Journal of the Department of Agriculture, Journal of the Department of Agriculture, Western Australia, Series 4 Western Australia, Series 4
Volume 7
Number 4 1966 Article 6
1-1-1966
Septoria leaf spot and glume blotch of wheat Septoria leaf spot and glume blotch of wheat
W A. Shipton
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Recommended Citation Recommended Citation
Shipton, W A. (1966) "Septoria leaf spot and glume blotch of wheat," Journal of the Department of Agriculture, Western Australia, Series 4: Vol. 7: No. 4, Article 6.
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PLANT DISEASES
SEPTORIA LEAF SPOT AND GLUME BLOTCH OF WHEAT
By W. A . SHIPTON, Ph.D., Plant Pathologist
SEPTORIA leaf spot and g l u m e b l o t c h of wheat occur throughout Australia and are cap- able of reducing crop yields. W h i l e no estimates of y i e l d losses are yet available in Western A u s t r a l i a b o t h diseases can cause serious damage t o crops.
Septoria leaf spot is caused by the fun- gus Septoria tritici Rob. ex Desm. and glume blotch by the related Septoria nodorum Berk.
Glume blotch and Septoria leaf spot were first recorded in Western Australia in 1905 and 1924 respectively (Sutton, 1920;
Carne and Campbell, 1924), and now occur in all the wheat growing districts of the State. In many overseas countries the diseases have been reported to cause con- siderable losses, yet few precise estimates have been made of these. In Indiana and New Zealand losses in yield of 24.3 and 9.7 per cent, were recorded from natural infections of Septoria leaf spot (Caldwell and Narvaes, 1960; Sanderson, 1964). No precise estimates of losses due to glume blotch are available, but total crop failure has been reported.
Septoria Leaf Spot
The organism causing leaf spot is also capable of infecting the leaf sheaths.
Symptoms
The first sign of infection is the appear- ance of light green to yellowish green spots between the veins of the leaf or leaf sheath. The pathogen spreads rapidly through the host tissue causing the devel- opment of light brown to light yellow irre- gular areas on the leaf and leaf sheath respectively (Fig. 1A). Eventually the dis- coloured areas assume a speckled appear- ance due to the formation of fruiting bodies or pycnidia (Fig. IB).
Environmental Conditions Favouring the Disease
Infection may take place over a wide range of temperatures. The disease is usually conspicuous in cool to mild, wet conditions, but may occur in warmer weather provided that there is sufficient moisture for infection.
Carry-over From Crop to Crop
The organism persists during the dry months of the year in infected plant debris (Hilu, 1956). In the autumn, spores are released from the moist straw and are dis- persed by wind and rain splash. These spores infect susceptible hosts. In Western Australia the organism has only been iso- lated from wheat; overseas it has been found on other hosts (Sprague, 1950).
Susceptibility of Wheat Varieties
Wide variations have been noted in the susceptibility of wheat varieties to Sep- toria leaf spot. Critical observations have been carried out for a number of years at various localities, and the wheat variety Kondut has consistently shown a degree of resistance. The wheat variety Festi- guay also appears to have some useful re- sistance.
Glume Blotch
The glume blotch organism is not re- stricted to infection of the floral bracts.
Infection of all the aerial parts of the plant may occur.
160
SEPTORIA LEAF SPOT
* k
FIG. 1.—A. W h e a t leaves a n d sheaths i n f e c t e d by Septcria t r i t i c i . B. Fruiting bodies or pycnidia o f S. t r i t i c i on wheat leaves.
GLUME BLOTCH
FIG. 2.—Septoria n o d o r u m on t h e leaves, sheaths, nodes, peduncles, and t h e glumes of wheat.
161
Symptoms
The lesions caused by the organism are often conspicuous on the floral bracts, but may also be conspicuous on other parts of the plant (Fig. 2).
The lesions are at first small, linear to oblong, and light green to yellowish green.
As the fungus spreads through the host tissues the lesions change to dark brown or purplish brown and on the nodes they may carry a bloom. They may spread and coelesce so that much of the host tissue becomes discoloured. Late in the season the floral bracts often assume a speckled appearance due to the formation of pycnidia.
The fungus is capable of causing light to dark brown spots on the grain, par- ticularly at the embryo end. However, not all grain discoloration is caused by S.
nodorum, and the symptoms caused by other fungi are, in general, indistinguish- able from those caused by the glume blotch organism.
Environmental Conditions Favouring the Disease
Infection and development of the organ- ism is favoured by ample moisture and mild conditions. The severity of the attack varies with the date of onset of infection, early infection leading to heavy losses
(Pirson, 1960). In Western Australia, late maturing crops are less liable to glume and grain infection because of the drier conditions at heading.
FIG. 3.—
A comparison of normal grain with small and shrivelled grain resulting from infection of Eureka wheat with both S.
nodorum and 5. tritici.
