| dc.description.abstract | Cabbage (Brassica oleracea L. var. capitata) is one of the most important vegetables grown in
Kenya for home consumption and as an important source of income to many small-scale farmers.
The production of cabbage is, however, constrained by several pests. Among those pests,
Diamondback moth (Plutella xylostella) is ranked as the most important pest and is regarded as
the most destructive insect pest of cruciferous crops worldwide. As an attempt to overcome the
problem, field experiments were conducted at the University of Nairobi, College of Agriculture
and Veterinary Sciences farm in 2008 and 2009. The study was carried out to screen six cabbage
varieties for resistance and evaluate the effects of border crops on Diamondback moth infestation
and damage on cabbage. Six cabbage varieties which were screened were: Drumhead, Sugarloaf,
Golden Acre, Gloria Fl, Copenhagen Market and Pruktor Fl. The experiment was set up in a
split plot design consisting of four replicates per treatment whereby one set of the treatments
were sprayed with Dimethoate and the others were not sprayed. The cabbage varieties were
compared in Diamondback moth damage and infestation. In border crops experiment, crops
evaluated were Indian mustard, Radish, Kale, Tomato, Coriander and Cleome. They were
planted around cabbage Copenhagen Market variety in the field 15 days prior to cabbage
transplanting. The experiment was laid out using a Randomised Complete Block Design (RCBD)
consisting of four replicates. In both experiments, five randomly selected plants per plot were
used to record the numbers of larvae, pupae and damage scores. The yield in terms of quality and
quantity of cabbage heads per variety were assessed on all the plants per plot at maturity stage. It
was evident from the study that there were significant differences (P<0.05) among the sprayed
and unsprayed varieties on infestation by the immature DBM. Among the sprayed and unsprayed
treatments, Copenhagen Market and Pruktor Fl had the lowest mean number of the immature
Diamondback moth. The unsprayed varieties recorded higher DBM damage compared with the
sprayed varieties. The lowest damage was recorded on cabbage var. Pruktor F 1 and Sugarloaf
both in sprayed and unsprayed treatments. Among the unsprayed varieties, cabbage var. Pruktor
Fl and Copenhagen Market had the highest number of the marketable cabbage heads. However,
the highest cabbage head weights were recorded from Pruktor F 1 in the sprayed as well as in the
unsprayed treatments. The study on border crops indicated that the mean number of immature
Diamondback moth was significantly lower (P<O.05) on cabbages surrounded by the Indian
mustard and Coriander border crops compared with those surrounded by the other crops. The
results also indicated that cabbage plots bordered with the Indian mustard had the lowest number
of damaged cabbage heads. Plots surrounded with Indian mustard and Coriander border crops
produced highest marketable cabbage heads and highest cabbage head weights. The results
obtained in these studies reveal that cabbage var. Pruktor Fl and Copenhagen market and Indian
mustard border crop can be adopted by farmers for the management of Diamondback moth on
cabbage. | en |
