Leafrollers are the caterpillars of Tortricid moths that feed and pupate in protected and rolled up leaves of many fruits and patterned trees in high humidity areas, especially the coastal climates in the US. Many species of leafrollers exist throughout the US, and each of them retains a specific habitat, But their damages and management practices are almost the same. Archips argyrospila is a fruit tree leafroller that invades ornamental and fruit trees, whereas Obliquebanded and Omnivorous leafrollers specifically feed on fruit trees. Besides these two, Orange Tortrix and Apple Pandemic are the leafrollers of fruits and vines in coastal areas. Most leafrollers species remain ubiquitous throughout the year in coastal areas whereas, in the northern climate they overwinter for longer, and their infestation is not a concern. However, they are widely present in the southern locations in landscapes, orchards, and home gardens and demand effective controlling strategies.
Most leafrollers originated from South America or Africa, whereas some originated from Europe and Asia, especially India and China. One of the worst leafroller, Cydia pomonella, also originated from Europe and now exists throughout the apple-growing regions of the world, including North and South America. Cydia pomonella is also called a codling moth, and it bores holes in apple fruit. The fruit tree leafroller is prevalent in landscapes, valleys, and orchards in California. Similarly, omnivorous and oblique banded leafrollers dominate warm valleys and coastal climates of California. Apple pandemic, orange tortrix, and light brown apple leafrollers are the pests of the cool coastal climates. Besides, fruittree and oblique banded leafrollers, redbanded leafrollers damage most apple gardens in the Kentucky area. The bean leafroller is present throughout Florida and coastal regions from eastern Texas to South Carolina. It also lengthens its range to southeastern and southwest states in the US.
The leafroller caterpillars are found inside the leaf sheath that they curl upward and match it with the other leaf end. They are between two leaves within the silk webbing. The most distinctive feature that differentiates them from the caterpillars of other species is twisting backward rapidly when disturbed. After twisting the leaves, they often drop from the leaf But, their silky thread remains attached to their bodies. They may drop on the ground or keep hanging in the air and climb the leaf again. It is often difficult to differentiate leafroller caterpillars at hatching in spring. The caterpillars of all species are green except for the head and thorax that range from pale brown to black. However, they can easily differentiate at maturity. The obliquebanded leafroller caterpillar possesses a brown to black head and brown or dull green thorax. The pandemic leafroller caterpillar may have a pale green to pale brown head, and pale green thorax. The fruittree caterpillar contains a black head and the thorax remains white or light yellow front margins. The caterpillars of fruittree leafrollers are often smaller than the obliquebanded caterpillar. The European leafroller is also green with a brown head and a brownish thorax.
Most leafrollers species overwinter in larval forms under plant debris like weed covers and fallen leaves, whereas only fruittree leafrollers overwinter as eggs and have one generation per year. The eggs are laid on the twigs and other plant debris, including broadleaf weed covers and grasses. Eggs hatch in late spring or early summer, and the caterpillars feed on planting materials for almost 30 days. They spin a cocoon and pupate there, which is often constructed using a leaf sheath or a similar material. The caterpillars pupate for about 10 or 12 days, and the moths that emerge could hardly survive for a week. They mate and lay eggs in leaf-protected coverings. The eggs hatch next spring for fruittree leafrollers, while the species come out of the cocoons.
Leafroller caterpillars feed on tender shoots and leaflets giving them an untidy look, and they often roll the leaves using a silken thread and shelter within them. Severe infestation may defoliate a tree completely or partially, and silken threads are seen hanging down the tree branches and surfaces. Since the caterpillars often drop to the ground for pupation, the silken thread can also defoliate the leaves beneath their infestation sites. The leafroller caterpillars also attack fruits, and premature fruit could fall from the tree because of the indentations formed by their feeding.
Since most leafrollers overwinter in the larval form on twigs and tree branches, they emerge into the gardens in spring. Moreover, fruit tree leafrollers overwinter as eggs that hatch in the late spring or early summer and show their presence.
Besides following all preventions and cultural control practices if leafroller caterpillars damage remains prevalent on fruit trees, here are the most proven ways to suppress their population using the biological, organic, and chemical methodologies;
Ladybugs offer an extended biological control on most slow-moving caterpillars while they are most active as maximum damage during the larval stages of their development. Ladybugs often feed on the caterpillars of many species in the field, including the leafrollers and beetles. They are a powerful weapon to control many soft-bodied pests on the plants. When ladybug's eggs get spread in a garden, they hatch in 5-days and start feeding on caterpillars within the next 3-days. Adult ladybugs lay eggs on the surfaces of the leaves. The eggs hatch and the ladybug's larva becomes ready to feed on leafroller caterpillars in 7-days. Ladybugs also feed on the eggs of fruittree leafrollers besides attacking their caterpillars.
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About 1500 live bugs can effectively control pests of all categories in 1000 square feet area infested with caterpillars of many leafrollers species.
Green Lacewings are excellent predators that feed on crawlers, especially caterpillars of initial instars. They are also equally effective against many chewing and sap-sucking pests that damage leaves and fruits and often cause excessive defoliation. Chrysoperla rufilabris feeds on leafroller caterpillars when they appear in late spring or early summer, and the same is a good time a release them in a fruit garden. Releasing them with Trichogramma wasp is quite a successful strategy to make a garden free of all types of pests. Green Lacewing is also friendly with Ladybugs, and releasing them together is also highly beneficial. 1000 Green Lacewings are enough for 500 square feet when released in the greenhouse, and they could cover up to 2500 square feet when released in the garden.
Their eggs hatch in around 4 to 5 days, and this remains the best time to release them in the garden against leafroller caterpillars.
It contains 80% mineral oil, and it's the best dormant season spray that could either delay eggs hatching or kill the leafroller larvae and pupae preparing to overwinter in curled leaves or under plant debris on the ground. Typically, this horticultural oil is not a poison only suffocates the entire stages of leafrollers and kills them at the sites where they hibernate in winter. The best application time is before the bud break on fruits trees and before flowering in vegetables. It is also safe to spray on all edibles and an OMRI-listed product.
Mix 1.5 to 2.5 ounces of horticultural oil per gallon of water and thoroughly apply it to the foliage and stems of fruit trees during the dormant period.
Bonide-Oil contains Clarified Hydrophobic Extracts of Neem oil up to 70% concentrated form. Neem oil is also an exceptional dormant spray with ovicidal properties. Besides that, it is also an insecticide and a miticide together. If applied as a late dormant spray, it will not only deter leafroller caterpillars But, can kill them on coming into contact. Neem oil is one of the exceptional products allowed to use in organic gardening, and most formulations are OMRI-listed.
Mix between ½ to one ounce per gallon of water and spray on the foliage using a handheld mister.
Monterey- Garden Insect Spray contains 0.5% Spinosad that derives from Saccharopolyspora Spinosa, a naturally occurring soil bacterium registered National Organic Program in 2003. However, some formulations are not OMRI-listed. Spinosad may be used as the last resort when caterpillars are young and ready to feed on fruit trees' foliage. The mode of action for killing the caterpillars remains both inhibiting Gaba and Nicotinic Channels that cause rapid muscle contraction and dehydrating them.
Add 2 ounces of the product concentrate per gallon of water and apply to the foliage of fruit-bearing plants when caterpillars feed actively.
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authorities should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used lawfully, consistent with the product's label.
Check out our other guides on common garden bugs.
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