(Jim Shroyer) Good morning, folks. Welcome to That’s My Farm. I’m Jim Shroyer, your host and we’re in luck because we’re on the campus at K-State and we’re going to be talking to Dr. Jeff Whitworth, our extension entomologist, and he’s got a lot to tell us about problems in sorghum, potential problems in soybeans and alfalfa. So, stay tuned. We’ll be right back after these words from our sponsors. See you in a minute.Closed Captioning Brought to you by Ag Promo Source. Together we grow. Learn more at agpromosource.com.
(Jim) Welcome back to That’s My Farm. I’m Jim Shroyer and with us, we have Dr. Jeff Whitworth, our extension entomologist, and he’s been out and about, looking at bugs and other critters of that ilk. Jeff, tell us a little bit about what’s going on in sorghum, what to be looking for. (Jeff Whitworth) The sorghum sugarcane aphid; in sorghum, every year, it is a problem, mainly because of chinch bugs and we have a lot of chinch bugs this year, Jim. There have been a lot in the last 3 or 4 years. I don’t know why there seemed to be more, but there are. And one of the problems with chinch bugs are early on everybody knows about the problem with seedling sorghum. (Jim) Right. (Jeff) But it also gets in this time of year, later in the season. And they will feed around the stock and they’ll weaken the stock. And lots of times you get premature lodging just because the chinch bugs. (Jim) Right. I had a farmer up in Mitchell county tell me that chinch bugs took the first 20 yards around the whole field. (Jeff) They will do that, and that’s a perennial problem we’ve had forever. In sorghum, the last few years since 2014, we’ve had a new invasive aphid species, called the white sugarcane aphid. We call it just as sugarcane aphid. In Kansas sorghum, there are three aphid species that we’ve had traditionally: the yellow sugarcane aphid, the green bug, which has been a problem since the 60’s or the 50’s, and the corn leaf aphid. But since 2014, we’ve had this new invasive species called the sugarcane aphid, or white sugarcane aphid. The problem with that is it seems to dominate the sorghum more than these other aphids do. In Kansas, we don’t normally worry about aphids later in the season. They’ve normally been an early season pest, but this thing doesn’t overwinter in Kansas, least it hasn’t. It’s a tropical or subtropical species of aphid. It generally comes in, migrates in or blown in by the wind later in the season: July, August. At least, that’s what we found the last two years. It will take over sorghum plants. The problem with this thing is very prolific; every aphid is a female. Those females produce females, those females produce females, so those populations can just rapidly expand and they have been, and they produce a lot of honeydew. The growers that experienced the sugarcane aphid last year 2015, they even had problems harvesting their sorghum because of the amount of honeydew – and it’s real sticky. The nice thing with this aphid that we found last year– Remember we’ve only had one year worth of problems with this, so we’ve only had one year to work with this thing, here in Kansas. One of the nice things we found that beneficial insects, lady beetles, green lacewings, and the little wasps really helped. So, if they came in late enough, if the aphid populations came in late enough that the beneficial populations were already there, they really helped regulate some of these populations. (Jim) Jeff, I want to talk a little bit more about control of the sugarcane aphid when we get back. Folks, we’ll be right back after these words from our sponsors.
