Several of our outstanding independent crop consultants found sugarcane aphids (SCA) in Floyd County late last week and early this week. So far, the populations are very light, hard to find, and as of this
morning, only along the ‘waterways’ leading westward up the caprock or on the
very few fields off the caprock farther east. These draws do cut a pretty
good way westward into the caprock region including Floyd, Swisher, and Hale Counties. One of the fields confirmed with SCA today was actually in
southwestern Floyd at the edge of one of these draws. It is very likely
we have SCA farther west right now than we realize, but at a level very difficult
to find without a fleet of entomologist in every field. At face value,
this looks like the same infestation pattern we have had for the two previous
years with the aphids either flying on the easiest route or pushed by wind up
these ‘funnels’ and drawn to the irrigated sorghum fields on the edges of the
draws. In terms of population today, the amount of infested plants are
all well <1% with less than 10 aphids per found colony. We all know
how fast this can change. There are not many winged aphids in these fields yet, but we will be watching closely.
We have been expecting the arrival of this aphid for sometime. Now that it is here, lets review our sugarcane aphid IPM for the Texas High Plains to make sure our sorghum remains profitable.
The following was written by Dr. Pat Porter just for this purpose:
Now that sugarcane aphid has been found in Floyd County it is safe to
assume that we will shortly find it in surrounding High Plains counties.
We all went through the aphid invasion last year and there is no need
to go in to great depth on scouting and management, so I will just hit
the highlights from lessons learned last year. If you want to read our
complete 2016 sugarcane aphid management publication
it is here.
Early planting is going to pay off
The earlier the aphid arrives during crop development, the more damage
it can do. Infestations prior to boot can cause sterile panicles and
decrease yields to essentially zero. Infestations at or after flowering,
while still very serious, are somewhat less potentially damaging. This
is why our treatment thresholds vary by crop stage.
Treatment threshold:
Pre-boot: 20% of plants with aphids.
Boot: 20% of plants infested with 50 aphids per leaf.
Flowering to Milk: 30% of plants infested with 50 aphids per leaf.
Soft dough through dough: 30% of plants infested, localized areas with heavy honeydew, and established aphid colonies.
Black layer: Heavy honeydew and established aphid colonies with treatment only for preventing harvest problems.
Our earlier planted sorghum has either finished flowering or is now
flowering and has moved to the place it can withstand more aphids. In
part this might matter because we have a relatively high number of
beneficial insects in the system, and they have a better chance of
keeping populations below treatment thresholds when those thresholds are
higher. And even if one insecticide application is necessary, the need
for a second application is far less likely in a much more mature crop.
Weekly scouting is a must
Under hot, dry conditions, the reproductive capacity of this aphid
(which is born pregnant) is something approaching Shock And Awe, and
everyone who went through the 2015 season will agree. Missing a weekly
scouting might mean missing populations low enough to be brought under
control with insecticides. In 2015 we had many fields that were sprayed
too late and adequate control was not achieved without a second
application. Once the aphid has been found in a field, then twice-weekly
scouting is important. Last year I would have linked to our
guide to recognizing the sugarcane aphid, but this year I think we all know what the enemy looks like.
"Tolerant" hybrids are susceptible hybrids
There are a few hybrids with resistance to sugarcane aphids, although
the seed industry chooses to call these "tolerant" hybrids because they
rightly don't want to give the impression they are bulletproof. Our best
resistant hybrids are what could be called moderately resistant, and
this won't stop the aphids from reaching treatment thresholds. It may
slow them down, and it may let the beneficial insects have more time to
exert control, but all other things being equal it is merely a delaying
action. Fields of "tolerant" hybrids should be scouted and sprayed based
on the treatment threshold just like fields of completely susceptible
hybrids.
Insecticide choice matters - a lot
Last year saw everything in the book, and some things not in the book,
being thrown at sugarcane aphids. Many of these insecticide products
were our old aphid standards, and what we found was that they were not
very good at killing aphids, but they were very good at killing
beneficial insects (the big guns in aphid control after an application).
Our insecticide trials confirmed this; we had massive aphid resurgence
where we killed the beneficial insects. There are only two good
insecticide choices for sugarcane aphid: Sivanto and Transform. Both of
these provide high efficacy with minimal impact on beneficial insects.
Make the first application count
Last year we observed insecticide applications of Sivanto and Transform
made with high rates and plenty of carrier volume most often did such a
good job of control that the few surviving aphids were cleaned up by
beneficial insects. Conversely, we observed that fields sprayed with
lower rates and/or insufficient carrier volumes frequently did not get
control and required a second application.
Experience is a good teacher
This pest is manageable. Last year was a bit of trial and error, but
after one growing season of intense aphid pressure we are much better
equipped in 2016.
