metamorphosis from one stage to another (Class 7). These insecticides are most effective when directed against crawlers at first appearance yet have no contact toxicity and tend to act very slowly.
Assail (Class 4) is a broad-spectrum neonicotinoid that also is most effective when directed against crawlers as they emerge. The efficacy of these materials is improved by the addition of oil, however, Esteem 35WP and Assail can be used effectively without the use of oil. The OP Imidan 70WP and pyrethroids can also be used against the crawlers during emergence in back to back applications at 7-10 days. Note that if Leverage is used, it will have efficacy against both BMSB and SJS.
Although Movento is an excellent material for control of SJS, it will require two weeks for optimum control. If you choose to use this material it should be combined with a contact insecticide labeled for SJS. As we are now in full harvest, be sure to read label restrictions (PHI, REI) on late season use.