Attempts to develop artificial diets for the Colorado potato beetle, Leptinotarsa decemlineata (Say), have had limited success (Hsiao 1972; Krzymanska and Zwolinska-Sniatalowa 1980). Consequently, all available rearing methods require the use of fresh potato foliage (e.g., de Wilde 1957) and large greenhouse space over an extended period of time. We needed a rearing method that could produce batches of beetles < 1 week old and with synchronized emergence (± 3 days) from a small laboratory colony of < 100 pairs of adults. One method might have been to induce adult diapause and break it whenever sufficient numbers had accumulated for testing. Unfortunately, this method requires mature adults that have fed for 1–2 weeks. not her procedure used in rearing a number of insect species uses a period of low temperature storage. For example, 2nd instar Choristoneura fumiferana (Clem.) can be stored at 1°C for 4–8 months (Grisdale 1970). Wegorek (1959) suggested that the hatching of eggs of L. decemlineata could similarly be delayed by placing them at relatively low temperatures. Wegorek observed that the incubation period of the eggs in Poland could take < 8 days in warm weather but last as long as 19 days in periods of cool weather when the temperature fell below 15°C. The feasibility of using this temperature dependence for incubation in our rearing program was investigated.

Corn lodging due to bent or broken stalks results mostly from feeding by the European corn borer, Ostrinia nubilalis (Hübner), and from stalk rot infections. Stalk rot of corn (Zea mays L.) is caused in southwestern Ontario mainly by Gibberella zeae (Schw.) Petch (Fusarium graminearum Schwabe), which attacks roots during the summer and invades the bases of the stems as the plants mature (Gates and Mortimore 1972). Several studies in the U.S.A. reported an association between the rot and the borer. Christensen and Schneider (1950) recorded severest stalk rot with highest borer infestation and found that inbred lines usually free from rot became susceptible when infested by the borer. Chiang and Wilcoxson (1961) reported a higher incidence of rot in plants artificially inoculated with Fusarium graminearum and borer larvae than in those inoculated with F. graminearum alone. A recent study in Iowa (Jarvis et al. 1982) showed that the greatest stalk rot damage occurred in high borer infestations. Carson and Hooker (1981), however, were unable to relate the incidence and severity of rot to corn borer infestation. In their 3-year study, the least rot occurred in the year of severest borer infestation. Since observations in corn fields in southwestern Ontario also indicated that there might not be a direct relationship between severity of stalk rot and severity of corn borer infestation, further studies were undertaken.

Western false hemlock looper, Nepytia freemani Munroe, is a cyclical pest in British Columbia which defoliates mainly Douglas-fir, Pseudotsugata menziesii (Mirb.) Franco, often near residential areas. Outbreaks were recorded from 1947 to 1949, 1963 to 1964, and 1972 to 1976; the current outbreak started in 1980 and, in 1982, covered 1,100 ha near Tappen, Canoe, Enderby, and Carquile (Ferris and Woensdregt 1983).

The pea aphid, Acyrthosiphon pisurn (Harris), is a serious pest of alfalfa (Medicago sativa L.) and is known to reduce the cold-hardiness of seedling alfalfa (Harper and Freyman 1979). To determine whether or not pea aphids also reduce cold-hardiness in older alfalfa, plants were grown in the field for 1, 2, or 3 years, then tested for cold-hardiness under controlled conditions of infestation, hardening, and freezing.