The bug issue
Stepping onto his porch one day last June, Jay Fogle looked out over his favorite alfalfa field on his farm in Peculiar, Mo. Something wasn’t quite right.
“He sent me a picture,” said MFA Crop-Trak Consultant Erica Wagenknecht, who scouts Fogle’s fields. “There was this triangle-shaped, yellow burn toward the leaf tips.”
For Fogle, a fourth-generation dairyman, alfalfa equals milk production, and he needed answers. When Wagenknecht arrived at the farm, she swept the field with a net and found the source of the problem—potato leafhopper—which causes a discoloration on the leaf tips known as hopperburn. It wasn’t an insect she had encountered before on this farm.
A native species, the potato leafhopper feeds on the underside of leaves in a wide variety of plants. As it feeds, it injects a toxin that, in alfalfa, reduces yield, lowers protein content and increases root rot and stand failure. In Missouri, potato leafhopper can produce two to three generations each summer.
“It overwinters in the south and migrates north with southern winds in the summer,” Wagenknecht said. “Because 70 percent of potato leafhoppers are female, and their eggs hatch in about a week, it can quickly become devastating for farmers.”
In addition to alfalfa, Fogle raises corn, soybeans and beef cattle, operates a bakery and milks 50 cows twice a day. He also experiments with other crops such as hay beans and sorghum.
“Being a dairy, there are challenges with treating an insect like this,” Fogle said. “We had to check the harvest interval and feeding restrictions. With alfalfa, there are only a few chemical options for treatment anyway. So we had to not only think about what we would spray and what would work but also how many days would we have to wait before we could harvest and feed it.”
Wagenknecht got to work and did some research, locating a product that would fit the requirements.
“I think researching residuals generally takes up most of Erica’s time,” Fogle said. “But bugs can be the difference between a good yield and a bad yield real quick, and it’s typically the least expensive thing to fix.”
Fogle has participated in MFA’s Crop-Trak for 10 years, and Wagenknecht has scouted roughly 200 acres of the farm for the past four years. The program employs independent consultants who work with farmers on cropping plans and scout fields once a week during the growing season. Fogle said he’s learned something from each agronomist who has scouted for him; in turn, Wagenknecht says she and her fellow consultants learn from scouting such a diverse operation.
“There’s a difference between driving past a field and walking through a field,” Fogle said. “By the time you can visually see a problem driving past it, you’re definitely in reactive mode. It is already well into an issue. That’s the difference in having someone walk the field. They can tell the changes in the field from this week to the next and know when they need to look deeper.”
Cultural, biological and chemical
Crop-Trak consultants encourage growers to use the integrated pest management model, which brings together a broad-based approach to control insects. Cultural practices such as crop rotation, soil health management and “trap” crops—planted to attract insect pests from another crop—help to reduce or eliminate harmful insect populations. Biological controls introduce insects’ natural enemies to reduce damage caused by a specific population. Chemical controls are sprayed to prevent, destroy or repel pests.
“Insects are like dealing with any other pest,” MFA Senior Staff Agronomist Jason Worthington said. “We put a lot of attention on our herbicide program ahead of season, and most growers understand with a weed like waterhemp that you have to attack it before it becomes a problem. If you let weeds get out of control, even if you clean them up, they’re going to rob yield from you. Insects are no different.”
There are some insects, like cutworms, that growers can’t react to fast enough, Worthington said, so preventative measures should be taken at the proper timing.
But not all insects in any given field are bad, he stressed. Lady beetles and their larvae control aphids and mites. Lacewings can quell aphids. Parasitic wasps can repress caterpillar populations and other insects. Even spiders and assassin bugs are predators that do their part. Eventually, Worthington said, he expects these biological controls to become more prevalent.
“In the future, we may be able to introduce beneficial microbes that, similarly to beneficial insects, could help control pest populations,” he said. “We are currently evaluating some of these products that are already on the market.”
From a stewardship standpoint, it’s important to understand what threats move so rapidly that preventative control is warranted, Worthington added.
