Spring-feeding caterpillars

Excerpt from Publication 310, Integrated Pest Management for Apples,
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Table of Contents

  1. Introduction
  2. Leafrollers
  3. Green fruitworms
  4. Eye-spotted bud moth
  5. Tent caterpillars
  6. Gypsy moth

Introduction

The spring-feeding caterpillar complex is comprised of several species of Lepidoptera (moth family). These include leafrollers, fruitworms, cankerworms, budmoths and tent caterpillars. In general, these caterpillars are active early in the season, from half inch green to mid June.

Leafrollers

There are numerous species of leafrollers belonging to a family of moths called Tortricidae that attack apple. These include the redbanded leafroller, Argyrotaenia velutinana (Walker), variegated leafroller, Platynota flavedana (Clemens), fruit tree leafroller, Archips argyrospila (Walker), and obliquebanded leafroller, Choristaneura rosaceana (Harris). The leafroller currently causing the greatest concern in Ontario is the obliquebanded leafroller (Figure 4-44). Development of organophosphate resistance has taken obliquebanded leafroller from a minor nuisance to a major pest of apples. Cross resistance to pyrethroids and certain insect growth regulators is also documented in some obliquebanded leafroller populations. Other leafrollers have minor pest status in Ontario. They may be a problem in orchards using reduced-risk pesticide programs or in situations where mating disruption for other species is implemented.

Figure 4-44. Obliquebanded leafroller larvae

Figure 4-44. Obliquebanded leafroller larvae

Description

For a description of obliquebanded leafroller see Obliquebanded leafroller.

Biology

Most leafroller species overwinter as larvae in hibernacula or as pupae. However, the fruit tree leafroller overwinters as an egg. There are two generations of most leafroller species. Female moths lay eggs on the upper surface of leaves in flattened, overlapping clusters of 20-200 pale yellow to brownish eggs. Leafrollers become active as soon as green tissue is visible, feeding on young developing leaves or boring into buds. As the leaves expand, larvae begin to web and roll terminal leaves, where they remain hidden when not feeding. Leaf feeding, if severe, can reduce photosynthetic activity. Leafrollers quickly become a major problem in nursery plantings and newly planted orchards if not controlled (Figure 4-45). Some leafroller species suspend themselves from silken threads, allowing them to disperse to other trees with the slightest breeze. Infestations are often most severe around the orchard periphery and adjacent to wood lots.

Figure 4-45. Leafroller damage to young orchards

Figure 4-45. Leafroller damage to young orchards

Damage

Leafrollers are general feeders, consuming leaves of many species of fruit and shade trees. Leafrollers also feed on blossoms and developing fruitlets. Early season feeding causes large corky scars and indentations on the fruit (Figure 4-46 and 4-47) - which often drops prematurely. Summer feeding on developing fruit results in downgrading of apples to juice quality (Figure 4-48).

Figure 4-46. Aborted fruitlet from early season caterpillar feeding

Figure 4-46. Aborted fruitlet from early season caterpillar feeding

Figure 4-47. Early season damage at harvest

Figure 4-47. Early season damage at harvest

Figure 4-48. Late season injury to fruit

Figure 4-48. Late season injury to fruit

Monitoring and threshold

Spring-feeding caterpillars feed on a wide variety of deciduous trees and shrubs, herbaceous plants and brambles.They are most often detected in apple trees at the perimeter of the orchard adjacent to alternative hosts. Many species are also dispersed deeper into the orchard interior by wind currents, so do not restrict monitoring to orchard perimeters.

In early spring, tiny larvae in buds and developing terminals are difficult to detect without pulling the plant tissue apart and observing with a 10-16x hand lens.

During the period between tight cluster to petal fall, check 5 terminal shoots and 5 fruit buds in each of 10 trees (50 terminals and 50 fruit buds in total) for signs of caterpillar feeding activity. An insecticide is generally recommended when the action threshold of 12-15 larvae per 100 terminals and fruit buds is observed.

