BEANS

ALTERNARIA BROWN

Symptoms:  A fungi which can occur at any time during the season which attacks young fruit, leaves and twigs, producing brown-to-black lesions surrounded by a yellow halo.  The lesions are generally circular but will often have a tail, following the leaf vein which gives the lesions an eye-spot appearance. The necrosis extends along the veins as the toxin spreads in vascular tissues. On young leaves, lesions can appear as early as 36-48 hours after infection. Lesions enlarge as leaves mature and can vary in size from 1-10mm (0.04-0.4in) and will be larger if the infection occurred earlier in the season. Cultivar susceptibility is also a factor that determines ultimate lesion size. A less susceptible cultivar will have smaller lesions. If brown spot is severe, the leaves may drop and entire shoots can wilt and die.  Is prevalent on plants that have been injured by spider mites or are showing signs of stress due to a lack of nutrients.

Control:  Prevention includes controlling problem insects and maintaining sufficient soil nutrient levels.

Treatment: Fungicides are the primary means of controlling Alternaria brown spot. 

ANTHRACNOSE

Symptoms:  Yellowish-brown or purple-colored, irregular, sunken spots with dark reddish-brown borders on cotyledon and stems which spread to the leaves.  Symptoms generally occur on the underside of the leaves as linear, dark brick-red to black lesions on the leaf veins.  These spots later turn to dark brown. Severely infected cotyledons senesce prematurely, and growth of the plants is stunted. Diseased areas may girdle the stem and kill the seedling.  As the disease progresses, the discoloration appears on the upper leaf surface.  The most striking symptoms develop on the pods. Small, reddish brown to black blemishes and distinct circular, reddish brown lesions are typical symptoms.  Mature lesions are surrounded by a circular, reddish brown to black border with a grayish black interior. During moist periods, the interior of the lesion may exude pink masses of spores. Severely infected pods may shrivel, and the seeds they carry are usually infected. Infected seeds have brown to black blemishes and sunken lesions

Control:  Spores are spread by water. Prevent infection by planting resistant varieties, as well as disease free varieties, rotating crops, avoiding overhead watering and handling plants while wet.  Fields should not be entered for cultivation or pesticide applications when the plants are wet. Avoiding unnecessary movement in infested fields will minimize the spread of the disease.

BEAN RUST:

Symptoms: A bacterial disease that causes withering leaves and can lead to a loss of bean crops. The Uromyce phaseoli, or Uromyces appendiculatus, fungus causes this ailment, and it's spread when spores from infected crops are carried along the wind and land on healthy plants.  

Controls:  Plant clean, uninfected seeds to ensure that only healthy bean crops grow. If you're growing seeds from your own crops, make sure that these mature plants don't contain bean rust by searching for reddish, brown spots on the underside of the plant's leaves. Further, consider choosing rust-resistant species of bean, which include some varieties of pinto, black, great northern, red kidney and small white. Arrange bean crops in wide rows that are parallel to the wind to minimize the chance of infected spores landing on healthy plants.  Water the ground around the bean plants in the morning, so that the leaves have a chance to dry. Any moist conditions can create an environment that is ideal to bean rust. Additionally, allow your bean crops to completely dry before you tend to them.  Clean up all plant material at the end of the growing season, and dispose of it so that it doesn't come in contact with young plants. Further, don't include any diseased plants in your compost piles, because the spores can remain in the resulting soil.  Implement a 3 year crop rotation schedule.

Treatment:  Remove any affected bean plant sections as soon as you notice problem areas to prevent other plants from being infected.   Several fungicides are available for the effective management of bean rust; however, use of fungicides invariably increase production costs.