Over-tree netting
(continued from last issue)
Over-tree netting
Information to date suggests that exposure to ultraviolet (UV) radiation is important for blush development and that blocking UV with nets and spray-on sunscreens could have negative consequences on colour development.
Preliminary studies have been undertaken in Australia at DEDJTR Tatura to examine the effects of netting on fruit surface temperature and colour in the new red-blushed variety Deliza®.
The netting used in this comparison reduced UV radiation by approximately 35% and direct solar radiation by 25% but did not affect air temperature.
Fruit surface temperature was reduced by up to 6.1C. Sunburn damage was substantially less under the netting but the data suggests that the average fruit red colour was reduced compared with trees that were not netted.
Rootstocks
In South Africa, Roberts et al. (2008) conducted a trial over two seasons to establish whether red colour could be improved by choice of rootstock.
Forelle pears were planted on three clonal pear (P. communis) rootstocks (BP1, BP3 and OHxF 97) and three clonal quince (Cydonia oblonga) stocks (QA, QC51 and BA 29).
Quince showed better red colour than pear rootstocks even though there were no differences in anthocyanin concentrations attributable to the different rootstock types.
Pears grown on quince stocks appeared redder because quince lowered skin chlorophyll (green) and carotenoid (yellow-orange) concentrations.
Research at DEDJTR, Tatura is investigating the effects of rootstock (including BP1, QA and QC) on colour development in the new red-blushed varieties Deliza®, Lanya® and ANP0534.
Trees are in their third leaf and results will be published after evaluation of harvested fruit in February 2016.
See this article in Tree Fruit March 2016
