Showing papers by "Richard W. Merritt published in 1989"

A broad evaluation of B.t.i. for black fly (Diptera: Simuliidae) control in a Michigan river: efficacy, carry and nontarget effects on invertebrates and fish.

Abstract: Efficacy for black fly control, carry and nontarget effects of B.t.i. (Teknar HP-D), applied in the Betsie River, Michigan, were studied in June 1988. Black fly mortality was high (approximately 100%) for a 2,200 m stretch downstream from the application site, declined to 30% at 3,200 m, and was nil at 4,500 m. Drift of black flies greatly increased after application at a downstream site, but did not change at an upstream site. There were no detectable nontarget effects of B.t.i. application on: 1) invertebrate macro- or micro-drift; 2) numbers of invertebrates in benthic Surber samples; 3) mortality or feeding of drifting and nondrifting insects; 4) growth or mortality of caged Stenomena sp. larvae; 5) invertebrate functional group composition; 6) mortality or weight change of caged rock bass; or 7) fish numbers, species composition, length-weight (rock bass only) relationships or rock bass diet. Sampling of Rheotanytarsus sp. midges on natural substrates indicated low (27%) mortality owing to B.t.i. at only 100 m downstream from the application site, with negligible mortality at all other downstream and upstream sites. This information, combined with no pronounced changes in numbers of midges in macro-drift after application, indicated that midge populations were not adversely affected by B.t.i. in the study.

Sampling, seasonal abundance, and mermithid parasitism of larval Coquillettidia perturbans in south-central Michigan.

Abstract: Seasonal abundance of immature Coquillettidia perturbans was studied at 3 sites in south-central Michigan in 1987 and 1988. A modified boat bilge pump and funnel separators proved to be good sampling and sorting devices. Pupae were found in late May to early July, first and second instars were most abundant in July and August, while third and fourth instars were present year-round. Overall, larvae were most numerous in August and September, indicating that Cq. perturbans has a single generation per year in Michigan, with midsummer to fall as the main period of larval development, and with third and fourth larval instars as overwintering stages. Parasitism of Cq. perturbans larvae by a previously undiscovered mermithid nematode was documented at 2 sites in late summer.