Leaf Rolls: Caterpillar Threats Chew

Growing fruit trees has its own challenges. Leafrollers are a family of insects that attack the leaves of fruit trees such as apples, pears, and peaches. They also target some ornamental trees like ash, poplar, and oak, as well as some ornamental plants like canna lilies. Unlike leaves that curl from disease or environmental stress, leaves that curl from leaf rolling are healthy leaves that are physically wrapped around an insect and secured with silk or netting. The leaves provide cozy shelter and a reliable source of food for the growing larvae inside.

Leafrollers shouldn't be a huge problem for your orchard or garden for most years. However, every few years it can grow into a large population that can cause significant damage. This informative piece is a resource that will help you identify and control leafrollers so they don't pose a great deal of risk to your fruit trees or ornamental plants.

Good products to control leafrollers:

Leafroller overview

Leaf rollsLeaf rolls are the larvae of a number of species of moths. Source: Futureman1

There are many different types of leafrollers, which are the larvae of moths in the tortricidae family. These moths are usually brown, gray, or brown in color and can easily blend into tree bark. Some species in this family are known pests, including the codling moth, which is known to attack apples and other pome fruits. Others, including the spruce budworm, can severely defoliate conifers.

Leafrollers in the Tortricidae family all have similar behavior in rolling up healthy leaves to protect and feed their caterpillars. These and many other tortricid moths are native to North America and play important roles in the ecosystem as a food source for other organisms and even as a biological control for invasive plants.

Most leafrollers aim for fruit or ornamental trees. Pandemis leafroller (Pandemis pyrusana), Obliquebanded leafroller (Choristoneura rosaceana), Fruittree leafroller (Archips argyrospilus), and European leafroller (Archips rosanus) are all tree species. The Canna Leafroller (Calpodes ethlius) and the Lesser Canna Leafroller (Geshna cannalis) specialize in the Canna lily.

Life cycle of a leaf roll

Eucosma spp leafroller mothLeafroller moths come in different colors, like this Eucosma moth. Source: Judy Gallagher

Leafrollers go through four developmental stages in their life: egg, larva, pupa and finally the adult moth. The most destructive stage for leafroller is the larval stage, when insatiable caterpillars serve their sole purpose of consuming plant material.

Different types of leafroller have different times for their life cycles. For example, the pandemic leafroller and the bias tape leafroller both have two generations per year while the fruit tree leafroller and the European leafroller only have one generation. The canna leaf rolls are very productive and can have more than three generations per year.

In pandemis and leafrollers with inclined ribbons, the adult moths lay a mass of 50 to 300 eggs in late May or early June. The egg mass starts out light green and then turns light brown. Shortly before the eggs hatch in mid to late June, the dark heads of the larvae can finally be seen in the eggs. After hatching, these caterpillars feed frantically on host plants and quickly mature into adult moths to lay another round of eggs in late August. This second generation winters in a hibernaculum or silk case until next spring.

The fruitless and European Leafroller moths lay masses of eggs on the bark of trees and let the eggs overwinter there. The eggs hatch from April and the larvae feed in mid to late May and mature in June. Adult moth activity peaks in late June.

Canna-leafrollers have very short life cycles that complete in 40 days and can have three or more generations per year. Both the canna leaf roll and the smaller canna leaf roll are caterpillars in the larval stage of the large brown skipper butterfly. Adult moths lay eggs on large canna leaves. After the larvae hatch, they spin silk and roll themselves into the leaves, forming long tubes. The larvae feed on the leaves inside-out and form another role as they feed on the previous leaf.

Common living spaces

Trioza spp Valerian LeafrollerThe name leafroller comes from their tendency to roll up leaves for shelter. Source: Jamie McMillan

The most common habitat for leafrollers at the larval stage is in rolled leaves, where they have created the perfect habitat for this part of their life cycle. Depending on the type of leafroller, they can overwinter in different parts of the plant. The pandemis and the sloping leafroller overwinter in the hibernaculum in protected crevices on the trees. The fruit tree and the European leafroller overwinter as eggs on smooth bark. Finally, canna-leafrollers overwinter as larvae in the leaves or stems of the canna plant.

What do leaf rolls eat?

The larvae of all these Leafroller species mainly feed on leaves, which are part of their protection. The canna leaf roll specializes in the canna plant as the only plant host. Other leafrollers can also damage various flowers or young fruits. The feeding tracks on the fruits are similar to those of codling moths.

How to control leaf pest pests

Boxelder LeafrollerThere are many different types of leafroller, like this Boxelder leafroller. Source: U.S. Fish and Wildlife Service

For most years, Leafroller shouldn't pose a significant threat to your fruit trees or deciduous plants. As with many insect species, especially those endemic to your area, we recommend using an integrated pest control approach to control the leaf roll threat and cause minimal harm to humans and the environment.

Environmental control

Before applying chemical or organic controls, the first step in treating a leafroller problem is to remove the affected leaves. These sheets are easy to recognize because they are rolled up and the sheets are often held together by bars. By effectively removing rolled leaves, the leafroller habitat is eliminated instantly. To treat severe cases of canna leafrollers, you can even remove most or all of the leaves to rejuvenate the plant. Cannas are fast growing plants and should recover quickly.

Organic or chemical control

The most effective way to control these pests for fruit trees is to control them right at the time of hatching or immediately afterwards. Bacillus thuringiensis (Bt) var. Kurstaki is an organic insecticide that is effective against leafrollers and other caterpillars. Apply Bt to the affected leaves, including the underside of the leaves while the larvae are young. Bt attacks the digestive system of leafrollers and disrupts their life cycle. It becomes much more difficult to control their population in late summer, when leaf caster larvae have already matured into adult moths. While spinosad can be another effective insecticide against leafroller, it is toxic to bees. Be careful not to use spinosad on flowering plants or just before a storm.

Biological control

Leafrollers are an important part of the food chain and have many natural predators. For example, leafroller larvae are hosts to several species of parasitic flies and wasps. Lacewing, killer bugs, ground beetles and spiders are also predators of this pest. Of course, if you create a welcoming environment for beneficial insects, these will help control the population of pests like leafrollers.

frequently asked Questions

Cotton Leafroller MothThe cotton leafroller moth is beautiful, but catastrophic to harvest. Source: Judy Gallagher

Q: Does Sevin Dust kill leaf rolls?

A: Sevin is a chemical pesticide with the active ingredient carbaryl. It kills pests such as leaf rolls in your garden, but it also kills beneficial insects. Sevin is not approved for organic horticulture or agriculture.

Q: Does neem oil kill leaf rolls?

A: Neem oil can help control leafroller when used at the larval stage. It could also be a good solution if the insects have developed resistance to other chemical treatments.

The green fingers behind this article:

Leave a comment