Rainfastening of Bifenthrin to Cotton Leaves with Selected Adjuvants

Abstract

AbstractThere are thousands of adjuvants on the market, yet little is known about their effects on the activity of insecticides on plant surfaces. The effects of 11 selected adjuvants on the rainfastness and retention of bifenthrin ([1α,3α‐(Z)‐(±)‐(2 methyl[1,1′‐biphenyl]‐3‐yl) methyl 3‐(2‐chloro‐3,3,3‐trifluoro‐1‐propenyl)‐2,2‐dimethylcyclopropanecarboxylate) on cotton (Gossypium hirsutum L.) leaves were investigated. In addition, the effect of the adjuvant Bond on the efficacy of bifenthrin and a Bacillus thuringiensis (Berliner) formulation was determined. Bifenthrin mixed with each adjuvant was applied to greenhouse grown cotton plants using a spray chamber. Simulated rainfall of 13 mm was then applied to treated cotton plants at 0.25, 1, and 4 h after treatment. Bond and Agrimax‐3 were the only adjuvants to significantly increase the rainfastness of bifenthrin on cotton leaves. Agri‐Dex, Soy‐Dex, and Dyne‐Amic significantly decreased the rainfastness of bifenthrin. In tests conducted with an immersion cell apparatus, Orchex 796 resulted in twice the retention of Agri‐Dex, the next highest retained adjuvant. Both petroleum and vegetable oils enhanced retention of bifenthrin on the leaf surface. Bond mixed with bifenthrin and a B. thuringiensis formulation did not reduce the activity of these insecticides against tobacco budworm (Heliothis virescens) and soybean looper (Pseudoplusia includens) larvae. Retention on the leaf may be related to spread and to the degree of binding of the insecticide to the surface by properties of the adjuvant. Yet, the properties of Agri‐Dex that enhanced the retention of bifenthrin to the cotton leaf decreased its rainfastness.