How to identify, treat and prevent this garden pest

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Raise your hand if you’ve encountered the annoying garden pest known as leafroller. If you are new to gardening, you will soon see them. If you’re experienced, you’re probably very familiar with leafrollers.

Budworms usually don’t do much damage, but some years they appear in large numbers, and that’s when they become a real pest. They can also weaken plants if they are already dealing with other pests or diseases.

Ready to know more?

What is a twister?

Budworms are not an individual species of moth or larvae. There are larvae of several species of tortrix family Tortricidae. They are related to the codling moth and the spruce budworm.

Leafrollers nest in the leaves of their target plants by wrapping a leaf around them and securing it with strands of silk.

They eat and make holes in the leaves wrapped around them. Sometimes they will wrap additional leaves around the first to create an extra large shelter.

Budworms can be brown, gray or tan and sometimes green. They can easily blend in with the colors of the garden and the trees they inhabit.

Plants Budworms love

Budworms feed on a number of fruit trees and ornamental plants. The most common leafroller is the fruit tree leafroller (Argyrospila Archips).

The plants on which these leafrollers are common are:

  • Apple
  • Pear
  • Plum
  • Almond
  • Citrus
  • Quince
  • Walnut
  • Box Elder
  • Elm
  • Maple
  • Poplar
  • Birch
  • Ash
  • California Buckeye
  • willow
  • Pink

Other leafrollers include the omnivorous leafroller (Platynota Sultana). It is a pest of many fruit trees, just like the orange tortrix (Argyrotaenia franciscana).

Apple pampemis (Pandemis pyrusae) also joins the group for fruit trees, especially in coastal areas. You will also often see the oblique bands (Choristoneura rosacea) leafroller and tan apple leafroller (Epiphyas postvittana).

The life cycle of a budworm

There are four stages in the life of the budworm. The stage that causes the most damage to plants is the larval stage. They devote their lives to consuming the plant. This is the stage you want to prevent or target.

Eggs

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 coated in a gray 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 step.

Larvae or caterpillar

In the spring, small pinholes appear in the glue and the larvae hatch. The caterpillar feeds on the interior of the rolled up leaves which they maintain with silk. If you disturb them, they may wiggle a lot or fall to the ground on a silken thread. Some leafroller species retreat further into the leaf.

Mature larvae can measure between half an inch and an inch in length.

Pupa

The leafrollers pupate in the leaf which they roll up and hold tightly together with silken threads. Silk will also surround the pupa.

adult butterfly

Adult butterflies are usually half an inch long. The wingspan varies but can be up to 7/8 inch.

Some leafrollers lay eggs and allow them to overwinter, but you will find adult moth activity peaks in June for most types.

Identification of leafroller damage

Leafroller larvae give tender new leaves a ragged appearance. They are aptly named and wrap leaves around them, held together by silk.

When there are many budworms on a plant, they can cause defoliation. They are known to cover an entire plant with threads of silk. Once a plant is defoliated, the larvae can move to another plant.

Leafroller larvae are also known to attack the fruit of the tree they are on. This can cause young fruit to fall off. Older fruits do not drop but leave scars in the form of raised surfaces of gold, yellow or bronze color.

The only good thing is that they don’t penetrate the fruit like a codling moth does.

Many other pests make the leaves look chewed and ragged like leafrollers, but they lack the telltale silken threads.

A point to note is that even if a tree is defoliated by the budworm, a healthy plant is likely to rebound. It’s better not to test the theory though. If there are a large number, consider an intervention.

4 natural ways to rid plants of leafrollers

I much prefer organic methods for ridding my garden of pests since I eat the plants or fruits I apply it to. Of course, if organic methods don’t work, I can choose chemical control, but that’s entirely up to you and the pest you’re dealing with.

Bacillus thuringiensis

Bacillus thuringiensis (Bt) is often found in commercial biological pesticides. It is a bacterium naturally present in the soil. Bt contains a toxin that is deadly to budworm larvae.

Sometimes Bt is sold under its own name, or it is an ingredient in other pesticides.

Spray it on the foliage before the leafroller feeds on it. Once the leaf is wrapped around the leafroller, it is difficult to get the spray to penetrate. Some gardeners say that using a high-pressure sprayer can get into the curled leaf.

remove the eggs

This may seem like an impossible task considering the size of the eggs. This is actually a good method to downsize during 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 arranged in straight overlapping rows. They look a bit like fish scales perfectly in unison, tight and compact.

If I see the eggs, I crush them, scrape them and burn them, or I remove all the foil they are on. Don’t just toss it aside, be sure to throw it in the trash or, better yet, burn it.

neem oil

I am a big proponent of neem oil. It is not, however, a quick and fast acting treatment. Neem should be sprayed regularly before and during the growing season.

Spray it early in the morning or in the evening when the beneficial insects are not out. Beware of neem and bees. You need to protect pollinating insects from neem oil.

Follow the mixing instructions on the brand you are buying.

Trichogramma wasps

Trichogramma wasps are a natural wonder that is an effective and clean means of controlling 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 in diameter, but they can decimate leafrollers from your plants.

Trichogramma wasps lay their eggs inside the leafroller’s eggs, preventing the caterpillar from emerging. Basically, the wasp stops the leafroller’s reproductive cycle.

Five wasp eggs can fit in one budworm egg. When the adult wasp emerges, it will live for about 14 days where it will target more budworm eggs. More the merrier, the merrier!

Trichogramma have become very popular beneficial insects to the point that they are one of the most common in the United States.

You can buy them at many outlets and they usually come in the form of eggs on a series of cards, which you simply hang up and wait for them to hatch and get to work. There are certain wasps for various plants and situations, so read the information before you buy.

I usually use Trichogramma brassicae for leafrollers in the orchard.

Budworm identification

The average gardener can’t quite tell what type of leafroller he has by looking at it. Here is a quick guide.

  • In the warm interior valleys where vines, ornamentals and fruit trees grow, you will usually see the omnivorous or oblique-banded fruit tree moth.
  • Cooler coastal areas with ornamental plants, fruit trees, and plants that do not produce crops usually have tan apple moth, orange tortrix, or apple pandemis.

Why is species important?

The fruit tree budworm 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 is no there aren’t a lot of them.

Obliquebanded leafrollers overwinter on trees as larvae under bud scales and have up to three generations per season.

Pandemis leafrollers can cause fruit to self-abortion or have scarred and deformed fruit. They can have up to two generations per year.

The larvae often move to a new leaf just before pupating.

One of the reasons budworms are difficult to control is that they have a different number of generations per season, they cause different types of damage to different plants, and in certain seasons their presence does not necessarily mean that they will be a problem.

It’s for this reason that I suggest choosing a control method that you follow each season.

Some seasons I will use neem oil regularly. In other seasons I will use Trichogramma wasps as it is the most natural way to do it. This also means that I don’t aim to eliminate budworms. My goal is to control their numbers and the damage they could cause.

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