5 Common Pests and Diseases of Beans and Peas

Posted on 24. Jul, 2009 by Tracey in Pests

In the past week or so I have had a couple of people ask me questions about pests and diseases that they have found on their beans, so I thought this might be a helpful post about the problems that can be associated with beans and peas.

Pea Aphids

1. Pea Aphid

The Pea Aphid is a small pale green bug with black or white stripes on its body and cannot fly as it is wingless. It is a fairly tiny creature with long legs and can form large communities on the stems of bean or pea plants during hot and wet summers. The pea aphid is also found on sweet peas, clover, vetch and alfalfa.

Plant Damage: The pea aphid sucks the sap from the stem and leaves of the bean or pea plant which results in wilting, deformed stems, leaves or damaged flowers and stunted plant growth. Pea aphids also secrete a sticky dew that coats the plants.

Time Period: The pea aphid’s life cycle overlaps during every generation so they could strike anytime during the year. They are particularly active and reproduce quickly in temperatures over 18 degrees Centigrade (65 degree Fahrenheit) and they love hot, damp weather.

Treatment: Aphid predators include lacewings, hoverflies, ladybirds, ground beetles and parasitic wasps. These can be attracted to your vegetable garden by growing flowers nearby and providing shelter boxes. Lacewings, ladybirds and parasitic wasps can be bought as a biological control online.

For more tips please view my post: Beneficial insects in your vegetable garden.

Photo By: Whitney Cranshaw, Colorado State University, Bugwood.org. Courtesy of Creative Commons License.

Pea & Bean Weevil

2. Pea and Bean Weevil

Weevils are small brown beetles about 5mm long. It is found on beans, peas, clover, laburnum, sweet peas and weevil larvae is found in the soil.

Plant Damage: The pea and bean weevil feeds on leaves leaving ‘U’ shaped indentations on the leaf edge. Its larvae feeds on the roots of plants.

Time Period: July is the month weevils emerge from the soil to attack the pea and bean leaves. They can attack anytime from summer to winter.

Treatment: Organic methods include putting a sticky card or bucket of water under the plant and shaking to remove the weevils from the plant. Then destroy the bugs underfoot or pick them off by hand. Established and strong plants will usually survive attack.

Photo By: Whitney Cranshaw, Colorado State University, Bugwood.org. Courtesy of Creative Commons License.

Downy Mildew on Leaves

3. Downy and Powdery Mildew

Downy and powdery mildew are fungal diseases which attack plants in wet and dry weather.

a) Downy Mildew

Plant Damage: Downy Mildew occurs in cool wet weather. The leaves of peas have yellow patches with brown mould on the undersides. If pods form they may be distorted and yellow spotted. Unaffected pea pods can be picked and infected plants should be destroyed instead of adding them the compost bin.

Treatment for Downy Mildew:

When watering try not to leave water droplets on the leaves, shake them or apply water directly to the base of the plant.
Plants will need good air circulation around them to avoid the fungus spreading to other plants.
Remove any debris or dead leaves from the base of the stem on the soil to remove spores and stop the fungus from breeding on weeds.
Grow Downy Mildew resistant pea varieties like Kelevdon Wonder, Oasis, Twinkle, Avola and Hurst Greenshaft.

Photo By: Robert Wick, University of Massachusetts, Bugwood.org. Courtesy of Creative Commons License.

Peas with Powdery Mildew

b) Powdery Mildew

Plant Damage: Powdery mildew occurs in dry weather and the leaves of the plant turn white or grey with the fungal disease. The pea pods can also be covered in the disease. The pea pods are ok to pick and eat.

Treatment of Powdery Mildew:

Cut out infected areas to reduce the spread to other parts of the plant
Water the roots regularly to prevent the plant drying out thus running the risk of the plant becoming infected
A layer of mulch can be applied around the plants to keep moisture in the soil to prevent the disease from occuring
Grow Powdery Mildew resistant varieties like Ambassador, Cavalier and Peawee.

Bean Plant on Right has Fusarium Wilt

4. Fusarium Wilt

Fusarium wilt is a seed and soil-borne fungus which occurs in high soil temperatures, high nitrogen levels in the soil, infrequent watering and when there are fusarium fungus spores in the soil through transplant of an infected plant.

Plant Damage: Fusarium wilt is a soil fungus which infects the plants roots and spreads upwards through the stem eventually affecting the leaves. Young plants will become stunted and mature plants tend to wilt and once the fungus has infected the whole plant all leaves will turn yellow. Other symptoms include curling of leaves and little or no crop. To confirm the diagnosis of Fusarium wilt, cut open the stem and check for brown streaks in the tissue.

Treatment:

Use healthy and in date seed that are free from blemish and from a certified source or seed company
Sow directly into the ground in warm temperatures to ensure a fast germination rate to prevent root rot and seed decay in the soil,
Crop Rotation on a 5 year scale will reduce soil borne diseases.
Regular watering reduces plant stress thus reducing the risk of root rot.
Grow Fusarium Wilt resistant varieties of peas like Rondo, Ambassador, Hurst Greenshaft and Onward.

Photo By: Howard F. Schwartz, Colorado State University, Bugwood.org. Courtesy of Creative Commons License.

Vegetable Plot - Beans & Peas

5. No Flowers or No Pods

Sometimes the most frustrating thing is if your bean or pea plant has had no flowers or no pods forming. These occurrences can be due to several reasons explained below.

No Flowers can be caused by:

High level of Nitrogen in the soil – i.e. too much manure or nitrogen based fertilizer has been added to the soil so you will get lots of green growth but no flowers. Try using a balanced fertilizer containing the specific ingredients of potash and phosphates for growing beans and peas
Pea Thrips – these are very very tiny black or yellow insects which infect the flower buds, leaves and pods with silvery patches and cause flower buds to wither leaving the plant unable to produce flowers or pods
Capsid Bugs – these bugs create brown edged holes in the leaves and shoots maybe affected however bean and pea plants do tolerate this pests damage and if the plant is strong will continue to grow, flower and produce pods. Remove the debris away from underneath the bean or pea plant to prevent them seeking shelter
Not waiting long enough – sometimes it takes longer than you think for the flowers to form.

No Pods can be caused by:

Birds – Birds can peck off the flowers once they have formed which means they haven’t had chance to be pollinated by insects, they seem to like the red flowers best, CD’s can be hung up to scare them away
Irregular Watering – Beans and peas require lots of watering during flowering so the plant has enough energy to produce the beans. Water frequently during this period.
High Temperatures – Sometimes the heat can affect the setting of runner bean pods. It may be worth growing a runner bean variety that sets in any weather like Red Rum.
Cool Weather – On the other end of the scale cool weather reduces the numbers of bees in the garden and therefore limits pollination
Not waiting long enough – sometimes it takes longer than you think for the bean pods to grow. If you are concerned about your flowers not being pollinated either put some flowers in pots next to your vegetable plot or you can attract bees by mixing up a spray of sugar and water then spray the flowers and await your insects.

Other Pests and Diseases Posts you may also be interested in:

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