Effectiveness of Insecticides Against the Mexican Bean Beetle1

The contact action of 21 insecticides was evaluated against 1st instars of Epilachna varivestis Mulsant by using a Potter spray tower. All insecticides were toxic to larvae, and differences were indicated by tabulated values of the LD50 and LD95, as well as their confidence limits. The most toxic materials were the synthetic pyrethroids, carbofuran, methomyl, and carbaryl. The least toxic, malathion, still gave 93% mortality at 100 mg of AI/liter. The same insecticides tested against eggs of E. varivestis gave less uniform mortality. The four pyrethroids were effective at low dosages, and 11 other insecticides prevented hatching when applied at levels ca. 10 times higher than the larval LD95 Azinphosmethyl, malathion, phosmet, endosulfan, and methomyl had little or no effect at 1,000 mg of AI/liter. Laboratory efficiency of insecticides was related to present recommendations for field control, and suggestions are presented for future field tests.