“And not only do they move rapidly, but how common are they? Are they something that we deal with most years? If they don’t fall into those categories, then do we have time to react?” he said. “Sometimes in terms of beneficials we can be doing more harm than good by spraying. So starting with a good plan for those frequent and quickly developing insect pests is paramount. Following up for those less frequent, but still potentially damaging, pests with thorough scouting is really the way to go.”
Monitoring and diligence
Year in and year out, MFA’s crop scouts and agronomists have an idea of what they need to watch for each season, Worthington said.
“Every year, we contend with cutworms in corn, Japanese beetles in soy and weevils in alfalfa,” Worthington said. “But the bigger question is what’s going to show up that we don’t expect? Are we going to have an army worm year or not? What are going to be our pod feeders? Are we going to see any invasives? I don’t know if it’s so much preparing for a specific insect. It’s more about making sure we’re diligent in our scouting efforts and looking for these things. It’s one of the big reasons we have Crop-Trak—to catch what we don’t expect.”
Invasives: the good, the bad, and the bugly
With global trade often comes invasive insect species. The Japanese beetle, for example, was first discovered in 1916 on the East Coast but is thought to have entered the U.S. as larvae via imported plants before inspections began in 1912. When dealing with eggs and larvae, it’s almost impossible to catch everything, but the issue with invasive species is their natural enemies usually don’t make the trip with them, said Dr. Kevin Rice, University of Missouri assistant professor of entomology and state Extension specialist.
“Typically with invasive species, they’re transported here unintentionally,” Rice said. “They hitchhike on our cargo. A couple of pregnant females reproduce, and they have explosive growth patterns because there’s nothing in this new environment to
Rice said the lack of natural predators leads to a couple of problems—higher populations and greater economic damage certainly—but it also means entomologists in the area typically haven’t studied the insect’s biology or ecology to figure out if there are better ways to manage it. Therefore, chemical control becomes the default.
“Unfortunately when we get these invasive species, our growers are sort of forced into relying solely on chemical control,” Rice said. “And because we don’t have any other management modes, they typically go to calendar-based weekly sprays, causing an imbalance in our integrated pest management and potentially disrupting what they’ve been working toward for many decades.”
Once forced to rely on chemical control, Rice said, there are often secondary pest outbreaks due to repeatedly spraying for one insect. For example, growers also may wipe out the natural enemies for a native pest species such as aphids, which can then grow out of control. Persistent spraying also puts products at risk for the target pest developing resistance.
“It’s a difficult problem because we can’t just give up that economic loss,” Rice said. “But we should keep established economic thresholds in mind to determine when spraying is necessary.”
Here are some of the invasive species Rice has been studying that could impact growers in MFA’s territory:
Before joining the MU staff in January 2018, Rice worked in Pennsylvania and outside of D.C. in field crops. But he said he’d never seen populations of Japanese beetles like he saw here in Missouri this past summer.
Though the beetle was introduced in the early 1900s, it moves slowly. It’s taken roughly 100 years to make it this far west. Missouri is right on the invasion front, Rice said.
“We had fewer beetles in the mid-Atlantic because several decades ago the USDA released these tiny wasps on the East Coast that parasitize Japanese beetle grubs,” he explained. “That has lowered the population in those areas, but we’re currently forced to deal with higher-than-normal populations until it makes its way here.”
The good news is the wasp, known as Tiphia vernalis or the more common “spring Tiphia” was redetected in 2018 after 10 years in Meramec State Park near Sullivan, Mo.
“It’s going to come behind the Japanese beetle, establish its own populations and lower the Japanese beetle population to a much less economically damaging level,” Rice said.
There are a lot of questions about chemical resistance and Japanese beetle, he continued, but currently the insect shows no resistance to standard controls.
“Pyrethroids and other classes are excellent at knocking these guys down,” Rice said. “You can spray on Monday and kill 100 percent of the adults in your field, but they move around so much that they will come in from your neighbor’s field and untreated natural habitats, making it a continual problem.”
