Sugarcane aphids are making the leap from sugar to sorghum
Aug. 6, 2014 at 6:06 p.m.
Updated Aug. 6, 2014 at 11:11 p.m.
• Behavior: Colonize lower surfaces of lower leaves first and then advance to the upper leaves.
• Natural enemies: Lady beetles, syrphid fly larvae, green lacewings and parasitic wasps
• Control: A Section 18 Emergency Exemption Label was requested for the insecticide Transform WG. It has been effective in tests when used at a rate of 0.75 ounce per acre.
SOURCE: Texas A&M Agrilife Extension
Texas grain sorghum farmers found themselves with an added nuisance this growing season: white sugarcane aphids.
The aphids were first seen in sorghum crops in Louisiana last year and later were found migrating through East Texas and up into Oklahoma.
"Typically, it's an aphid that affects sugarcane. That's how you get the name of it. And last year, beginning in Louisiana, it shifted hosts to where it began to savor grain sorghum and other sorghum species like Johnsongrass," said Stephen Biles, the integrated pest management extension agent for Calhoun, Victoria and Refugio counties.
Extension agents monitored Johnsongrass, which is also of the sorghum genus, for aphids during the winter.
"It overwintered on our Johnsongrass. We never had a freeze that actually killed it," Biles said.
The aphids were not seen on local grain sorghum, which is predominately used as feed for chickens and cattle, until late May or early June this year. In some fields in the Crossroads, aphids were found on up to 10 percent of grain sorghum, also known as milo, Biles said.
"There are other parts of the state where it got considerably worse than what we experienced here," he said. "Here in Victoria, Calhoun and Refugio, I don't know that we saw much grain loss from a grain yield standpoint, except in a very few fields that weren't monitored really closely."
The tiny, soft-bodied insects have caused up to 50 percent yield loss in crops in 2013, according to a Texas A&M Agrilife extension report. Plants move carbohydrates from one place to another through a tissue called the phloem.
Aphids feed on the phloem, preventing the carbohydrates from moving from the place they are being produced - in the leaves through photosynthesis - to the head.
"So you're talking about the carbohydrates - the energy source of the plant - that don't get from the leaves to the head, where they need to be for producing grain," Biles said.
While farmers in the Crossroads were largely spared yield losses, the insects caused some problems with harvest.
As aphids feed on the honeydew of the phloem, they secrete some of the sugary water.
"It's pretty sticky. And the stickiness of it is what causes problems. It can cause problems with the flow of the grain through the machine and just gumming things up," Biles said.
The goo doesn't damage equipment but causes farmers to halt harvest to clean equipment before being able to continue.
Jerry Hroch, 56, of Victoria, harvested grain sorghum in his 200-acre field about 8 miles south of Victoria on Tuesday and Wednesday.
The ongoing drought had the unintended benefit of saving Hroch from the worst of the aphids. Hroch planted his grain sorghum about a week later than usual because the moisture content of the soil was too low for him to feel comfortable planting on time.
"In this area, the earlier planted crops had the aphid problem, and we planted probably a week behind everybody else, and the later stuff didn't have that problem," Hroch said.
Hroch saw some aphids on the outskirts of his fields earlier in the season, but the insects weren't heavy enough to spray insecticide.
"We didn't have enough of an aphid population to amount to anything, and it didn't affect the machinery one bit," Hroch said.
At one point in the year, there was a fear that the aphids would take over, said Sammy Fischer, an agronomist and salesman with Helena Chemical Co. in Placedo.
But a Dow insecticide called Transform WG, which received a Section 18 Emergency Exemption Label, was able to keep the insects at bay. The Environmental Protection Agency granted the exemption to control sugarcane aphids in sorghum.
"Because of the way the milo plant is structured, its hard to get spray all the way to the bottom of the plant. So, (the aphids) build back rather quickly. We had fields this year that we sprayed up to three times. We were able to keep the population under control but never got rid of them," Fischer said. "On the other side of the coin, we didn't lose fields to the insects, either."
Because this was the first full growing season Texas milo farmers were affected by the sugarcane aphids, many questions remain about how best to manage the pests and whether they'll stick around.
"All over the state where we're finding this insect, we're doing trials trying to figure out what is a damaging population. What is a population that we don't need to manage? Those are questions that we need to answer first," Biles said.
Sugarcane aphids are not expected to change the price of chicken or beef, Fischer said. But it may deter farmers from continuing to grow the crop. Sorghum is a fairly easy crop to grow in arid locations and doesn't need a lot of attention.
"If this becomes a continuos problem, it may make the crop less profitable. If this becomes a serious problem, some might turn to other crops," Fischer said.