Effect of Pretreatment Environment on 2,4-D Phytotoxicity

Abstract

Growth chamber studies were conducted to determine the influence of several pretreatment radiation, humidity, and temperature regimes on the response of peas (Pisum sativum L. ‘Alaska’) and velvetleaf (Abutilon theophrasti Medic.) to foliarly-applied (2,4-dichlorophenoxy)acetic acid (2,4-D). Under the conditions of these studies, growing peas under solar or fluorescent-incandescent lamp radiation, in high or low humidity, or in temperatures between 10 and 25 C prior to treatment did not influence their response to 2,4-D. The response of velvetleaf to 2,4-D was slightly greater when pretreatment growth was under solar radiation rather than under fluorescent-incandescent lamps. Similarly, high pretreatment humidities and temperatures produced slightly greater responses to 2,4-D in velvetleaf than low pretreatment humidities and temperatures. Herbicide uptake and translocation were greater when pretreatment pea growth was under solar radiation, but spray retention and rate of 2,4-D metabolism were not affected by pretreatment radiation. This study indicates that pretreatment light, temperature, and humidity conditions play only a minor role in determining the response of peas and velvetleaf to 2,4-D.