Soil treatments aren’t recommended for Japanese beetles for similar reasons. Killing all the grubs in one field doesn’t prevent them from moving in from adjacent areas. It isn’t an economically viable solution, Rice said.
Soybeans are also resilient plants that can withstand some leaf damage, he added.
“In soybeans, we see a lot of defoliation, but a lot of times it looks worse than it really is,” Rice said. “When judging the amount of damage, growers and scouts should look at the entire plant. The upper leaves may have 20 percent damage, but if the whole plant doesn’t have 20 percent damage, you don’t need to spray. Those lower leaves are still getting enough photosynthesis to protect your yield.”
In corn, damage from Japanese beetles is largely cosmetic, he said. At silking, they can reduce pollination, but if the silks aren’t present, the issue isn’t that bad.
Soybean Gall Midge
A more recent discovery, the soybean gall midge, began making headlines in the Midwest in 2011. Initially isolated to a few fields, the pest has been reported in several states including Iowa, Nebraska, South Dakota and Minnesota. Because of its proximity to state lines, Rice said he’s willing to bet it’s also in Missouri but hasn’t been detected yet.
“The soybean gall midge is related to the Hessian fly,” Rice said. “It produces this orange maggot under the stem of soybeans and attacks healthy plants. It actually looks like some of the bacterial rot you might see, but then the stem falls over. If growers are seeing this, I would encourage them to cut open the stem to see if they have the larvae.”
Unchecked, a 100 percent infestation results in significant yield loss. The damage usually starts to appear on the edge of fields and may correspond with disease.
“We don’t know a whole lot about this insect,” Rice said. “We’re getting a lot of this information from our colleagues in Nebraska. It’s possible there is a correlation with disease, but we don’t know if the insect is increasing disease because it’s making a mechanical wound or if the disease comes first.”
Though the soybean gall midge hasn’t been found in Missouri, Rice is advising growers, scouts and Extension agents to be on the lookout in the upcoming growing season.
Brown Marmorated Stink Bug (BMSB)
BMSB made its way to the U.S. in the early 2000s. Native to Asia, the BMSB is an extreme generalist and feeds on more than 200 species of host plants, including vegetables, fruits, field crops, ornamentals, woody shrubs and hardwood trees. The insect also overwinters in houses, which is often where it is first reported.
The way to tell BMSB from native species is to look for light and dark banding on the antenna. The instars, which look like little ticks, also sport similar coloring, making it distinguishable in all stages of the life cycle.
“BMSB has a high dispersal capacity,” Rice said. “On average females will fly about five kilometers a day, but when we put them on flight mills and forced them to fly, they can fly up to 80 kilometers a day.”
BMSB likes to switch up its diet, consuming a balance of protein and carbohydrates as it flies between tasty choices like soybeans and orchards. By balancing their diet, females produce more eggs, ensuring the continuous survival of the species. Due to its varying appetite, BMSB is mostly found on the edges of fields near woody areas as the pest moves back and forth between meal sources.
“We studied BMSB a lot in the mid-Atlantic because it has done a ton of damage there,” Rice said. “For apple growers in 2010, it caused $37 million worth of damage. The good news is, if you do it right, one well-timed border spray will wipe out most of this species.”
BMSB reduces quality and yield in both corn and soybeans. Intense early-season feeding can damage seeds and seedlings. Growers may notice what is called “stay green syndrome,” in which the plant fails to continue developing. This causes problems at harvest if the interior of the field is dried down but the edges aren’t.
By running a series of weather and temperature models using data from the last 30 years, Rice determined that BMSB produces two generations in Missouri. Further evaluation will investigate how temperature increases change the population boundaries in Missouri and neighboring states.
Because BMSB was doing so much damage in the mid-Atlantic, in 2005 the USDA sent agents to Asia to find a natural predator to the stink bug variant. There, they located the Samarai wasp, which is native to China, Japan, Korea and Taiwan.
“What’s interesting about this story is that, of course, you can’t just go get something and throw it into the environment,” Rice said. “You have to test to make sure it’s not going to attack bees or butterfly species. During the course of testing, in 2014, the researchers found a Samarai wasp outside, very close to their experimental station in Maryland.”
