The eggs of bean leaf beetles are orange, shaped like a lemon, and has an average length of .85 millimeter. When they are in the larval stage, on the other hand, they are white with dark brown plates. The length can be as long as 10 millimeters with an appearance that is similar to corn rootworm larva. Meanwhile, its pupa has an average length of 5 millimeters and has a white soft body. Lastly, once it grows into an adult, the color can range from light tan to red with an approximate length of ¼ inch. It has a black triangle on its back and four trapezoid spots on the middle. You can see its head from the above.
Bean Leaf Beetle’s Habitat
This pest survives in the different parts of the plant depending on its specific stage of development. The adults will hide on decaying vegetation or plant debris. They usually start feeding on their hosts in April or when the temperature ranges from 50 to 55 degrees Fahrenheit. They commonly attack the leaves when they are adults. On the other hand, the larvae will thrive on the roots, nodules, and stems. The adults will lay their eggs in clusters, which you can find in the soil or adjacent to the stem of the plant where it will feed as an adult.
Identifying Bean Leaf Beetle’s Damage
This is a destructive pest that feeds mainly on soybeans. Other common hosts include dry edible beans, snap beans, clover, alfalfa, and wild legumes, among others.
The following are some of the most common signs that will be indicative of damages by bean leaf beetle:
- One of the parts that will demonstrate the signs of the damage is the leaf. There will be holes on the surface and crooks on the edges. It will start with little oval holes and eventually will eat up the whole leaf. With severe foliar damage, the leaf will fall off.
- When the foliage matures, it is no longer that attractive for bean leaf beetles. This is the point wherein they will start feeding on the pods of their host plant. They will eat the green tissue and end up with a thin membrane that is visible on the seed. These membranes will crack and serve as an entry point that will attract pathogens, causing more damages on the plant.
- The root module is another breeding ground for bean leaf beetles. This leads to a reduction in crop yield, killing the plant while it is still young.
Results of Infestation
When the population of lady beetles is too high, it will quickly destroy young plants, and hence, inhibiting their growth. They prefer tender and young tissues, which is why the damages will be apparent from early on the growth of the host. They result to the reduction of vigor of the plant where they thrive and restrict the nutrients that they receive. In turn, this will cause severe defoliation, and in some cases, death of the plant. They can also be a carrier of different plant diseases, although not as big as a problem as other common garden pests.
How to Get Rid of Bean Leaf Beetles
Natural and Organic Solutions
For a safe and effective way to eliminate bean leaf beetles in the garden, the following are some of the solutions that will work:
- Manual removal of the bean leaf beetle will be a promising solution. However, this works best only in a small garden as it can be an exhausting task. Hand-pick the adult beetles and make sure to throw them in a bucket with water and mild soap. This is a mixture that will kill the beetles. Do not just throw them in the garden as they will easily find their way back to their host plant.
- The use of floating row covers will also work. This is more of a preventive than a control measure. The cover will provide a protective barrier, which will hide the plant. Nonetheless, at one point, you will need to take out the cover when the plant needs pollination.
- Companion planting also holds a lot of promise. To prevent the bean leaf beetle from growing in soybeans and other common hosts, it is best to grow marigold, yarrow, daisy, sweet alyssum, and rosemary.
- There are also natural predators that you can encourage in the garden. They are available for commercial purchase, although you have to make sure that their number is more than enough for the size of the area you will treat. Among its natural enemies, parasitoid wasps are some of the most effective. You can also consider having plants with sweet nectar to attract wasps that can kill bean leaf beetles.
- Another organic solution that will work is neem oil. Unlike conventional pesticides, they do not contain toxic ingredients. You can apply neem oil even without having protective equipment. The best thing is that they will kill only the pest and not beneficial insects. They will also not harm your pets.
It is common for commercial growers to resort to the use of insecticides containing ingredients that will kill the bean leaf beetles. While this will work, especially for large-scale infestation, this is not an eco-friendly solution. It kills not only the bean leaf beetles, but even the beneficial insects that will be essential in controlling their population.
Some of the most common ingredients in pesticides to control the population of bean leaf beetles are esfenvalerate and permethrin. Among others, some of the most common brand names of insecticides that will work best for bean leaf beetles include Asana, Baythroid, Brigade, Karate, Prolex, and Sevin.
How to Prevent Bean Leaf Beetles
Among others, one of the best preventive measures is to keep the garden clean. Because they often hide in leaf litter, it is important to remove the latter so that they won’t be a breeding ground for pests. Also, taking proper care of the plant will be a good measure. Water it often, but make sure that there is proper drainage. Regular inspection is necessary to prevent severe damages. It will also help if you will plant resistant varieties.