(Jim) Welcome back to That’s My Farm. I’m Jim Shroyer. Jeff Whitworth didn’t run off during the break and I appreciate that, Jeff. Let’s continue. (Jeff) [Laughs] I didn’t know that was an option. [Laughter] (Jim) Well it’s not, really. (Jeff) [Laughs] (Jim) Let’s continue about the sugarcane aphid and some of the problems, and control, and confusion lately. (Jeff) Yes, like I said, there are actually now four species of aphids that apparently are going to be common in sorghum. The three that have been traditionally: the green bug, the corn leaf aphid, and the yellow sugarcane aphid. Those are in every sorghum field throughout the state. But it’s the numbers, and traditionally they don’t build up in the numbers that have caused the problem. (Jim) As fast. (Jeff) Yes, or as fast as this sugarcane aphid, the white sugarcane aphid does. The minor exception is the green bug. The green bug gets on wheat. If you have a lot of green bugs in wheat early on and you don’t have too many beneficials, sometimes they can get into early season sorghum. They used to be a real problem in the 60’s and 70’s, not so much anymore, because we do have resistance to the green bug. (Jim) How do you control the sugarcane aphid? (Jeff) The sugarcane aphid, we got a lot of questions last year. Remember, last year, 2015, is the first year we had the numbers that justified treating. The two products that are currently registered and work well in our trials on the sugarcane aphid are SIVANTO and Transform, and they seem to be relatively mild on the beneficials. They don’t seem to bother the beneficials. One of the common questions we got last year is if I spray my head worm, my corn earworm problem that traditionally gets in the head of the sorghum plant, and they feed right on the marketable product. They’ll feed right on the kernel, and they cause 5% loss per head per worm, okay. If I spray those, will that take care of the aphids also? It won’t. Now we did put out some trials where we tried that. Some of the growers wanted to use an insecticide that would work well on the corn earworm and the sorghum head worm, same species, whatever you were trying to kill in the head of the sorghum plant. And put in a little of the SIVANTO or the Transform, if that would actually work to control the aphids. It does not; simply because the worms are right up in the head, where they’re easily exposed to the insecticide. The aphids are on the underneath side of the leaves, down in the canopy. So, you cannot get the amount of insecticide required to get the aphids in the canopy as you can, if they were up exposed on the head. It just doesn’t work out that way. (Jim) How do you get those two products down low enough and underneath the leaves to do a good job? (Jeff) Good question. Those products work really well, but you have to use a lot of carrier. You have to increase the amount of carrier. We generally say 15 or more gallons per acre and carrier, put drop nozzles on if you can, and it just depends on your setup, but you’ve got to get the insecticide to where they are, because that’s another good question. A lot of the guys say, “Well, are these insecticides taken up by the plant and are they systemic and translocating the plant – they’re not”. They’re all – (Jim) Contact. (Jeff) – contact insecticides. So they have to contact the insect, in order to get control. (Jim) What about the confusion between, if they have the corn aphid there and then they spray for that, thinking that’s the sugarcane aphid, I mean you really have to identify. (Jeff) You do, you want to make dang sure you get proper identification of the aphids. The corn leaf aphid puts out a lot of honeydew. They get in the head. Generally they’re a problem, if they’re going to be problem when the sorghum’s in the whorl stage, and they’ll be in the head, and they’ll put out a lot of honeydew. Sometimes, it actually retards the extension of the head. But it will be a field wide problem. I’ve never seen it be a field wide problem. I mean, in early to mid August you could go around and find sorghum plants that were in the whorl stage with pretty good populations of corn leaf aphids, but that has really helped because the beneficials are building up on these corn leaf aphids and on the yellow sugarcane aphid, and the green bugs. At least that’s what we found last year, so that by the time the sugarcane aphid gets here, there’s pretty good populations of these beneficials would seem to help. (Jim) Okay. (Jeff) You’re exactly right. You want to make sure you get proper identification of whatever aphid species it is. So take it into your local extension agent and ask them to help you make a proper identification. (Jim) Yes. Let’s take a break. (Jeff) Okay. (Jim) Folks stay with us. We’ll be right back after these words from our sponsors.
