- Dig up entire seedlings to best diagnose pest and disease problems.
- If you find disease or feeding, check your seed treatment label to see what worked or didn’t work.
- Check your seeding depth and uniformity. Record and make plans to fix issues in the future.
Is that missing corn plant a victim of a cutworm? A planter skip? A rotted seed?
There’s only one way to tell.
“You can’t scout from the road — you have to dig up the plant and look at the roots or the seed,” said Stephanie Porter, an agronomist with Burrus Seed. “That’s the only way to know if it’s a planter skip or a pest.”
So grab a spade or a pocketknife — and bookmark this article. From insects to diseases to weather problems, here are the most likely culprits for sick, missing or ugly seedlings this time of year.
CUTWORMS AND OTHER INSECTS
“Cutworms are the hot topic right now,” Porter said. Entomologists from across the Midwest have been tracking black cutworm moth flights for a couple weeks now, which means their larvae will soon be hatching and looking for food. Your corn seedlings will be an attractive option.
Fields that had a cover crop, heavy winter annual weed pressure, or those adjacent to woody areas will be especially vulnerable, Porter said. “The moths are looking for cover to protect their eggs,” she said.
Keith Peters, who farms south of Columbus, Ohio, takes a proactive approach to cutworms, which love his rotation of rye into corn. “Cutworms work so quickly, you can get behind in a hurry,” he said. Peters puts down a soil insecticide along with his pre-plant herbicides to get a jump on the pest.
Since cutworms bed down under the soil, they can dodge pre-plant insecticide treatments, especially if there is no rain to move the chemical down into the soil, Porter warned. Growers should scout regardless, and make a note of whether cutworms survived insecticide applications, Bt traits or seed treatments, she said.
Cutworms can cut off entire plants when they are small, and will leave a distinctive hole pattern in the leaves of larger plants, after eating through the whorl. While black cutworm is the most common pest this time of year, other types of cutworm, such as glassy cutworm or dingy cutworm, are also potential pests, Porter noted. See this guide to black cutworm management from Penn State: https://extension.psu.edu/…, as well as this cutworm identification guide from DeKalb: https://bit.ly/….
Wireworms and white grubs are common early season pests that can attack seedlings and leave dead or stunted plants. Digging up these seedlings to look for the insect in question is key, Porter said. For help identifying the many types of grubs, see this guide from Michigan State University entomologist Chris DiFonzo: http://www.msuent.com/….
“There is no rescue treatment for these, but you can go back to see what kind of seed treatment you had on there and figure out what went wrong,” Porter said.
See an article from North Carolina State University entomologist Dominic Reisig on how to scout for these seedling insects here: https://entomology.ces.ncsu.edu/….
DISEASES & WEATHER DAMAGE
Cold, wet soil is a playground for certain soil-borne diseases, particularly Pythium and Phytophthora, which have swimming spores that can thrive in standing water. They both cause seed and root rot, and while there is no in-season treatment, it’s important to know if your seed treatment did or did not protect your seedlings, Porter said.
A newer fungicide active ingredient called ethaboxam is available from Valent to fight Pythium. It can help growers facing strains of the disease resistant to a common fungicide active ingredient, metalaxyl, but it isn’t a silver bullet and growers with this new chemistry should still scout, Porter warned.
AgFax Weed Solutions
Porter also advised growers to be on the lookout for rhizoctonia in soybeans, which favors moist soils and can cause seed decay or stunted plants. See more details here: https://cropwatch.unl.edu/….
Remember that damaged seeds and week seedlings can also result from weather damage. If soybean or corn seeds take in chilled water in the first 24 or 48 hours, respectively, they are at risk for imbibitional chilling. See more details from the University of Nebraska here: https://cropwatch.unl.edu/….
If you are missing plants and have ruled out insects, disease, and weather injuries, it might be time to worry about your planter.
Porter always recommends hopping out of the planter in each field to check for uniform seed placement and depth. Heavy residue, uneven fields, compaction or wet soil conditions can all affect your planter’s performance.
Shallowly planted seeds risk losing out on moisture or being exposed to the elements and predators. Seeds placed too deeply can get trapped in compacted or crusted soils.
See this article from Michigan State on why seeding depth matters for soybeans: http://msue.anr.msu.edu/…, and a similar discussion on corn from Purdue corn agronomist Bob Nielsen: https://www.agry.purdue.edu/….
Emily Unglesbee can be reached at Emily.firstname.lastname@example.org
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