Pests & Diseases - Beans

Buchid Trap Placement - 24.04.14


1. Chocolate spot in beans PGROChocolate spot (Botrytis fabae, B. cinerea)

  • Symptoms appear as brown spots, which enlarge to give a more damaging aggressive phase in cool, wet or damp weather.
  • Autumn sown beans are more likely to suffer yield losses, especially where the plant population is high and the crop becomes tall.
  • See Technical Update TU13.

Leaf and pod spot (Ascochyta fabae)

  • 2. Ascochyta leaf and pod spot in beans PGROThis produces brown spots containing distinctive black fruiting bodies (pycnidia).
  • Autumn sown beans are more prone to serious attacks especially in wet conditions.
  • The disease is seed-borne, air-borne and splash dispersed.
  • It is advised that farm-saved seed should be tested by PGRO.
  • Infection can be transmitted from bean volunteers in neighbouring fields.
  • See Technical Update TU13.

3. Bean downy mildew PGRODowny mildew (Peronospora viciae)

  • Mildew causes greyish-brown, felty growth on the under-surface of the leaves.
  • It is prevalent on spring beans.
  • Some varieties have resistance to the disease and ratings are given in the Recommended List of Varieties.
  • See Technical Update TU13.

4. Bean rust PGRORust (Uromyces fabae)

  • Rust is characterised by numerous small reddish-brown pustules on the leaves.
  • It is more serious on spring beans and all varieties are susceptible.
  • Most damage occurs if infection begins during flowering and pod set.
  • See Technical Update TU13.

5. Sclerotinia in beans PGROSclerotinia (Sclerotinia trifoliorum, S. sclerotiorum)

  • This disease occasionally infects winter beans in damp autumn weather.
  • Plants develop a watery stem rot, which can spread between plants in dense stands.
  • The related fungus, Sclerotinia sclerotiorum infects spring beans, peas, rape, linseed, lupins and a range of field vegetables.
  • See Technical update TU17 and the PGRO Pulse Agronomy Guide.

6. Foot rot in beans PGROFoot and root rots (Fusarium culmorum, F. solani, Phoma medicaginis var. pinodella)

  • The disease causes browning of the stem base and wilting of the leaves.
  • It can occur on seedlings and on more mature plants.
  • Foot and root rots in beans appear to be more sporadic than those which occur in peas, and the bean crop in general appears less sensitive to root rots than peas.
  • See Technical Update TU34 and the PGRO Pulse Agronomy Guide.


7. Bean weevil damage PGROPea and bean weevil (Sitona lineatus)

  • The adult is 4-5 mm long with a narrow body, short snout and angled antennae.
  • The larva is white and legless with a brown head.
  • Leaves of attacked plants show characteristic ‘U’ shaped notches around the edges.
  • The main damage occurs as a result of the larvae feeding on the root nodules.
  • The pest causes damage to spring sown beans if large numbers appear when plants are small.
  • Autumn sown beans, although still prone to attack, are usually too advanced in growth for the weevil or the larvae to have any appreciable affect on yield.
  • See Technical Update TU08.

8. Black bean aphid colony PGROBlack bean aphid (Aphis fabae) and Pea aphid (Acyrthosiphon pisum)

  • Black bean aphid adults are 1-2 mm long, black with distinctive white or grey markings on the upper body.
  • Pea aphid adults are 1-2 mm long, bright green, pear shaped with slightly dark legs and have distinctive red eyes.
  • Black bean aphid can be very damaging to field and broad beans if colonies develop just prior to flowering.
  • Spring-sown crops are usually more likely to suffer damaging attacks than autumn sown beans.
  • As well as forming dense, smothering colonies on the upper part of the stem these and the less obvious pea aphid are able to transmit viruses which affect yield.
  • See Technical Updates TU05 and TU06.

9. Bean stem nematode PGROStem nematode (Ditylenchus gigas, D. dipsaci)

  • Stem nematode is a slender, transparent, microscopic pest, invisible to the naked eye.
  • The pest is seed-borne and can also infest soils, causing a problem for future bean crops.
  • Plants appear distorted, stunted and twisted, and stems may show symptoms of reddish blistering.
  • The nematode has become a major pest in field beans and can cause severe problems in wet seasons.
  • Farm-saved seed from an infested stock that has been multiplied for several generations is a particular risk.
  • Seed should be tested for nematode, and only clean stocks should be sown.
  • See Technical Update TU09.

10. Bean bruchid beetle PGROBean seed beetle (Bruchus rufimanus)

  • The beetle is 4-5mm long, light to dark brown with greyish flecks on the wing cases.
  • It is found in field and broad bean crops once temperatures reach about 20°C and can be readily found in flowering crops on warm days.
  • The main damage is caused as the pest emerges from the seed at harvest leaving a 2-3mm circular hole in the seed.
  • The beetles do not breed in grain stores.
  • Damaged produce may not be accepted for quality markets.
  • See Technical Update TU10.
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