By Alain VanRyckeghem, BCE
The rice moth can be considered the Indianmeal moth of the tropics. It is found in Hawaii and occasionally in some southern U.S. ports. It is much less common on the mainland than the Almond moth, (Ephestia cautella), which it is often misidentified. The larvae are general feeders and prefer warm climates and occur commonly in the equatorial regions of Asia, Africa, and Caribbean.
The adult moth is grey, often with darker spots or venation on the wings; the under wings are off white. The wingspan is 20-23 mm. The tips of the wings are more rounded than those of the Ephestia spp moths. The larva of the rice moth will grow to 15 mm long and are white or cream in color. The body is covered with fine hairs. A good clue that rice moth larvae are present is the excessively thick layers of webbing.
This moth undergoes a complete life cycle in as short as 26 days in warm (88°F; 31°C) humid (70% rh) conditions to as long as 75 days under cooler temperatures. The female will lay 100 to 200 eggs over her short life span of one to two weeks. The eggs will not hatch at temperatures below 61°F; 16°C and pupae will fail to emerge above 100°F; 38°C. Eggs will also fail to hatch below 20% rh. Larvae develop in 33-55 days under average conditions.
BIOLOGY AND BEHAVIOR
The rice moth is a major pest of flour mills in the tropics. It is a general feeder and can be found infesting stored millet, sorghum, rice, cocoa beans, biscuits, flour, and other seeds. The rice moth populations develop well in hot damp or dry (> 20% rh) areas. These moths can infest mills and storage areas simultaneously with Almond moths.
The moth is usually seen in large numbers on walls, poles, or containers where grains are stored. The larvae are exceptionally good at producing “paper thick” webbing for its cocoons. The caterpillars produce a large amount of frass (in which they hide) compared to other stored food moths. This material can attract other stored food pests such as Flour
beetles (Tribolium spp).
This species of moth is especially sensitive to cold temperatures. Control and prevention of infestation can be easily achieved if product is stored below 59°F; 15°C. Eggs will not hatch and larvae will die. Heat treatment may be available as well if internal temperatures of stored foods can reach 95°F; 35°C for 24 hours.
Fumigation is one of the most effective ways of killing all stages of this insect in commodities and buildings. Fogging with a 0.5% pyrethrin is recommended only for knocking down exposed adult stages. Use of longer lasting synthetic pyrethroid and insect growth regulators in a fog will give superior results.
Both male and female moths produce pheromones that attract each other. The moths are excellent fliers and a typical grid pattern can be established to monitor for their presence and population trends. These moths will not be attracted to the pheromones of other stored food moths such as Indianmeal moths and Almond moths. Separate traps and lure combinations should be used in order to monitor each species efficiently if both species are present.