Training Manual Development Of Cultivars And Seed ... - icrisat

quantity and quality of grain. Severely infected grain appear discolored to the naked eye. Grain molds
are often accompanied by sprouting of the seed while still on the plant with severe consequences for
viability and seed quality.
Sorghum downy mildew. Characterized by chlorotic, stunted plants with white downy growth on the
abaxial surface of infected leaves. Sorghum downy mildew (Peronosclerospora sorghi) may cause the
death of the plant when infection occurs early. In later stages, leaves turn yellow and often show
shredding at the tip. Diseased plants are often barren or partially so.
Other diseases. Sorghum is subject to a large number of other fungal, bacterial, and viral diseases, most
of which are of local or sporadic significance. These include: seedling rots (Pythium, Fusarium,
Aspergillus, Rhizoctonia, Phoma spp), foliar diseases (gray leaf spot, zonate leaf spot, rough leaf spot,
oval leaf spot, sooty stripe, rust, and crazy-top), and panicle and seed diseases (head smut, loose kernel
smut, covered smut, long smut, head blight, and ergot). Several of these diseases are of significance for
seed multiplication as they can be seedborne.
Insects
Shoot fly. Found only in Asia and Africa. Shoot fly (Atherigona soccata) attacks the seedling before the
sixth leaf stage and causes drying of the central leaf and deadhead symptoms, particularly in late
sowings. Smaller plants may be killed but larger ones usually survive by producing tillers. Tillers often
flower later than the main stem, resulting in crop losses.
Stem borers. Four species of stem borers are of significance in sorghum in various parts of the world:
the spotted stem borer (Chilo partellus), maize stalk borer (Busseola fusca), African pink borer (Sesamia
calamistis), and African sugarcane borer (Eldana saccharina) are the main concerns. They attack the
crop at any stage, causing deadheart symptoms in young plants, shot holes in the leaves, and tunneling
of the stem and peduncle. Late attack can cause breaking of the peduncle and reduced grain filling.
Sorghum midge. Larvae of sorghum midge (Calocoris sorghicola) feed on developing grain and cause
empty/chaffy spikelets. Grain yield is directly affected as infested spikelets invariably set no seed.
Head bugs. Two main species, Calocoris angustatus in India and Eurystylus immaculatus in West Africa,
suck the developing grains. This causes direct losses and also predisposes punctured grain to mold
attack. Grain attacked early fail to develop, while older grain are reduced in size, thus affecting grain yield
and quality.
Other insects. A number of other insects attack sorghum at various stages of growth and can cause
losses. Most are sporadic in occurrence and of limited general importance. They include: seedling pests
(wireworms and white grubs), foliage feeders (spittle bugs, aphids, shootbug, armyworms, grasshoppers,
and spider mites), and storage pests. As with diseases, several of these insects are of significance for
seed production as they can cause reduced seed size or quality resulting in impaired viability.
Parasitic Weeds
Striga. Several species of Striga (S. hermonthica, S. asiatica, and S. forbesii) attack sorghum plants by
sticking to the root and drawing water and nutrients from the host plant, particularly under dry and lowfertility
conditions. Striga attack can severely stunt the sorghum plant and cause drying and failure to
produce seed heads.
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