(Jim) Welcome back to That’s My Farm. Jeff Whitworth is still with us and he is still the extension specialist in entomology. (Jeff) I don’t know. Time’s running… [Laughter] (Jim) Okay Jeff, let’s finish up with sorghum. There are some other critters on sorghum that we need to think about and they move over in the soybeans. (Jeff) Yes. We were talking about corn leaf aphids in the whorl. Well also in the whorl, you can find what they call rag worms. They’re lepidopteran larvae. They’ll turn into moths, okay. There’s two different species that are mainly the culprits in Kansas, the fall armyworm or the corn earworm. And we’re finding them both throughout the state. They rag up, that’s the reason they got the name rag worm. They cause considerable concern every year because of their feeding inside the whorl. And when the whorl, as that leaf grows out, then it has some pretty ragged looking defoliation on it. Those are larvae. We do not recommend treating those things for two reasons. Number one, by the time that damage grows out of that whorl, the worms mostly finish feeding, so they’re going to crawl down to the soil and pupate, and leave. But, the problem is, they’re not going to go away. They’re just going to leave that field and they’re going to go to sorghum fields that are heading out, or they’re going to go to soybean fields. So, they prefer sorghum, but there’s just a two-week period in sorghum when it’s vulnerable to head worm damage, and that’s from flowering to soft dough. I say two weeks. It depends on the weather and the variety, but generally, it’s from flowering to soft dough. (Jim) Where there’s a kernel there. (Jeff) Where there’s a soft kernel there they can feed on. The moth will lay an egg, those larvae will feed, and you get 5% loss per worm, per head. That’s kind of our treatment ratio. Okay? Nice thing about it, they’re easily controlled, because they’re right up there where they’re vulnerable to the insecticides. We’ve never had a problem in controlling them. It’s just you want to make sure you get out and detect the infestation early on before you’ve lost much grain. Then those moths will fly to soybeans. The sorghum will become past the soft dough stage, so they’re looking for another place to lay eggs. And we have a lot of soybeans that are still, they’re indeterminate so they’re still putting pods on and setting seed. Those moths then will lay eggs in the soybeans, and those little larvae will feed on the seed itself and the soybean pod. (Jeff) They feed right through the pod, and they feed right on the seed. The reason that’s important is because the bean leaf beetle adult will also feed on the pod. It doesn’t feed on the seed, it feeds on the pod. So, if you’re checking your field and you have a lot of seed feeding, you have about two weeks, and that’s going to go away. If you have pod feeding, those pods are going to be fed on from now until it gets cold, because the adult bean leaf beetle doesn’t go away. It’s just going to feed on the more succulent pods as the plants set the pods. (Jim) And they will go up the plant. (Jeff) They will. Right. They move up to the plant. So that’s why it’s important to make – like we talked about aphids, make sure you properly identify those – make sure you properly identify what’s feeding on your soybeans, because it makes a difference. (Jim) We have got to take another break. Folks, stay with us, we’ll be right back after these words from our sponsors.
(Jim) Welcome back to That’s My Farm. Jeff, let’s continue our conversation on the problems with soybeans. (Jeff) Yes, the soybeans, especially double crop soybeans, that’s mainly what we’re concerned about. Every year we get questions about whether they should use an insecticide seed treatment on double crop soybeans, and sometimes it’s not a bad idea, because the insecticide seed treatments will help on bean leaf beetle larvae, which feed on the roots of the soybean plant and swell. They also will help against soybean aphids. Every year since 2002, we’ve had soybean aphids migrate into the state. We don’t think they overwinter in Kansas, yet. They overwinter on a tree, which is kind of strange, called buckthorn, and back in the ’50s, K-State went around and planted buckthorn or provided seed for windrows, for growers to plant buckthorn. So we do have a lot of overwintering hosts for this new invasive species. (Jim) Potentially. (Jeff) Potentially, yes. But I think maybe the winters are a little bit too cold yet in Kansas for overwintering of the soybean aphid. But anyway, every year since 2002 we get the soybean aphid migrating into the state. (Jim) How long will those insecticides be affected? (Jeff) The insecticide seed treatments last 21 to 28 days. (Jim) Okay. (Jeff) I say 21, that’s the low. You have two different rates for seed treatments. If you use the low rate, it’s about 21 days. If you use the high rate, you get about another week. (Jim) Okay. (Jeff) Good question. But, one of the things that confuses growers, that’s from the time you put that seed into soil until the time it germinates, just not the time it germinates. Because if you plant and it happens to be cool or dry– (Jim) Slower to get out. (Jeff) Yes, it doesn’t germinate; your time is running on the insecticide. (Jim) The clock is ticking. (Jeff) It is. (Jim) Okay. (Jeff) So, 21-28 days on the insecticide activity of the seed treatment. But the soybean aphid, every year– It was first detected in United States in year 2000. We got it in Kansas in 2002. Every year since then, we’ve had it; we find it in the state. We detected it this year in early August. One of the nice things I guess you would say about the soybean aphid, they seem to be pretty well regulated by hot temperatures. So if you have temperatures over 95 degrees for daytime temperatures, they really don’t reproduce