Beans Pests and Diseases, Control Methods

Beans pests and diseases, control methods: Beans are very easy to grow and provide excellent nutritional value. The common bean can be bushy, vine-like or climbing depending on the bean variety being grown. The plant leaves grow alternately on the stems, are green or purple and are divided into 3 oval leaflets with smooth edges.

A step by step guide to beans pests and diseases, control methods

Beans can be vined or bushy and come in several sizes and colors. They are mainly a warm-season vegetable that is best grown in spring but can also be started for late summer harvest in some temperate zones. Growing beans in containers are useful for early starting where soil temperatures remain too cool for in-ground potting. In this article we also discussed about below topics;

  • Pests attack beans
  • Diseases of beans
  • Yellow Leaves On Bean Plants
  • Protect beans from insects
  • Growing conditions for beans

You can apply this pests and diseases information for growing beans in pots, growing beans from seed, growing beans in home, growing beans from seed indoors, growing beans on terrace, growing beans in the backyard, growing beans in the balcony, growing beans outdoors, and growing beans in containers.

Conditions for growing beans

Common beans are warm-season crops and planted after all danger of frost has passed and the soil has warmed. Beans will grow best at soil temperature ranges between 15.5 and 29°C (60–85°F) and are sensitive to cold temperatures and frosts. Beans will grow best in fertile, well-draining soil with a pH level between 6.0 and 6.5. Beans will perform well in full sunlight.

Plant bean seeds about 1 to 1½ inch deep, a bit deeper in loose, sandy soil. Plant bush beans about 3 to 4 inches apart; set rows 18 to 24 inches apart. Plant pole beans about 4 to 6 inches apart; set rows 30 to 36 inches apart. Pole beans can be planted on small hills or mounds 5 or 6 seeds to a hill; space hills 40 inches apart.

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Beans Growing Conditions.
Beans Growing Conditions.

Set a trellis, teepee poles or stakes, or other supports in place at beans planting time. Bean seeds will germinate in 8 to 10 days at 70° temperature. Thin to the strongest seedlings about 4 to 6 inches apart. Remove weaker seedlings by cutting them off at soil level by using scissors being careful not to disturb the roots of the remaining seedlings.

Common pests and their effects in beans plants

Beans can be mainly attacked by aphids, Mexican bean beetles, flea beetles, cucumber beetles, leafhoppers, mites, and slugs.

Aphids, leafhoppers, and mites can be sprayed away with a blast of water from the hose or also controlled with insecticidal soap. Look for eggs and infestations and crush them between fingers and thumb. Pinch out and then remove large infestations.

Mexican bean beetles, cucumber beetles, and flea beetles can skeletonize plant leaves. Hand-pick adults, larvae, and also egg masses. Spray large populations by insecticidal soap, canola oil, or kaolin. Control slugs with diatomaceous earth spread around the base of beans plants.

Aphids of beans pests and diseases

Aphids are very small, green, red, or gray insects that are most prevalent during the early summer but can appear anytime. They don’t eat holes in the plant leaves, but pierce leaves and stems, sucking the juices from the plants. Plants may droop or leaves could turn yellow during aphid infestations. You may notice honeydew, a sticky substance secreted by aphids, on the leaves and soil. An increase in ant populations indicates aphid infestations because the ants feed on honeydew. Look on the undersides of the plant leaves for the aphids themselves.

Aphids tend to appear cyclically so they will probably move on by themselves in a few weeks. Ladybugs, predatory wasps, and lacewings prey on aphids and could keep populations under control without any help from you. If, the aphids are damaging your bean plants, spray them with a steady stream of water from the hose or apply insecticidal soap to the leaves, coating both the tops and bottoms well to cover the aphids.

Thrips of beans pests and diseases

Thrips are small, barely noticeable insects that suck the juices from bean plants. If they appear while beans are flowering, the beans can fail to pollinate or the resulting pods may be deformed. Lay aluminum foil on the soil after planting to repel thrips.

Caterpillars on beans plants

Corn earworms and cabbage loopers aren’t as picky about diet as their names imply. Both insect pests eat beans. These pests are most troublesome in late-planted crops and can quickly decimate an entire row of beans plants.

