Fireworm
(Rhopobota naevana)

Overview

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The species Rhopobota naevana corresponds to the common name of Black headed Fireworm, which is an important pest of cranberries. The insect over-winters in the egg stage. The eggs can be found on the underside of cranberry leaves and are yellow in colour. Newly hatched larvae burrow into the leaf near the egg, then move up to the growing tip of uprights or runners. Larvae may tunnel into unopened buds or web together terminal leaves of uprights with silk and feed inside this shelter or "tent." Each larva may make five or six tents before it pupates.

Main description

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The larvae of the Fireworm are typically caterpillar-like with a distinct head, and measure up to 1.5 cm long when fully grown. The larvae range from cream colour to greyish green and are covered in fine short hairs. The adult fireworm is greyish-brown, with the female being larger than the male.

Scouting

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When scouting for fireworm eggs, monitoring should be conducted in early spring to determine the number of over-wintering specimens. From five locations on each bed, collect 20 uprights and examine (with a hand-held magnifying glass) for the presence of eggs. The young larvae are the most damaging stage for the plants, so preventing the population increase by means of a timely and effective insecticide application at this stage of growth is very important.