well. That doesn’t really kill them but they don’t reproduce well. So, since 2002, we’ve only had two years in August and September where we’ve had to treat for soybean aphids. But, every year, we need to get out and monitor, because every year they come in. The easiest way to find soybean aphids, find ants. If you find ants in your soybean canopy, you’ll have aphids. (Jim) It’s because they’re eating all the honeydew. (Jeff) They eat the honeydew. And I don’t how you can go out in the middle of the soybean field, never find an ant through the year, but as soon as the first soybean aphids arrive, the ants, they find them. They’re very good at detecting those soybean aphids, much better than we are. (Jim) Follow the ants. (Jeff) So if you find ants in the soybean canopy, you have aphids someplace. Not necessarily the reverse is true, because sometimes they don’t find them too quickly. But in most cases, they find them very quickly. The nice thing about it, we haven’t had to treat them – only two years since 2002 – but you need to make sure you monitor. The soybean aphid is the only aphid that actually colonizes in soybeans. You know, you can a find a lot of aphids in soybeans, but they’re the only ones that colonize it. By that I mean, produce little ones, so if you find a large aphid, that’s relative, and a bunch of small ones around it, that’s a soybean aphid. A lot of products were registered for use, for soybean aphids. They all work pretty well, because most of the time they’re up in the top part of the canopy where the insecticide will get to them. (Jim) Okay. (Jeff) But make sure it’s a soybean aphid. Make sure you need them before you treat. And so, the treatment threshold is 50 per leaf up until R3 or R4 stage. (Jim) Okay, so pod elongation. (Jeff) Yes. Once they get to the reproductive stages, anything that stresses the plant can have an impact on yield, so it’s kind of same thing with soybean aphids. (Jim) We have to take a break. Folks, we’ll be right back after these words from our sponsors.
(Jim) Welcome back to That’s My Farm. I’m Jim Shroyer. With us we have extension entomologist, Jeff Whitworth. Jeff, let’s talk a little bit more about soybeans. (Jeff) Yes. One of the other problems we see in soybeans are the Dectes stem borer. We can’t manage that, I’m just alerting here about the fact that every year they’re around and about. But also one of the questions I get are the potato leafhoppers. The potato leafhoppers are very common in soybeans. All during the month of August they’re on soybeans. They will feed on the soybean plant. They really don’t cause a problem in Kansas. They may curl the leaves a little bit, but where we’re really worried about potato leafhopper is in the alfalfa. (Jim) Not soybean, but they got– they can do some serious damage. (Jeff) They’ll be in soybeans, but we don’t really have to manage them in soybeans – but it’s alfalfa. They cause what we call hopper burn in alfalfa, and a lot of guys don’t recognize that damage in mid to late summer. They think the alfalfa is turning yellow just because of the hot dry conditions where, if you get out and look, your pant leg or your shoes might be covered with these little lime green colored bugs that have a herky-jerky type of movement. Those are potato leafhoppers. And they’re very common this year. We’ve probably seen more than usual, In the last two years, the potato leafhopper – it doesn’t overwinter in Kansas – but the last two years, we found it clear up until the first part of November. (Jim) Oh my. (Jeff) Which I say, they don’t overwinter in Kansas. Maybe they’re going to start, I don’t know. But normally they don’t, so they migrate in every year. So it hasn’t been a problem late, but in alfalfa we usually don’t swathe after the first part of October, so that plant can put the reserves back into the root system for surviving the winter. (Jim) Exactly. (Jeff) Well, when we have potato leafhoppers that are feeding, sucking those reserves out, causing hopper burn in October-November, that can– (Jim) Weaken the plant. (Jeff) Yes, that could be very problematic. (Jim) You have a slow growth in the spring with not only– (Jeff) Exactly. That’s something I’m worried about, that we haven’t seen before, just the last two years. And we are starting to see hopper burn clear up until the last part of October. (Jim) Just describe that hopper burn just briefly. (Jeff) The hopper burn’s where the tip of the alfalfa leaf turns yellow, and then as feeding progresses, the whole leaf will turn yellow and go down the stem. Go down the whole stem and can actually kill out the plant. (Jim) Now, are they injecting something? (Jeff) Yes, they are. They suck the juice out the plant, but also while they’re feeding, they inject their toxin. That’s what causes hopper burn. (Jim) That’s what causes hopper burn. (Jeff) Yes, that’s exactly right. (Jeff) Yes, exactly. (Jim) Okay. Jeff thanks for taking time out to talk to us about things that are happening and are going to be happening here in the next month or so. I appreciate it. Folks, thanks for being with us on this show, That’s My Farm, and don’t forget, next week about this same time we’re going to have another That’s My Farm. See you then.
Closed Captioning Brought to you by Ag Promo Source. Together we grow. Learn more at agpromosource.com.