Much of the sorghum crop isn’t even in the ground yet, but it’s time to start thinking about the upcoming pest season.
Sugarcane aphids have been prevalent the last few years, first coming on the scene in 2013. It’s a relatively new pest to sorghum in the United States, and according to the Sorghum Checkoff, it is capable of causing substantial damage to the crop if left unmanaged. It is important for producers to be proactive and constantly scout for and monitor the pest because early detection is critical to minimize the aphid’s harmful effects.
The sugarcane aphid, Melanaphis sacchari, will only survive and multiply significantly in sorghum genotypes, including Johnsongrass, shattercane, sorghum-sudangrass, sudangrass, forage sorghum and grain sorghum. This type of aphid struggles to survive on other crops—corn, cotton, soybeans or wheat. It’s often distributed by the wind.
J.P. Michaud, entomology professor with Kansas State University, told producers in early February, there’s been a lot of focus on aphids in sorghum.
“I’m sure you all realize this is like the seventh year we’re going to be facing SCA,” he said. “But the problem does seem to be in decline.”
He said the SCA is in the endemic phase, and that’s a good thing.
“When we get endemic, it means its like all the other aphids in sorghum and we probably won’t need to spray for it hardly ever,” Michaud said. “Problems continue to diminish annually. Fewer and fewer acres treated.”
Some producers went ahead and sprayed for SCA in 2018 because they needed to economically.
“It’s still advisable to be vigilant,” he said. “Still advisable to plant as early as possible; get as much growth on the plant before the aphids come out.”
Some resistant sorghum varieties can help with infestation, and Michaud warns producers to see how those varieties have performed in the past.
“But if they haven’t, if it was me I’d probably say I wouldn’t even worry about that,” he said.
Scouting often and early is critical.
“Accept you’re going to have to go and start checking that field every 3 to 4 days for aphids once it becomes past boot stage or further on,” Michaud said. “And the reason I say that, around my area a lot of those people chose an aphid-resistant cultivar based on that. They did not really perform that well.”
Some resistant varieties aren’t suited to perform well in certain areas, and Michaud heard the complaints. It might be more affordable to spray multiple times than spending even more money on the resistant varieties.
“If you’ve had good results with the resistant variety that you like, then by all means,” he said. “But I would select a high yielding variety if you can just accept the fact and keep an eye on it.”
Often a threshold for plants being infested pre-boot is about 20 percent and post-boot it reaches 30 percent, he said.
“Again, the earlier the plant gets infested the more you stand to lose before it gets under control,” Michaud said. “That’s why the threshold is higher later.”
Timing effective treatment to control SCA in sorghum depends on the size of the SCA population.
K-State recommends if no SCA are present, or there are only a few wingless/winged aphids on upper leaves, continue once-a-week scouting. If SCA are found on lower or upper-canopy leaves, begin twice-a-week scouting.
For more detailed information about scouting visit K-State’s resource card at www.myfields.info/sites/default/files/page/ScoutCard%20KSU%20v05312017.pdf.
Kylene Scott can be reached at 620-227-1804 or email@example.com.