Thesis Abstract and Dissertation Abstracts
Management of Aphids in Collards: Effect of Companion Crops and Nitrogen Application
Abstract Category: Science
Course / Degree: Master of Philosophy in Crop Protection
Institution / University: MOI University, Kenya
Published in: 2007
Collard (Brassica oleracea var. acephala D.C) is an important vegetable crop serving as a source of income to many small scale farmers in Kenya and also is a major dietary component for many Kenyans. The production of collards is however constrained by poor soil conditions and several pests, with cabbage aphids (Brevicoryne brassica L.) being one of the major pests. Control of the aphids has mainly been by chemical sprays, which is costly to small scale farmers, poses a threat to environment and may lead to pest resurgence and resistance. This study was, therefore, an attempt to look into an environmentally friendly way of controlling cabbage aphids, which could be combined with a certain optimal nitrogen application rate, to improve the performance of collards. Field studies were thus carried out in two collards growing seasons of the year 2006 in Moi University, Chepkoilel farm (0035¡¯N; 35018¡¯E), Eldoret, Kenya to determine the effects of companion crops and nitrogen application on the aphid infestation and performance of collards. The experiment was laid out in a randomized complete block design with three cropping systems [spring onion or chilli intercropped with collard to serve as companion crops, and a collard monocrop (sole collard)]. The collards in each of the cropping systems were top ¨C dressed with Calcium Ammonium Nitrate (CAN) at different rates (20, 25, 30 and 35g plant -1). Collard plants were selected randomly and tagged for data collection. The data collected included the aphid density (number of aphids per plant), number of leaves per plant, height and leaf fresh weight/yield (t ha-1). Sampling started 35 days after transplanting of collards and continued for 20 days at intervals of 5 days.
ANOVA, DMRT and correlation analysis were done using SPSS (version 12) and MS Excel (XP version). Spring onion intercrop had the lowest aphid density (12 aphids) v and the best collard performance; in terms of number of leaves (15.4 leaves plant-1), yield (18.6 t/ha), and plant height (25 cm). Collard monocrop had the highest aphid infestation (371 aphids) and the lowest collard performance: 9.2 leaves plant-1 , height 13 cm and yield 7.8 t/ha. Although chilli intercrop had slightly low aphid infestation and slightly higher collard performance, it did not differ significantly (p¡Ü0.05) from sole collard at most of the sampling dates in the two seasons. The increase in nitrogen application rate led to an increase in aphid density but improved the performance of collard under all cropping systems. However, the performance of collards was best at a nitrogen application rate of 30g per collard plant; a yield of 18.4 t/ha. The interaction between nitrogen application and cropping systems was significant (p¡Ü0.05) in some observational cases but not in others. The best collard performance was under an intercrop of spring onion, top ¨C dressed with a CAN of 30 g plant-1. The correlation between the aphid density and the collard performance parameters was significant (p¡Ü0.01) in the first but not in the second season. The aphid density significantly (p¡Ü0.05) contributed to decline in the yield, number of leaves and the plant height of collard at the some sampling dates of the first season. In some other observations, the increase in aphid infestation was accompanied by a significant (r = 0.386; p =0.020, r = 0.476; p =0.003) improvement in the yield and number of leaves of the collard respectively, implying that the crop had compensated for the damage by the aphids.
It was thus concluded that aphid infestation is reduced by intercropping collards with spring onion, and therefore, with the reduced aphid infestation, it is possible to raise the nitrogen application rate from the blanket recommendation of 20 g to 30 g per collard plant, an approach that consequently perk up the performance of collards, consequently an improvement in income and food to the growers.
Thesis Keywords/Search Tags:
collards, aphids, nitrogen rates, spring onions, chilli
This Thesis Abstract may be cited as follows:
MUTIGA, S. K., GOHOLE, L.S. AND AUMA, E. O. (2008).MANAGEMENT OF APHIDS IN COLLARDS: EFFECTS OF COMPANION CROPS AND NITROGEN APPLICATION. DEPARTMENT OF CROP, SEED AND HORTICULTURAL SCIENCES, MOI UNIVERSITY. PO BOX 1125, ELDORET, KENYA
Submission Details: Thesis Abstract submitted by Samuel Kilonzo Mutiga from Kenya on 06-Oct-2008 22:41.
Abstract has been viewed 3507 times (since 7 Mar 2010).
Samuel Kilonzo Mutiga Contact Details: Email: smutiga@yahoo.com
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