Bean Plants: Understanding and Preventing Sunscald
Bean plants are generally easy to care for, but like all plants, they can be affected by certain pests and diseases. Two common problems that affect bean plants are spider mites and rust fungus. Another common issue, especially during hot and sunny weather, is a disorder known as sunscald.
What is Bean Sunscald?
Sunscald is a common problem in bean plants that occurs when the leaves are exposed to too much intense sunlight, causing sunburn. Just like humans can get sunburned, plants can also experience burning or scalding from strong UV rays. Bean plants seem to be particularly susceptible to sunscald.
The first signs of sunscald appear as bronze or red-brown speckling on the upper leaves of the plant. Over time, these small spots can merge together, causing entire leaves to turn brown. Sunscald can affect any part of the plant, but it’s usually most prevalent where the plant receives the most sunlight, such as the top leaves. In severe cases, leaves may drop, wither, or crumble away. From a distance, infected bean plants may resemble those with fungal rust, but upon closer inspection, they won’t have the powdery brown spores characteristic of fungal rust.
Causes of Sunscald in Bean Plants
While the sun may seem like the obvious culprit for sunscald, it’s not always the only factor involved. Several other factors can contribute to the development of sunscald in bean plants:
- Fungicide application: Spraying fungicide on bean plants during hot, sunny days can increase their susceptibility to sunscald. It’s best to spray fungicide on cloudy days or in the evening to avoid scorching.
- Overfertilization: Bean plants that have been overfertilized with high-nitrogen fertilizers are more likely to develop sunscald. Avoid using any fertilizer on bean plants that are already showing signs of sunscald. As a preventative measure, always use fertilizers with low nitrogen levels and follow the instructions on the product label carefully.
- Poor soil drainage: Soil that is too moist or drains poorly can also lead to sunscald in bean plants. When planting bean plants, make sure to choose a site with well-draining soil.
Preventing Sunscald in Bean Plants
Sunscald is most common in spring, when periods of cool, cloudy weather are followed by hot and sunny days. While there is no cure for sunscald, it’s usually just a cosmetic problem that doesn’t kill the plant. Here are some tips to help prevent sunscald in bean plants:
- Provide shade: If you live in a warm climate, consider providing dappled afternoon shade for your bean plants to shelter them from the hot afternoon sun.
- Remove damaged foliage: You can pick off badly scalded leaves to improve the appearance of the plant, but it’s usually best to let the plant adjust to the increased sunlight gradually.
- Water wisely: Avoid overwatering bean plants, as this can lead to poor soil drainage and increase the risk of sunscald.
- Fertilize responsibly: Use fertilizers with low nitrogen levels and follow the instructions on the product label carefully to avoid overfertilization.
- Plant disease-resistant varieties: Some varieties of bean plants are more resistant to sunscald than others. Consider planting these varieties if you live in an area with intense sunlight.
Treating Sunscald in Bean Plants
If your bean plants do develop sunscald, don’t panic. While there is no cure, the following steps can help minimize the damage:
- Stop spraying fungicide: If you’ve been spraying fungicide on your bean plants, stop immediately, as this can worsen the sunscald.
- Reduce fertilizer: Avoid using any fertilizer on bean plants that are already showing signs of sunscald.
- Improve drainage: If the soil around your bean plants is too moist or drains poorly, consider amending the soil with organic matter to improve drainage.
- Provide shade: As mentioned earlier, providing shade for your bean plants can help reduce the risk of sunscald.
Sunscald in bean plants is a common problem, but it can be prevented and treated with the right care. By following these tips, you can help your bean plants thrive and produce a bountiful harvest.