By Guy K. Ames, NCAT Horticulture Specialist
Major pests of apples, peaches, plums, cherries, and pears enter and/or become active in orchards as soon as the petals begin falling from the flowers. In the eastern half of the United States the plum curculio (photo at right) moves from overwintering sites in or near the orchard and begins to feed and lay eggs in the fruit as soon as the fruit begins to develop.
The tiny fruitlets don’t have to be any larger than your little finger’s fingernail to draw the attention of the curculio and other fruit tree pests like apple maggot, cherry fruit fly, and codling moth (see photo 2).
Identifying Petal Fall
A close look at photo 2 reveals a blossom still in full bloom (upper right hand corner) as well as some flowers that have just recently lost their petals (to the side and just below the fruitlets). This common situation—apple flowers and fruits in different growth stages on the tree at the same time—can confuse a beginning apple grower who has been informed that “petal fall” is the time to put on a “first cover” spray. Perhaps that confusion can be dispelled by identifying a main reason for waiting until petal fall to spray: we don’t want to attract bees or other pollinators to the tree if we’re going to spray something that might kill the pollinators or interfere with their work!
Photo 3 illustrates nearly perfectly when a flower is no longer attractive to pollinators. Though the petals haven’t quite fallen from the pedicel yet, you can probably intuit that these flowers are no longer attractive to bees. The nectar is gone, the pollen spent, and the petals lack luster.
So, petal fall is the time to consider putting that first spray on most of your fruit trees, especially apples, plums and peaches which are favorite hosts for the plum curculio. The curculio will not only feed on and lay eggs in your fruit, but it can also spread diseases from one fruit to another.
Pest Control Options
A very good spray for organic growers at this time is Surround™. This finely ground kaolin clay product inhibits the pest from finding the fruit it wants. Research shows that this safe, non-lethal product can be very effective against the plum curculio and other pests IF a fine dust of the product can be kept on the trees’ foliage for around 4-6 weeks beginning at petal fall. This can be problematic because of rainfall washing the material off of the foliage. The grower simply needs to assess the situation and apply more Surround™ if a dust is not kept on the fruit (photo 4). More conventional pesticides can also be applied at petal fall and then again 10-14 days later. Those two sprays are often enough to provide greater than 90% control of these important, early-season fruit pests.
For more detailed information on control for fruit tree pests, see the separate ATTRA Sustainable Agriculture publications on organic production of apples, peaches, pears, and plums: https://attra.ncat.org/publications/#horticultural.
Guy and our other agriculture specialists are available to answer your questions! Call the ATTRA helpline at 1-800-346-9140 or email firstname.lastname@example.org.
About the Author
Guy K. Ames is a Horticulture Specialist with NCAT and its ATTRA Sustainable Agriculture Program. He has over 40 years of experience gardening, farming, and orcharding. Guy has a B.A. in history from Texas A&M, Commerce and an M.S. in horticulture (fruit crops and pest control in fruit crops) from the University of Arkansas, Fayetteville. Guy has operated Ames Orchard & Nursery since 1983.