Other insects which have a taste for haricot beans include the corn seed maggot,
green stink bug, spider mites, cutworms, armyworms, root-knot nematodes and
several storage insects.
Diseases: very common, especially fungal and bacterial diseases in lowland humid
tropics and subtropics, and viral diseases in drier climates:
- Anthracnose—attacks the leaves, stems and pods. Seed-borne, and it also
survives for at least two years in the soil. Control: resistant varieties, rotation and
clean seed. - Bean Rust—the leaves develop small white spots, which become rust coloured,
the leaves then turn yellow and dry up. Control: burn infected plants and crop
rotation; some varieties have some resistance to some of the races of Bean Rust. - Ashy Stem Blight—seed-borne. Black marks on very young seedlings. Control:
clean seed. - Angular (Grey) Leaf Spot—grey spots on the underside of leaves, which become
brown, and brown spots on upper leaf surfaces. Control: very difficult, though some
varieties have some resistance; also the use of clean seed and crop rotations, and the
destruction of infected plants. - Powdery Mildew—all plant parts except the roots are infected. Control: various
fungicides and resistant varieties. - Root Rots controlled with crop rotations.
- Sclerotinia Wilt (White Mould, Water Soft Rot)—usually after warm, humid
weather. Control is not easy, but widely spaced plants and crop rotations, with
cereals for example, or fungicides can limit the spread of this form of Wilt. - Southern Blight (Southern Wilt, Crown Rot)—mainly in hot climates, the lower
leaves become yellow and fall off. Very difficult to control. - Bacterial Diseases—such as Common Blight, Halo Blight and Bean Wilt. Halo
Blight is different from the other bacterial diseases in that it is more common in
cool, wet areas, while Common and Fuscous Bacterial Blights (Xanthomonas) are
more important in warm, wet areas.
Symptoms: irregular dark spots on leaves or pods, each spot surrounded by a
yellow band or “halo”. Control: clean seed and resistant varieties. - Virus Diseases—at least five viruses attack haricot beans: Bean Common Mosaic
(BCM, or Bean Virus 1) is the most common.
Also Bean Yellow Mosaic (BYMV, or Bean Virus 2), Curly Top, Golden
Mosaic and Mottle Dwarf Virus Diseases.
YIELD
The global average yield of dry grain is approximately 500–1200 kg/ha, and in fact
the haricot bean generally has a bad reputation for low yields even though its yield
potential is at least 3.5 MT/ha. The average yield in Ethiopia is about 800 kg/ha.
Yields of the green pods are more stable and reliable, and vary from about 3
MT/ha in India and Africa to about 7 MT/ha in Europe.
UTILISATION
- Dried beans of haricots provide the bulk of the protein intake of huge numbers
of people in many parts of South America, and some tropical parts of Asia and
Africa. The beans can also be processed into protein concentrates such as milk
substitutes. Although the nutritive value of haricot beans can be very high, it