Determining Pollinators, Floral Calendar And The Effect Of Pollination Deficit Of Avocado Persea Americana Mill In Kandara, Murang’a County, Kenya

ABSTRACT

Avocado Persea americana Mill is an important fruit in Kenya. It is a source of vitamins, oil and income to farmers. However, its optimal production is dependent on insect pollinators. This study was undertaken to determine diversity and abundance of insects visiting avocado flowers, their diurnal visitation counts, the crop floral calendar and the effect of pollination deficit of avocado at Kandara, Murang’a County. The study was carried out in farmers’ fields in upper midland 2 agro ecological zone, for three cropping seasons, from August 2015 to March 2017. A total of 60 trees were randomly selected from 12 farms for the study with a minimum distance of 10 m and 200 m between trees and between farms, respectively. Treatments included unlimited access and no access of flowers by pollinators. On each tree, two randomly selected terminal branches with inflorescences of the same age and size were identified, where one was bagged using nylon mosquito nets to deny access by pollinators while the other was left open for unlimited access by pollinators. As soon as flowers wilted, the nets were removed, and fruits on the tagged terminal branches counted. Data collected included identity of the pollinator, number of individuals observed pollinating per species, time of the day, the time (seconds) taken by the pollinator on the flower per visit, the percentage flushing, percentage flower buds, percentage flowering and percentage fruiting. Number of male and female flowers was recorded from 0900 h to 1700 h. Fruit counts were done monthly. At maturity, fruits were harvested and their weight, polar diameter, equatorial diameter, seed weight, ovary polar and equatorial diameters were determined in the laboratory. Pollination deficit data were analyzed using Student’s t-test. Findings showed that honey bees Apis mellifera were the major flower visitors followed by blow flies Chrysomya putoria. Others included hoverflies Eristalis tenax, wasps Polistes sp., butterflies Colias electo, ants Iridomyrmex reburrus and beetles Drypta ruficollis. Opening and maturity of female and male phase flowers overlapped between 1200 h to 1659 h, with the peak overlap from 1300 h to 1359 h. Fruit set was significantly (P