Green Fruitworms
Beginner
Scientific Name
Othosia hibisci (Guenee)
Identification
Eggs:
- 0.8 mm in diameter,
- 0.5 mm in height,
- White with a grayish tinge.
Larvae:
- 30-40 mm long,
- Lime to dark green colour, including the head,
- Small white spots cover the body with several white longitudinal stripes running the length of the caterpillar.
- 20-30 mm in length,
- 100 mm wide.
Adults:
- Dark forewings and hind wings that are much lighter,
- Wingspans of 25-40 mm.
Often Confused With
- Leafroller injury- The deep corky feeding scars of green fruitworm are difficult to distinguish from leafroller injury.
Period of Activity
Green fruitworm begins emerging in early spring. Their eggs are laid on new leaves forming on trees. After the eggs hatch, they begin feeding on leaves and the forming fruit. Green fruitworms are only active in orchards until early summer.
Scouting Notes
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.
Scouting for green fruitworms follows the same procedure as all spring-feeding caterpillars. 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.
Thresholds
An insecticide is generally recommended when the action threshold of 12-15 larvae per 100 terminals and fruit buds is observed.
Advanced
Scientific Name
Othosia hibisci
Identification
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. 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.
Often Confused With
- Leafroller injury- The deep corky feeding scars of green fruitworm are difficult to distinguish from leafroller injury.
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.
Period of Activity
Green fruitworm begins emerging in early spring. Their eggs are laid on new leaves forming on trees. After the eggs hatch, they begin feeding on leaves and the forming fruit. Green Fruitworms are only active in orchards until early summer.
Scouting Notes
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.
Scouting for green fruitworms follows the same procedure as all spring-feeding caterpillars. 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.
Thresholds
An insecticide is generally recommended when the action threshold of 12-15 larvae per 100 terminals and fruit buds is observed.
Management Notes
- Many predatory and parasitic insects attack spring-feeding caterpillars. Predators include ground beetles (Carabidae), stink bugs (Pentatomiidae), assassin bugs (Reduviidae) and spiders. 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. For information on the toxicity of pesticides to beneficial insects click here. Depending on spring temperatures, timing of this spray may occur either pre-bloom (usually at pink) or at petal fall.
- Birds such as chickadees, bluebirds, warblers and woodpeckers also feed on caterpillars but rarely provide economic control.
- 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.
- Insecticide options are provided in OMAFRA Publication 360, Fruit Crop Protection Guide - Chapter 2 Apples or Apple Calendar only :
- Recommendations for green fruitworm at Tight cluster, as well as in Non-bearing orchards
