Perennial milkweed, Asclepias perennis, with oleander aphids; notice the brown aphid mummies that have been parasitized. Photo credit: Mary Salinas UF/IFAS Extension.
Milkweeds are appreciated for their beauty, but often we cultivate it for the benefit of the monarch butterflies who lay their eggs only on this plant genus. Avid butterfly gardeners want the monarch caterpillars to eat up the milkweed and become beautiful butterflies. Often instead, thousands of aphids show up and compete for space on the plants. These bright yellow aphids are known as oleander aphids.
Just how do aphids build up their populations so quickly? It seems that one day you have a small number on a few plants and then a few days later, thousands are all over your milkweed. Oleander aphids have a few advantages for quickly building their populations:
All oleander aphids are female and do not need to mate to produce their young
Aphids give birth to live young who immediately start feeding on the plant
Aphids start reproducing when they are 4 to 10 days old and keep reproducing during their one-month life span
When populations get heavy or the plant starts to decline, winged individuals are produced to migrate to new areas and plants.
Parasitic wasp and aphid mummies. Photo credit: University of California.
What can or should you do to control this pest?
One option is to do nothing and let the natural enemies come in and do their job. One of the best is a very tiny wasp that you will likely never see. This parasitoid lays its eggs only inside aphids. The wasp larva feeds on the inside of the aphid and turns it into a round brown ‘mummy’ and then emerges when mature by making a round hole in the top of the aphid. Look closely with a hand lens at some of those brown aphids on your milkweed and you can see this amazing process. Another common predator I see in my own garden is the larvae of the hover fly or syrphid fly. You will have to look hard to see it, but it is usually there. Assassin bugs and lady beetles also commonly feed on aphids. The larvae of lady beetles look nothing like the adults but also are voracious predators of aphids – check out what they look like.
Lady beetle larva feeding on aphid on tobacco. Photo credit: Lenny Wells University of Georgia Bugwood.org.
If you think your situation requires some sort of intervention to control the aphids, first check carefully for monarch eggs and caterpillars, keeping in mind that some may be very small. Remove them, shoo away any beneficial insects, and spray the plant completely with an insecticidal soap product. Recipes that call for dish detergents may harm the waxy coating on the leaves and should be avoided. The solution must contact the insect to kill it. Always follow the label instructions. Soap will also kill the natural enemies if they are contacted. One exception is the developing wasp in the aphid mummies – fortunately, they are protected inside as the soap does not penetrate. Oils derived from plants or petroleum can serve the same purpose as the insecticidal soap.
Syrphid fly larva and oleander aphids. Photo credit: Lyle Buss, University of Florida.
You also can squish the aphids with your fingers and then rinse them off the plant. If you only rinse them off, the little pests can often just crawl back onto the plant.
There are systemic insecticides, like neonicotinoids, that are taken up by plant roots and kill aphids when they start feeding on the plants. However, those products also kill monarch caterpillars munching on the plant and harm adult butterflies, bees, and other pollinators feeding on the nectar. So those products are not an option. Always read the product label as many pesticides are prohibited by law from being applied to blooming plants as pollinators can be harmed.
In the end, consider tolerating some aphids and avoid insecticide use in landscape.
Veteran Master Gardener, Les Furr shares an idea he and his wife had to hide an ugly debris pile following Hurricane Michael. He planted a temporary sunflower screen to block something ugly with something beautiful. Sunflowers can be planted along a road or fence, and provide a lovely addition to your property. The seed can be saved and frozen to provide beauty to your property year after year.
Oleander caterpillars, which are active on some oleanders during summer, can provide a number of gardening lessons.
Oleander caterpillar moth on lantana flower. Photo credit: James Castner, UF
The adult moth is striking in appearance. The bluish to purplish moth has white dots on its black wings. The moths resemble wasps as they fly in and around oleander shrubs.
It’s the orange caterpillars with black spots and black hairs that cause problems for some gardeners.
Caterpillars are the larval stage of butterflies and moths. In order to enjoy watching butterflies and moths feeding on the nectar of flowers, some of the caterpillars must survive to become adult butterflies and moths. This is lesson number one.
Oleander caterpillars usually only feed on oleander plants. Oleanders are native to areas of Europe and Asia. This is lesson number two.
Oleander caterpillar, Photo credit: Paul Choate, UF
Oleander caterpillars benefit by us planting their food source in Florida.
This relationship between pest and plant is referred to as the key plant, key pest concept. Some other examples include St. Augustinegrass and chinch bugs, gardenias and whiteflies, crape myrtles and crape myrtle aphids, azaleas and azalea caterpillars, camellias and tea scale, roses and black spot, pecans and pecan scab, squash and squash vine borers.
Understanding this concept can be helpful in designing a “low maintenance” landscape.
When you plant roses, you plant everything that goes with roses, including the time and money required to maintain them. This applies to St. Augustinegrass, pecan trees, squash and oleanders. This is lesson number three.
