After a busy summer season, sweet corn harvest is beginning to slow down across Delaware.

The popular crop’s harvest typically starts at the end of June and runs through early October.

Sweet corn is one of the largest vegetable crops in Delaware, occupying more acres than most other vegetable crops, said Emmalea Ernest, an extension fruit and vegetable specialist with University of Delaware Cooperative Extension. 

“If you’re going to have a farm stand, you almost have to be selling sweet corn,” Ernest said. “It’s sort of an expected product.”

One of Ernest’s areas of focus is testing numerous varieties of sweet corn to see how well they fare against different environmental pressures and how well they yield. Seed companies often develop new varieties and take older varieties off the market, and Ernest gives recommendations to farmers on which varieties to grow. 

“Most varieties grow great under ideal conditions,” Ernest said, “but it is also important to identify varieties that perform well under stressful conditions like heat, excessive rain or drought.”

Many sweet corn varieties are available to farmers. In recent years, growers who produce processing sweet corn (that will be commercially canned or frozen) and those who ship their corn to grocery stores have been growing mostly supersweet corn varieties. Supersweet varieties have a crisp texture and maintain sweetness after harvest. Synergistic and Augmented Shrunken varieties have tender kernels which are more appealing to some consumers but they are usually only available from farm stands or farmers markets because they can be damaged by rough handling in shipping.

Seaford farmer Gary Calloway saw a mediocre sweet corn crop this year, partly due to excessive rains and partly due to the varieties of corn he chose. He grows about 250 acres of sweet corn, focusing on supersweet corn, something his farm transitioned to five years ago. Calloway grows white supersweet corn varieties Leadoff, Magnolia and Glacial.

“The Magnolia and the Glacial varieties don’t yield quite what I would like them to,” Calloway said. “But those have the longest stalk life of anything that I've used, because they have a smaller kernel to begin with. We sacrifice some yield for eating quality and flexibility of timing on harvest.”

Like many Delaware farmers, Calloway is prepared to fend off pesky insects that can decimate his corn crop in late summer, especially corn earworm, which feeds heavily on corn ears. 

Since the 1970s, the University of Delaware Cooperative Extension has maintained a statewide insect trapping network to help producers and businesses keep pests at bay. David Owens, an extension specialist in agricultural entomology, said the network, with an economic impact between $80,000 and $100,000, includes blacklight and pheromone traps to prevent corn earworm and other critters from getting to farmers’ corn. 

“With the data from those traps, we can give our farmers and crop consultants recommendations on how often they should be spraying their sweet corn to keep it clean,” Owens said. “Nobody wants to see a worm in their sweet corn.” 

Typically, a corn earworm flight — when the adult moths are most active — happens in the end of May to early June and then between the end of July and middle of August, Owens said.  

“At some point between the end of July and middle of August, the earworm flight kicks in with a bang,” Owens said, “and those traps will catch anywhere from 20 to close to 100 moths at night, depending on the year.” 

But this year, as the end of July rolled through and mid-August came and went, sweet corn farmers heard crickets (literally and figuratively).

“This year has been a bit of an odd year,” Owens said. “Farmers should be monitoring and paying attention to extension scouting reports so they can adjust things quickly.” 

And then it happened in late August, two weeks later than what Delaware farmers typically see.

Calloway, the Seaford corn farmer, had no issues with earworms until the corn earworm numbers “exploded” in late August. 

“It’s just been really peculiar,” said Calloway, during an interview in late August. “When I drive across the farm, I see these pheromone traps. When I see that they’re full of moths, I know that we have a tighter spray program coming. And they’re loaded right now.”

For farmers, an insect flight is a sign they need to adjust their insecticide spray schedules. Calloway talks to Owens around twice a week, usually about any pest issues, from corn earworm to aphids to spider mites, and what to do about them to protect his sweet corn as well as fruit crops such as watermelon.

“The University of Delaware is a huge help for us,” Calloway said.