WHAT IS THRYVON™ COTTON?
ThryvOnTM is a cotton biotechnology trait that expresses the
Mpp51Aa2 protein (also known as Cry51Aa2). Unlike other Bt proteins used in
cotton, this particular Bt protein does not affect caterpillar pests like
bollworms. However, it has activity on thrips and plant bugs.
HOW
DOES THRYVON TECHNOLOGY AFFECT GROWERS’ THRIPS MANAGEMENT DECISIONS?
ThryvOn cotton provides excellent control of thrips and eliminates
the need for additional insecticide inputs. Against thrips, ThryvOn provides
protection by deterring feeding and oviposition (egg-laying). Thus, adults may
still be readily found in ThryvOn cotton, but they will not be feeding as much,
or laying eggs, and will be repelled. The fact that fewer eggs are laid results
in a great reduction in immature thrips. Comprehensive field trials conducted
throughout Texas have demonstrated that ThryvOn has excellent activity on all
commonly encountered early-season thrips species, including tobacco thrips,
western flower thrips, eastern flower thrips, and onion thrips.
Data collected by Texas A&M AgriLife
Extension has demonstrated that ThryvOn cotton does not economically benefit
from additional thrips control delivered from insecticide seed treatments,
in-furrow insecticides, or foliar insecticides. ThryvOn cotton not treated with
these insecticide treatments may exhibit slightly more damage from thrips feeding,
but the damage is very superficial and is not economically significant. In
essence, ThryvOn cotton should not need additional control measures for thrips.
However, seed treatments or in-furrow insecticides may still be desired for
aiding in the management of wireworms, nematodes, or other early-season pests.
ARE
INSECTICIDE SEED TREATMENTS OPTIONAL IN THRYVON COTTON?
Yes and no. While current research has
documented limited benefits of adding insecticide seed treatment to ThryvOn,
the seed will be marketed only with an imidacloprid seed treatment in the
eastern half of Texas, where tobacco thrips are the predominant early-season
thrips pest. Insecticide seed treatment is optional in the western half of
Texas (Fig. 1). The reason for requiring insecticide seed treatment in the
region of the state where tobacco thrips are common is for resistance
management. The risk of tobacco thrips developing resistance to ThryvOn is
considered higher than for other thrips species.
Fig. 1. ThryvOn cotton seed planted in the counties highlighted in blue will
only be sold with the addition of an insecticide seed treatment, whereas an
insecticide seed treatment will be optional for the red counties.
HOW
EFFECTIVE IS THRYVON ON TARNISHED PLANT BUGS?
Although the Bt protein expressed in ThryvOn cotton has activity
on tarnished plant bugs, it primarily offers suppression. ThryvOn has little
known activity on adult plant bugs, but it can kill small nymphs. Thus, plant
bug populations should not develop as quickly in ThryvOn as in non-ThryvOn
cotton. However, insecticide applications targeting plant bugs may still be
required. Currently, Texas A&M AgriLife Extension recommends utilizing the
same action thresholds for plant bugs in ThryvOn cotton as for non-ThryvOn
cotton but anticipates fewer insecticide applications being necessary.
DOES
THRYVON HAVE ANY ACTIVITY ON COTTON FLEAHOPPERS?
ThryvOn cotton is not labeled for managing
cotton fleahoppers. However, data collected by Texas A&M AgriLife Extension
has demonstrated that ThryvOn has activity on cotton fleahoppers, similar to
that observed for tarnished plant bugs. ThryvOn cotton will be readily
colonized by adult cotton fleahoppers, but fewer large nymphs will survive.
Furthermore, the authors have observed that ThryvOn does affect cotton
fleahopper feeding behavior, which results in less cotton fleahopper-induced
square loss. Thus, when cotton fleahoppers are present, ThryvOn cotton tends to
have better square retention relative to non-ThryvOn cotton. Currently, Texas
A&M AgriLife Extension recommends utilizing the same action thresholds for
cotton fleahoppers in ThryvOn cotton as for non-ThryvOn cotton. However, data
suggests that cotton fleahopper management with insecticides in ThryvOn cotton
will be superior to non-ThryvOn cotton.
