Biology and fertility of Melanaphis sacchari at different temperatures

Since 2013, sugarcane aphid (Melanaphis sacchari) has emerged as an economically important sorghum pest in the southern part of the United States.  Among the factors that affect the aphid’s fitness, temperature is one of the most important.  Understanding sugarcane aphid’s population growth rates under different temperature regimes is  necessary for determining economic thresholds.  Moreover, temperature studies determine thermal thresholds that are important in predicting population peaks and geographic distribution.  Currently, there have been no studies published investigating the effect of temperature on sugarcane aphid.  The purpose of this study was to model development of M. sacchari under constant temperatures and to determine the upper developmental threshold.  Apterous adults were placed individually in 30 ml SOLO cups containing an excised leaf of grain sorghum on 10 ml of a 1% water-agar solution in growth chambers under constant temperatures ranging from 15 to 35°C.  After 24 h, the adult and all except one first instar nymph were removed.  All single first instars were the cohort for that temperature regimen for the duration of the experiment, 50 nymphs per cohort replicated three times.  Nymphal mortality, reproductive period, longevity, development time, daily and total reproduction were recorded and intrinsic rates of increase calculated.  Sugarcane aphid failed to reach adult at 35°C and developmental time was shortest at 30°C.  At 25°C, reproductive period was longest, with high daily and total reproduction, but at 15°C longevity was the higher.  This data will be used to predict sugarcane population dynamics in sorghum fields.