Currant spanworm

The currant spanworm (Itame ribearia) is a moth species belonging to the order Lepidoptera and the family Geometridae. This pest is a well-known defoliator that specifically targets small fruit bushes, often causing significant damage to gooseberry and currant plantations in North America.

The host plants for this insect are primarily members of the Grossulariaceae family. The larvae exhibit a strong preference for foliage, but under high pressure, they may also consume buds and flowers. This leads to severe defoliation of the bushes, which prevents the plant from photosynthesizing efficiently and severely stunts berry production.

The life cycle of Itame ribearia follows a seasonal pattern typical for the family. The species overwinters in the egg stage, with eggs deposited on twigs and branches. Larvae emerge in the spring, coinciding with the bud-break of the host plants. They progress through several larval instars, feeding voraciously until they drop to the soil to pupate.

The primary damage is caused by the caterpillars, which have a characteristic looping movement. Their feeding leaves behind skeletonized leaves, leaving only the veins intact. In severe outbreaks, entire shrubs can be stripped of leaves within a matter of days, which causes great stress to the plant and increases susceptibility to diseases and winter injury.

Effective management requires a combination of monitoring and physical or chemical interventions. Key strategies include:

• Regular monitoring during the spring growth phase.
• Hand-picking larvae in smaller gardens or organic setups.
• Applying biological insecticides, such as Bacillus thuringiensis, if the threshold is reached.
• Removing debris from under the bushes to destroy pupating larvae.