04/28/2017 – Orange Aphids Live Their Lives without Males (Karen Benson)
These soft-bodied insects are Oleander Aphids. They are all females and can reproduce without males. Large colonies of these orange aphids can infect milkweeds and oleanders, sucking the plants’ juices. Fortunately, our native ladybugs prey on Oleander Aphids, keeping the pests under control. Karen Benson Photo.
You probably have seen aphids on your houseplants or in your garden at some point. They are tiny, only about 1/8th of an inch long, but they are numerous. Usually when you find them, you find a whole colony!
I used to think that all aphids were green or greenish white. Not so! When I examined my Tropical Milkweed recently I saw a mass of orange bugs on the growing tip. Using a magnifier, I could see that it was a thriving group of several hundred aphids.
These bright orange-colored aphids with black legs are known as Oleander Aphids. They are non-native. Most plant scientists believe they originated in the Mediterranean, which is where oleander comes from. How Oleander Aphids reached our shores is unknown, but they are doing very well in the warmer climates of North America. Gardeners in Florida and Southern California, as well as South Texas, are plagued by these beasties. They even have a nickname for them: Little orange vampires!
Aphids suck the sugary sap from the tender stems and leaves of plants. This robs the plant of the food it just made, but an aphid infestation rarely kills the plant. However, the bugs can cause the leaves to curl or have brown edges. Moreover, the swarms of aphids are unsightly to gardeners. Therefore, we try to get rid of them.
The easiest way to remove aphids is to wash them off the plant with a stream of water. The pressure needs to be just strong enough to knock them off without breaking the plant, so you need to hold the plant stem with one hand and spray the water with the other. Although this process works, it does not last. The aphids will be back.
Some people just squish the aphids with their fingers. Ewww…! This is obviously messy and not for the faint-hearted. Usually the aphids will recolonize their favorite plants within days anyway.
Where do the aphids come from? Well, mother aphids, of course. In the case of the orange Oleander Aphids, they are all mothers! Biologists believe that this aphid species is an “obligate parthenogenetic species.” This means the females reproduce without having mated with a male. One source claims these orange aphids have no males at all in their populations. They are obligated to reproduce by having females lay eggs that develop without fertilization. The developing young aphids are all females. Soon they also produce eggs the same way. No males needed.
The system works beautifully for the aphids because they can produce hundreds of nearly identical females quickly. Orange Oleander Aphids have another trick up their sleeves, too. The females are livebearers. They skip the egg stage. They pop out young that are already in the first nymph stage. These nymphs are tiny miniatures of the adults and they can suck plant juices from the moment they are born!
Orange aphids are successful for another reason. Aside from oleanders, they love plants in the milkweed family. Oleanders and milkweeds contain toxic compounds called cardiac glycosides and insects feeding on them absorb the poisons in their bodies. Orange aphids can repel some of their predators, certain kinds of spiders for instance, by exuding the toxic substances.
This business of incorporating toxic compounds into the body of an insect probably sounds familiar to you. It is how Monarch Butterflies become distasteful to birds that otherwise would prey on them. As Monarch caterpillars eat the leaves of milkweeds, they concentrate cardiac glycosides in their tissues.
Since most of us want to help the iconic Monarch Butterfly to survive in our modern world, we are doing everything we can to provide food and protection for it. This means growing more milkweed plants for the caterpillars to feed on. However, Oleander Aphids get on the milkweeds too and we dare not use pesticides for fear of killing the Monarch larvae.
What to do? Regular squishing or washing off aphids helps. On the other hand, you can do as I do: I leave aphids for their natural predators. The familiar ladybugs are avid aphid-eaters. Ladybugs are immune to the toxic substances in the Oleander Aphids’ bodies. Both adult ladybugs and their juvenile forms gobble up dozens of aphids a day. A thriving population of ladybugs will keep your garden pests under control.
It is possible to purchase ladybugs over the Internet. They are sold in bags of 1000 insects. This is a huge number of predators to dump into your garden all at once. In itself, such an act might upset the balance of nature in an area. Better to buy fewer ladybugs.
This Saturday, April 29th, the Beeville Garden Club will be selling smaller numbers of ladybugs to local gardeners. From 9AM to Noon, the Club’s ladybug wranglers will gladly herd a dozen or so of the beneficial insects into a recycled pill-bottle for your purchase. The Beeville Garden Club’s Annual Plant (and Ladybug) Sale is held at 178 Fairway Ridge in north Beeville. Come stock up on some nice plants and the predators to protect them!