Effect of temperature and cultivar on pea aphid, Acyrthosiphon pisum (Hemiptera : Aphididae) life history

Life history parameters of the pea aphid, Acyrthosiphon pisum were studied at five constant temperatures on two cultivars of peas, Scout and Sancho. T he development and mortality of juveniles and the life-span, age-specific f ecundity and survivorship of adult aphids were recorded and used to constru ct life tables. The juvenile development period (from birth to adulthood) w as longest at 11.9 degreesC (16.8 days on cv. Scout and 16.2 days on cv. Sa ncho) and shortest at 26.7 degreesC (8.5 days on cv. Scout and 8.8 days on cv. Sancho). At all temperatures, except 26.7 degreesC, juveniles developed faster on cv. Sancho than on cv. Scout. On both pea varieties juvenile mor tality was highest at temperatures above 19.6 degreesC and lowest at 19.6 d egreesC. Highest cumulative juvenile mortality was recorded on cv. Scout at 26.7 degreesC when only 9% of aphids survived from birth to reproductively mature adults. Fecundity rates were unaffected by temperature in the range tested on cv. Sancho but increased with increasing temperatures between 11 .9 and 19.6 degreesC on cv. Scout. These differences in life history parame ters were reflected in the population growth (r(m)) of aphids on both pea c ultivars which increased with increasing temperatures between 11.9 and 23.1 degreesC on cv. Sancho and 11.9 and 19.6 degreesC on cv. Scout, declining thereafter. Population growth was consistently greater at all temperatures for aphids reared on cv. Sancho than those reared on cv. Scout.