When you're experiencing the spring rush of new growth in your orchard, it's easy to anticipate an excellent growing season. Of course, with new leaves come new pests, some of which can be extremely detrimental to your plants' health. Consider the leafroller, for instance — a particular kind of caterpillar that can leave lasting damage on both the beauty and fruit production of your apple and pear trees.
What are Leafrollers?
Leafrollers are actually moth larvae that get their name from the fact that they shelter themselves in (and later eat their way out of) rolled up leaves. They sometimes gather multiple leaves together and make full-on cocoons. They eventually grow up to fly free, but in their youth, they like to hole up in fruit trees for both protection and food. Unfortunately, it’s pretty hard to identify non-descript moth larvae, so most people don’t know they have a leafroller infestation until the bugs start to become visibly noticable after hatching.
How Can I Tell if Leafrollers are on My Apple Trees?
If you notice silken threads around rolled-up leaves on your apple or pear trees, there's a pretty good chance that you have a leafroller infestation on your hands. Another sign to look out for is a particular kind of deformation and brown scarring on maturing fruit. This happens because leafroller larvae tend to eat parts of the fruit, even though they don’t make their homes inside of it.
It's worth dealing with these pests for the sake of the fruit alone, but it'll also help with the appearance of your trees. Their chewing creates ragged, brown leaves that make your fruit trees much less beautiful. If their eating goes on too long, defoliation can occur, reducing the plants' photosynthetic potentials and making it harder for them to survive.
Leafrollers can also damage fruit so much that it falls right off the tree. To avoid losing fruits or simply having unsightly trees, you'll want to start taking measures to keep the leafroller population in your yard under control.
How Can You Get Rid of Leafrollers?
The best way to deal with leafrollers is before they even hatch, if you can. If you see egg masses in the joints of a tree or on the bark, brush or scrape them away into a bucket of soapy water. This is best done in the late fall or early spring.
Even if you miss a few eggs, you should still be able to best the leafrollers before they make a dent in your leaves. Leafrollers have better and worse years, though, so you'll have to handle them differently depending on how severe the infestation seems to be. If you only see a few rolled-up leaves, gather some soapy water and pruning shears. Clip all affected leaves and drop them in the water to quickly and easily dispose of the larvae without having to rely on harmful chemicals.
If, however, you fear that the infestation is too extensive to quickly and carefully clip out, you may have to turn to a chemical like Bacillus thuringiensis, a bacterium that targets the caterpillars' digestive systems. Spraying it can be less effective, so if you have a nozzle that you can use to pump small amounts into and around each end of a rolled leaf, you'll probably have much better success. The caterpillars will be killed, but the plants themselves won’t be affected, which makes Bt one of the better insecticides to use on them. If you have enough trees to merit spraying, consider spraying at 10-day intervals, since small doses of Bt only tend to incapacitate leafrollers for around 10 days.
While a variety of other oils and sprays exist for leafrollers, it's important to note that the larvae develop resistance to chemicals fairly quickly. For that reason, your best bet will be to regularly swap out the products you're using. Still, prevention is a lot easier than treatment, so monitoring your trees for potential egg sacks is always a better strategy than simply checking for leafrollers later on.
With this information in mind, any year that your garden is faced with a substantial leaf roller infestation still won’t be a bad year for you. That's good news for you, and even better news for your apple and pear trees!