Cl. Mckenzie et Rl. Byford, CONTINUOUS, ALTERNATING, AND MIXED INSECTICIDES AFFECT DEVELOPMENT OFRESISTANCE IN THE HORN FLY (DIPTERA, MUSCIDAE), Journal of economic entomology, 86(4), 1993, pp. 1040-1048
Susceptible populations of horn flies, Haematobia irritans (L.), were
selected with six insecticide treatment regimens: continuous use of pe
rmethrin, diazinon, or ivermectin; permethrin/diazinon (1:2) mixture;
permethrin-diazinon rotation; and permethrin-ivermectin rotation. Inse
cticide selection was applied as low-volume sprays on steers infested
with horn flies housed in environmentally controlled rooms. During the
study period, horn fly populations developed an apparent resistance t
o all insecticide treatment regimens. Selection with permethrin diazin
on, and ivermectin resulted in development of resistance in generation
s 21, 31, and 30, respectively. Selection with insecticide mixtures an
d rotations resulted in the delay of any apparent resistance developme
nt for an additional one to seven generations. The magnitude of this r
esistance ranged from 1.470-fold for the single continuous use of perm
ethrin to <3-fold for ivermectin in the permethrin-ivermectin rotation
. Compared with single continuous insecticide selections, the onset an
d degree of resistance development was significantly reduced by altern
ating and mixing insecticides.