Identification of Worms on Blueberry Bushes

Cranberry Fruitworm Identification

• The adult cranberry fruitworm has a gray-black body and is very small, only 6 mm or 1/5 inch in length when it's a moth. It lays flat, rounded, milk-colored eggs on fruit and shoots. Larvae first appear inside fruit in June and are pink in color. You can differentiate between cranberry and cherry larvae by the tiny hairs located at the abdomen's end, found only on cranberry larvae. The cherry fruitworm has a pink-red body with a brown-black head.

Cherry Fruitworm Identification

• A mature cherry fruitworm grows up to 11 mm or 1/2-inch in length in its moth stage. It has two gray-brown forewings on its back that each has unique, whitish triangle markings. It produces eggs that initially appear white, then turn yellow and finally orange before hatching. Eggs are usually visible on fruit and shoots. Like the cranberry fruitworm, the cherry fruitworm's larvae are also found in fruit in June. Cherry larvae are very light yellow-green in color with dark heads, and they have a length of 15 millimeters or 3/5-inch, nearly twice as long as cranberry fruitworms.

Damage

• Both the cranberry and cherry fruitworms consume immature fruit, which leads to premature ripening, diminishing quality yields. Although the cranberry fruitworm enters up to two berries during its life cycle, the cherry fruitworm infiltrates as many as six, so crop destruction is more widespread. Each fruitworm type produces silk webbing used to travel from berry-to-berry. A mass of silk webbing between berries is generally a good indication of the presence of fruitworms.

Control

• Employ the same control methods for eliminating both cranberry and cherry fruitworms. Parasitic wasps attack fruitworms and their larvae, and offer a decent biological control when combined with a low toxicity insecticide that doesn't harm predatory wasps. Use a chemical control, such as an insect growth regulator, during the egg-laying phase. Spray the insecticide on blueberry bushes, making sure to completely cover blossoms and shoots to eliminate larvae. The insecticide is most effective immediately after the larvae hatch before they penetrate the berry. Once the larvae enter the berry, a chemical control is much less effective, as the berry serves as a barrier.