| dc.description.abstract | A study was undertaken to assess the efficacy of some neonicotinoid formulations used in
snap bean production as seed dressings and soil drenches against snap bean pests and to
evaluate some commercial varieties for resistance to the pests. The study was carried out in
Mwea, Central Kenya where most export snap beans are grown by small scale farmers. The
study consisted of two experiments carried out from December 2009. to January 2011. In the
first experiment, four neonicotinoid seed dressing (Gaucho, Monceren, Cruiser, Apron Star)
and two soil drench formulations (Actara and Confidor) were tested on Amy variety in a
randomised complete block design replicated three times. Untreated plots were included as
control. Seed dressing chemicals were applied on site just before planting whereas the soil
drenching chemicals were applied twice on the 3rd and 13th day after emergence. In the
second experiment, seven commercial snap bean varieties, Amy, Alexandra, Bravo,
Serengeti, Paulista, Tana and Mara, were tested with and without a pesticide (Confidor) in a
split plot design. Confidor pesticide formed the main plots and variety the sub-plots. Data
was collected weekly on the number of plants per plot, bean fly maggots, whitefly nymphs,
bean fly ovipuncture marks, number of thrips on leaves and flowers and finally on pod yield.
The number of bean fly maggots was significantly (P<0.001) lower in plots treated with
Confidor, Actara, Gaucho, Monceren and Cruiser than in Apron Star and non-treated control
plots. Plots treated with Confidor and Actara had significantly (P<0.001) lower bean fly
infestations and gave significantly (P<0.001) higher yields. After partial economic analysis,
Cruiser, Apron Star and Monceren had the highest benefit-cost ratio of 1.82, 1.60 and 1.24
respectively while Actara and Gaucho had the lowest benefit-cost ratio of -0.11 and 0.24
respectively. Thus neonicotinoid treatments with Cruiser, Monceren or Confidor in snap bean
production can effectively reduce bean fly infestation and increase yields, hence offering
great benefits to snap bean growers. Therefore, growers and seed packers should be
encouraged to seed dress with Monceren or Cruiser or drench with Confidor to protect the
crop against bean fly as they are effective and give good financial returns. The snap bean
varieties were significantly different (P=0.001) in the number of plants as well as in the
marketable (P=0.001) and total pod yields (P=0.001). Alexandra and Serengeti varieties had
higher plant stand and yields than the Amy variety, the commonly grown variety in Mwea.
Treatment with Confidor further improved plant stand and increased pod yield by between 50
% and 490 %. Some degree of resistance was noticed in Alexandra and Serengeti varieties
against bean fly which was enhanced by treatment with Confidor. Resistance to other pests
was not apparent. Alexandra and Serengeti varieties should be recommended to snap bean
growers in areas like Mwea which experiences high pest infestations. For effective protection
against snap bean pests, use of safe insecticides such as Confidor should be integrated with
resistant varieties in the production system | en |
