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Global Warming and the Rose Grain Aphid
Ma, C.S., Hau, B. and Poehling, M.-M. 2004. The effect of heat stress on the survival of the rose grain aphid, Metopolophium dirhodum (Hemiptera: Aphididae). European Journal of Entomology 101: 327-331.

What was done
In the words of the authors, "detailed experiments were conducted on the effect of high temperature (27, 28, 29, 30, 31, 31.5, 32.5, 33 and 34C), period of exposure (2, 3, 4, 6 and 8 h per day for 1, 2, 4, 6 days) and developmental stage (2nd, 3rd, 4th instar nymph and adult) on the survival of the aphid [Metopolophium dirhodum (Walker)]," which they say "is the most abundant of the three cereal aphid species in Germany and central European countries."

What was learned
Ma et al. report that "temperatures over 29C for 8 h significantly reduced survival, which decreased generally as the temperature increased." They also determined that "exposing aphids to 32.5C for 4 h or longer significantly reduced survival" and that "mature aphids had a lower tolerance of high temperatures than nymphs."

What it means
In light of what they observed in their experiment, as well as what a number of other scientists have observed, Ma et al. conclude that "global warming may play a role in the long-term changes in the population abundance of M. dirhodum." Specifically, they note that "an increase in TX [daily average temperature] of 1C and MaxT [maximum daily temperature] of 1.3C during the main period of the aphid population increase would result in a 33% reduction in peak population size," while "an increase in TX of 2C and MaxT of 2.6C would result in an early population collapse (74% reduction of population size)." Consequently, a little global warming could greatly decrease aphid infestations of cereal crops grown throughout Germany and Central Europe.

Reviewed 22 September 2004