Chemical Control Of Barley Smut

Press, Volume CIX, Issue 32274, 17 April 1970, Page 8

Chemical Control Of Barley Smut

Trials carried out during the last two years in a number of localities have demonstrated the effectiveness of a new chemical compound for the control of the damaging fungus disease, loose smut, in hnrlpv

Loose smut is most obvi ous in barley crops whet the heads are emerging from the sheath. Instead oi normal green tissue the ' i tire head, apart from the central spike, has been re placed by a mass of powdery black spores. The dispersal of the spores takes place when the surrounding crop is flowering. Wind-borne spores lodge in the heads, germinate and infect the developing seeds. To all outward appearances the grain is healthy but seed which has been infected will produce smutted beads in the following season.

It is important to know that the infection is carried within the seed and not merely on the surface. Chemical seed treatments

previously available did not kill the fungus inside the seed.

The only effective method of control was hot water treatment of the seed. Grain was first soaked in cold water, then plunged into hot water held at exactly 127 degrees Fahrenheit for five minutes, then cooled in fresh water and finally dried. In 1925 the Ute Mr C. H. Hewlett, then manager of the Canterbury (NX.) Seed Company, Ltd, in collaboration with Mr J. C. Neill, field mycologist. Department of Agriculture, began a series of experiments to test the value of hot water treatment on barley for loose smut control Their results showed the disease could be controlled and that significant increases in yield were also, obtained. In IS3I Mr J. H. Hewlett (present manager of the Canterbury (NX.) Malting Company) analysed the trial work up to that time and showed

that net profits to farmer; '• increased by 15.5 per cent a as a result of the hot watei | treatment of seed. * Since 1965 there has been an increase of loose smut in 8 barley crops. This increase <■ has coincided with the inJ troduction and widespread 1 growing of Zephyr, a suscep- ! ttble variety which has been ’ found to carry up to 10 per ! eent of infection in some ■ lines. ! The excellent disease con- • trol formerly obtained has 1 been largely lost. Hot water 1 treatment is effective but requires great care; if the ! water temperature is too high, loss of germination results. Control is also poor if temperatures are too low. Because few have the facilities and the labour needed to carry out the treatment, its use has been confined to nucleus lines. “Vitavax." the trade name of the chemical used in

these trials, was developed Amount of Chemical per 100 lb of seed 2 oz 4 oz Untreated

soi/ Moisture

The Winchmore irrigation research station reported yesterday that the soil moisture deficit on the non-irrigated area on the station was 147 points compared with 204 at the same time last year. The deficit has now been 200 points or greater on 63 days this season compared with 77 days last season. The deficit on the irrigated area was also 147 points. This area, last irrigated on February 23, may next be irrigated on Monday.

The authors of the accompanying article on chemical • ’trol oj loose smut tn 'ey are Messrs R I Mulholland, of the Department of Scientific and Industrial Research at Lincoln, and W J Thompson, field representative of the Canterbury Malting Company

jointly in Canada and the United States by B. von Schmeling and Marshal Kulka, of Uniroyal Inc., who first reported on the action of the chemical in 1966. It differs in one very important point from those chemicals previously used for seed treatment. When a seed dressed with this material germinates and develops, the chemical is absorbed by the plant and moves in the sap stream to the growing point. Thus the fungus growing within the seed is prevented from further development and a healthy plant results. Such a chemical is known as a systemic fungicide of which there are now a number being developed. A line of Zephyr barley carrying 11 per cent loose smut infection was used in the 1969-70 trials described here. Seed was dressed with Vitavax using a commercial slurry treater. Rates used were two or four ounces of formulation for every 1001 b of seed. In the results in the table below bulk search figures were obtained by three observers, each counting the number of smutted heads in separate drill rows 120yds long. Av. number of smutted heads per drill row

These results Indicate that the chemical treatment gave better control of loose smut. Control waa better than that achieved with hot water treatment at all the sites.

Although the cost of treating seeds with chemicals for loose smut control is equal to hot water treatment, the ease of application will mean that a greater proportion of seed barley ean be treated. This will lead to an overall reduction of the amount of inoculum in the barley growing areas. When the amount of smut infection has been reduced to the pre-1965 level ft may be possible to maintain this with lower rates of chemical It was found during these trials that two ounces of chemical, combined with increased amounts of water in the slurry treater, gave control equal to the higher (4 ounce) rate. However, due to the generally poor mixing and coverage obtained with normal amounts of water in commercial machines, the lower rate of chemical cannot be recommended at present

Grain samples from this year’s trials will be analysed for residues by the local agents (Ivory Spray Chemicals, Ltd). Provisional registration for Vitavax has been granted by the Agricultural Chemicals Board and it is hoped that full registration will be obtained for this coming season.

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