Yellow aphids can appear in large colonies and are often a terrifying sight as they devour milkweed plants. They are a non-native insect and they can multiply very quickly. However, they are not a direct threat to monarch caterpillars because they feed on the milkweed plant only. They can indirectly affect caterpillar health by depleting nutrients in their only host plant.
What are oleander aphids?
The oleander aphid (Aphis nerii), sometimes called the milkweed aphid, is a common pest of milkweed plants. It is a non-native bug, most likely originating in the Mediterranean region where it's principal host plant, oleander, grows.
The Oleander aphid is a bright yellow insect with black legs, and stalks known as cornicles on the back of the abdomen.
Method One: Manual Removal
Although, time-consuming, the safest way to remove aphids is manually by squishing them between your fingers (use gloves to avoid staining your fingers) and then using a hose to dislodge them from the plant. Always check for monarch eggs and caterpillars before spraying because you could damage or dislodge them in the process as well.
It is best to catch the aphids before they become an aphid army, so even if there are just a few on the plant, remove immediately.
Method Two: "Contact Only"
This is a method recommended by Monarch Watch and was shared by Vic Jost @ Jost Greenhouses through Elliott Duemler at Taylor Creek Nursery. A mild solution of dish soap and water will also work.
• 1 part (e.g. 1 oz) Blue Dawn
• 1 part Isopropyl Alcohol
• 1 part white vinegar
• 128 parts (e.g. 1 gal) water
"Contact only" means that the insects have to have the mixture applied directly to their body for it to work.
*Use caution with this method because it will also kill monarch larvae if they come in contact with the solution. Rinse the plant when finished so you do not injure monarch larvae and other beneficial insects.
Monarch Joint Venture
Natural History of Orange County and nearby places.
Gardens, lawns, fields, roadsides, right-of-ways all provide vital habitat for monarchs and other pollinators. How we manage this habitat must be done with care to help protect our monarchs!
When are monarchs present in my area?
Timing is crucial when planning your mowing and other land management practices. To find out where the monarchs are, you can view up-to-date monarch observations at Journey North or Western Monarch Milkweed Mapper.
Remember that this will vary each year.
In addition, you can conduct your own survey by checking your milkweed patch/field daily.
Once you understand where the monarchs are and when they will be visiting your habitat, you can create a strategic mowing plan.
Limit the frequency of your mowing
Mowing milkweed mid-summer in areas where there is a lull in monarch activity, such as the Southern Great Plains, may promote milkweed growth and late summer or early fall breeding (Baum and Mueller 2015; Fischer et al. 2015). Always, do a quick survey for monarchs before mowing and check Journey North's website to see where the monarch is in their migration.
Leave a pollinator refuge area
Instead of mowing the entire area, leave refuge areas that may be good for nesting or overwintering sites for pollinators and other wildlife. If necessary, make a sign that indicates that site is an overwintering refuge.
Avoid mowing milkweed and blooming flowers
Blooming flowers provide essential nectar sources for pollinators. In addition, check to see if the flowers have began dispersing their seeds.
Increase your cutting height
Increasing your cutting height by a few inches will remove the seed heads of the invasive plants while still providing some habitat for other bugs and pollinators to thrive.
Fischer, S. J., Williams, E. H., Brower, L. P., & Palmiotto, P. A. (2015). Enhancing monarch butterfly reproduction by mowing fields of common milkweed. The American Midland Naturalist, 229-240.
Habitat Enhancement and Best Management Practices in Highway Rights-of-Way.” Prepared by The Xerces Society for Invertebrate Conservation in collaboration with ICF International. 68 pp. Washington, D.C.: Federal Highway Administration.
Journey North. journeynorth.org/monarchs
Knight, S. M., Norris, D. R., Derbyshire, R., & Flockhart, D. T. (2019). Strategic mowing of roadside milkweeds increases monarch butterfly oviposition. Global Ecology and Conservation, 19, e00678.
Monarch Joint Venture. Mowing and Management: Best Practices for Monarchs.
Western Monarch Milkweed Mapper. https://www.monarchmilkweedmapper.org/
Written by Jennifer Coolie
Supporting the population of our beautiful monarch butterflies goes beyond planting colorful, nectar rich plants. “It’s easy enough to plant species that butterflies like to feed on, but you need to do more than that to support your local populations,” says Butterfly Conservation’s Richard Fox. Monarch butterflies are absolutely wonderful creatures, and need to be well looked after due to their dwindling population. Help make your garden more butterfly friendly by creating water sources for the butterflies to “puddle” in. "
Butterflies can be found sipping moisture from puddles or wet soil after a rain (known as "puddling"). Not only are they being hydrated but they also pick up salts in the process.
