INFLUENCE OF TEMPERATURE ON CONTACT AND VOLATILE TOXICITIES OF APHICIDES AGAINST THE GREEN PEACH APHID, MYZUS PERSICAE (SULZER) (HOMOPTERA: APHIDIDAE)

Abstract

Laboratory studies indicated positive temperature coefficients for 6 aphicides when applied directly to the green peach aphid, Myzus persicae (Sulzer) on spinach, Spinacia cleracea L., leaves, at 32, 24, 16, or 8°C. At 32°C order of toxicity was RH7988 > pirimicarb > mevinphos > phosphamidon > acephate > dimethoate. Although the relative order of contact toxicity did not change as temperature was reduced, temperature coefficients varied from +5.15 for dimethoate to +1.47 for RH7988. Thus low temperature adversely affected contact activity of dimethoate more than RH7988. Mevinphos and pirimicarb were the only tested compounds that produced substantial GPA mortality through volatile activities. Furthermore, their effectiveness was reduced at low temperatures as indicated by positive temperature coefficients. Data from this study demonstrate the necessity of applying presently registered spinach aphicides, i.e., dimethoate and mevinphos, at warm temperatures. As additional aphicides become available for cool season crops such as spinach, this necessity may not be as critical.