Oleander caterpillars can temporarily damage the appearance of oleanders. But they cause no long-term damage for the plant. This is lesson number four. The damage is aesthetic. Oleander caterpillars can consume great numbers of leaves. However, if the plant is otherwise healthy, new leaves will be produced and the plant will continue to grow. The damage is temporary; there will be no evidence the plant ever had a problem.
To spray or not to spray for oleander caterpillars has to do with a person’s tolerance level.
If you can’t tolerate having oleander caterpillars around and the temporary aesthetic damage they cause, consider the use of Bacillus thuringiensis. It is sold under a number of brand names and many times is referred to as Bt. This bacterium only controls caterpillars so it is friendlier for the beneficial insects. When using any pesticide, always follow the label directions and precautions.
Here are links to UF/IFAS Extension publications with more info.
We hope you were able to join us for Gardening in the Panhandle LIVE! Butterfly Gardening on July 9th to learn about attracting butterflies to your Florida gardens. As promised, we have compiled a list of butterfly resources that we talked about during the webinar and a few extra that we didn’t have time to cover.
If you were not able to join us live, you can still watch the videos on Facebook or YouTube
Click on the topic of interest for links to resources:
Don’t forget to tune in for our next Gardening in the Panhandle LIVE! on July 23rd for Prepping for the Fall Garden. Register for that webinar on Zoom or Follow our Facebook Event for updates.
Sunflowers, Helianthus spp., are a great choice for gardeners who are looking for some cheerful color in their landscape. Here in Florida, we have the main ingredient for success, lots of sunshine!
‘Skyscraper’ Sunflower bloom. Photo courtesy of Ray Bodrey.
Sunflowers are short-lived annuals. The average time between planting and bloom is roughly 65 days. You can typically plant sunflowers in Florida beginning in late winter until early fall. Only the coldest months cause problems, and for most years that’s only November – January. Sunflowers can be planted almost anywhere there is full sun. The major selling point with sunflowers is, of course, the impressive blooms (figure 1). These yellow to sometimes orange or red-petaled flowers develop a central seed disc, with most variety’s flowers having approximately an 8” diameter.
When planting, you may choose to plant in narrow rows with close seed spacing in order to cull weaker plants later. A final row and seed spacing of 2’-3’ is recommended for full height and development of most varieties. However, you may also choose to plant in a bed, using a close pattern as seen in the photo below. In any event, sunflowers are easy to propagate by seed and are very low maintenance. Occasionally, powdery mildew and spittle bugs can be a nuisance. A general garden fungicide and insecticide will help if problems occur.
‘Skyscraper’ sunflowers planted on close spacing. Photo courtesy Ray Bodrey.
Sunflowers are available in many varieties, consisting of different color blooms and plant sizes. These sizes range from dwarf (1’-3’) to tall (10’-15’) varieties. You may wish to stake taller varieties at some point, as plants will tend to lean with no wind break in place. Here’s a few garden variety common names to look for: ‘Sunbright’, ‘Sonja’, ‘Sunrich Lemon’, ‘Sunrich Orange’ and ‘Autumn beauty’. Seed companies also have mixes available in packets. For tall plants, ‘Mammoth’ or ‘Skyscraper’ varieties will do the trick.
If you are fond of the sunflower bloom and looking for a groundcover, there are a couple of native perennials that fit this category. Beach sunflower, Helianthus debilis or swamp sunflower, Helianthus angustifolius, are groundcovers/ornamentals for landscapes and thrive in dry, hot climates and in a range of soil types. They also are great pollinator attractors.
For more information on growing sunflowers, contact your local county extension office.
For the 13th year we celebrate National Pollinator Week June 22-28 to bring awareness to the importance of our pollinators and the challenges they face. This is an opportunity to learn about ways to protect pollinators in our own landscapes. Every one of us can make a difference.
When we hear the word ‘pollinator’ most of us immediately think of honeybees. They are very important but there are so many other creatures that are important pollinators:
Native bees – Florida alone has over 300 species of bees
Hummingbirds – their long beaks can reach into long, tubular blooms
Bats – they pollinate over 500 plants including banana, mango, and agave (used to make tequila)
Beetles – considered to be a messy and minor pollinator; they pollinate the native paw paw
Butterflies – a minor pollinator as most have long legs that keep them perched above the pollen
Flies – pollinators of a variety of native plants
According to the USDA, 75% of flowering plants and about 35% of food crops around the globe rely on these animals for pollination. Without pollination, these plants would not reproduce or provide us food.
So, what can the average person do to make a difference?
Avoid using any insecticide unless it is absolutely necessary. Predators like assassin bugs, dragonflies and birds help to keep pests in check. Our songbirds rely on protein-rich insects (especially caterpillars) to feed their growing babies.
Don’t treat areas where pollinators are visiting the flowers, whether in the lawn or the landscape beds.
If you need to apply an insecticide to the lawn, mow first to remove the blooms from any weeds. Always follow the label instructions carefully.
Avoid using a systemic insecticide on plants that bloom and attract pollinators. The insecticide can remain in plants for a long time.