Water’s Role In Survival
Like humans, having a water source is essential to protect monarch butterflies. In the overwhelming heat of the summer, butterflies will gather extra minerals and vitamins through a behavior known as puddling. Through puddling, monarchs will take small drinks in shallow water areas rather than diving into a deeper water source. While it is important to create a butterfly garden rich with nectar plants and flowering shrubs, having a water source in the area is equally essential to promote butterfly survival. Creating a garden with water features that gives the butterflies an opportunity to puddle only helps make your garden space friendlier for future monarch butterfly populations.
The Shallower The Better
When choosing a water feature to help the endangered monarch population, look for multi-level fountains that have one of the levels with a shallow water line. Shallow water is more attractive than deep standing water for butterflies. If you prefer bird baths to fountains, this can still work because butterflies can puddle on the shallow edges of the birdbath. Alternatively, you can also create a butterfly oasis in the middle of a deeper water feature by simply adding in rocks, marbles or pebbles to make a perching paradise for the butterflies to puddle in.
Other Ways To Boost The Butterflies
If you’re looking to go above and beyond to make a perfect puddle paradise, add minerals to the water source. To supplement your butterfly water source with added minerals, sprinkle in some table salt or composting fruits (in small amounts to avoid polluting the water). Keeping the soil around your water feature damp can help the butterflies, says the Farmer’s Almanac. Finally, keep your butterfly water source in one consistent area so that your monarch friends can keep coming back.
It’s win-win: by placing a water feature in your butterfly garden, both you and the monarch butterfly population will benefit. You hear the tranquil sound of running water while your butterflies receive their essential minerals.
What are host plants?
Host plants are the vital food source that caterpillars live on. Adult butterflies will seek out these plants to lay their eggs on because they know that the caterpillar cannot travel far and will not survive if placed on a plant that they cannot eat.
The key to a successful butterfly garden is to plant both nectar and host plants so that the butterflies will have a food source in all stages of their life cycles. Nectar plants are simply plants that produce nectar as a reproductive strategy. Almost all flowering plants produce nectar and many host plants double as a nectar sources.
Why plant native?
The evolutionary relationship between butterflies and host plants is the main reason for planting native plants in your garden. As a defense mechanism, plants have evolved to produce chemical alkaloids, also known as secondary metabolites, in order to deter herbivory (wildlife feeding on plants). In response, each butterfly species has evolved to be resistant to the toxins of just a small number of plants so their caterpillars have something to feed on.
Few native butterfly species use exotic or non-native plants as their hosts because they haven't created an evolutionary relationship with them. When we plant non-native glasses and exotic ornamentals such as Butterfly Bush (Buddleia davidii), we often remove the vital food sources for caterpillars and this leads to decreased populations. Ironically, butterfly bush does not serve as a host plant for any native species of caterpillars. To find out which plants are native to your area visit the Native Plants Database.
Be prepared for your plants to be eaten.
It is important to remember that the leaves of these plants will get eaten but that is the whole point! For this reason, it might be a good idea to plant them in less visible areas.
Black Eyed Susan (Rudbeckia hirta)
Host plant for: Silvery Checkerspot, Gorgone Checkerspot, Bordered Patch butterfly
Host plant for: Pearl crescent, Painted Lady and more
Coneflower (Echinacea spp.)
Host Plant for: Silvery Checkerspot and more
Hollyhock (Alcea spp.)
Dill (Antheum graveolens)
Host plant for: Black Swallowtail, Anise Swallowtail and more
NOTE: The Black Swallowtail will feed on any plants within the Parsley family.
Sunflower (Helianthus spp.)
Host plant for: Silvery Checkerspot, Painted Lady and more
Milkweeds (Asclepias spp.)
Host plant for: Monarch
Mallow (Malva spp.)
Violet (Viola spp.)
Host plant for: Great Spangled Fritillary, Variegated Fritillary, Falcate Orangetip, Meadow Fritillary and more
Tall Verbena (Verbena bonariensis)
Host plant for: Common Buckeye, White Peacock and more
Bringing Nature Home: How You Can Sustain Wildlife with Native Plants by Douglas W. Tallamy, Publisher: Timber Press; Exp Upd edition (April 1, 2009)
Caterpillars of Eastern North America by David L. Wagner, Publisher: Princeton University Press; 1St Edition edition (August 14, 2005)
Butterflies and Moths of North America
Native Plant Database
Penn State Extension Office