Management

Many predatory and parasitic insects attack spring-feeding caterpillars. Predators include ground beetles (Carabidae), stink bugs (Pentatomiidae), assassin bugs (Reduviidae) and spiders. Birds such as chickadees, bluebirds, warblers and woodpeckers also feed on caterpillars. Parasitic wasps (Braconidae, Ichneumonidae) and flies (Tachinidae) attack caterpillars and minute Trichogramma wasps often parasitize moth eggs. A number of fungal and viral diseases also impact caterpillar populations, particularly during warm, wet springs. However, beneficial insects are not usually effective in providing economic control. To conserve and encourage natural enemies of spring-feeding caterpillars, apply insecticides only if the action threshold is reached and then select the most benign and narrow-spectrum materials available.

Depending on spring temperatures, timing of this spray may occur either pre-bloom (usually at pink) or at petal fall. Insecticide options are provided in OMAFRA Publication 360, Fruit Production Recommendations.

Green fruitworms

The most common species of green fruitworm in Ontario orchards is the speckled green fruitworm, Othosia hibisci (Guenee).

Description

Eggs are 0.8 mm in diameter and 0.5 mm in height, and white with a grayish tinge. The full grown caterpillar is quite large, 30-40 mm long and a lime to dark green colour, including the head (Figure 4-49). Small white spots cover the body with several white longitudinal stripes running the length of the caterpillar. Pupae are 20-30 mm in length about 100 mm wide. Adults have dark forewings and hind wings that are much lighter. Moths have wingspans of 25-40 mm.

Figure 4-49. Green fruitworm larva

Figure 4-49. Green fruitworm larva

Biology

The pupa overwinters underground. Moths - members of the Noctuidae family - emerge in early spring. After mating, eggs are laid singly on developing leaves and are whitish grey with distinct ridges on the sides, visible when viewed through a microscope. Larvae, resembling tiny inchworms when they first hatch, feed on buds, leaves, blossoms and developing fruitlets. There is only one generation per year.

Damage

The deep corky feeding scars are difficult to distinguish from leafroller injury. Approximately 70% of attacked fruit will abort prior to or during June drop. Larvae often feed extensively on one fruit, but sometimes can damage up to a dozen or more.

Monitoring and threshold

For monitoring and thresholds for all spring-feeding caterpillars, see the leafroller section.

Management

For management options for all spring-feeding caterpillars, see the leafroller section.

Eye-spotted bud moth

The eye-spotted bud moth, Spilonota ocellana (Denis and Schiffermullar), is an occasional pest of apples in Ontario.

Description

Eggs are oval and 0.8 mm in size, creamy white in colour initially, and turn yellow over time. Larvae are chocolate brown, and the head varies from medium brown to black. Mature larvae are 9-14 mm in length (Figure 4-50). Pupae are golden grown and 6-7 mm in length. Adult moths are gray brown with a 12-16 mm wingspan. The forewing is darker with a series of light streaks on the outer part.

Figure 4-50. Eye-spotted budmoth larvae

Figure 4-50. Eye-spotted budmoth larvae

Biology

The eye-spotted bud moth overwinters as a partially grown larva within a silken case attached to the base of spurs and twigs. Larvae become active in early spring, when apples reach the half inch green stage. The insect burrows into, and feeds on, opening flower buds and forms shelters by tying leaves together. Bud moth larvae also burrow into developing shoots, causing economic damage in nursery and non-bearing plantings when infestations of the pest occur.

Larvae pupate after five to seven weeks and emerge as small moths with grey and white markings and resemble bird droppings when at rest. A second generation is active in mid July through early August. Young larvae from this generation feed on leaf undersides and construct shelters of leaves and frass. Fruit in contact with infested leaves may also be attacked.

Damage

Feeding injury is characterized by tiny, shallow, circular excavations on the fruit surface (Figure 4-51), similar to injury from summer generation obliquebanded leafroller.

Figure 4-51. Eye-spotted bud moth injury to fruit

Figure 4-51. Eye-spotted bud moth injury to fruit

Monitoring and threshold

For monitoring and thresholds for all spring-feeding caterpillars, see the leafroller section.

Management

For management options for all spring-feeding caterpillars, see the leafroller section.

