SUSCEPTIBILITY OF STABLE FLIES (DIPTERA, MUSCIDAE) FROM SOUTHEASTERN NEBRASKA BEEF-CATTLE FEEDLOTS TO SELECTED INSECTICIDES AND COMPARISON OF 3 BIOASSAY TECHNIQUES
Pcrg. Marcon et al., SUSCEPTIBILITY OF STABLE FLIES (DIPTERA, MUSCIDAE) FROM SOUTHEASTERN NEBRASKA BEEF-CATTLE FEEDLOTS TO SELECTED INSECTICIDES AND COMPARISON OF 3 BIOASSAY TECHNIQUES, Journal of economic entomology, 90(2), 1997, pp. 293-298
Insecticide susceptibility of field populations of stable flies, Stomo
xys calcitrans (L.), was assayed using 3 exposure techniques: treated
filter papers, treated glass petri dishes, and topical applications. B
oth topical applications and residual exposure to treated glass surfac
es were suitable for testing susceptibility of stable flies to permeth
rin, stirofos, or methoxychlor. Residues on filter papers yielded inco
nsistent results with stirofos and methoxychlor. Significant concentra
tion-mortality regression lines were generated with permethrin residue
s on filter papers, but approximate to 1,000 times more insecticide wa
s required to produce a toxic response when compared with permethrin r
esidues on glass. Because of higher variability in response and the gr
eater amount of insecticide required, residues on filter papers do not
appear appropriate to test insecticide susceptibility in stable flies
. Paired comparisons of field (F) and susceptible (S) stable flies res
ulted in field to susceptible ratios significantly >1.0 only when the
flies were treated topically, which suggests that topical application
is more sensitive than residues on glass for the insecticides tested.
Topical treatment with permethrin resulted in one FS(LD90) of 1.8-fold
. Topical treatment with methoxychlor resulted in one FS(LD90) of 3.4-
fold. However, the magnitude of these ratios is not larger than the si
gnificant differences observed within the susceptible laboratory colon
y from one generation to another. Intense exposure to insecticides is
not known to have occurred in these field populations, indicating that
the observed differences are the result of natural variation among st
able fly populations and unrelated to prior selection with insecticide
s.