Tiny Inchworms Devouring Japanese Holly: Organic Control Options

A homeowner in Scotch Plains, New Jersey, discovered a severe infestation of minuscule inchworms—barely 1/16 to 1/8 inch long—inside the leaves of a Japanese holly hedge. The pests were so numerous they produced an audible crunching sound when disturbed, and the foliage showed yellowing and spotting.

While horticultural oil spray is a viable treatment, a highly effective organic alternative is Bacillus thuringiensis (BT), sold under brand names like Dipel or MVP. This naturally occurring bacterium specifically targets caterpillars and worms without harming humans, pets, or beneficial insects. Applied as a dust, BT disrupts the pests' digestive systems within days. It's widely available at garden centers and through online retailers such as Gardens Alive.

For best results, apply BT when the worms are actively feeding, and repeat as needed. Combined with good cultural practices—like proper watering and pruning to improve air circulation—this approach can rescue the hedge without resorting to harsh chemicals.