R. Van Den Boogaard et K. Thorup-kristensen, The effect of defoliation on phenological development and yield in cauliflower, J HORT SCI, 74(2), 1999, pp. 269-275
Decision support models used to reduce inputs of pesticides require a preci
se modelling of the changes in assimilate production and distribution, but
also of possible changes in developmental rates due to sub-optimal conditio
ns. Changes in developmental rates, which shorten or prolong the growing ti
me may aggravate or reduce the effects of sub-optimal conditions on yield.
Therefore, the effect of defoliation on development of cauliflower was inve
stigated in a number of field experiments. Reduction in curd growth due to
defoliation during the curd growth phase was compensated by an increased du
ration of curd growth. It was estimated that defoliation during curd induct
ion corresponded to an increase in temperature sum requirement for curd ind
uction of 15 to 25 degree days, while defoliation during curd growth increa
sed the temperature sum requirement with 12 to 60 degree days Measurement o
f maturity by means of curd specific weight showed that defoliation delayed
maturity. This implies that yield losses due to defoliation can to a large
extend be avoided by postponing the harvest of curds. A model that would n
ot include this effect on development of defoliation by pests and diseases
would overestimate the need for pesticide application.