Hands up if you have experienced the annoying garden pest known as leafroller. If you’re new to gardening, it won’t take long before you’ll see them. If you are experienced, you’re probably very familiar with leafrollers.
Leafrollers don’t usually do much damage, but some years they appear in huge numbers, and that’s when they become a real pest. They can also weaken plants if they’re already dealing with other pests or diseases.
Ready to learn more?
What Are Leafrollers?
Leafrollers aren’t one individual species of moth or larvae. There are the larvae of several species of leafrollers from the Tortricid family. They’re related to codling moths and spruce budworms.
Leafrollers nest in the leaves of their target plants by curling a leaf around themselves and holding it together with silk strands.
They eat and make holes in the leaves curled around them. Sometimes they will curl additional leaves around the first one to create an extra-large shelter.
Leafrollers can be brown, grey or tan, and sometimes green. They can easily blend into the colors of the garden and the trees they inhabit.
Plants Leafrollers Love
Leafrollers feed on a number of fruit trees and ornamentals. The most common leafroller is the fruittree leafroller (Archips argyrospila).
The plants these leafrollers are common on are:
- Box Elder
- California Buckeye
Other leafrollers include the omnivorous leafroller (Platynota stultana). This is a pest for many fruit trees, as is the orange tortrix (Argyrotaenia franciscana).
Apple pamdemis (Pandemis pyrusana) joins the group as well for fruit trees, especially in coastal areas. You’ll also often see the oblique banded (Choristoneura rosaceana) leafroller and the light brown apple moth (Epiphyas postvittana).
The Lifecycle of a Leafroller
There are four stages in the life of the leafroller. The stage that causes the most damage to plants is the larvae stage. They dedicate their lives to consuming the plant. That is the stage you want to prevent or target.
Although there are slight differences in where the various leafrollers lay their eggs, it is generally on small branches and twigs. The eggs are laid in groups and are covered in a grey substance that glues them all together. Depending on the type of leafroller, there could be up to 300 eggs.
This substance eventually turns white before the next stage.
Larvae or Caterpillar
In spring, small pinholes appear in the glue, and the larvae hatch. The caterpillar feeds on the inside of rolled leaves they hold together with silk. If you disturb them, they may wriggle a lot, or drop to the ground on a silk thread. Some species of leafroller retreat further back into the leaf.
Mature larvae can be anywhere from a half-inch to an inch in length.
Leafrollers pupate in the leaf it rolls and holds together tightly with silk threads. Silk will also surround the pupa.
The adult moths are generally a half-inch long. Wing spans vary but can be up to 7/8 of an inch.
Some leafrollers lay eggs and allow them to overwinter, but you will find that adult moth activity peaks in June for most types.
Identifying Leafroller Damage
The larvae of leafroller cause new, tender leaves to have a ragged appearance. They live up to their name and roll leaves around themselves, held together by silk.
When there are a lot of leafrollers on a plant, they could cause defoliation. They have been known to cover an entire plant with silken threads. Once a plant is defoliated, the larvae can move to another plant.
The larvae of the leafroller are also known to attack the fruit of the tree they are on. This can cause young fruit to fall off. Older fruit doesn’t fall off but is left with scarring in the form of raised surfaces that are gold, yellow, or bronze-colored.
The only good thing is they don’t enter the fruit as a coddling moth does.
Many other pests make leaves look chewed on and ragged like leafrollers, but they don’t have the telltale silk threads.
One point to note is that even if a tree is defoliated by the leafroller, a healthy plant is likely to bounce back. It’s best not to test the theory though. If there are large numbers, consider intervention.
4 Natural Ways to Rid Plants of Leafrollers
I much prefer organic methods to rid my garden of pests given I’m eating the plants or fruits I’m applying it to. Of course, if organic methods don’t work, I may choose chemical control, but that is entirely up to you and the pest you’re facing.
Bacillus thuringiensis (Bt) is often found in commercial organic pesticides. It’s a bacterium that naturally occurs in soil. Bt has a toxin fatal to leafroller larvae.
Sometimes Bt is sold under its own name, or it’s an ingredient in other pesticides.
Spray it on the foliage before the leafroller feeds on it. Once the leaf is curled around the leafroller, it’s difficult to get the spray to penetrate. Some gardeners say that using a high-pressure sprayer can achieve penetration into the curled leaf.
Remove the Eggs
This may sound a lot like an impossible task given the size of the eggs. It’s actually a good method of reducing the numbers over the season.
From late spring to early summer, eggs will appear on the leaves. They can be on the upper and lower sides.
The eggs are quite distinctive. They are laid in straight rows that overlap. They look a little like fish scales that are in perfect unison, tight and compact.
If I see the eggs, I squash them, scrape them off and burn them, or I remove the whole leaf they’re on. Don’t just cast it aside, make sure you throw it in the garbage or even better yet, burn it.
Spray it in the early morning or evening when beneficial insects aren’t out. Be wary of neem and bees. You must protect the pollinating insects from neem oil.
Follow the mixing instructions on the brand you buy.
Trichogramma wasps are a natural wonder that is an effective and clean way to control leafrollers and many other species of moths and butterflies, at least 200 of them.
These wasps are tiny. Their wingspan is about 1/50th of an inch across, but they can decimate the leafrollers in your plants.
Trichogramma wasps lay their eggs inside the eggs of the leafroller’s eggs, stopping the caterpillar from emerging. Basically, the wasp stops the reproductive cycle of leafrollers.
Five wasp eggs can fit into one leafroller egg. When the adult wasp emerges, it will live for about 14 days where it will target more leafroller eggs. The more the merrier!
Trichogramma have become very popular beneficial insects to the point they are one of the most released in the US.
You can buy them from many outlets, and usually come as eggs on a series of cards, which you simply hang and wait for them to hatch and go to work. There are certain wasps for various plants and situations, so read the information before buying.
I generally use Trichogramma brassicae for leafrollers in the orchard.
Identifying the Leafroller
The average gardener can’t really tell what sort of leafroller they have by looking at it. Here is a quick guide.
- In warm, inland valleys where vines, ornamentals, and fruit trees are growing, you’ll usually see the fruittree, omnivorous, or oblique banded leafroller.
- Cooler coastal areas where ornamentals, fruit trees, and plants that don’t produce crops are growing usually have the light brown apple moth, orange tortrix, or the apple pandemis.
Why Does The Species Matter?
The fruittree leafroller only has one generation per season, so by the time you see the ragged leaves or larvae, there is no real reason to treat them with anything as long as there aren’t huge numbers.
The oblique banded leafrollers overwinter on trees as larvae underneath the bud scales and have up to three generations per season.
Pandemis leafrollers can cause the fruit to self-abort or have scarred and deformed fruit. They can have up to two generations in a year.
The larvae often move to a new leaf just before becoming a pupa.
One of the reasons leafrollers are hard to control is because they have different numbers of generations per season, they cause different sorts of damage to different plants, and in some seasons their presence doesn’t necessarily mean they will be a problem.
It’s for this reason that I suggest choosing a control method that you stick to each season.
Some seasons I will use neem oil regularly. In other seasons I’ll use Trichogramma wasps because it is the most natural way to do it. It also means I don’t have a goal of eliminating leafrollers. I have a goal of controlling their numbers and any damage they may cause.