WHAT
ABOUT THRYVON’S ACTIVITY ON OTHER COTTON PESTS?
The Mpp51Aa2 protein in ThryvOn has no known activity on
caterpillars, stink bugs, aphids, or whiteflies. However, it is unknown whether
this technology will impact mid- to late-season thrips species, such as chili
thrips, bean thrips, or Kurtoma thrips. Additionally, it is unknown if ThryvOn
has activity on cotton pests similar to plant bugs, such as the verde plant bug
or the rapid plant bug. Efficacy data on these pests has yet to be collected.
DOES
THE THRYVON TECHNOLOGY HAVE ANY IMPACT ON BENEFICIAL ARTHROPODS?
ThryvOn has little impact on the most beneficial arthropod
species. The Mpp51Aa2 protein has been shown to have some activity on minute
pirate bugs in that it delays their development. Also, it does affect thrips,
which are often important predators of spider mites.
ARE
THERE ANY UNEXPECTED RISKS FROM PLANTING THRYVON COTTON?
Because ThryvOn has very good activity on
thrips and thrips are effective predators of spider mites, it has been
observed, but not quantified, that spider mite outbreaks may be more likely in
ThryvOn cotton than in non-ThryvOn cotton. However, more research is necessary
to better understand the magnitude of this risk.
HOW WOULD THRYVON HELP WITH OVERALL CROP
MANAGEMENT?
ThryvOn does offer some management flexibility to growers.
Managing insecticide applications across a large span of farmland with limited
equipment can pose timing challenges. Weather conditions can exacerbate this
issue. ThryvOn offers growers a level of flexibility, enabling them to
undertake certain activities that were previously unattainable under such
circumstances. For instance, during a cool and damp period in the initial
stages of the growing season, maneuvering a sprayer across the cotton field might
be unfeasible despite the presence of thrips actively feeding. However, with
the inherent thrips protection integrated into ThryvOn cotton, growers would
not have to worry about this issue. Another advantage of the built-in
protection is the elimination of concerns related to chemical wash-off problems
and potential insecticide loss due to heavy rainfall events.
DOES
THRYVON COTTON NEED A DIFFERENT PLANT GROWTH REGULATOR (PGR) REGIMEN THAN
NON-THRYVON COTTON?
Overall, ThryvOn cotton exhibits better fruit retention than
non-ThryvOn varieties, which can affect plant growth and maturity. Thus,
although the ThryvOn trait in itself does not warrant a different PGR regimen,
better square sets may reduce the need for some PGR applications.
DOES
THRYVON OFFER GREATER ECONOMIC RETURNS THAN THE NON-THRYVON COTTON?
The economic benefit from planting ThryvOn cotton is dependent
upon the pest pressures of thrips, tarnished plant bugs, and cotton
fleahoppers. If these pests are not common issues on a particular farm, there
is probably little benefit from planting the technology. However, eliminating
the need for an insecticide seed treatment or foliar insecticides can provide
tangible benefits. In general, if the cost of one insecticide application can
be realized on ThryvOn, the cost of the technology will easily pay for itself.
THRYVON
TAKE-HOME POINTS
ThryvOn Bt technology has excellent
activity on thrips and eliminates the need for supplemental thrips control
measures. This technology will aid in managing plant bugs and cotton
fleahoppers. Though it will not eliminate the need for insecticides to manage
these pests, it may reduce the number of insecticide applications necessary.
Timely field scouting, use of action thresholds, and insecticide selection are
still important for plant bug and cotton fleahopper management in ThryvOn
cotton. Finally, ThryvOn cotton has no efficacy on insect pests, such as
aphids, spider mites, grasshoppers, stink bugs, etc., and therefore, regular
field scouting and monitoring is still critical in ThryvOn cotton.
Authors: Suhas Vyavhare and David Kerns; Extension Entomologists, Texas A&M AgriLife Extension Service
