By: Sarah Adams
Member of the Big Country Master Gardeners
This month’s bug is the Aphid. Aphids are in the Animal Kingdom, Phylum Arthropoda, Class Insecta, and the Order Hemiptera. As a review, all insects within the Class Insecta have three body segments: the head, the thorax, and the abdomen. Aphids are soft-bodied insects that are small (1.5 to 3.5 millimeters) and have piercing-sucking mouthparts. There are more than 250 species of aphids throughout the world and many species can be a problem in Texas and the Big Country. The best way to contain an aphid infestation is to stop it before it starts. Most aphids secrete a sticky substance called “honeydew” on the plant. The substance itself is not particularly harmful but it is a warning sign of things to come. Anytime a plant that is not supposed to be sticky is sticky then it is time to start looking for aphids.
Aphids draw sap from the plant tissue with their piercing-sucking mouthparts. Some aphids feed on foliage, while others feed on fruit and flowers. Further, some aphids inject a toxic salivary secretion into the plant as they feed on it. If the aphid population is allowed to flourish, they can stunt plant growth, transmit diseases, and cause the deformation and improper development of leaves, bud and flowers. Aphids are efficient spreaders of plant viruses, capable of transmitting viruses from infected plants to other healthy plants. In addition to the damage done by the aphids feeding, the honeydew that aphids secrete falls on the leaves of the plants and a fungus called “sooty mold” colonizes and causes the surface to be covered in this black fungus. This black fungus restricts photosynthesis and stresses the plant. Honeydew, which is similar to sugar-water, also attracts other insects to the plant which can have mixed results.
Aphids thrive when the weather warms up and when plants start growing in the spring, feeding on the softer new plant growth. A greenhouse environment is also a perfect environment for aphids. Adult female aphids can overwinter, but most aphids overwinter as eggs on perennial plants. Aphids have an interesting lifecycle in that while most aphids reproduce sexually, lay eggs, and develop through metamorphosis, they can also reproduce asexually and bear live young instead of laying eggs. This allows for a very short time between generations and makes aphids difficult to control. The overlapping of generations and the increased reproduction can and likely will increase the rate of development of resistance to insecticides.
So, how do we best control the aphid population? We do not need to eliminate aphids; we just need to make sure that the population does not increase to the point that our plants are damaged. First and foremost, we must be monitoring our plants. Every week, or at the most every two weeks, simply look at your plants that are good environments for aphids. Look under the leaves and particularly on the new growth of the plant. Gardeners can use yellow sticky cards to see if any aphids are present in the area. These cards are coated in a sticky substance that attracts and then captures insects in their adult stage. This is a cost-effective way to determine whether an insect is present in the area and whether the population seems to be increasing or decreasing. Make sure that the plants are not overcrowded or over-watered. Stressed plants are the most susceptible to being infested by a number of insects. When the plant is at the end of its growing season, remove the plants so that it doesn’t become an invitation to pests.
If the aphid population is too high, start with a high-pressure spray of water directed at the aphids on the plant. This will physically remove them from the plants. Try to attract natural aphid predators like lady bugs, lady bug larvae are the best at keeping the aphid population under control. You can buy lady bugs and release them into the garden; however, unless you have a good environment for the lady bugs in place, they will simply leave the garden and go somewhere more suitable.
And remember if you use pesticides in the garden to kill the aphids or any pests, then you are likely to kill lady bugs and other beneficial insects disrupting the delicate balance of bugs in our garden. Insecticidal soaps can help control the population of any soft bodied insect including the aphids by penetrating the aphids body and dehydrating them until they die. Read the label of anything that you put in your garden or on your plants because no product does just one thing. Even some insecticidal soaps can negatively affect plants. Always try the product on a small test area of the garden or plant and see how the plant reacts to the product.
If you have any questions, call the Taylor County Extension Office at 325-672-6048 or email us at mgardeners@yahoo.com. We hope you visit bcmgtx.org for information on all Big Country Master Gardener events, like us on BCMGA Facebook, and check out training presentations on BCMGA YouTube. We are here to help you.
