Aphids… Those sticky little green critters that bug commercial growers and home gardeners whenever there’s a green leafy plant in sight. Fortunately, there’s a lot you can do to get on top of aphids and even prevent an infestation. Here are the University of California’s top tips for integrated aphid control.
Decide Whether Control is Necessary
No matter where they choose to land, aphids cause an unsightly mess. They leave a sticky honeydew all over the leaves and often cause the leaves to curl. Some species of aphids also release toxins and viruses into the leaves, causing further curling and inhibiting growth.
However, annoying as these critters may be, aphid control is not always necessary. On mature citrus trees, for example, aphids are unlikely to do major damage and actually provide food for beneficial insects. In other cases, the risks of damaging beneficial insects along with the aphids may make control measures undesirable.
Organic Aphid Control Techniques
For crops other than mature citrus, staying on top of aphids is necessary. Check your plants for aphids (and their natural predators like parasitic wasps) at least twice a week during rapid growth, especially in late spring when these critters cause the highest amount of damage. Ants are also an indicator that aphid populations may be present.
As soon as you spot an infestation of aphids, it’s essential to get rid of them early — before they cause the leaves to curl around them and shelter them from their natural enemies. Pruning or high-pressure hosing may be sufficient. Otherwise, try these methods of aphid control:
Ants and aphids can best be described as partners in crime. Ants love eating aphid excrement and protect the aphids from their natural predators. If you’ve got an ant-and-aphid problem, start with the ants:
- Apply sticky bands around tree trunks (placing fabric between the band and the tree) to stop ants from climbing up to the aphids.
- Place ant stakes or baits in containers on the ground.
- Prune away ant pathways such as branches that connect the plant to trees, buildings, and the ground.
Lady Beetle Releases
Lady beetles are a well-known natural enemy of aphids. However, aphid control using lady beetles isn’t as simple as finding a lady beetle and placing it on the infected leaf. For effective organic aphid control, there are several guidelines you’ll need to follow to give your lady-beetle release any chance of success:
- Use the convergent lady beetle, Hippodamia convergens, for aphid control.
- Calculate the number of lady beetles you will need.
- Refrigerate the lady beetles until release.
- Release the lady beetles at dusk.
- Mist the lady beetles and leaves lightly with water.
- Place the lady beetles at the base or in the “crotch” of the lowest branches on the plant so they can climb up.
- Repeat the treatment one week later if necessary.
Cultural improvements for aphid control include measures that help prevent infestations from becoming established in row crops like vegetables and melons. These are some of the most effective cultural improvements for preventing aphid damage to row crops:
- Remove any existing sources of aphids near the field, including infected sowthistle and mustard weeds.
- Check all of your transplants for aphids and pick or prune them off before planting.
- Use only small portions of nitrogen fertilizer at any one time and limit yourself to either urea-based time-release formulations or organic fertilizers.
- Cover new seedlings or keep them in a greenhouse until they grow large enough to tolerate aphids.
- Remove the weeds and cover the ground with silver-colored reflective mulches to deter aphids from settling. Remove any silver mulches before summer so as not to overheat your plants.
- Spray affected leaves with a strong burst of water early in the day to wash off the aphids and honeydew.
Insecticidal Soaps and Oils
For aphid infestations, organic aphid control is usually the most effective. Even if the previous methods of aphid control prove to be insufficient, the kinds of (chemical) spray you’ll try next are generally quite gentle so as to avoid killing off predators in the process.
- Water mixed with soap
- Petroleum-based horticultural oil
- Neem oil
- Canola oil
Create a water-based solution with 1-2% oil and spray the affected leaves thoroughly on top and underneath. These preparations will kill aphids (and their predators) on contact but don’t leave any toxic residue. You might need to repeat the application again until the aphids are brought under control.
Other chemicals that are used for aphid control on ornamentals include malathion, permethrin, and acephate. These chemicals also kill aphid predators and bees and are only used in non-edible crops — never on leafy greens that are destined for consumption.
Find Organic Aphid Control Solutions at Fruit Growers Supply
If you have an aphid control problem, Fruit Growers Supply Company has solutions! Your one-stop shop for specialty crop supplies, we offer an extensive range of horticultural oils as well as covers and mulches in our retail stores. On a larger scale, we provide custom solar-powered irrigation systems that are specific to your crop type and site requirements. Give our team a call today to see how we can help you succeed.