Growing and harvesting perfect apples depends on many factors that are often unpredictable - rainfall, temperature changes, bee presence and wind conditions. There are, however, some more predictable factors. Insect pests and diseases prey upon apple trees, buds, and fruit at different stages of the growing season. To combat these threats, apple growers use different agricultural sprays.
Because frost dates differ wildly from state to state, it is best to spray according to bud and fruit development rather than by date. Spray with dormant oil while the tree is still sleeping in early spring, and temperatures will not drop below freezing for at least 24 hours. Dormant oil spray protects the apple trees by smothering any over-wintering eggs from the following pests.
- San Jose scale ruins fruit and kills twigs, limbs, and eventually entire trees
- Rosy Apple and Wooly Apple aphids destroy young apple trees and produce misshapen fruits
- European red mites cause leaf wilt and drop
"Pink" development refers to the appearance of separated apple blossom buds on elongated stems. At this point, buds are on the cusp of opening fully, and now is the time to spray an insecticide for sawfly and tent caterpillar. The larvae will hatch and feed on immature fruitlets, causing fruit to rot and fall off the tree.
When blossoms are fully open, bees are hard at work pollinating your trees. Protect these bees by not using insecticide sprays. Instead, it is a great time to spray for fungus and bacteria such as fire blight and scab. Rainy springs only worsen these diseases, so this will help give your trees get ahead of possible infections. Both scab and blight damage leaves, fruit, and can kill a tree.
Plum curculio becomes a threat after all the blossom petals have fallen, called "Petal Drop." Now that the bees are gone, spraying is once again safe. Plum curculio eats blossoms and burrows into the tiny fruit to lay their eggs. As each infected apple matures, it is scarred and drops from the tree early.
When summer arrives, your spraying schedule changes to two-week spraying intervals. Aimed at controlling any new and emerging aphids and mites, spraying also controls new invaders. Here are a few:
- Codling moth
- Apple maggot
- Leaf rollers
The apple spraying season is varied and busy in the quest to combat diseases and pests. The quickest and easiest way to switch spray tanks is to employ cam lock hose fittings.