Spot blotch (wheat)

[1][2] Cochliobolus sativus also infects other plant parts and in conjunction with other pathogens causes common root rot and black point.

[3] The tan spot forms of foliar blight appears in United States causing significant yield loss.

[3] The spot blotch form of foliar blight is severe particularly in warmer growing areas characterized by an average temperature in the coolest month above 17 °C.

In the past 20 years, HLB has been recognized as the major disease constraint to wheat cultivation in the warmer eastern plains of South Asia.

If spikelets are affected, it can result in shrivelled grain and black point, a dark staining of the embryo end of the seed.

[2] typical spot blotch sysmtom In recent years, Helminthosporium leaf blights (HLB), caused by both Cochliobolus sativus and Pyrenophora tritici-repentis, have emerged as serious concerns for wheat cultivation in the developing world.

Seed treatments with phytoalexin inducer appeared to provide good protection to wheat seedlings against B. sorokiniana infection.

Fungicide seed treatments include: captan, mancozeb, maneb, thiram, pentachloronitrobenzene (PCNB) or carboxin guazatine plus, iprodione and triadimefon (Stack and McMullen, 1988; Mehta, 1993).

[10] Clearing or ploughing in the stubble, grass weeds and volunteer cereals reduce inoculum as does crop rotation (Diehl et al., 1982).

More quantitative information is required on the role of alternate rotations, soil and plant nutrition, inoculum sources and climate.

Cook and Veseth (1991) note that the kind of rotation crop may not be so important to root health as the length of time out of wheat.

Tan spot has been controlled largely by cultural practices, such as rotation with non-host crops and removal or burial of stubble (Rees and Platz, 1992).

Since this probably increases inoculum of tan spot, it highlights the need for integration of disciplines to determine how best to achieve attainable yields.

Recently, a few Chinese wheat genotypes from the Yangtze River valley were identified with acceptable levels of resistance to spot blotch.

One of the interesting phenomena associated with foliar blight in some of susceptible cultivars is tolerance (low yield loss even at very high level of disease severity).

The chlorophyll or general health indicators, SPAD and AUSDC values were higher in spot blotch resistant and tolerant genotypes.

[7] The index includes days to heading (maturity related trait), thousand kernel weight, and area under foliar blight disease progress curve.