Author: Mark Hoddle, Reuben Hofshi, Mary Lu Arpaia,

The importance of honey bees as pollinators of avocado flowers is a contentious issue. The reason for this is that there is no clear or consistent experimental evidence unequivocally demonstrating that honey bees are essential for pollinating avocado flowers and promoting maximum fruit set. While many different types of insects are known to visit avocado flowers (e.g., beetles and flies) and it is assumed that these insects play some role in pollination, their exact importance is not known. One group of insects, thrips, in particular flower thrips (i.e., Frankliniella), are commonly found in avocado flowers during bloom. These tiny hairy insects have not been specifically studied for their ability to act as pollinators of avocado flowers. It is very likely that given the small size of these insects, their hair covered bodies, their high numbers and almost constant presence in flowers, and predilection for feeding on pollen and nectar, they may be important, but overlooked pollinators of avocado flowers. If this is the case, then conflicting conclusions resulting from bee studies using exclosure cages may be explained by thrips moving pollen within and between trees. Thrips pollination could occur because cage mesh used to exclude honeybees is not small enough to prevent thrips and other small insects access to flowers, thus allowing pollination to occur either by thrips resident on trees at time of caging, or moving between trees. Consequently, equal rates of fruit set between caged and uncaged trees could be explained via the thrips-pollinator hypothesis, rather than the assumption that wind pollination was the primary cause for self and cross-pollination. Therefore, the objective of this proposal is to ascertain the role that ubiquitous flower thrips, especially Frankliniella spp. play in pollinating „Hass‟ avocados in California and its significance relative to the role of wind and honeybees.