TIMING THE TREATMENT OF CATTLE WITH TROLENE FOR SYSTEMIC CONTROL OF THE CATTLE GRUBS HYPODERMA LINEATUM (DE VILL.) AND H. BOVIS (L.) IN ALBERTA AND BRITISH COLUMBIA
Experiments on timing the oral treatment of calves for cattle grub control with Trolene at 100 mg./kg. were carried out on ranches near Lethbridge, Alberta, and Kamloops, British Columbia. Groups of 30 and 25 calves, respectively, were treated in November, January, March, and April at Lethbridge and in December, January, February, and March at Kamloops.Control of the pre-hypodermal grubs was equally effective on the first three treatment dates, varying from 94 to 98 per cent mortality. However, variations in the numbers of grubs precluded stating the mortality more precisely than within a range of 95 to 100 per cent at Lethbridge and 89 to 100 at Kamloops.There was no significant difference in mortality between the two species of cattle grubs. However, the third hypodermal instar larvae of both species were less affected by the treatment (P <.01) than those of the preceding instars. Early autumn treatments are recommended to avoid the presence of third-instar larvae and to forestall early damage caused by the hypodermal grubs.Slight symptoms of toxicity, in the form of lethargy and reduced food consumption at Kamloops and ataxia of the hindquarters at Lethbridge, were observed in the calves treated in December and January, respectively. The symptoms disappeared within 48 hours of treatment without the use of antidotes at either locality. The level of treatment used in this study was lower than that reported in the literature to produce first symptoms of toxicity.