Citheronia

The genus Citheronia belongs to the family Saturniidae, order Lepidoptera. These moths are widely known for their impressive size and the distinct appearance of their larvae. The most iconic species, Citheronia regalis, also known as the Royal Walnut Moth, is a significant defoliator in North American orchards and forests.

The larvae primarily target host plants within the Juglandaceae (walnut family) and Rosaceae families. Trees such as hickory, walnut, persimmon, and various fruit trees are vulnerable to infestation. While they are often viewed as a curiosity due to their size, their feeding capacity can be detrimental to young trees or nursery stock if left unmanaged.

The biology of Citheronia is characterized by a single generation per year in most regions. The adult moths emerge in early summer, mate, and deposit eggs on host leaves. The larvae go through five distinct instars, increasing their food intake significantly as they grow. They eventually descend to the ground to pupate in the soil, entering a stage of hibernation until the following spring.

The damage caused by these insects is primarily defoliation. As the larvae grow, they consume large amounts of leaf tissue, often starting from the edges or the tips of leaves. A high population of larvae can strip a tree of its foliage, leading to physiological stress, reduced sugar storage in roots, and a decrease in the overall vigor of the tree for the following growing season.

Management strategies focus on monitoring and early intervention. For small-scale plantings, hand-picking the larvae is the most effective approach. For larger areas or commercial settings, application of Bacillus thuringiensis (Bt) is highly effective, as it specifically targets lepidopteran larvae while sparing beneficial predatory insects. Maintaining healthy tree vigor through proper fertilization and watering also helps trees withstand limited defoliation.

• Regular monitoring of tree canopy during mid-summer.
• Manual removal of caterpillars from smaller trees.
• Application of bio-rational insecticides when larvae are small.
• Tilling the soil beneath host trees to disrupt pupation.