Tent caterpillars

Eastern tent caterpillars are sometimes found in orchards located near deciduous woods and can cause extensive defoliation on localized branches or limbs.

Description

The full-grown larva is 40-50 mm in length, hairy and brownish black with blue spots along the body and a white stripe running the length of the back. Eggs are golden brown masses encircling young twigs. Adults are reddish brown with two distinct pale stripes that run diagonally across each wing.

Biology

The eastern tent caterpillar, Malacosoma americanum (family Lasiocampidae), overwinters as egg masses encircling young twigs (Figure 4-52), which are often detected during winter pruning. Each egg mass has 200-300 eggs. Eggs hatch in early spring and young larvae spin a characteristic tent in a limb crotch (Figure 4-53) - where they reside as a colony - only leaving to feed on newly developing leaves in mornings and evenings. Adult moths emerge in late June with egg laying occurring in July.

Figure 4-52. Eastern tent caterpillar egg masses

Figure 4-52. Eastern tent caterpillar egg masses

Figure 4-53. Eastern tent caterpillar nest in tree

Figure 4-53. Eastern tent caterpillar nest in tree

Damage

One colony can strip the leaves of whole branches. Fruitlets on these branches fail to develop. There is only one generation per year.

Monitoring and threshold

Take note of tent caterpillar activity during regular orchard inspections while monitoring for other pests.

Management

Tent caterpillars do not require insecticide treatment. Pruning out of infested branches is the most practical approach.

Gypsy moth

The gypsy moth, Lymantria dispar (Linnaeus), is normally considered a forest pest. It is native to southern Europe, northern Africa, central and southern Asia and Japan, and was introduced into North America with the intent of developing a strain of silk moth resistant to disease. Some of the caterpillars escaped, and outbreaks of this pest have significant affects on hardwood forests. Gypsy moth often move into the orchard from adjacent woodlots.

Description

Egg masses contains from 300-1,000 eggs and are covered with a fibrous mat of hairs. They are buff colored initially, and later bleach with exposure. Larvae are yellow, gray or black with long wispy hairs. Starting just after the head, there are five pairs of blue spots followed by six pairs of red spots down the back. These spots distinguish gypsy moth larvae from any other large, hairy larvae. Mature larvae are about 6-7 cm in length (Figure 4-54). Gypsy moth pupae are covered with brown, tear-drop shaped protective shells about 2.5-5 cm long. Adult moths are black and white. The female has white wings with black patterns, and males have dark gray wings with lighter coloured patterns. Full grown larvae are 30-65 mm in length and very hairy. Adult females cannot fly and rely on pheromones to attract males for mating.

Figure 4-54. Mature gypsy moth larva

Figure 4-54. Mature gypsy moth larva

Biology

Gypsy moth overwinters as egg masses of 100-1,500 eggs on tree trunks and the undersides of branches and bark. The egg masses hatch in the spring and larvae emerge and begin feeding on leaves. Larvae pass through five to six larval instars, then enter the pupal stage in mid summer. First to third instar larvae feed from dawn to mid morning, then seek shelter from the heat of the day under bark or in ground cover. Fourth to sixth instars feed at night from sunset to sunrise, but if population density is high larvae will feed day and night. The larva stage lasts approximately 40 days from egg hatch to pupation, and the pupal stage lasts about two weeks. Overwintering eggs are laid in August and December. There is only one generation per year.

Damage

Larvae chew on the leaves, leaving small holes referred to as shothole feeding on the leaf (Figure 4-55). When not feeding, they rest on a mat of silk they make on the underside of the leaf.

Figure 4-55. Gypsy moth "shothole" feeding injury on leaves

Figure 4-55. Gypsy moth "shothole" feeding injury on leaves

Monitoring and threshold

For monitoring and thresholds for all spring-feeding caterpillars, refer to the leafroller section. Take note of gypsy moth activity during regular orchard inspections while monitoring for other pests.

Management

For management options for all spring-feeding caterpillars, refer to leafroller management.


For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca


Author: OMAFRA Staff
Creation Date: 21 July 2011
Last Reviewed: 21 July 2011