Gardenbite: More than monarchs: Insects on milkweed | #GoodGrowing

Welcome to the good growing podcast. I am Ken Johnson, horticulture educator with University of Illinois Extension coming to you today from Jacksonville, Illinois with a garden bite. And on this week's garden bite, we're gonna talk a little bit about milkweeds and some of the different insects we can find feeding on them besides monarch caterpillars. So milkweeds have become a popular garden plant in the last several years, primarily because people have been planting these to support monarch butterflies, because milkweed is going to be the sole food source for monarch caterpillars. Milkweeds contain toxic compounds, and these are cardiac glycosides, and the plants have these to deter animals from feeding on them, like insects and mammals.

However, monarchs have evolved to be able to feed on these plants, and additionally, monarchs can take these chemicals and incorporate them into their bodies, which is going to make them unpalatable to other animals. So if you grow milkweed and you've ever gone out and checked your plants for monarch caterpillars, you may have been surprised to find other insects living and feeding on your milkweed plants. After all, they are toxic to other animals. However, there are some other insects that have evolved to be able to feed on milkweed, and like monarch caterpillars, some of them have become milkweed specialists. So some of the different animals or some of the different insects we can find feeding on milkweed include, there's several different species of longhorned beetles.

One of the most commonly found one is going to be the red milkweed beetle, and the adults of these are bright red, they have black spots, and they have long antennae. That's the longhorned beetle name, and they're about half an inch long. And if you ever pick these up, the the adults will squeak when disturbed, which is kind of interesting if you ever try this out. The adults are going to feed on the leaves, buds, and flowers of the plants. And when they're gonna be feeding when they feed on leaves, they're gonna cut the leaf veins below the area where they're going to start feeding.

And this is gonna cause the latex from the leaves to drain out so it doesn't gum up their mouthparts. Females are gonna lay their eggs near the base of milkweed plants. And when the eggs hatch, the larvae are gonna burrow in to and eat the stems and roots of the plants. The larvae are gonna overwinter in the roots before pupating, and and then they'll pupate in the spring. The adults are gonna emerge early in the summer, right about when milkweeds begin to bloom, and the cycle will continue.

One cool thing about red milkweed beetle is their eyes. So the genus they belong to, the pterotropes, comes from the Greek tetra, meaning four, and ops, meaning eye. So the eyes of these insects had actually been divided into two by their antennae. So it makes it like they have four eyes. So if you ever find some of these, pick them up, see if they'll squeak for you, and check out their eyes.

Another type of beetle we can commonly find on milkweeds here in Illinois is going to be the swamp milkweed leaf beetle. And as their name implies, they prefer swamp or rose milkweed, but they will also feed another species of milkweed too. Like the red milkweed beetles, the adults and the larvae, in the swamp milkweed leaf beetle case, they're also gonna cut the veins of the milkweed before feeding on them. The adults of the swamp milkweed leaf beetle are dome shaped. They have a black head in pronotum, and that's that area behind the head, the pronotum.

The elytra or the wing covers are gonna be yellow to orange, and they're gonna have black to dark blue markings on them. The larvae are going to be gray to orange with a row of black spots along their sides. When the larvae are fully grown, they're gonna drop to the ground and pupate, and then they're gonna emerge as adults in the fall. And they also start feeding, and then they'll overwinter and plant debris, usually near this the base of milkweed plants or in the soil. And then the adults will emerge in the spring, they'll lay eggs, and the cycle will resume.

There are a couple different species of true bugs or insects in the order of Hemiptera that can also be found feeding on milkweed. We have the large and small milkweed bugs. So adult large milkweed bugs are about three quarters of inch long, orange to reddish orange, and they have a black band across their back. The nymphs and the adults are gonna feed on milkweed, particularly the seeds, and they're gonna be found commonly found clustering on the seed pods of plants. And monarchs are famous for their migration down in the Eastern Half of The United States down into Mexico where they will overwinter.

And large milkweed bugs will also migrate. They'll also travel south for the winter. So when temperatures begin to cool, days start getting shorter, the adults are gonna start migrating south. Eventually, they end up in the Southern Atlantic and Gulf Coast states, and they're gonna spend the winter there. And as temperatures begin to warm in the spring, those large milkweed bug populations will begin their journey back north.

