Indian meal moth
Plodia interpunctella (Hübner)

Order: Lepidoptera
Family: Pyralidae
Acronym: PIN

Ecology

The Indian meal moth, of Old Word origin, is now found across Canada. It is an important pest in many granaries, homes, stores and processing facilities.

Damage

The larvae feed on grains, nuts, peas, beans, dried fruits and other dried foodstuffs. Only broken kernels of grain and grain dust are attacked as larvae cannot penetrate undamaged grain. Infested foodstuff is covered with silky webbing and excretion from the larvae, rendering it unsightly and inedible. In addition the webbing sometimes clogs milling machinery.

Life history

In unheated buildings, Indian meal moths overwinter in the larval stage. In heated buildings, feeding and breeding continue through the winter. The larvae are dirty white, though often they have a distinct green or pink tint, depending on the food they have consumed. When full grown they reach a length of 13 mm. The growth and development of the larvae is highly temperature dependent, taking anywhere from 2 weeks to 2 years for them to reach maturity. The larvae pupate in a silken cocoon on the surface of the food material or nearby. Moths emerge in 4 to 30 days. Adult moths are 10-12 mm long, with a wingspan of 2 cm. The front one-third of their forewings are pale grey to tan, the back two-thirds reddish-brown to dark grey. The minute white eggs are laid in clusters of 12 to 30 in or near a suitable larval food source. In heated buildings there may be six generations per year.

Control

In stored grain and associated processing facilities, the Indian meal moth can be readily managed by thorough sanitation, monitoring, and control practices. As adult moths fly, it is important to clean and monitor upper areas of storage structures. Mass trapping and exposure to cold temperatures are effective means of non chemical control.

Images

Adult Indian meal moth

Clemson Univ./USDA CES, Bugwood.org
Adult Indian meal moth.

Clemson Univ./USDA CES, Bugwood.org
Larva of an Indian meal moth.