Spray the beans with Bt, to control feeding caterpillars. Bacillus thuringiensis is a natural soil bacterium that paralyzes the gut of these insects, slowly starving them. The process takes 3 or 4 days, but the insects stop feeding almost immediately. Bt doesn’t damage beans and is safe for other animals and insects. 

Bean growing tips to avoid insect pests

Several insect pests attack beans plants. However, most of them can be simply removed by hand or with soapy water. If you’re having problems growing beans, you could want to check the garden for evidence of insect damage. Frequent inspection and prompt removal are very important steps to control or alleviate the development of heavy infestations, which usually require more drastic measures, such as the use of pesticides. And many insects overwinter in nearby shrubs, trees, and brush. Keeping the garden area free of debris could help control bean problems associated with insect pests.

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Healthy Insect free Beans.
Healthy Insect free Beans.

Common diseases and their effects in beans plants

Beans plants are susceptible to powdery mildew, anthracnose, blight, and mosaic virus. For disease prevention select plant disease-resistant varieties. And keep the garden clean and free of debris. Avoid handling beans plants when they are wet so as not to spread fungal spores. Remove diseased beans plants; put them in a paper bag and put them in the trash. Beans are susceptible to several soil-borne diseases; rotating beans so that they do not grow in the same location more than every 3 years will reduce soil-borne diseases. Spray-mist beans with compost tea or a mix of one part skim milk to 9 parts water; both are anti-fungal solutions.

Anthracnose of beans pests and diseases

Anthracnose can reduce bean quality, as well as crop yield. Losses can be severe during cool and rainy weather. It is a seed-borne disease. To control this disease, use seed grown in regions where it does not occur. Practice a crop rotation of 3 or 4 years when possible.

Cause, Symptoms, and Signs – Anthracnose disease is caused by the fungus Colletotrichum lindemuthianum. This appears on all aboveground parts of the plant but rarely on roots. Lesions are dark brown and may contain pink spore masses during moist weather. Elongate, angular spots could appear on lower leaf veins. As the fungus spreads into surrounding tissue, lesions appear on the upper side of veins. And affected seeds become discolored. Plants grown from infected seed can develop lesions on the cotyledons. Small brown spots appear to enlarge into dark sunken lesions. Often lesion margins will be dark brown as lesion centers remain light in color.

Disease management – Plant disease-free seed since the fungus can be carried on the seed. Also do not save seeds from diseased plants. Follow good weed control. Deeply incorporate (plow under) or remove plant residue promptly after harvest to decrease overwintering of the fungus at the site. Do not work in plantings as the foliage is wet. Fungicide sprays can be helpful.

Bacterial blight of beans pests and diseases

Bean blights, caused by different species of bacteria, occur in most of the bean growing areas of the world. Bacterial blight is seed-borne, and the control measures are the same as for anthracnose.

Cause and Symptoms of Bacterial Brown Spot – This disease mainly caused by Pseudomonas syringae pv. syringae, is common on lima beans than other bean types. Small, water-soaked spots on plant leaves become red-brown. Spot centers dry out, turn grey, and can fall away. Veins on the underside of the leaves could turn red-brown. Spots on stems and pods are more elongated than those on plant leaves.

Disease Management – Use commercially grown, certified disease-free bean seed. Planting a locally saved seed is risky because the seed could harbor bacterial pathogens. Commercial growers must purchase seed that has been treated with streptomycin. Rotate beans to non-legume crops leaving 2 to 3 years between crops. Do not work in bean plantings when beans plants are wet. Spray plants at the first sign of disease with a fixed copper bactericide.

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Early risk pests and diseases in beans

Pea and bean weevil (Sitona lineatus)

The pest can cause damage to spring beans plants if large numbers appear when plants are small. And spray treatment is justified when pest pressure is high and winter beans show retarded growth.

Stem nematode (Ditylenchus spp)

The nematode has become the main pest in field beans and causes severe problems in wet seasons. The pest is seed-borne and can also infest soils, thus becoming a problem for future crops of beans. The seed must be tested for nematode, and only clean stocks should be sown.

