Uncovering Sweet Corn Pests | A Must-Know Guide for Gardeners

Hey there, Dan Fillius with ISU Extension Horticulture here and we're checking out my sweet corn project here. There's definitely bird damage to the tips of the sweet corn and it's a hard one to manage really. There's bird scare tape, there's those used car lot like inflated guys, there's all sorts of different things that are out there. But basically when you're trying to scare away birds or other wildlife from your fields, the best way is to keep things moving, to keep things different. So they get used to anything. Scare cannons, people use these propane powered cannons that send out a boom, but if you just leave it in one place or you always have it on or it's one pattern, it just sort of fades into the background for the animals and they are not scared of it anymore. We're talking about pest control in sweet corn and for deer and raccoons, you need to exclude them from the field so you can't just scare them away. And we've got two different ways of doing that here. And one of them, this little short fence here, this electronet, this one is for raccoons. Doesn't need to be super high, but it does need to come up a certain way and they can't get below, through, or over it. And you see right here, a nice technique on the T-post that is being used for the other electric fence, they've got this PVC that just goes over so that it can wrap around and not ground out there. This was mowed about a week and a half ago, I think, and it probably could use it again, but we're pretty much at the end of the season, so I think there's diminishing returns there for that. This other fence we've got here is this strand right here. Oh yeah, I unplugged it earlier. It is about, oh, three feet off the ground. And then we've got these other two strands, so this strand plus this one and this one on two separate post runs is a 3D fence, three-dimensional fence, and this one is for deer. And it's a more cost-effective one than getting one that is, say, eight feet tall that a deer can't jump over. This one's electrified also and baited so that they're drawn to it and they know that it will shock them. And it works because their depth perception isn't really great, and they can jump high and they can jump far, but they can't jump both high and far, apparently. And so this is a more cost-effective way of using just some electric line that you might have already and setting up a fence around your perimeter. We're in the sweet corn talking pests. We've got some Japanese beetles down here. Here's the culprit right here, and here's the damage. We've got clipped silks, and the silks, there's a bundle of them like this one right here. This one's one that has not been clipped, but you can tell that this one's been cut short and here's the damage, the evidence down here. And each one of these silks is connected to a kernel in the ear down below, and if any of them is compromised, then that can prevent pollination of that kernel down there and can give you incomplete fill in the corn. And if it's bad enough or noticed, then that makes that ear unmarketable. They're getting ravaged here, like that one right there. Typically, I look for nice fat ears, a nice fill to get to the tip as an indication of ripeness, but this is exceedingly fat, so it's definitely a sign that this is corn smut. And where each of these kernels has been infected with a fungus, a mushroom, and this is the resultant mushroom. And this is a delicacy for many, and it's probably a good time for picking right there. Wheat lococha, exactly. And we'll notice in here also a common pest of corn and other things, picnic beetle, sap beetle. I broke it. Here's another sap beetle right here, crawling in there trying to eat the wheat lococha. Okay, let's see, maybe down in here, huh? We've got some nice, I think, let me just double check, oh yeah, here's the picnic beetles. So these picnic beetles, they're typically secondary pests. Maybe you can see they've got a little, they're not fully black. They've got a little bit of coloration on their backs, like either dark red, burgundy, maroon. Oh, they keep falling. Anyhow, this was damaged by earworm at the tip here. And here we have a tiny baby, is that an earworm? I think it is. Right there. They're not usually that small and delicate. The one that did this damage was a bigger one. And anyway, after it gets damaged and the sugars start fermenting, the picnic beetles, they sense that fermenting sugar, that's their cue, and they'll come in and crawl in and start feasting also. So if you've got that damage from one, you often get the damage from the other also. There are some odd years when the picnic beetle does seem to be the primary pest rather than the secondary pest, but anyhow, this is otherwise, this is a fantastic looking ear of sweet corn. And so if you could just cut that tip right there, oh my goodness, look at that thing. It's gorgeous. So a major pest of corn and sweet corn definitely is corn earworm. And I've got one in here, I believe, that is, oh yeah, look at that guy, he's hiding his face. Let's get him. You see this, they're very varied in their appearance. Some can be bright green, but they definitely have a contrasting colored head. See how that is kind of tan-ish, orange-ish there? That head is contrasting in color. So even if the body is all green, you might see a difference in the head there. And there's other things too, bristles and dots and things like that, but I'm not an expert. I just know that they eat the tip of the sweet corn and that damages it and makes it, for the most, unmarketable. And for control of corn earworm, the best, best way to do it is to trap with a pheromone trap in your field so that you can see when the moths arrive. Because when the moths arrive, then they start to lay eggs on the green silks. And that's what these corn earworms then burrow down, following the silks into the tip of the ear. And getting them at that point, as they're hatching and then burrowing, that's the time when they're vulnerable. But that's a very short window of time. So you either have to spray something that has a little bit more residual, or get it more frequently out there. And corn earworm is a problem in field corn too. And there's a lot of chemicals that corn earworm has become resistant to. There's only a few that really work. And at this point, spraying every couple days is really what it takes to get this. Or to plant a corn that is producing Bt. But that is, you know, it worked at first when those corns came out. But the corn earworm has become resistant to certain proteins that those Bt corns produce. And at this point, there's only one or two Bt sweet corns that is currently effective. And at least this is what growers are finding in their experience. When conditions, this year, we had very wet conditions that kept growers out of the fields a lot. And they were not able to get those sprays out every couple days as they might need to. And that led to more wormy sweet corn this year. Additionally, corn earworm was back, the earliest it's been back by one grower's memory, in 20 years. The earliest in 20 years. And none of the field corn was pollinating at that time. Of course, early sweet corn is always pollinating earlier than the first field corn. But when the corn earworm comes back earlier, it's the only thing pollinating that they're going to be going after. And so, though there may not have been high numbers, every single one of them found a sweet corn patch and here we go. Oh my gosh, speak of the devil. I was just mentioned in a comment on Instagram by Iowa Fruit Guy, Randall Voss, mentioned me in a comment, hey, corn earworm on sweet corn, what do you know?