Carry-over from Crop to Crop
As with Septoria leaf spot, the glume blotch organism persists from crop to crop in the infected plant debris. Spores are released from the infected straw when it has been moist for a sufficient time, and are dispersed by wind and rain splash
(Scharen, 1964). In Western Australia the disease has been found on wheat and the commonly occurring "ripgut" brome grass (Bromus gussonii Pari.). Overseas it has been found on a large number of grass hostsv (Sprague, 1950).
Susceptibility of Wheat Varieties
In other countries it has been shown that there is a wide range in the sus- ceptibility of wheat varieties to the disease.
Observations made to date in Western Australia have failed to show differences in the susceptibility of commercial wheat varieties to the disease. The position is complicated by the possibility that differ- ent strains of the organism may exist here as has been demonstrated eleswhere (Thomas, 1962).
Losses
No exact estimates of yield losses are as yet available for Western Australia. How- ever, it is known that in cases of severe infection by both diseases the crop may not be worth harvesting for grain.
The yield losses associated with infec- tion by S. nodorum are generally caused by shrivelling and weight loss of grain
(Bockmann, 1962). Seed-borne infection may damage the emerging shoot, chiefly the coleoptile, which may result in de- creased plant vigour (Kietreiber, 1961;
Noble, 1956).
Septoria leaf spot has been shown to lead to a delay in grain maturity, to yield and bushel weight losses, and to flour of inferior quality (Chester, 1945).
Fig. 3 shows the poorly-developed and shrivelled grain which resulted from a heavy infection of both diseases on early sown wheat at Beverley in 1964.
Control
Control of these diseases is difficult but their incidence can be minimized by the following measures.
• Treat the seed with an organic mercury dust. This will control the seed-borne phase of S. nodorum
(Burhardt, 1954; Ponchet and Auge, 1959).
• Dispose of crop residues either by burning or deep ploughing.
• When practicable, grow wheat on land well separated from paddocks cropped to the cereal during the previous seaon.
• Plant the wheat varieties recom- mended for the district at the cor- rect time, and feed-off crops which are forward.
• Use resistant varieties when they are available. Only provisional re- commendations can be made at present. The wheat varieties Kon- dut, and, to some extent, Festiguay, have shown resistance to Septoria leaf spot.
REFERENCES
1. Bockman. H. (1962). [Artificial inoculation tests with Septoria and Fusarium on various winter wheat varieties in the Northeast Polder in summer 1961.] Tech.
Ber., ned. Graan—centrum, 8:1-23. Ab- stracted in Rev. appl. Mycol., 42: 189-190.
2. Burhardt, Z. I. (1954). [Septoria nodorum Berk, on tillering spring wheat.] Trud.
vsesoyuz. Inst. Zashch. Rast., 5: 120-130.
Abstracted in Rev. appl. Mycol., 37:33.
3. Caldwell R. M., and Narvaes, I. (1960).
Losses to winter wheat from infection by Septoria tritici. Phytopathology, 50:630.
4. Carne, W. M., and Campbell, J. G. C. (1924).
Mildew, Septoria, leaf spots and similar diseases of cereals. Bull. 121, Dept. Agric.
W. Aust., pp. 6.
5. Chester, K. S. (1945). Defoliation and crop losses. Plant Dis. Reptr, 29: 162-168.
6. Hilu, H. M. (1956). Inoculation, life cycle and host-parasite relationship of Sep- toria tritici Rob. on Triticum species. Diss.
Abstr., 26:1550.
7. Kietreiber, M. (1961). [The diagnosis of Septoria infection of wheat grains by seed testing.] PflSchBer., 26:9-10. Ab- stracted in Rev. appl. Mycol., 42:87-88.
8. Noble, M. (1956). Cereal seed health. R e - sults of a laboratory seed survey. Scot.
Agric, 36:86-90.
9. Pirson, H. (1960). [Testing of different winter wheat varieties for susceptibility to Septoria nodorum Berk, using artificial infections.] Phytopath. Z., 37:330-342.
Abstracted in Rev. appl. Mycol., 39:466.
10. Ponchet, J., and Auge, G. (1959). [At- tempts at control of damping-off of cereal seedlings.] Phytiatrie-Phytopharm.,
8:141-149. Abstracted in Rev. appl.
Mycol., 39:466.
11. Sanderson, F. R. (1964). Effect of leaf spot (Septoria tritici) in autumn-sown wheat crops. N.Z. Wheat Rev., No. 9
(1962-1964) pp. 56-59.
12. Scharen, A. L. (1964). Environmental in- fluences on development of glume blotch in wheat. Phytopathology, 54:300-303.
13. Sprague, R. (1950). Diseases of Cereals and Grasses in North America. New York:
The Ronald Press Co., pp. xvi 4- 538.
14. Sutton, G. L. (1920). Take-all, Septoria, rust and wheat mildew. Practical methods of control. Bull. 69, Dept. Agric.
W. Aust., pp. 27.
15. Thomas, M. H. (1962). Factors affecting glume blotch development of wheat and variation in the casual organism, Sep- toria nodorum. Diss. Abstr., 23:789.
163
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