The small milkweed bugs are also orange and black, but instead of a black bar on their back, they have kind of a heart shaped patch on their back, along with two black patches on either side of that. Additionally, as their name implies, they're gonna be smaller than large milkweed beetles, herd large milkweed bugs, about half an inch long. In addition to feeding on their preferred food source, which is milkweed seeds, they may also feed on other plants, feed on nectar from flowers, and occasionally they may feed on other insects when food is scarce. Unlike large milkweed bugs, small milkweed bugs are gonna be permanent residents here in Illinois. They do not migrate at all.

There are also other caterpillars we can find on milkweed plants. We have the milkweed tussock moth, and the newly hatched caterpillars are gonna be pale and hairless with black heads. And when they're young, we often will find these feeding in large groups. They're gregarious, and they're gonna feed in between the veins of the milkweed leaves, and it'll cause them to have a skeletonized appearance. So if you're familiar with what Japanese beetle damage looks like, it's gonna be similar damage to that caused by these tussock moths.

As they develop through the different instars, they become covered with tufts of black, white, and orange hairs. The larger caterpillars are gonna cut the veins of the leaves, again, to reduce the amount of latex in the leaves, and this is going to allow them to consume entire leaves of the plants they're feeding on. As they get larger, they also start to wander away from the groups that they've been feeding on, and you often find them feeding alone or in pairs, not in large groups anymore. Populations get really high of these caterpillars. They are capable of defoliating milkweed plants.

So if you're concerned with the milkweed tussock moth eating all your milkweed plants and leaving no foliage for your monarchs, don't be too alarmed. Milkweed tussock moths, the caterpillars tend to favor older foliage, while monarchs tend to prefer younger foliage. So they're not necessarily competing for the same resources there. When caterpillars or the Tuscan moths are fully grown, they're gonna drop to the ground and spin a great cocoon, and they will then pupate. They don't moths.

They're kind of nondescript. They have gray wings. However, when they lift those up, can see their orange abdomen is gonna have black spots. And the the tussock moths, they're gonna lay their legs in large masses on the underside of leaves, unlike monarchs, which usually lay their eggs singly. Last insect we'll talk about is going to be oleander aphids, and these are probably the ones that people have most have the most questions about when they find these on their milkweed plants.

So these are these bright yellow aphids that have black legs and cornicles, these little tube like projections off the backside of the aphids. They're native to the Mediterranean region of the world, and their primary host is oleander, which happens to be in the same family as milkweed. Females reproduce without mating, they can do parthenogenesis. So basically, are giving birth to live clones of themselves. They don't lay any eggs, which means their populations are capable of growing very quickly.

Like other aphids, they are found often found on the clusters of new growth, maybe new leaves, flowers, things like that, and they have straw like mouthparts, they're gonna suck the sap from the plants, kinda like a juice box. And if if you have a lot of them, excessive feeding can cause plants to be stunted, cause them to become deformed, twisted, and things like that. And additionally, they're gonna produce honeydew, which can lead to the development of sooty mold, which is a black fungus that'll grow on that honeydew. Doesn't directly hurt the plant. It's not growing on the plants or infecting it.

It's growing on that honeydew that can block sunlight and reduce photosynthesis. So a lot of times when people are growing milkweed for monarchs, they aren't particularly excited or happy to find other insects feeding on their milkweed plants. However, all of these insects, with the exception of the oleander aphids, are native to The United States and have been feeding on milkweed with monarchs for a very long time. This has been happening for thousands and millions of years. Out of all the insects, oleander aphids are probably the only ones you would consider pests or that should be really considered pests that may need some sort of management.

Oftentimes, with aphids, you can just spray them off with a strong stream of water. However, if you do this, you do run the risk of removing small monarch caterpillars or other insects from those plants as well. Fortunately, as with other aphids, natural enemies like ladybugs, lacewings, syrphid flies, parasitoid wasps will often come in and manage populations and get them under control. Insecticides could be used. Again, not really recommended because any insecticides you apply to your plants are also going to affect monarchs and all the other insects feeding on them as well.

So generally, do not recommend applying insecticides to your milkweed. So instead of being concerned about the presence of these other insects, we should be happy that we're providing an environment that is suitable for them to thrive as well. Just remember, they depend on milkweed just as much as the monarchs do. That's all I've got for you for this week's garden mite. Hopefully, you've learned a little bit about some of the different insects we can find on our milkweed.

Thank you for doing what you do best and that is listening, or if you're watching us on YouTube watching. And as always, keep on growing.