7 Ideas for Keeping Milkweed Aphid-free
One problem that plagues almost all gardeners across North America is the relentless attack of oleander aphids. They suck the life from milkweed like little orange vampires.
The degree to which their infestations effect plant health is debatable, but the ugliness they unleash upon your butterfly garden is not!
In 2011, they showed up in droves on our tropical milkweed. I cringed every time I walked by those plants and wondered if I should consider other milkweed varieties to cut down their numbers. A couple gardeners assured me the milkweed would be OK. Miraculously, I even found two 5th instar caterpillars crawling over the orange-covered leaves!
However, I believe the seeds I collected that season gave me a better indicator of milkweed health…only 20% of my seeds sprouted the next season! Every other year without heavy aphid infestations, my seed viability has been at least 90%.
Little did I realize, I could have stopped this infestation from getting so out of control. Now that I know how to better control aphids, I’m here to help you avoid my aphid-blanketed milkweed debacle of 2011.
Of all the questions I receive about butterfly gardening, “how can I control aphids on my milkweed?” is probably the most frequent. A good idea for all gardeners is to check your plants regularly. In the following photo, you might see two harmless aphids sitting below tropical milkweed flowers…
…but I see the potential beginnings of an aphid army!
Here’s are some tips to keep that army from ever forming, so you can save your precious milkweed plants:
1. RUB THEM OUT: some people simply get rid of aphids by rubbing them off with their fingers and thumbs . This can be effective when the numbers are low if you’re not afraid to get your hands (or gloves) dirty.
2. HOSE THEM DOWN: a steady stream of water on the aphids can also displace them. You’ll need to hold the milkweed plant with your other hand to avoid stem breakage. Using a spray bottle on stream is also effective.
3. ALCOHOL OVERDOSE: This was reported in the LA Times as the secret to killing milkweed aphids and not monarch eggs
Please note that if isopropyl alcohol is applied directly to monarch eggs or caterpillars it will kill them.
4. WASH THEIR MOUTHS OUT: a little soap never hurt anybody, but it can kill those pesky aphids. There are many homemade “recipes” floating over the internet. Obtaining information from credible .edu sites can help to avoid creating dangerous concoctions that harm plants or surrounding wildlife: Aphid Control: Soaps and Detergents
5. CUT IT OUT: if you don’t catch the aphids right away, you can still avoid harsh chemical solutions by cutting off plant stems with the heaviest infestations (and using #2 , #3, or #4 for less infested areas). Make sure to discard the cuttings far away from the garden to avoid a touching aphid-family reunion. I suggest using a yard waste can if you have one.
Still have aphids? You have a couple options left to regain aphid control. Unfortunately these options are unpredicatable and can have unintended consequences…
6. WHO’S BUGGING WHO NOW?!: Introducing beneficial insects to eat the aphids sounds like a great natural solution, but beneficial bugs like ladybugs and mantids also feed on monarch eggs and larvae. There are already enough monarch predators in your garden…what will happen if you unleash thousands more?
7. REPEL WITH PLANTS: Some plants, including onions and marigolds, have been shown to repel aphids and naturally reduce their numbers. Planting these repellents close to milkweed can attract more butterflies while keeping aphid numbers down to reasonable levels.
8. WORLD WAR G(arden): If it’s come to the point where aphids have completely engulfed your milkweed, cut back all areas of moderate to heavy infestation and throw out.
Aphids lay eggs when it starts to cool, so cutting down the mating population in late summer/early fall can help you avoid an aphid Gardageddon next season!
You could also apply a professional grade pesticide like
malathion, but it’s likely that monarchs, other wildlife, and the environment could suffer injury (or worse) from using harsh chemicals. There’s a reason most butterfly gardeners use organic pest control…it won’t kill the butterflies!
Whatever solution you choose to control aphids, remember that early intervention is your best chance for for defeating these sap sucking pests.