Bacillus thuringiensis and Pirimicarb: Selective Insecticides for Use in Pest Management on Broccoli2

Abstract

The effectiveness and selectivity of the combination Dipel^® (Bacillus thuringiensis Berliner var kerstaki) plus pirimicarb^® for control of the complex of lepidopterous larvae [Trichoplusia ni (Hübner), Pieris rapae (L.), and Plutella xylostella (L.)], and aphids [Brevicoryne brassicae (L.) and Myzus persicae (Sulzer)] attacking broccoli were evaluated on 5 different plantings at 2 locations in southern California. During the preheading stage of plant growth, Dipel 1.0 Ib + pirimicarb 0.25 lb AI/acre, applied as needed, significantly reduced lepidopterous larval and aphid populations. However, control of larvae was less consistent than that by methomyl at 0.9 lb AI/acre. Weekly applications of Dipel 1.0 Ib + pirimicarb 0.25 lb during head formation were as effective as methomyl 0.45 lb in preventing insect contamination of the heads. B. brassicae was consistently the most serious insect contaminant of the broccoli heads. The effects of the Dipel + pirimicarb and methomyl treatments on parasitization of T. ni and P. xylostella at 14 days posttreatment were minimal. At 6 and 7 days posttreatment, Dipel + pirimicarb interfered less with parasitization than did methomyl.