RESPONSE OF CATERPILLAR PESTS AND THE PARASITE DIADEGMA-INSULARE TO COLLARD CULTIVARS AND A PYRETHRIN INSECTICIDE

There were no differences in mortality, plant preference, or plant dam age when diamondback moth (DBM) (Plutella xylostella L.) larvae were t ested in no-choice and free-choice tests using leaf disks of resistant ('Green Glaze') or susceptible ('Vates', standard commercial cultivar ) collards (Brassica oleracea Acephala group). No residuals of the pyr ethrin insecticide Asana-XL (esfenvalerate) were detected 6 days after its application when DBM larvae were exposed to excised foliage for 7 2 hours. In a field test, more imported cabbage worm (ICW) (Pieris rap ae L.) eggs were found on 'Vates' treated with the insecticide than on nontreated 'Vates' or nontreated or treated 'Green Glaze'. The fewest ICW, cabbage looper (CL) (Trichoplusia ni Hubner), and DBM larvae wer e found on the insecticide-treated cultivars. Fewer caterpillars were found on 'Green Glaze' than 'Vates'. An additive effect of plant resis tance and insecticide application lowered counts of DBM, ICW, and CL l arvae. Percent parasitism of DBM by Diadegma insulare Cresson (Hymenop tera: Ichneumonidae) was lower on cultivars treated with the insectici de. Field plant damage ratings were higher for nontreated 'Vates' and lowest for treated cultivars, but nontreated 'Green Glaze' had a signi ficantly lower feeding damage rating than nontreated 'Vates'. Chemical name used: (S)-cyano (3-phenoxy phenyl) methyl-(S)-4 chloro-alpha (1- methylethyl) benzeneacetate [esfenvalerate (Asana-XL)].