Pollination studies in cashew

Abstract

Investigation on the various aspects of pollination viz., flower opening, fruit set and fruit drop under natural pollination and assisted pollination, effect of pollinating agents and intensity of pollen in the atmosphere were undertaken at the Cashew Research station, Madakkathara and Department of Agricultural Botany, College of Horticulture, Vellanikkara during 1983-84, on six year old BLA-139/1 trees (air layers) under uniform cultural and manurial conditions. The data were subjected to various statistical analysis. The results have shown that the period of flower opening in both male and hermaphrodite flowers was same, starting after 23 hr and extending upto 15 hr next day. The peak period of flower opening for male flowers was between 7 and 9 hr and for hermaphrodite flowers between 9 and 11 hr. Climatic factors such as temperature, sunshine hours, relative humidity and wind velocity have not shown any significant influence on the magnitude of flower opening. Type BLA-139/1 has a relatively low sex-ratio of 1: 2. 83 resulting a higher percentage of hermaphrodite flowers. There is variation in sex-ratio even within the panicles of the same tree. When compared to natural pollination, assisted pollination resulted in significantly higher initial fruit set indicating the inefficiency or inadequacy of pollinating agents. But the higher initial fruit set was not fully reflected in the percentage of fruits harvested since a major portion of the set fruits dropped at different stages of development. In both cases of natural and hand pollination, fruit droop was more in early stages of nut development. This necessitates the need for improving the initial fruit set and more over reducing post fertilization drop for higher yields in cashew. In completely bagged panicles no fruit was set, confirming the cross pollinated nature of cashew. The failure of fruit set in water sprayed panicles rules out the possibility of water as a pollinating agent. Wind plays a significant role in cashew pollination along with insects like red and black ants, honey bees and butterflies which frequently visit cashew inflorescence. The intensity of pollen grains on the atmosphere was 20 times higher than that of hermaphrodite flowers in a unit area.