April 2020 - 21

BIOCONTROLS & BIOPESTICIDES
the overall cost of using pesticides.
Consumer trends also show they want
ornamentals to have limited-to-no
exposure to pesticides.
Using beneficial insects to control
pests and minimize damage to
crops could be an important aspect
of sustainable production, he said.
There are numerous studies showing
the effectiveness of using beneficial
insects in commercial settings in more
temperate climates, especially in fruit
and vegetable production, but very
little information about how they
manage pests of ornamentals in hot,
humid areas like east Texas.
Previous studies have tended to
focus on the use of a single beneficial
insect, such as a parasitic wasp, he said.
" The goal is to determine whether
the combination of two beneficial
insect species to manage whiteflies
can work better than just one
for poinsettias in a greenhouse
environment, " he said. " I want to know
how the wasp and mite work together
to suppress whiteflies. "
Vafaie is looking to determine how
introducing beneficial predatory mites
and parasitic wasps affect the need
for pesticide spray treatments. His
study started with determining initial
whitefly populations on poinsettia
cuttings at the grower facilities over
two years, whitefly retailer thresholds
for two years, and small-scale studies
to determine if the combination of
the two beneficial insects works better
than either one alone.
Vafaie and his assistant scouted
for whiteflies in both greenhouses
managed under conventional
insecticide rotations and greenhouses
that relied mainly on the wasps and
mites for whitefly control.
So far, so good
At Location 1, Vafaie said spot
sprays were required in addition
to the beneficial insects in sections
of the greenhouses after whitefly
populations moved in. At Location 2,
no pesticide applications for whiteflies
were necessary in the beneficial insectmanaged
greenhouse, but fire ant bait
was needed to manage the fire ants,
which were consuming the beneficial
insects.
In Overton, two broadcast
applications were needed to bring
whitefly populations back down to
manageable levels for the beneficial
insects.
In small-scale trials, Vafaie said
the combination of wasps and mites
worked as well as either predator
alone. Scouting for whiteflies and spotspraying
alone helped decrease the use
of pesticides during the study.
Pesticides that do not kill the wasps
and mites are typically used, or a spray
that will not leave residuals that will
harm the beneficial insects following a
treatment, he said.
" Throughout the small-scale
study, the combination of mites and
wasps were more reliable in handling
simulated whitefly migrations into
the greenhouses, " he said. " Mites are
thought to wait and intercept incoming
whiteflies, while wasps actively
move around and encounter new
populations of whiteflies. "
Wasps were released every week
while mites were released every four
weeks, Vafaie said.
Vafaie said applications of beneficial
A predatory mite feeding on a whitefly
nymph on the underside of a poinsettia
leaf. Photo: Erfan Vafaie/Texas A&M
In the most recent year, Vafaie has
focused on commercial trials to manage
whitefly populations using beneficial
insects in three locations where
poinsettias are being grown - two local
commercial growers' greenhouses
and Texas A&M AgriLife Research
greenhouses holding poinsettia trials
in Overton.
The mites, which are tiny spiders, and
wasps, which are smaller than fruit flies
and do not sting humans, are natural
whitefly predators. The mites feed on
small soft-bodied insect nymphs and
eggs, including eggs and young nymphs
of whiteflies and thrips. The wasps lay
eggs under middle-aged nymphs, and
the young wasps ultimately feed on the
whitefly nymphs.
Wasps have a better ability to move
around and often encounter dense
populations of whiteflies, whereas
mites' dispersal is much more limited,
Vafaie said.
insects took less time and labor than
spray applications. Although the
cost of beneficial insects was roughly
equivalent to the typical cost of
pesticide inputs, a full cost comparison
between conventional insecticide
rotations and the beneficial insect
strategy is still pending.
" The key to this strategy is to use
the beneficial insects to maintain
whiteflies below the retailer threshold, "
he said. " Unlike pesticide applications,
biological control is a numbers game;
each beneficial insect can only eat or
lay eggs under so many whiteflies for
a given period of time. If whiteflies
are reproducing at a faster rate than
the beneficial insects can consume,
then it's time to knock down whitefly
population with some selective
pesticides to levels manageable by the
beneficial insects again. "
Vafaie hopes to extend the study
further and incorporate an economist
to analyze the cost benefits of using
beneficial insects compared to
conventional preventative insecticide
rotations for commercial poinsettia
production. VGN
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VGN | APRIL 2020 | 21
http://www.belchimusa.com
April 2020

Table of Contents for the Digital Edition of April 2020
