PCC June July 2021 e

Minimizing Drift
from Orchard
Spray Application
by Spray Backstop
System
By ALIREZA POURREZA | Director, Digital Agriculture
Lab, UC Davis
A sprayer working in a young almond orchard in Northern California (all
photos courtesy Digital Agriculture Lab.)
Thermal view of spray cloud escaping the canopy from the top.
A prototype of the spray backstop system developed at the Digital
Agriculture Lab at UC Davis.
Cotton ribbon stretched around two rows of trees for continuous
loop sampling.
Spray backstop blocking the spray cloud from moving upwards.
The use of pesticides can be very
effective in protecting trees from
pests and diseases. However, many
times this is also accompanied by
negative impacts on humans and the
environment. Off-target movement
of chemical spray has always been a
challenge for growers because it can
contaminate the environment, reduce
spray efficacy and impose liabilities.
California has stringent pesticide laws
and regulations and orchard spray
application is considered a high-risk
operation. California law establishes
a buffer between schools and any pesticide
spraying location. Growers are
required to notify the public when they
spray pesticides. This includes schools,
daycare facilities, and county agricultural
commissions.
Spray drift can be reduced by choosing
the right type of nozzle, adjusting and
calibrating sprayer settings, defining
shelter zones and specifically modified
practices in the downwind rows. Reducing
the movement of spray droplets
to sensitive areas might be accomplished
by these methods, but they are
in clear contrast with strategies that
lead to a uniform on-target deposition.
For instance, spraying with larger droplets
can reduce the amount of drift, but
it also decreases the effectiveness of the
spray at higher parts of a tree. Likewise,
16 Progressive Crop Consultant July / August 2021