Diet rearing is sometimes the most productive and economical way to mass rear stem-borers, especially those of woody perennials. Singh (1977) defined an artificial diet as 'an unfamiliar food which has been formulated, synthesised, processed, and/or concocted by man, on which an insect in captivity can develop through all or part of its life cycle'. Smith and Wilson (1995) commented that 'use of artificial diet saves space and handling time, prevents cannibalism of younger larvae by older larvae, and reduces mortality that could occur if transferring larvae from stem to stem.' They added that 'it allows accumulation of larvae, manipulation of development rates using refrigeration to provide synchronous emergence ... and is a suitable medium in which to transport larvae...'.

Various artificial diets can be used to rear weed biological control agents. Wheatgerm-based diets (Adkisson et al. 1960; McMorran 1965), devised for rearing pest Lepidoptera, have been used for rearing stem-boring Lepidoptera for weed biological control. Gardiner (1970) modified McMorran's diet by including dried and ground host-plant material to successfully rear over forty different cerambycid beetle species, although none of these were biological control agents. Another diet for cerambycids was devised by Harley and Willson (1968) for Plagiohammus spinipennis an agent for lantana. This did not include dried host-plant material. Tomley (1990) modified the Harley and Willson (1968) diet for the Baccharis halimifolia cerambycid Megacyllene mellyi by substituting dried and ground B. halimifolia wood for the normal cellulose and reducing the water content. For rearing the clear wing moth Carmenta mimosa, a biological control agent for Mimosa pigra, Smith and Wilson (1995) modified a diet developed for the cerambycid Phytoecia coerulescens, an agent for Echium plantagineum, by adding dried and ground M. pigra leaves. The Phytoecia diet was based on the Harley and Willson (1968) diet and a Shorey and Hale (1965) diet for noctuids containing ground dried beans (Smith and Wilson 1995).

Hygiene is an important aspect of diet rearing. The diet medium should be produced, stored and dispensed under conditions as sterile as possible. Containers should be sterilised before use. Diet medium should be stored under refrigeration. It is important that each larva placed on diet is in an individual container or cell to prevent cannibalism and minimise cross-infestation by culture pests. Diet in use can quickly deteriorate due to feeding by the larva, therefore its condition should be monitored frequently. Particular attention should be paid to outbreaks of fungi or mites and to rancid odours. Larvae should be transferred to fresh diet before the old diet breaks down or becomes contaminated. Contaminated containers should be isolated from the others and decontaminated, using, for example, liquid chlorine bleach.

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