Controlling Difficult Apple Pests - Woolly Apple Aphid and San Jose Scale

Woolly apple aphid and San Jose scale are pests apple growers have dealt with for years and which routinely impact the harvestability and marketability of fruit. These pests can cause damage like curled leaves or black sooty mold from woolly apple aphids and red feeding spots from San Jose scale.

Woolly Apple Aphid

Woolly apple aphids feed on both the tree canopy and on roots. This feeding can cause gall formations on roots and twigs, stunting or weakening of the tree. Honeydew deposits from these insects can result in sooty mold growth on fruit.

Management Tips:

• Scout the prior season looking for white cottony fluff on internal canopy scaffolding.
• When using broad spectrum insecticides, be aware that these may control target pests, but flare secondary pests like woolly apple aphids and even San Jose scale.
  • Some products used to control codling moth can flare woolly apple aphids. Be prepared next spring to come back in and treat.
  • Some products knock out the natural enemies of woolly apple aphids (e.g., parasitic wasps, lady beetles, green lacewings, mirids, and even earwigs), which can lead to flare-ups.
• During petal fall, woolly apple aphids are migrating up the tree -- having a foliar insecticide spray at this time can enable the product to reach and control populations in the orchard.
• The outside covering of woolly apple aphids is thick, which can present a barrier difficult to penetrate for products that only offer control on contact. Utilizing higher rates, adjuvants, or switching to products with translaminar and systemic activity can help achieve better efficacy in those scenarios.
• If prior year populations were high, follow-up your petal fall spray 14-21 days later to continue to reduce and control that migrating population.

San Jose Scale

San Jose scale suck the plant juices from twigs, branches, and fruit. This activity can cause red spots on fruit, reduce yields, and kill limbs. Scales may enter orchards from a variety of sources (forests, adjacent orchards, etc.). They tend to live in cracks and crevices in the tree, which makes them hard to reach with regular spray programs and allows them to build up over time.

Management Tips:

• Pre-bloom control of San Jose scale is important, but complete control may not be achieved under heavy pressure.
• Follow up your pre-bloom program with a petal fall application targeting immature scales and sterilizing any adult females.
• Proper coverage is essential -- make sure your sprayer is calibrated to deliver an adequate amount of water for thorough coverage in order to reach scales.
• Do not go over the speed that the equipment has been calibrated for; doing so will negatively impact coverage, which will dramatically affect products that only offer contact activity.
• For in-season control, the addition of a horticultural mineral oil increases your ability to achieve adequate coverage.
• To maintain fruit quality under heavy pressure, apply an additional spray 14-21 days after petal fall before crawlers emerge and mark the fruit.

A New Insecticide Solution
New Senstar™ Insecticide from Valent U.S.A. offers apple growers control of aphids (including woolly apple, rosy apple, and green apple) and scales (including San Jose and European fruit lecanium) with two effective modes of action to control pests at all life stages, including eggs.

Applying Senstar at petal fall will result in good coverage and control from the start, as well as break the population lifecycle to help control pests later in the season. Senstar delivers fast translaminar movement and dual systemic activity to control pests moving into new vegetative growth as well as pests that populate in already developed foliage. Do not apply Senstar fewer than 45 days prior to harvest.

Senstar is an excellent fit in Integrated Pest Management (IPM) programs because it provides selectivity to harmful insect species with minimal disruption of beneficial arthropods. To learn more about Senstar, talk to your retailer or visit Valent.com/Senstar.

Always read and follow label instructions.

* First published by the U.S. Apple Association as part of their Thought Leadership series. Republished on the permission of the U.S. Apple Association.