Field Evaluation on Effects of Common Spices in the Control of Diamondback Moth ( Plutella xylostella L.) Pest of Chinese Cabbage ( Brassica campestris L.) Commercial Cultivar

摘要

An experiment was carried out to assess the effectiveness of commonly used spices in controlling diamondback moth (DBM) ( Plutella xylostella L. (Lepidoptera:Plutellidae)) field pest of Chinese cabbage ( Brassica campestris L. sp. Perkinensis (Lour) Olson). The trial was conducted during the short rains of November to February 2004/2005 at the Horticultural field plots of Sokoine University of Agriculture, Morogoro, Tanzania. Test materials consisted of cabbage seeds; water extracts of garlic stems, fruits of hot pepper and cloves and barks of cinnamon as insecticidal pesticides. Ten treatments consisted of two controls viz., one of no pesticide and the other of standard actellic super, the rest were sole spices and their various combinations. The pesticides were applied once a week starting at seedling emergence to the completion of data collection. Treatments were laid in a Randomized Complete Block Design with three replications. Data on insect damage was recorded weekly commencing at five weeks after sowing for 3 consecutive weeks. Pest incidence decreased with time while significant treatment effects were observed for pest severity and incidence and marketable leaves. Actellic super, pepper, combination of garlic and cloves and the trio combination of garlic, pepper and cloves significantly excelled the control of no pesticide application in reducing severity and incidence of diamondback moth and having higher number and percentage of marketable leaves. Actellic super significantly excelled the other treatments in having the lowest severity and incidence of DBM. The trio combination of garlic, pepper and cloves was statistically the same as actellic super in having high number and percent of marketable leaves. Negative relationships were observed between pest severity and incidence with number and % marketable leaves. On the other hand, positive relations were observed for pest severity with incidence and number with % marketable leaves.