Ready When You Are

Small pests can cause big problems

Insects such as the lesser grain borer, rice weevil and flour beetle may only be about 3 millimeters long, but these small pests can cause big problems when it comes to storing harvested crops. Infestations can cause significant losses in both grain quality and quantity, literally eating into a grower’s profits.

The cost can be staggering. Kevin Daniel, manager of MFA Agri Services in Sedalia, Mo., saw the negative impact firsthand when a customer brought in a load of corn heavily infested with weevils

“It was so damaged that it wasn’t worth half the price,” Daniel said. “We didn’t want to mix it in with other customers’ corn and bring their quality down. It was quite an issue. If he’d just spent a few cents per bushel to protect it going into the bin, he wouldn’t have had the problem coming out of the bin.”

It’s a widespread issue that farmers and elevator operators deal with every year. Post-harvest insect infestations account for the destruction of up to 10% of the U.S. grain crop annually, according to Johnny Wilson, technical services specialist for Central Life Sciences (CLS) Grain Protection and Specialty divisions. And the longer grain stays in storage, the greater the risk of infestation or damage that can compromise the return on investment for farmers.

“Crop management doesn’t end when harvest is over,” Wilson said. “We like to brag to our friends and neighbors about how we were able to coax out an extra 5 bushels an acre by implementing a new technique or product. Checks don’t get cut based on crop yield, though. They get cut after delivery. By utilizing good sanitation practices, good management practices and properly protecting your grain, you can rest easy knowing you did everything to maximize your profits.

Identifying the enemy

Crops most susceptible to insect damage are wheat, corn, rice, barley and oats, Wilson said, and knowing what pests are most threatening can help determine the best control methods. Internal-feeding insects such as the rice weevil, granary weevil and lesser grain borer do their damage by penetrating through the outside of the kernel and eating the interior components of the grain. They also use the kernel as a nesting ground to lay eggs and hatch the next generation of feeders.

“By laying eggs inside of the kernel, it provides them protection from chemical grain protectants and even fumigants,” Wilson said. “This allows the immature larvae to pupate inside the kernel without coming into contact with an insecticide, even if one is applied, because it is all on the exterior of the kernel.”

Stored grain is also threatened by “secondary feeders,” which are insects that do not burrow into the kernel but act more as scavengers. They tend to be invasive in processing facilities where grain is being broken down and in situations where the grain has become compromised due to damaged kernels. This class includes such insects as red flour beetles, merchant beetles and Indian meal moths.

“While not directly damaging whole grain, their presence can disrupt the temperature and moisture of stored grain as well as serve as a warning that damage is occurring due to internal feeders,” Wilson explained. “Since they don’t have the luxury of burrowing into the grain, the eggs and immature insects will be susceptible to chemical protectants.”

Assessing the damage

Wilson, who holds a Ph.D. in grain science, has been studying the economic impact of insect damage in stored grain. Specifically, he is spearheading trials at the CLS facility in Dallas, Texas, to measure the degree and type of grain loss that occurs over time in storage due to insect damage.

“In our current trial, we are measuring losses in whole corn infested with lesser grain borers and comparing it to corn treated with a grain protectant prior to insect addition,” Wilson explained. “We have just completed our 60-day testing, and the amount of damage we already see is shocking.”

Over that two-month period, Wilson said the grain incurred a loss of 1.5% in dry matter shrink when no insect-control treatment was applied. That doesn’t factor in the fines generated by the insects, which account for another 0.5% loss.

“Now, we’re at a 2% dry matter loss, and we haven’t even factored in the effect it will have on grade,” Wilson added. “To quantify the impact to the producer, at $5-per-bushel corn, a 2% loss is 10 cents per bushel. That alone will give a positive return on investment for insect-control measures without even factoring in the severe penalties for grain quality.”

He said perhaps the most shocking dataset from the study is the percentage by weight of insect-damaged kernels. The untreated corn had a whopping 14% of kernels with signs of insect damage while the corn treated with CLS’s new stored-grain insecticide, Gravista-D, showed virtually no damage before insect mortality occurred.

“That percentage is enough to kick a sample of corn down from U.S. No. 2 grade all the way to U.S. sample grade and result in rejections,” Wilson said, adding that he anticipates an even greater loss when the study concludes after 90 days. “Even blending corn with this level of damage into other bins for a quick sale will be very difficult.”

In future seasons, Wilson said CLS will be conducting scale-up trials with the USDA to quantify losses and the value that can be generated by preserving grain. These trials will take place in a variety of storage situations and at a scale much more representative of commercial grain operations.

“Every operation’s different, so we can’t realistically test every variable,” he said. “But if we can at least give a good starting point to say, in an average year, if you’re putting grain in this type of scenario and holding it for this long, this is the amount of shrink that you can realistically expect from insects, damage from respiration, water, migration, all these different things. And then we can show the value of treating before grain goes in there.”

Making the grade

It doesn’t take a scientific study, however, to convince Mel Gerber to protect the quality of the wheat he grows on his farm in Versailles, Mo. He treats every load as it goes into the bin with CLS’s Diacon IGR Plus, an insecticide that provides two modes of action through an insect growth regulator plus adulticide.

“If you’re going to be profitable growing wheat, it has one real market—human-grade consumption. And that means it must be quality wheat,” Gerber said. “If it’s only fit to feed to cattle or pigs or chickens, you’re not going to get much money for it. Anything we can do to make wheat safer, better and higher quality is what we need to do. The market does not like nasty wheat.”

Gerber uses a liquid applicator he created and calibrated to dribble the insecticide over the wheat as it goes into the bin. The practice takes little extra effort, he said, and the cost is minimal compared to the discounts that poor-quality grain might encounter at market.

“Look at it this way. It only costs you 6 or 7 cents to treat a bushel. How much are they going to dock you if you have weevils in your wheat? 40 cents? 60 cents?” Gerber said. “You may be spending money, but you’re actually saving money and protecting quality.”

As harvest season approaches, now is the time to think about storage plans and how to best protect high-value grain crops from the threat of damaging insects. It’s important to have a multi-pronged approach, Gerber said.

“Insect control’s fairly easy, but it’s not enough by itself,” Gerber said. “You shouldn’t depend just on insecticides for your storage solutions, especially if you’re keeping that grain long term. Unless you’ve got the most high-tech system available, I think it’s a good idea to move that grain every so often, and that solves a lot of the problems. You can examine it. Check to make sure the moisture is OK. You can retreat if you need to. Even if you have to move from one bin to another and then put it back, you can at least see how you’re doing.

Insect control in stored grain is unique to each facility. Challenges such as regional climate, outside insect pressure, carryover, facility age and dozens of other factors make blanket recommendations impossible, Wilson said. When it comes to best practices in grain storage, he said he likes to follow the “S.L.A.M.” method: Sanitation, Loading, Aeration and Monitoring (see accompanying sidebar).

“I would love to be able to say all you have to do is use CLS products, and all your problems will go away,” he said. “But unfortunately, real life is not that simple. I like to preach integrated pest management. Any pest control method—from protectants to fumigants to heat treatment—will not be as effective as it could be if it is not completed as part of a whole program.”