June 2023 - 22

PLANT HEALTH
To start, the predatory mite
Amblyseius swirskii and the beetle
Delphastus catalinae feed on whitefly
eggs. Whitefly females produce
approximately 200 eggs per female
in their lifetime on poinsettia. Each
Amblyseius swirskii feeds on 10
whitefly eggs per day, while the beetle
Delphastus feeds on 160 whitefly eggs
per day. This is why Delphastus is often
used on hot spots due to its enormous
appetite for whitefly eggs. Once whitefly
eggs hatch, larval stages one (L1), two
(L2) and three (L3) follow.
The wasps Encarsia formosa and
Eretmocerus eremicus have two
" modes of action. " Both wasps do host
feeding by probing the younger larval
stage with their ovipositioner, and then
turn around and consume the fluids,
killing the whitefly larvae in the process.
Encarsia can host feed on three to
four L1 per day whereas Eretmocerus
eremicus can host feed on 20 to 30 L1
per day. The second " mode of action " is
parasitism. Both wasps lay eggs in the
older whitefly larval stage.
Encarsia formosa is not very suitable
for Bemisa tabaci (sweet potato
whitefly) which is most common in
poinsettia crops but does an excellent
job parasitizing greenhouse whitefly in
other greenhouse crops. Eretmocerus
eremicus can parasitize both sweet
potato and greenhouse whitefly larvae,
depositing an egg underneath the
whitefly larva. Once this egg hatches,
it enters the whitefly larva from
underneath and uses the now whitefly
pupae as a host to develop into a new
wasp. As a result, a new wasp emerges
from the pupa instead of a new whitefly.
By combining these four different
BCAs, we are covering a large part of
all the life stages of whiteflies, making it
easier to keep the whitefly population at
a low level. The only stages that are not
being covered in this pitchfork approach
are the pupae and adult stages.
Using several BCAs against one
particular pest problem and their life
stages makes biological control much
more robust. Using the pitchfork
approach, and BCAs focused on
different parts of the life cycle of pests
such as whitefly and thrips will keep
these pest problems from becoming a
problem. This is in essence the " mode
of action " of biological control. Avoiding
pests from becoming a problem in the
first place rather than fixing an already
established pest population.
Ronald Valentin is director of corporate IPM
at Mastronardi Produce. He can be reached
at ronald.valentin@sunsetgrown.com.
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JUNE 2023 GPNMAG.COM
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June 2023

Table of Contents for the Digital Edition of June 2023