The news hit the media, and the fear was the researchers had let the quarantined wasp escape.
“Through independent DNA tests, they determined the wasp they had in their colony was very different from the wasp they found outside,” Rice said. “It had actually made the trip on its own.”
Since that time, the Samarai wasp has been found in 10 other states, indicating it’s been in the U.S. for some time.
Rice said that’s a positive for those facing BMSB damage. Female wasps lay their eggs in the stink bug eggs, and the larvae develop in the eggs and emerge.
“In Asia, these wasps control 90 percent of BMSB,” Rice said. “We hope it establishes and spreads one day, making its way to Missouri.”
And though it looks similar to BMSB, Rice reminds scouts and growers that the spined soldier bug is a “good guy” and preys on a variety of other insects.
Also native to Asia, the kudzu bug was first detected in Georgia in 2009. It’s currently in nine states, including parts of the Bootheel.
“In the South, it feeds on kudzu,” Rice said. “The bad news is it also feeds on soybeans, shrubs and trees. It initially caused 50 percent soybean yield loss in Georgia. It’s not that bad now, though, because we’ve learned some things about its biology and how to control it, For example, if you control weeds along the edges of fields, that helps prevent it from actually moving into the field.”
Like BMSB, the kudzu bug is also found on field borders, produces several generations per year and overwinters in homes. In addition, kudzu bugs release a chemical that causes skin rashes.
The sugarcane aphid was first discovered in the 1970s in Florida, but in 2013 large populations of the pest made a switch from sugarcane to sorghum. It is now in 15 states, including Missouri, Arkansas, Illinois, Kansas and Oklahoma.
“If you have sorghum, a sugarcane aphid infestation can result in 100 percent yield loss,” Rice said. “The female aphid produces live young. It’s one of the only insects to do this. One interesting fact is that when the female has her baby, that baby already has another baby inside of it. Because of this, within a few days you can have thousands upon thousands of aphids, especially if there isn’t anything eating them.”
There are several insecticides that work well on the aphid, but frequent scouting and early detection are important. If the population gets to a certain threshold, insecticides can’t control it.
“Because they reproduce asexually and hide underneath leaves, you won’t get full coverage with chemicals at a certain point,” Rice said. “Field scouting and knocking them down early is really the only option we have right now.”
Spotted Lantern Fly
Detected in 2014 in Pennsylvania, the spotted lantern fly feeds primarily on grapes and sometimes hardwood trees. When they feed, they produce honeydew, which can lead to secondary problems of sooty molds.
“The wine industry there has taken a massive hit,” Rice said. “There has been 100-percent yield loss in vineyards, and it’s actually killing the vine. It’s not only that one year of yield loss. Now you have to replant, which is devastating for vineyards.”
The spotted lantern fly lays its eggs on any flat surface, including stone, wood and metal, which means it has the potential to move throughout the country easily on transports such as semi-trailers, vehicles and railroad cars.
“From my point of view, the spotted lantern fly could show up anywhere in the United States on any given day if it’s laying eggs on metal,” Rice said. “Asian literature says it feeds primarily on grapes, but last summer we found it feeding on soybeans in Pennsylvania in addition to corn and alfalfa.”
The spotted lantern fly was originally thought to contain cathartin, a bitter acid that is harmful to mammals if ingested, especially foraging animals such as cattle and horses.
“The Penn State chemical institute did a lot of tests and found out it does not contain cathartin,” Rice said. “That was really good news, but vineyard owners are still saying that their dogs are getting really sick when they’re eating these. We’re testing further to see if it’s a similar chemical that makes the mammals sick.”
The spotted lantern fly is a slow flyer and doesn’t look like anything native to the United States. If growers and scouts see one in their fields, Rice advises that they put it in alcohol and send him a picture for a definitive ID.
“It was reported in five states last summer, and I’m going to predict this is a freight train that’s coming across the whole United States,” Rice said. “We’re going to have to react quickly when we find it.”
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