The
sugarcane aphid arrives on the southern High Plains
Blayne
Reed, Patrick Porter and Ed Bynum
We have been watching for the possible
arrival of the sugarcane aphid, Melanaphis
sacchari, on the High Plains, and we must now report that it has been found. Clay Golden, an independent crop consultant
serving the area, discovered a small pocket of the aphids on soft dough stage
sorghum in an extreme northwestern portion of Floyd County on September 9, 2014. Upon his find Clay enlisted the aid of Blayne
Reed, EA-IPM Hale & Swisher counties, who supported Clay’s identification
of the aphid. Dr. Pat Porter and Dr. Ed
Bynum were then presented with aphid samples and confirm the identification.
Given the proximity of this aphid population
to neighboring counties; ½ mile from Briscoe, 2 miles from Swisher, and 7 ½ miles
from Hale, combined with some possible smaller and un-confirmable sugarcane
aphid hits in nearby sorghum in Swisher and Hale and that this aphid is often
dispersed by prevailing winds, it is logical to assume that it is present over
a wider area encompassing small portions of all four counties. Many of the
aphids in Clay’s sample were at the developmental stage just prior to becoming
winged adults, so we expect that further dispersal is happening now.
After
Clay’s discovery, we asked for some help and perspective from our downstate
colleagues who have been dealing with this pest since last year. Here is a
summary of information from Raul Villanueva, Robert Bowling, Stephen Biles and
Mike Brewer.
1)
It takes ten days to two weeks for isolated aphids to establish significant
colonies on sorghum. So scouting should be concentrated on finding the first few
infesting aphids in the field on lower leaves.
2)
Stephen Biles, Extension Agent IPM in
Victoria, has done some very recent work on an action threshold in sorghum in
the reproductive stage. Stephen’s work suggests that a good action threshold
for treating is an average of 100 aphids per leaf. He suggests sampling 10
plants per location within a field (several locations) and picking the leaf
below the flag leaf and an additional leaf from the middle of the plant. If
there are an average of 100 aphids per leaf (2,000 total on all 20 leaves), then
come back in two days and re-sample to see if the population is increasing. If
the numbers are going up then consider treating. If the numbers are not going
up then don’t treat but continue to monitor. Observations of this aphid from
downstate have shown that some populations can crash very quickly. We don’t
know how to predict which populations will crash and which will increase.
3)
Transform (available under a Section 18 exemption) is the most effective
insecticide. It can be used at a rate of 0.75 to 1.5 ounces per acre. Our
downstate colleagues have had good results at the 0.75 ounce rate, but good
coverage is essential at this rate. They strongly recommend 10 gallons of
carrier volume per acre by ground and, if this can’t be achieved with aerial
application, they recommend a bare minimum of 5 gallons per acre and a minimum
rate of Transform of 1.0 ounces per acre. (Which is to say the 0.75 oz rate of
Transform may not work by air at 5 gallons per acre.) We do not know if a 1.0
oz rate can be put out at less than 5 gallons per acre. Our colleagues have
also said that Dimethoate is not a good option because it is not a consistent
performer.
This aphid is not going to be Atilla the Hun
on the High Plains. Invasive species often do
the most damage in their first year or two of invasion before natural enemies
can respond to the new pest. For this
year at least, the aphid is arriving late in the season and will not be
infesting whorl stage plants which will be limiting the aphid in time to build
into an economic problem. We also have products that have proven to control
this aphid. This, combined with the implementation of good scouting techniques,
give us confidence that this aphid can be effectively controlled if necessary. The
Section 18 allows for two applications of Transform (1.5 oz maximum per
application), with the total application for the season not exceeding 3.0 ounces.
There is also a mandatory 14-day waiting period between the first and second
application. So this gives us six weeks of good control, assuming 14 days of
activity from each application. This should be sufficient to carry us through
harvest.
It is not known whether the sugarcane aphid
can overwinter on the southern High Plains; it is a subtropical species and
overwintering survival is very much in doubt. We also do not know how fast the
sugarcane aphid can reproduce given the predicted cooler temperatures in this
week’s weather forecast. We will have to
watch for it next year when our sorghum is in the whorl stage, but for this year
we can handle the problem if it arises.
The
sugarcane aphid is fairly easy to recognize and distinguish from our other
common aphids. Look for black-tipped antennae and legs. Dr. Ed Bynum recently
posted an article on identifying the sugarcane aphid: http://amarillo.tamu.edu/files/2010/11/PPU-V6i6-5-23-2014.pdf
. Our publication Sugarcane Aphid: A New Pest of Sorghum is available here: http://www.agrilifebookstore.org/product-p/ento-035.htm
. We will of course keep you informed of new developments.
I
should also note, particularly to this audience, a few details. Today the sugarcane aphid is only officially
confirmed in Floyd County. This
confirmation comes from a currently very small pocket population that remains
hard to find within that field, even for Clay who has walked this field all
season long and visited the exact spot several times now. I have not found any pockets of the sugarcane
aphid in our program fields. Whorl stage
sorghum type hay crops could be at the highest risk. I would also like to doubly stress that it is
very late in the season and we have a proven product in our pest control toolbox
if need be. While the history and proven
damage of this aphid makes it worth a closer than normal check in area sorghum
for this late in the season I would personally like to sum it up this way:
These guys are mean and nasty, but they came wearing Bermuda shorts, they did
not pack a coat, and the ‘wanted dead not alive’ posters are hot off the press.
Blayne
Reed
