How do I get rid of pests, like aphids, from my garden or habitat? Are they hurting my monarchs?
Many people are concerned about infestations of insects in their garden or habitat; we get the most questions about aphids. There are a few key points to remember when thinking about pest control. First, with good quality habitat comes a higher diversity of insects using the site. This diversity is providing resources for a wide variety of wildlife using the habitat and overall contributes to the health of the ecosystem. Some of these insects may compete with monarchs for milkweed, or even kill monarchs, but we can trust that in a healthy and diverse ecosystem/habitat, some monarchs will evade predators and contribute to the population. Second, remember that almost all insecticides will kill more than just the target species. If you spray an area with insecticide to kill aphids, other insects (including monarchs) that are in the area will be affected. For this reason, we don't recommend using insecticides in your monarch or pollinator habitat.
If you have a severe issue with aphids on your milkweeds, the safest way to remove them is manually. While a high concentration of aphids on your milkweed may look "bad", these insects are not necessarily causing harm to monarchs; unless they are in extremely high density, there are usually not enough aphids to kill the plant. You can squish the aphids and then rinse the plants with water to dislodge them from the plant. Make sure to check for monarch eggs and caterpillars first! A mild solution of dish soap and water can also be used to kill aphids on milkweed plants (again, after monarchs have been removed). Spraying this solution directly onto the aphids effectively kills the insects. Rinse the plants about a day after they've been treated with this insecticidal soap to remove any residue or dead aphids. This method is only effective when the solution directly hits the target insects; it acts by blogging the spiracles, so the residue will not kill insects. You can find a variety of recipes for home made insecticidal soap online, using simple ingredients typically found in your home.