What are Leafrollers?
Leafrollers are small greenish to green/brown caterpillars (moth larvae) that feed on leaves, buds, and fruit. They’re the worm in your apple (Or 1/2 worm as the case may be).
They are a common problem on fruit trees and ornamental trees, occasionally on vegetable garden plants, but rarely. Some of the more prevalent and bothersome varieties include red-banded leaf roller, fruit tree leaf roller, oblique banded leaf roller, variegated leaf roller, omnivorous leaf roller.
Leafrollers larvae feed on both fruit and foliage. Foliar injury is generally not a major concern.
Larvae may seal leaf surfaces together and live between them or fold leaves together and live in the folds. Larvae also feed within berries and fruit as the worm in your apple, and may not be noticed until harvest time, or at consumption. Young larvae feed on unfolded leaves.
Older larvae fold the leaves in half and hold them in place with webbing. Damage results from the larvae feeding within the folded, rolled, or webbed leaves, causing them to turn brown and die.
Monitoring
Monitoring should begin early. Look for folded or rolled leaves among the plants. The leaves may be discolored or show some feeding damage such as small holes in the leaves. Pick the rolled leaves carefully and examine for leaf roller larvae. If the rolled leaves do not have any larvae present, it is too late to control the larvae.
Leafroller Caterpillar Treatment and Control
Now you will be dealing with the adults, spraying would be ineffective and costly at this time. Inspect branches and twigs showing as new foliage emerges and look for signs of feeding, as well as the tiny caterpillars.
Look for egg masses, and check them for signs of larval exit holes. Fruit trees should be sprayed no later than petal fall to prevent leafroller larvae from injuring developing fruit.
There are predatory insects that attack leafrollers and help to keep their populations in check. Parasitic wasps are one. Others are the Lacewing larvae, assassin bugs, and Birds which will sometimes feed on the larvae and pupae.
Diverse gardens that also attract many natural native predators by mingling varying plants and flowers blooming at different intervals throughout the season are advantageous.
When there is evidence of a leafroller infestation, such as early spring defoliation, foliar sprays are of little use because the most common species of leafrollers produce only one generation annually, by the time defoliation is noticed the caterpillar stage is generally completed.
Bt Bacillius thuringiensis
Sold under a variety of trade names and is effective against the larval stages of leafrollers. Bt does not harm beneficial insects, pets, or people. Leafrollers will cease eating within hours after feeding on a sprayed leaf and die within a few days.
Insecticidal oil sprays applied during dormancy will help control leafroller eggs on fruit trees.
Spinosad
Another eco-friendly insecticide that is effective against leafrollers and is also widely available.
Proper sanitary practices are vital to the health of your garden. Proper sanitation can help to ensure disease-free pest-free and productive gardens.
Try to keep the garden free of any diseased dead or damaged plant materials. Remove cuttings from pruning and trimming and either destroy them – if diseased or send them to the compost pile. Leaving rotting fruits and vegetables in the garden is like a written invitation to unwanted pests and diseases.
If a diseased or dead plant part has to be cut, the microorganism that caused the problem is probably on the tool you just used. Like a surgeon, sterilize all tools by washing in soap and water – rubbing alcohol wouldn’t hurt either. If you pinch off diseased plant parts, wash hands before handling any other plants.
Keep Weeds under control. Till the soil in the spring before planting to expose and kill larvae that wintered over in the soil.