Late-summer insects abound
When we get to the end of July, there are many insects that start to build their populations. These insects like the hot weather because they have plenty of plants to feed on or their prey is increasing.
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So, when we get to this time of the year, there are certain insects that we should look out for. Some are beneficial and some are pests on plants.
The first insect is beneficial, but many people are terrified of this insect: the cicada killer. This intimidating insect can measure from 1 1/2 to 2 inches in length and is black or brown with colorful yellow markings on the abdomen and a stinger measuring a quarter-inch long. Cicada killers typically fly close to the ground. Most of the time they fly around knee height or 16 to 20 inches above the ground.
Sightings are common from mid to late summer as the adults are emerging or searching for cicadas. After emerging, the adult wasps will feed on flower nectar and then mate, then dig burrows preparing for the next generation.
Once it is ready to reproduce, the adult female will capture a cicada and sting it. This paralyzes the cicada. The cicada killer then carries the paralyzed cicada to a previously dug burrow measuring 10 inches to 4 feet in length. The wasp will then lay a single egg on the paralyzed cicada, and then she seals the chamber.
When the egg hatches, the larva will start to eat the insides of the still-living cicada for four to 10 days. When everything but the outer shell has been devoured, the wasp larva spins a silken case and prepares to overwinter. In the spring, the larva begins to pupate and turns into an adult. The next generation of adults will crawl out of the ground and start the process again.
As frightening as these insects might appear, they are typically not aggressive and are actually considered to be beneficial. These wasps will not sting unless cornered or accidentally touched or stepped on. In this case, a cicada killer's sting can be very painful. The sting is not dangerous unless the victim is known to be allergic to bee stings or shows signs of an allergic reaction.
The only places this insect can pose a real threat are where people, especially children, tend to congregate or play. If one gets too close to a burrow, one might encounter an inquisitive male guarding the area. There is no real need to worry, for he is only bluffing and possesses no stinger. It is best to leave them alone unless they are in an area where there is a lot of traffic from people.
The following insects are ones that we need to pay attention to because they can cause plant damage: azalea lace bug and whiteflies.
If your azaleas have white or yellow mottling on the top of the leaf and black specks on the bottom of the leaf, you have azalea lace bugs. These insects live on the bottom of the leaf and suck the juices out of the leaf. The lace bugs over-winter as eggs, and will start emerging the end of March through April. There are two generations during the year. The second generation will emerge in August.
The key to controlling the lace bug is to control the first generation. Two insecticides that are effective for controlling lace bugs are acephate and imidacloprid. When sprayed on a leaf, acephate moves throughout that leaf. Imidacloprid is applied to the root system and moves throughout the plant. With either of these products, there is no need to spray the bottom of the leaf.
The next insect is very similar to the azalea lace bug in that it sucks the sap from plants: the whitefly. These insects have two generations a year and they occur in the same time frame as the azalea lace bug. If you did a good job of controlling the whiteflies in the spring, you should have very few whiteflies now.
You can look at the bottom of the leaves on your plant to check for whitefly eggs. They will be oval-shaped and whitish in color. You will find these on plants that whiteflies like, such as gardenia, privet and ligustrum. If you have whiteflies in August, you can reduce the number that you will have in the spring by controlling them now. You can use imidacloprid as a control.
Another product that can be used contains the insecticide disulfoton. If you are looking for a spray product, you can use bifenthrin, or one of the pryrethrin products. Another control option is insecticidal soaps. This is an organic solution that will work if you follow a strict spray schedule.
The key to controlling these pests is to scout your plants and find them early.
Columbia County Extension Agent Charles Phillips can be reached at (706) 868-3413 or by e-mail at charlesp@uga.edu. The Extension Web address is www.ugaextension.com/columbia.