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The "webby" Feed Problem
By T.E. Roudybush
For Exotic Bird Report Number 3 (1/1/1985)


A recurring and annoying problem faced by many aviculturists is “webby’ feed, which is a result of infestation by the Indian Meal Moth (Plodia interpunctella) or the Mediterranean Flour Moth (Anagasta kuhniella). In warm weather the Indian Meal Moth may pass through the egg, larval and pupal stages In 6 to 8 weeks, while the Mediterranean Flour Moth takes about 8 to 9 weeks. The small larvae hatch from eggs in a few days and as they mature may travel far from the original site of infestation. As they travel they spin silken threads, causing webbing and matting particles of feed. Later the full-grown larvae spin silken cocoons in which the insect pupates (Davis, et al., 1975).


The webbing and matting produced by the larvae of these moths clots feed so that it does not flow in gravity feeders, and nutrients used by the larvae are lost to the birds. This infestation can be controlled without using chemical pesticides by spraying the feed with spores of a bacterium (Bacillus thuringiensis). Spores that are eaten by the larvae become harmful bacteria in the insects’ gut and the larvae die. The spores, which germinate at a pH of 9 or higher, are not harmful to cockatiels or other birds that have been tested because the acidic nature of the gut contents of birds prohibits the germination of the spores. Ingestion of infected caterpillars has likewise been harmless to birds which have been tested. The spores are active only against the larvae, not the flying adults, hence the action is slow.


There are several products that contain the spores of B. thuringiensis, but some of them include liquid carriers that have not been tested on birds. One dry, wettable powder product, Dipel, is marketed by Acme Burgess, Inc., Chemical Division, Libertyville, Illinois, 60048, and is designed primarily to combat caterpillar infestations on plants.


Treatment of feed. To treat 50 pounds (22.7 kilograms) of feed, mix one rounded tablespoon (3.5 g) of Dipel in 1/2 to 1 cup (125-250 ml) of water in a plant mister. Spray the entire mixture onto the feed, mixing the feed as you spray. The Dipel need not be uniformly mixed, but no large amounts of feed should go untreated. Treated feed can be fed immediately after treatment. No new webs should appear after about a week; moths should disappear within two weeks. If the infestation continues, look for other infested material such as spilled feed, small feed containers that were overlooked, or flours or grains stored nearby.


Reference: Davis, S.C., A.S. Deal , V.E. Burton and J.E. Swift, 1975. Common Pantry Pests and Their Control, Leaflet 2711, Division of Agricultural Sciences, University of California.