Growing Food: A Guide to Food Production

Septoria Glume Blotch—very similar to Leaf Blotch.

observe this. Control by crop rotation, seed dressing and cultural strategies eg

preparation of a firm seedbed helps a little.

legume.

shrivelled grain.

YIELD

According to FAO, the global average yield of wheat in 1988/90 was between 0.8

and 5.1 MT/ha, for the bottom 10% and top 10% of countries respectively.

The average projected yields for the top and bottom 10% of countries is

estimated by FAO to be 1.2–6.4 MT/ha by the year 2010.

The FAO estimate for the global average yield in 2004 was 2.9 MT/ha, from a

low in Eritrea of 302 kg/ha to a high in Belgium of 8.98 MT/ha.

Hybrid varieties grown in good conditions can yield around 10 MT/ha.

148 TONY WINCH

Septoria Leaf Blotch —very similar to Leaf Blight. Brown, speckled areas appear

on the leaves, which then die. Control: crop rotation, destroy volunteer plants and

seed dressings.

Take-all—especially in wheat monoculture. Plants are yellow and wilted, with pale

and often empty ears. Roots are short and thick, and poorly developed. Stems are

black and shiny just above the soil level - the leaf sheaths must be removed to

Loose Smut—Ustilago nuda. A mass of black spores appears in place of the seed-

head. Control: use clean seed, either from clean fields or by anaerobic seed treatment.

Covered Smut is often more serious in wheat, and Loose Smut is often more serious

in barley.

Bunt—Tilletia spp. Worse in drier regions and seasons. Infected plants have smut

balls instead of grain. A sample of infected grain smells of fish. Control is by seed

dressing.

Pythium Root Rot—especially in moist soils and in wheat monocultures, and

with heavy applications of Nitrogen. Control is by crop rotation, preferably with a

Virus Diseases—there are several, such as Wheat Streak Mosaic seen in hard red
wheats; yellow-green stripes appear on the leaves, which die, stunted plants, and