Agriculture Reference
In-Depth Information
know what the fruit set will be and you run the risk of thinning too heavily.
For example, cold, wet weather can interfere with pollination and fertiliza-
tion. A late frost can damage flowers and developing fruits, as can hail and
heavy winds. In the generally warm, arid or semiarid fruit growing regions
of western North America, applications during bloom appear suitable. The
objectives in this region are to thin out some of the flowers and to reduce
pollination and the percentage of fruit set. For eastern fruit growers, Cornell
University suggests waiting to make the first application of fish oil/LLS un-
til petal fall, when danger of frost has passed and you can better determine
how much fruit has set. Apply a second spray 4 to 7 days after the first, and
a third spray may be needed.
The downside of the Cornell approach is that it appears to be less effect-
ive than making applications during full bloom, and there is a greater risk
that the lime sulfur will damage the leaves and fruit. Lime sulfur is also toxic
to beneficial organisms and repeated applications of LLS can increase pest
problems. The present theory for why the oil/LLS sprays work is that:
▪
The liquid lime sulfur inhibits photosynthesis and puts a stress on trees
when their reserves are low and demands for those reserves from flowers
and fruit are high. This stress causes some of the developing fruits to
drop.
▪
The liquid lime sulfur directly damages the flowers and reduces the per-
centage of flowers that are successfully pollinated and develop into fruits.
▪
The oil increases the plant uptake and efficiency of the LLS.
Cornell fruit specialists note that dark, cloudy weather for about 2 days or
more before or after applying chemical thinners increases the thinning re-
sponse. If you expect cloudy weather just before or after applying oil/LLS,
consider reducing your rate of application.
Temperatures also influence the effectiveness of chemical thinners. In
general, higher temperatures increase the rates at which chemical reactions
