BY: STEPHEN E. MALOBA A22/0043/2007 CROP PROTECTION MAJOR SUPERVISOR: DORA KILALO EFFECTS OF INTERCROPS ON DIAMONDBACK MOTH(Plutella xylostella) AND APHIDS (Bravicoryne brassicae)ON CABBAGE(Brassica oleracea var. copen hagen )

INTRODUCTION  Cabbage is of great economic importance.  Useful food for all classes of livestock and when suitable varieties are grown, high value crops can be produced for human consumption.  Cabbage prefers moist, heavy soils and seasons with plenty of rainfall. (Lockhart, 1983)

CABBAGE PRODUCTION IN KENYA  The major cabbage growing provinces in Kenya include Central and Rift Valley with 40% and 39% 0f the total national production respectively.  Average production from was 416,373.0 tons.  A little quantity is exported.

Cont…  Major constraints of production in Kenya are -pests and diseases –Diamond back moth(P. xylostella) -Species of aphids – Brevicoryne brasscae, Lipaphis erysymi and myzus pericae. -Diseases-Black rot and soft rot

Problem statement  Diamond back moth is an important pest of cruciferous crops.  In its control, farmers tend to use insecticides repeatedly which result in the development of resistance to many common insecticides.  Destruction of diamond back moth coupled with its capacity to develop resistance rapidly has posed a great challenge to farmers.

JUSTIFICATION  Diamondback moth is known to have potential capacity to develop resistance to pesticides in a short period of time.  The pesticides are able to affect negatively even beneficial insects and also produce contamination occurs.

Objectives General objective - To investigate the effects of intercrops in the management of Diamondback moth and aphids in cabbage. Specific objectives -To determine effective management of DBM and aphids on cabbage by intercrops. Hypothesis -Intercropping is not effective in the management of DBM and aphids.

MATERIALS AND METHOD  The study was carried out at Kabete field station in a complete randomized block design. T1T2T3T4 Ctrl T3 T4 Ctrl T2 T1 Ctrl T1T3 T4 T2 T3 T1 Ctrl T4

Cont…..  Plots measuring 2x2metres(four replicates) were used.  Repellant plants used: spider plant, coriander and onion  Chemical used: Dimethoid  Cabbage, the main crop was used as the control. PARAMETERS COLLECTED  Number of eggs on cabbage  Number of larvae on cabbage  Number of pupae on cabbage  Damage scores in cabbage

RESULTS

Effects of intercrops on DBM TreatmentEggsLarvaPupaDamage scores Spider plant3 (82%)1.13(80%)0.45(89%)0.63 (84%) Corriander7.75 (46%)3.00(46%)1.62(59%)2.25 (43%) Onions5.33 (63%)2.04(63%)1.12 (71%)1.38 (65%) Chemical10.08 (30%)3.92(29%)2.5 (10%)2.96 (25%) Control14.33 (0)5.5(0)3.91 (0)3.96 (0) LSD CV %26.4%47.3%44.1%23.2%

DISCUSSION  I deduced that spider plants worked the best as a result of its strong repellant smell against the DBM.  Chemical control results were as observed probably as a result of DBM’s resistance to the Dimethoid used or ability to develop resistance rapidly.  Aphids’ populations were not greatly affected by the repellant effect of the intercropped plants hence, their higher population.

CONCLUSION AND RECCOMENDATION  Intercrops have an effect on DBM and aphids.  Cleome gnandra is able to reduce the DBM and aphids on cabbage more than Coriander dhania and onions.  Farmers to be advised to intercrop their cabbage with spider plant.  Farmers to limit the use of chemicals in the management of DBM and aphids in order to preserve environment, limit produce contamination and cut down on the cost of production.

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