What is in this article?:
- No silver bullet for aflatoxin control
- Host-pant resistance being studied
- Combination of practices best option.
No silver bullet, no magic potion, no miracle medicine exists to eliminate aflatoxin as a threat to Southwest corn production.
But growers do have options to increase their odds of producing grain with levels low enough to avoid dockage or, at worst, being refused at the elevator.
“When we plant in a high risk aflatoxin environment, we want to get levels low or to even zero,” says Seth Murray, Texas AgriLife Experiment Station corn breeder, who spoke at the recent Blackland Income Growth Conference at Waco.“It takes an integrated approach, a combination of practices.”
Murray and Texas AgriLife Extension Pathologist Tom Isakeit discussed ways to minimize the contamination threat of the devastating fungus, Aspergillus flavus.
Murray is looking at varieties with improved tolerance to aflatoxin contamination. “No resistance exists,” he notes, but factors such as heat resistance, insect tolerance and certain physical aspects of the corn ear and kernel may play a role in reducing infection. “Insect control and cultural practices, along with biological controls, are other possibilities.”
Reducing insect pressure may be a factor in some areas. “In some locations, insect vectors are a major factor in aflatoxin contamination,” he says. “But in College Station, we see little effect from insects as a vector.”
Kernel hardness and stress tolerance in corn hybrids are important — hybrids with open husks are more prone to aflatoxin. “We see more fungus and more toxins in these hybrids; they are geared to Midwest conditions because they dry down better.”
A harder endosperm resists contamination better. Ear droop also plays a role. Many newer hybrids produce ears that stand straight. Those that droop are less likely to collect moisture that creates a favorable environment for the fungus, Murray says. The fungus is much more likely to enter injured seed.
Commercial breeders have not done a lot of work on developing aflatoxin-resistant hybrids. With support from the Texas Corn Producers Board, three new inbred lines less susceptible to aflatoxin contamination were recently released by the Texas AgriLife Experiment Station.
“So far, the best resistance we’ve found does not yield well. Improving yields in these strains takes time.” It will be a few years before growers find these traits in commercial hybrids.
In the meantime, Isakeit says, growers should select hybrids best adapted to their specific growing areas. “Look at performance trials for those specific areas and conditions.”
“Don’t rely on transgenic hybrids to control mycotoxins,” Murray says. “We’ve seen a small effect from Bt corn in reducing insect damage, but no significant reduction in aflatoxin levels. We do see significant differences in aflatoxin contamination from hybrid parent lines.”