Melonworm
Diaphania hyalinata
Lepidoptera: Pyralidae
The Melonworm occurs throughout most of Central and South America and the Caribbean.
Host plants and damage
Primary hosts are Cucurbitacae. Especially attacked are Cucumis sativus (cucumber), Cucumis melo (melon), Cucurbita moschata (pumpkin), Momordica charantia (bitter gourd), but also Zea mays (maize), and Vigna unguiculata (cowpea).
Adult moths attack host plants during vegetative and generative growth stages. Melonworm larvae feed primarily on foliage, but attacks also fruits/pods, and stems. Young larvae feed on fruit surface, if larvae become older they can burrow into fruits. Because they cause scars on fruit surfaces growers refer to them as rindworms.
Morphology & biology
Females deposit eggs in small clusters during the night on host leaves, buds and stems. They are initially white or light green and turn later yellow.
Larvae hatch after 2-4 days and have two dorsal white stripes on the length of the body. There are five instars and the last one a length of up to 18 mm length. During daytime older larvae they hide in a loose silk structure on the underside of leaves.
Adult moths have velvety black wing margins with lighter, pearly-white areas. The wingspan is about 2.5 cm. Moths are generally inactive during daytime.
The Melonworm can complete its life cycle in about 30 days.
Monitoring
Sex pheromones are identified but not yet commercial available. Therefore check plants for early stages of leaf damage.
Pest management
Biological control
Among the natural enemies of the melonworm are the Braconidae Hypomicrogaster diaphaniae () and Pristomerus spinator ().
In Puerto Rico parasitism by Tachinidae flies, Nemorilla pyste () and Stomatodexia cothurnata () can reach 24 %.
Bacillus thuringiensis is commonly used for controlling melonworms.
Cultural control
D. hylinata prefers squash to most other host plants. This offers the possibility of using squash as trap crop.
Chemical Control
D. hyalinata feeds preferred on the foliage and is relative easy to control with insecticides. There are no resistances to insecticides reported yet.