Pre/early flower pests and diseases in beans

Black bean aphid and pea aphid  

Black bean aphid can be damaging to field beans if colonies develop just before flowering.  Spring-sown crops are more likely to suffer damaging attacks than winter beans. Aphids could be controlled using pirimicarb as soon as 5% of the plants have been colonized. Care should be taken if using other insecticides, particularly when flowers are present on the crop, as there is a serious risk to bees.

Chocolate spot (Botrytis fabae)

The symptoms are reddish-brown spots; eventually enlarge to give a more damaging aggressive phase in cool, wet weather. Winter beans are likely to suffer yield losses, especially where the plant population is high and the crop becomes tall. Early fungicide treatment is necessary if the crop shows symptoms at the first bud or early flower. A second spray can be required 3 to 4 weeks later if damp conditions persist. Additional sprays are unlikely to be economic unless prolonged rain is experienced, and losses due to damage mainly caused by the sprayer may be significant.

Late flower/early pod beans pests and diseases

Bean seed beetle (Bruchus rufimanus)

Bean seed beetle is also known as bruchid beetle, can affect both winter and spring varieties.  Adults emerge from the bean seed leaving a circular hole. The beetles do not breed in grain stores, but damaged produce could not be accepted for quality markets. Adults fly to beans plants during flowering and lay eggs on developing pods. The larvae bore through the pod and into the seed, where feed until mature.

Bacterial diseases of beans

  • Brown spots, common blight, and halo blight are very important bacterial diseases of beans.
  • These diseases attack leaves and pods and favored by periods of wet weather.
  • The use of certified, disease-free seed and resistant varieties is an effective means of control.
Bacterial brown spot on beans 

Brown spot disease symptoms initially appear as small about 1/8 to 3/8 inch, circular, necrotic, or brown spots on the leaves, surrounded by a narrow yellow halo. The spots sometimes fall out, giving the plant leaf a “shot-hole” appearance. Water-soaking and bacterial ooze are not generally seen with this disease. Small (1/16 to 1/8 inch diameter), dark brown spots can increase on pods, and early pod infections can result in the development of malformed pods.

Management strategies for bacterial brown spot contain crop rotation, the application of copper-based bactericides, and the use of resistant varieties. Sanitation practices for field equipment and avoiding working in fields when beans plants are wet will help limit the spread of the disease. The use of resistant varieties is the best process to control bacterial brown spot

The common blight of beans

The initial symptoms of common blight are water-soaked spots on the plant leaves. As they develop, then these spots become necrotic, light brown, irregular-shaped lesions with distinct, bright yellow margins. Leaf symptoms initially appear water-soaked spots that become necrotic, light brown lesions of an irregular shape with distinct, bright yellow color margins. These lesions enlarge to 10mm or greater and could kill the leaflet.

The use of certified, disease-free seed is very important for the control of common blight. Sanitation practices for field equipment, avoiding working in fields when beans plants are wet, and the application of copper-based bactericides can help slow the spread of common blight.

Halo blight

Halo blight initially develops as small, angular, water-soaked spots on the undersides of plant leaves. The spots become necrotic and reddish-brown, surrounded by greenish-yellow halos that greatly in size. Symptoms of halo blight initially appear as small water-soaked spots on the underside of the leaflets, eventually developing into numerous small, reddish-brown lesions on the plant leaves. Greenish-yellow halos, highly variable in size, subsequently increase around these spots. During severe infections, the disease becomes systemic and cause yellowing and death of new foliage. At temperatures above 80°F halos are small or absent. The use of resistant varieties, along with the use of the disease-free seed, is the most effective means for managing this disease.

Virus and yellow leaves on beans

Yellow leaves on plants might be from blight. Halo blight is a disease that causes round yellow spots, which slowly blend to turn the leaf yellow. The bacteria that cause this disease live in soil and introduced in infected seed. Select a seed that is resistant to the blight and rotates your bean crop.

Garden beans with yellow color leaves can also be the result of a viral infection. If bush beans or pole beans have yellow leaves, the problem might be a virus. Unfortunately, there is no cure. Virus problems could be developed from low nutrient levels or even herbicide injury but are most likely from infected bean seeds. Do not save seeds from year to year, as they could harbor the virus. Some viruses are transmitted from sucking insects, such as aphids. Practice good pest control and use a mosaic resistant bean seed to decrease the chance of yellow leaves on beans.

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