Sorghum Borer—very similar to Stem/Stalk Borer, but chemical control is very
uncertain. Burn all infected plant material.
African Armyworm—the adult moths of Spodoptera exempta can fly for hundreds of
kilometres and their larvae can cause devastating damage, normally at the end of the
maize growth period. All of the leaves can be eaten, leaving only the midribs.
Lesser Armyworm—much less damaging, and easily controlled with Malathion.
Earworm(Bollworm)—eggs of Heliothis armigera are laid on the silks, and larvae
feed on them and the developing grain.
Maize Leafhopper—transmits Mosaic Streak Virus (MSV) and other virus diseases.
Some hybrid varieties have some resistance.
possible by preparing the seedbed six weeks or more before planting, and then
keeping weeds well under control, or by using baits of wheat bran or maize meal.
Diseases: the global yield loss from maize diseases has been estimated at almost
10%, mainly caused by:
(White) Leaf Blight—Helminthosporium. Oval, grey papery lesions on the leaves,
which may die. Control by using resistant varieties.
Maize Streak Virus—spread by a leafhopper, more serious on late planted crops.
Downy Mildews—Sclerospora spp. - pale yellow streaks on the upper leaves, which
become brown and necrotic. Plants are stunted and may produce nothing. Control is
difficult; early planting may help, some varieties have some resistance, and systemic
seed dressings are also available.
Crazy Top—Sclerophthora macrospora, a form of Downy Mildew in which the
tassel and/or ear develops a proliferation of bizarre, unproductive growth.
Common Maize Rust—symptoms appear at tasselling time, or on the seedling;
leaves become covered with tiny brown spots, and then dry up. Not a serious
problem.
Maize Smut—Galls form all over the plant, which then produce black spores. The
best control is by cultivating resistant varieties.
Head Smut—ears and tassels are converted to shoot-like growths, and the plants are
stunted. Controlled with seed dressings.
Eyespot—decimates the leaves; can be a problem in Europe and elsewhere.
YIELD
According to FAO the global average for 1988/90 was 0.6–4.9 MT/ha, for the
bottom 10% and top 10% of producer countries respectively. In 2004 the global
average was 4.9 MT/ha, Israel recording the highest (16.0 MT/ha) and Botswana the
lowest (119 kg/ha).
The yield potential, using hybrids in optimum conditions, is well over 20 MT/ha.
some control. Some varieties are said to have some resistance. Burn all infected
plant material.
larvae have already entered the stems, but some of the systemic insecticides give
Cutworms—a serious soil pest, especially in fields which were weedy before land
preparation. Seedlings are attacked, often bitten completely through. Some control is
point. Later on they enter and eat the developing cobs. Control is very difficult if the