When weather conditions become favorable in the spring, these insects and diseases become active again. The fungal and bacterial diseases begin to multiply, sporulate, and are carried by wind and rain to susceptible plant parts. This begins a new disease cycle. Knowing how these diseases and insect pests overwinter and spread is crucial in their control. This is why cultural methods such as sanitation, pruning and using disease-resistant plants are so important. Pruning removes the source of the overwintered pathogen or insect pest. Some pruning guidelines are listed below.
- Prune out and destroy dead, diseased, or insect-infested twigs and branches.
- Prune branches that rub against each other.
- Try not to leave a stub when pruning; remove the whole branch if possible.
- Do not prune in fall or early winter. This will make trees more susceptible to winter injury.
- Prune to "open" trees, which will facilitate disease control. Pruning promotes better air circulation and light penetration, facilitates the drying of plant surfaces, and enhances spray distribution.
- Prune out cankers in stone fruit to discourage borers.
- Prune out fire blight cankers and all other cankers caused by disease organisms.
- Remove leaves and other plant parts containing insect egg masses.
- Remove and destroy decayed, injured, and mummified fruit left in the tree or on the ground.
- Pick up, burn, bury, or destroy fallen fruit.
- Rake and burn leaves and other litter under the tree to destroy overwintering disease and insect habitats.
- Eliminate weed hosts. Many insects and diseases overwinter in weeds.
- Avoid excessive nitrogen fertilization.
- Avoid wounding plant parts and fruit during the season. Wounds are excellent entry points for insects and diseases
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