Beginner

Scientific name: Helicoverpa zea

Identification:

• Damage in tomatoes consists of deep holes or burrows, typically in green fruit
• Larvae is often found inside the fruit
• Larvae range in colour from yellowish, to green or brown. They have a fine double stripe running down the length of their backs. They grow up to 4 cm (1.5 in.) long.

Period of activity: Adult moths usually appear in mid-to-late July, or earlier, depending on the season. In cooler years, Northern and Eastern Ontario growing areas may not experience corn earworm at all.

Scouting notes: Pheromone traps can be used to monitor tomato fruitworm (corn earworm) populations. Fruit can be inspected for damage and for larvae inside fruit.  A large hole will be visible if the larvae has entered the fruit.

Thresholds: The pest is not usually found at economically damaging levels in tomato. However, a threshold of 7 moths/trap/week is a trigger for intensive scouting.

Advanced

Scientific name: Helicoverpa zea

Identification: Damage in tomatoes consists of deep holes or burrows, typically in green fruit. The larvae is often found inside the fruit. Rotting of the fruit soon follows.

Larvae range in colour from yellowish, to green or brown. They have a fine double stripe running down the length of their backs. They grow up to 4 cm (1.5 in.) long.

The adult is a buff or tan-coloured moth with a wingspan of 3.5 to 4 cm (1.25 to 1.5 inches).  The forewing may have several darker markings and always has a central brown dot, clearly visible on the underside of the wing and faintly visible from the top.

Earworm eggs are laid individually on corn silks.  In tomatoes they are laid on the underside of leaves near flowers or fruit.  Each egg is perfectly round and about the same colour and diameter as a corn silk. Tomatoes are attractive egg-laying sites during flowering and fruiting, especially if surrounding corn is not in an attractive stage for egg-laying.

Biology: Corn earworm do not overwinter in Ontario. They move from the U.S. and Mexico on tradewinds.

Period of activity: Adult moths usually appear in mid-to-late July, or earlier, depending on the season. In cooler years, Northern and Eastern Ontario growing areas may not experience corn earworm at all.

Earworm activity is highest in hot weather conditions. Peak flights often occur immediately after severe thunderstorms.

Scouting notes: Pheromone traps can be used to monitor tomato fruitworm (corn earworm) populations. Fruit can be inspected for damage and for larvae inside fruit.  A large hole will be visible if the larvae has entered the fruit.

Thresholds: The pest is not usually found at economically damaging levels in tomato. However, a threshold of 7 moths/trap/week is a trigger for intensive scouting.

Management Notes:

• Pyrethroid insecticide resistance has been identified in tomato fruitworm (corn earworm) populations arriving from cotton-growing regions of the Southern States.  Use an insecticide from a different chemical family when pest pressure is high or the crop is susceptible to damage.
• In tomatoes, treatment is only necessary during flowering, as the females will not lay eggs in tomatoes after this stage. If trap counts reach threshold and scouting indicates high numbers of eggs or larvae, insecticide treatment may be needed.
• Insecticide treatments in tomatoes are most effective if applied prior to egg hatch and before larvae enter the fruit.