Adjuvants Prolonging the Residual Activity of Dichlorvos and Mevinphos in the Laboratory12

Abstract

Seventy-four materials were screened as potential adjuvants to prolong toxicity of dichlorvos and mevinphos on 3rd-instar larvae of the Mexican bean beetle, Epilachna varivestis Mulsant, and 4th-instar larvae of the southern armyworm, Prodenia eridania (Cramer). Residues of the toxicants and toxicant-adjuvant combinations on lima bean foliage (‘Fordhook 242’), when 24 hours old, were infested with insects. After 24 additional hours the respomes to the combinations were compared with responses to the toxicant alone. Most adjuvants tested appeared to have some promise. Four materials, Keltose (alginate). Dacagin (polysaccharide gum), Plaskon 9405 (polyester resin), and Hetron HLR 254 (unsaturated polyester resin), were exceptionally effective. Patterns of effectiveness were observed also among individuals and categories of adjuvants. Klucel G (cellulose ether) and Methoccl MC 8000 (hydroxymethyl cellulose) were effective only in combination with mevinphos. Cellosize QP 52,000 (hydroxyethyl cellulose) and Hetron PR 130 (polyester resin) were only effective with dichlorvos. Klucel I (cellulose ether) was effective with both toxicants but only against Mexican bean beetle. On a numerical basis the carbohydrate, polyester resin, and polyvinyl derivatives categories were superior to the other categories. Approximately 90% of the above-mentioned materials produced minimum mortalities of 85%, even though they contain only about 50% of the materials tested.