Control of Hypoderma lineatum and H. bovis in California, 1970–72, Using Crufomate, Fenthion, and Imidan in New Low-Volume and Usual Pour-On Formulations12

Comparative evaluation data for control of Hypoderma boris (L.) and H. linealtum (deVillers) are presented on dermal applications of conventional pour-on solutions of fenthion and crufomate (both ready-to-use) and Imidan® (O, O-dimethyl phosphorothioate S-ester with N-(mercaptomethyl)phthalimide) (diluted with water before use) and new, more concentrated formulations of fenthion and crufomate utilizing a low volume of material. These animal systemics were tested on 4842 cattle in 10 regions of California but only 4366 cattle were available for evaluation of grub control. Grub reduction following LV and pour-on applications to 14 herds averaged, respectively, 96.4 and 95.9% for fenthion, and for crufomate to 4 herds they averaged 91 and 100%. Average grub reduction for pour-on applications only were 98.6% for Imidan to 93.6% for fenthion in 3 herds, and 99.9% for crufomate to 98.3% for fenthion in 6 herds. Grub control of only 38–57% following both fenthion and crufomate LV applications to one herd was believed to be due to treating the cattle during a rain storm. Fair grub control (69%) with LV fenthion in one herd was accounted for by an under dose of 3.9 mg/kg compared with 99–100% control following the recommended dose of 7.9 mg/kg to similar-weight calves in 5 herds. Individually weighed cows in one herd which received accurate LV dosages but under doses of pour-on in heavier weight possibly showed erratic grub reduction, and such results possibly were due to abnormal absorption and metabolism in some animals. Nearly all herds were examined at times when H. lineatum reached peak counts in the backs of animals, except for 2 of 19 herds in which H. bovis was the only species found. No adverse side effects were observed in any cattle tested with the various animal systemics despite late-season treatment of 2 herds which had cut grubs of H. lineatum present. A modified Bimco automatic syringe greatly facilitated low-volume application of the systemic. Additional advantages of this treatment method are discussed.