Plum curculio is a fancy name for a weevil that attacks apple trees and other fruits. The adults feed on the apple buds, blossoms, leaves and young apples, but the worst damage they do is from their egg-laying activities. The adult weevil chews a small hole in the fruit for the eggs which causes the fruit to become scarred and distorted. The fruit becomes further distorted as the larvae feed inside the apple. The damage may cause the apple to (drop)to the ground where the larvae then migrate into the soil, much like the apple maggots.
In fruit trees such as peach or apple, the presence of blooms or fruit availability will greatly influence immigration of plum curculio, Conotrachelus nenuphar. In particular, it is extremely detrimental where stone fruits (such as peaches, plums, and apricots) are interplanted with pome fruits (such as apples and pears). The host range of plum curculio includes apple, pear, nectarine, plum, cherry, peach, apricot, and quince. It can also survive on hawthorn, wild plum, and crabapple.
Controlling Plum Curculio
The trick is to prevent the adult beetles from getting a chance to lay their eggs.
Two Weeks Before Flowers Start To Bloom - Sticky Wraps Around The Trunk -The adults initially appear in apple orchards during bloom. They can’t fly so they have to walk up the trunk to get to the leaves and fruit. Ideally you stop them right then and there.
Handpicking – If you forgot the sticky tape you can knock weevils from trees using a padded stick, and let them fall on a sheet spread below. Gather and destroy the weevils. Collect infested fruit, especially early drops.
Just After Bloom Time – Spray AzaMax - Most beetle activity occurs during the first warm period after petal fall, when the maximum temperature is 70°F or higher. Periods of cool, rainy weather with maximum temperatures below 70°F are not suitable for adult activity. Adults can be found in orchards for 5 to 7 weeks. AzaMax is a natural product with a broad spectrum of pest control and broad plant applications. AzaMax is an anti-feedant and insect growth regulator which control (kills) pests through starvation and growth disruption within two or three days. Therefore you use this product when the weevils are chomping away on your plant. Spray in the early evening to get them as they climb the tree to eat. Any sprayer can be used to apply AzaMax. For more information about AzaMax go to the Yardener's Tool Shed; click here
Egg laying activity by the pests you did not get earlier starts once the fruit begins to form, with egg hatch occurring after 7 days. In successfully attacked hosts, the hatching larva burrows into the fruit's center, where it makes large irregular cavities. Fruit that are successfully attacked by larvae are prone to (drop)prematurely. Clean up all fallen fruit
Two Weeks After Fruit Begins To Form – Spray Predatory Nematodes - After 14-16 days within the fruit the larvae exit and enter the soil where they form a pupation chamber for an additional 10-12 days before transforming into adults. Applying predatory or beneficial nematodes is one of the best techniques for dealing with weevils which are always tough to control using a spray insecticide. Predatory nematodes will go down into the soil seeking out the larvae of the weevil, thus knocking them out before they even become adults able to eat the leaves of the landscape plant. Release them early in the season when the soil has warmed up; around planting time for tomato seedlings. These microscopic insects are compatible with other beneficial insects. Beneficial nematodes are shipped live in the box and may be mixed directly into the soil and are applied with a sprayer.
Mid-to-late July – Spray AzaMax - New adults can appear in the orchards in mid- to late- July with emergence continuing until early September.
September – Spray Predatory Nematodes If You Have Not Done So Earlier - In September and October adults begin seeking overwintering quarters. The adults overwinter in the top few inches of leaf litter in nearby hedgerows, trashy fields and woods (especially on the south edge of an orchard). Here’s where the song birds and beneficial insects pull their weight. There is only one generation per year in the North. There is a second generation in eastern Virginia and southward.