Managed honeybees as Pollinators and Vectors of Bio-Control Agent (Trichoderma harzianum) Against Grey Mold Disease for Increased Strawberry Yield and Quality in Kenya

Abstract

Pollination by bees and other animals significantly increase both crop yields and quality. Bees also support the transfer of bio-control agents for suppression of crop pests and diseases through bio- vectoring technology that has not been applied in Africa. Two farms were set up to test the ability of honeybees to disseminate Trichoderma harzianum to control Botrytis cinerea, on strawberries. At on-station farm, three treatments (bee-vectoring inoculum, spraying and control) with 4 replicates each were set up; while on-farm, normal farmer practices were employed. A nuclear beehive fitted with a two- way dispenser was loaded with two grams of T. harzianum inoculum. Fifteen bees and flowers from each treatment were picked and cultured in the laboratory. Fruits and flowers infected with B. cinerea were recorded. Healthy fruits were counted, weighed and both the equatorial and polar diameter determined. Each bee carried 22.4±4.9×102 colony -forming units of T. harzianum. Flowers from the sprayed treatment had significantly higher Colony-Forming Unit’s (P˂0.05) than the bee- vectored treatment. Grey mold disease levels on fruits were significantly lower (P˃0.05) in sprayed, bee- vectored and control treatment than in farmer’s practice treatment. Fruits from spray treatment weighed significantly higher than those from control treatment (P˂ 0.05). The number of seeds, equatorial and polar diameter per berry were significantly higher, P˂0.05) in farmer’s practice treatment. Honeybees proved effective in vectoring T. harzianum but, sufficient Colony-forming units had to be delivered for effective control of grey disease. The use T. harzianum and open pollination by feral bees proved effective in improving the quality and yield of strawberry plants.