By Peter Spartos

 


What are these orange bugs all over my milkweeds!?

A monarch butterfly feeds on the flowers of a swamp milkweed.

There are two common yellowish-orange bugs of the six-leg variety that frequent milkweed plants. Both insects are easy to spot and easily identified due to their bright color. They also both commonly appear in very dense clusters, which makes them downright hard to miss. Surprise! Neither of these insects is the majestic monarch butterfly, which is also orange, or the monarch caterpillar, which is not (it is yellow and green).

At Highview Creations we often hear from clients concerned about the presence of the milkweed bug (Oncopeltus fasciatus) or the oleander aphid (Aphis nerii). Most people plant milkweed hoping to attract and support monarch butterflies (Daneua plexippus). When a bunch of other bright yellowish-orange bugs show up we often hear the same good questions: Will they bite me? Are they bad for the plants? Are they bad for monarch butterflies? Fret not, neither the milkweed bug or the oleander aphid are dangerous to humans and are unlikely to harm either your plants or butterflies. They are easy enough to live with and easy enough to get rid of, the choice is yours.

So there are orange bugs all over your milkweeds! Now what?

Take a deep breath and try not to panic.  Then observe, and ask yourself some questions:

What do you see?  

Are there many bugs or just a few?

Where on the plant do you see them?  

Are they moving?  

What size are they? 

Do you see more than one type of bug? 

 


Identifying the oleander aphid

A dense population of oleander aphids clusters on the stem of this milkweed plant. They aren’t the prettiest of insects. We ultimately applied some treatments of non-toxic neem oil to the plants in this area

If your bugs are found in a dense concentration on the stem of the plant, are of consistent color, and all about 1.6 to 2.5mm in diameter, then you likely have oleander aphids. They resemble smooth boogers with stick legs. Typically found at the nodes of newer growth along the main stem, the oleander aphid likes to feed on the juices of the plant through its tender green skin. You might also see them clustered around leaf veins but they will  almost never be on the outer foliage. Also, because they feed by sucking juice straight out of the stem, they tend not to move around much.

These little folks are often accompanied by a gooey substance called honeydew, which can give the leaves on your plant a glossy appearance. Honeydew is just aphid poop, and it is almost pure sugar. In fact, the poop of aphids is so nutritious and high in calories that sometimes ants will live on the milkweed and “farm” the aphids, protecting them from predators to ensure the aphids keep providing them with food. Look closely and you might see some of these ant aphid-farmers on your own milkweed! Another interesting fact about this particular aphid is its reproductive life history. There are no male oleander aphids in the wild. Females reproduce asexually through a process called parthenogenesis in which the egg develops an embryo without fertilization!

So you have aphids and they are all over your beautiful milkweed.  What to do?  

My preferred mode of attack for oleander aphids is to do nothing. Oleander aphids are rarely fatal to milkweed and typically don’t bother other species if milkweed is around. They are also a great food source for beneficial bugs and can help support a healthy population of aphid predators. That means good bugs are more likely to stick around your garden and defend other plants from attack. Where infestations are particularly unsightly and/or parts of the plant have died off, I employ selective pruning. In extreme cases I have cut milkweed all the way to the ground which typically yields strong new growth and allows you to hopefully remove the entire aphid population.

A dense concentration of oleander aphids on the stem of this young milkweed was likely the major contributor to its stunted condition.

My second go-to approach is to buy beneficial predators and release them in the garden. Ladybugs, a voracious aphid predator, likely already exist in your garden, but it’s unlikely they will show up in high enough numbers to be effective against a large aphid infestation. We run into this problem on rooftops, which can be very isolated environments and difficult for insects to reach on their own. There are several online purveyors of live bugs, including ladybugs, that will ship right to your door. Release the ladybugs at the base of your plant and watch them go to work. Once they have exhausted the food source in your garden they will likely turn on you as the next available protein option so be prepared to fight them off at some point. Jokes aside, ladybugs (which are actually beetles) are phenomenal and a gardener’s best friend. At Highview Creations we have deployed them with success on numerous occasions

If you are determined to completely eliminate oleander aphids from your garden chemical application offers the best route. Insecticidal sprays are one approach that can be employed very effectively. In my experience, a few applications of diluted insecticidal soap mixture or neem oil, which are less toxic than some other options, is sufficient to yield good results. In large gardens with lots of plants, a one gallon mister can make for a quick application, but in smaller settings a simple hand spray bottle works just as well. Apply the diluted soap to the vegetation and stem of the affected plants and to plants in the vicinity as oleander aphids are generalists to some extent and will occupy other plant species if milkweed is unavailable. Be very careful not to spray buds and blossoms because insecticidal soap is a general insecticide and will kill beneficial bugs like pollinators and predators. For this reason, I tend to only use insecticidal soap as a last resort and sparingly when I do.  

 


Identifying the milkweed bug

If you have orange and black bugs, but they are not aphids, then you likely have milkweed bugs. Juvenile milkweed bugs resemble oleander aphids, with a bright orange color and jet black legs but… even as juveniles milkweed bugs are much bigger. The only tricky thing about identifying milkweed bugs is there are striking morphological differences between adults and juveniles. Milkweed bugs are hemimetabolous and go through a gradual series of morphological stages from egg through adulthood over roughly 30 days. This means adults look very different from juveniles. Since it is common to see all stages of the insects’ life cycle on one plant a group of milkweed bugs may at first glance appear to be several different species!

A cluster of mostly juvenile milkweed bugs on a swamp milkweed seed pod.
An adult milkweed bug showing its distinctive black and orange markings.

Adult milkweed bugs are 10-18mm in length and elongated from head to butt with a small distinct head and a much less distinct thorax and abdomen, similar to a beetle. They are black with a large orange X on their back that tells predators “Stay away! I taste really bad.” From hatching, the first nymph stage is all orange with black legs and no wings. As the nymph stages progress towards adulthood the insect begins to elongate and increase in size. The body parts become more distinct and antennae and wings appear. The closer to adulthood the nymph stages get, the more black will be present.

Milkweed bugs on milkweeds, a concern?

The appearance of milkweed bugs tends to coincide with the development of seed pods and concentrations are usually spotted near the crown of plants where the seed pods are located. This is because milkweed bugs feed on the seeds of the milkweed plant. Milkweed plants are aggressive seeders and if you want to limit their spread milkweed bugs can be helpful allies.

What might be a little harder to stomach is that milkweed bugs don’t just eat seeds but are generalist predators and sometimes eat the eggs of monarch caterpillars. They are not the only insect that eats monarchs, however. Predation of both juvenile and adult monarchs is simply a part of a healthy ecosystem and spraying chemicals will certainly do more harm than good.

If you are bothered by the dense concentrations of milkweed bugs on your plants the best approach is to prune your milkweed plants periodically to limit or eliminate seed pods, their primary food source. Deadheading flowers after the bloom has expired is a good way to prevent seed pods from forming altogether. And if the bugs do show up you can just prune out the parts of the plants that have bugs on them. Since the bugs clump together a few cuts are often all that is needed to remove the bulk of the population.

Large gatherings of bugs in your garden can be alarming but are natural and usually not something to be concerned about. It is even possible to see these unexpected guests as one of the great joys of being surrounded by plants! If you are like me, curious and patient, you will quickly learn to live with them. But, if you want the pesky creatures gone, doing so is very doable with persistence and care.