Kiwifruit flower pollination : Wind pollination efficiencies and sprayer jet applications

A  thesis submitted in fulfillment of the requirements for the Degree of Doctor of Philosophy  in  Chemical and Process Engineering
There  has  been  a  move  in  the  kiwifruit  industry  to  pollinate  by  machine,  allowing orchardists flexibility in timing, and other advantages.  The traditional pollinators, bees,
are unreliable and are susceptible to diseases such as the varroa mite.  No measurements
have been done on the efficiency of single-flower collection of pollen and the influence
of aitjet characteristics, to put this  activity on a firm quantitative basis.  For predictive
purposes,  a robust model  of pollen  behaviour around  a single  Green kiwifruit flower
(Actinidia deliciosa)  was built in this study by using a commercial computational fluid
dynamics (CFD) package.  The theoretical study first looked at the wind pollination of
flower buds  at different opening stages.  Within the range of draft velocity recorded in
the orchards,  stigma are predicted to  capture more pollen in  a wind  approaching from
the front than from  the side and back.  Also,  the pollen deposition on stigma increases
as the bud opens wider and loses its petals.  An estimation based on the predicted pollen
collection efficiency  indicated that  wind pollination alone is  insufficient to  produce a
minimum exportable fruit,  which is in agreement with  the observations reported in the
literature.  The question whether kiwifruit is  a wind-pollinated plant is  also discussed.
Experimental  checks  of the  modelling  were  carried  out.  Visualization  of flow  paths
around a real kiwifruit flower in a wind tunnel compared well with the CFD predictions.