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 34°C), 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 29°C for 8 h significantly reduced survival, which decreased generally as the temperature increased."  They also determined that "exposing aphids to 32.5°C 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 1°C and MaxT [maximum daily temperature] of 1.3°C 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 2°C and MaxT of 2.6°C 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.