Evaluation of Insecticides for the Management of Diamondback Moth, (Plutella xylostella (L.) (Lepidoptera: Plutellidae) on Cabbage under Field Condition

Abstract

Diamondback Moth (DBM) is one of the major constraints for the profitable production of cabbage in the country as well as Ambo highlands in particular. The field study was conducted to evaluate the susceptible varietal resistance of cabbage (Brassica oleracea var.capitata) against diamondback moth (DBM) (Plutella xylostella) infestations and damages at the Ambo university farm in a relay cropping (Rain season) in 2019. Varietal resistance was compared with conventional spraying using Randomized complete block design (RCBD) spraying chemical of insecticides at different spray interval. The Cabbage varieties were Copenhagen from local market. Sampling was done by weekly counting of larvae and pupae, and scoring pest damage on six randomly selected plants per plot for 5 weeks from the third week after transplanting. The number of damage and undamaged cabbage heads were counted on all plants per plot at maturity stage. Results showed that sprayed and unsprayed plots had significantly (P<0.05) different numbers of DBM stages (larvae and pupae). The yield losses of cabbage caused by DBM could reach up to more than 80% as several infestations occurred in the field. Due to this problem, farmers in Ambo highlands are preferred to apply the broad spectrum of non-systematic insecticides rather than implementing other pest management strategies. The demand for insecticides in Ambo highlands seems endless until today, but more aggressive. This paper highlighted the possibility of implementing intercropping cabbage with six treatments in reducing pupae and larvae populations of DBM in the polyculture system. The distributions of pupae and larvae population of DBM against the factors of temperature and rainfall also have been addressed in this study. A total of six treatments were indicated, that including Cutter, Trigger, Ethiozenon, Nomax, Fastac and Control which arranged in (RCBD). The result indicated that nonsignificant variations (P<0.05) were observed among the population of pupae and larvae at all seven treatments tested compared with the control. Moreover, pupae and larvae of DBM were negatively correlated with temperature and rainfall factors. The results also showed that a critical period of DBM infestations was detected in the pre-heading stage (< 30 DAT). In terms of performance among treatments, our finding also has shown that Nomax was the best treatment acted as a repellent.

Keywords: Diamondback Moth, Management Strategies, (Plutella xylostella ) Insecticide Resistance.

DOI: 10.7176/JBAH/11-23-04

Publication date: December 31^st 2021