Western tent caterpillar

Systematic position: The Western tent caterpillar (Malacosoma californicum) belongs to the order Lepidoptera, family Lasiocampidae. It is a well-known defoliator that periodically experiences outbreaks, causing significant ecological and economic impact in orchards and forests.

Host plants: This species is a generalist feeder with a wide range of hosts. It primarily targets fruit trees such as apple, cherry, and plum. Additionally, it frequently infests deciduous trees like poplar, aspen, willow, and oak, often causing visible damage in both urban and wildland settings.

Biology and life cycle: The species completes one generation per year. It overwinters in the egg stage, which is usually deposited in ring-like masses around small twigs. In early spring, larvae hatch and begin to feed gregariously. A defining behavior is the construction of silken tents, which serve as communal resting places during the larval stage.

Damage and pest status: Larvae feed on foliage, initially skeletonizing leaves and later consuming the entire leaf blade. During population peaks, heavy infestation can lead to complete defoliation of host trees. This loss of canopy significantly stresses the tree, reduces photosynthetic activity, and can lead to branch dieback or reduced fruit quality in agricultural settings.

Control measures:

• Physical removal of egg masses during winter pruning.
• Manual pruning and destruction of larval tents before larvae mature.
• Application of biological insecticides containing Bacillus thuringiensis (Bt).
• Use of registered chemical insecticides if the infestation levels exceed economic thresholds.