DAMAGE TO WHEAT

Press, Volume LXXIII, Issue 22201, 18 September 1937, Page 21

DAMAGE TO WHEAT

Causes Investigated In Canterbury REPORT BY RESEARCH COMMITTEE ,-»r. 'Thursday's meeting of the Wheat .fit-search Institute Committee it was reported that there were numbers of cases in which wheat crops had failed to become properly established, and it was explained that an attempt was being made to analyse and tabulate all the different cases recorded by seed merchants, the Agricultural Department. and the Wheat Research Institute. Concurrence was expressed with the record made by Mr R. MeGillivray, of the Department of Agriculture, that the condition of tattered leaves was due to slugs, and it was reported that the staff of the institute, with Mr L. Morrison, of Lincoln College and of the Plant Research Bureau, were engaged in investigating, any ether causes of bad establishment. The following is an interim report of the investigations to date. The affected crops are fairly evenly distributed over the various districts of the province, between Culverden and Ashburton. From all accounts severe damage is restricted to a comparatively small number of crops, although presumably not all affected crops have yet been ascertained Variety and Seed Treatment On the outset it was necessary to eliminate as many factors as possible which might conceivably be the causes of poor germination or establishment. There is every reason to believe that in the cases investigated the trouble is not due to any factors connected with the seed. The question of varietal susceptibility could be excluded after full inquiry, since all the major varieties, viz., Tuscan, Cross 7, and Hunters, are affected. The method of harvesting, whether heading, stock or stack threshing, can have no bearing on this case, since the affected crops are derived from lines which include all of them. Finally, the question of seed treatment, and in particular the newly introduced mercury dusts, have received considerable attention. A series of observations in the affected areas has led to the conclusion that these treatments can definitely be excluded from responsibility. Thus, some of the worst paddocks had not been submitted to any seed treatment, and one had been “wet-pickled.” In one paddock at Tinwald, sown with dusted seed, part of the crop is well established, whilst another part of the same paddock was wiped out in two consecutive sov/ings. This clearly shows that the cause of the damage can in no way bo due either to seed or seed treatment. Soil Factors Observations on the various affected crops, as well as on those in the neighbourhood, led to the conclusion that soil factors, such as excessive moisture, cannot be solely responsible for the damage. Further, Dr. M. M. Burns, of Canterbury Agricultural College, found that soil acidity in the badly affected crop was perfectly normal. Soil temperature and moisture during the last season did not deviate largely from normal standards. On the other hand it became apparent that, whatever, the cause, a strong interaction exists between soil factors and the damaging agents. In many of the affected fields the crop on the headlands was distinctly better than that on the rest of the paddock. In one field at Seaview, sown on three consecutive days, the first day’s drilling gave a better establishment than that of the following. It was further noted that in more than half of the affected crops, wheat followed peas. Available data are barely sufficient to draw general conclusions from this observation. Plant and Animal Parasites Samples submitted to the Plant Research Bureau at Palmerston North by Mr R. McGillivray, Fields Superintendent of the Department of Agriculture, yielded the report that no sign of fungus attack could be ascertained. This result has been confirmed by Mr I. D. Blair, of Canterbury Agricultural College, on affected seedlings from crops in the Halswell district. A thorough study of crops in the Yaldhurst and Halswell districts and in various parts of the Ashburton County has been conducted by Mr L. Morrison,* who supplied the following statement: Mr Morrison’s Observations It is very evident that slugs arc extremely abundant this year, and many wheat crops show signs of slug damage; the above ground portions of the plants being chewed and eaten so as to give a rather frayed appearance to many leaves. This type of damage is particularly marked, where, for some reason, the crop is abnormally thin and there are fewer plants to provide food for the hordes of sing. In the Seaview district a crop of wheat which was rather thin and patchy was found to be fairly heavily infested with porina, a night-feeding caterpillar. Porina was present in sufficient numbers to account for the damage showing. An interesting feature in regard to this crop was that the adjoining paddock had carried a heavy crop of clover the previous summer, and was extensively damaged by porina, large areas of the paddock being still quite bare. In the Lyndhurst district one farm which was inspected proved to be carrying a large wireworm population. A crop of wheat after grass and a crop of wheat after bare fallow were each showing the effects of wireworm damage. Other wheat crops which were partial or complete failures were practically free of slugs, porina, and wireworm. It would appear that the main cause of the present trouble is eelworm. All the damaged crops whicn have been examined, except one m the Halswell area, which was suffering from slugs only, and one in the Seaview area, which had been attacked by porina, were eelworm infested. The eelworm concerned in this instance appears to be the “stem eelworm,’ 1 ' which is usually associated with damage to clover, lucerne, oats, narcissus and hyacinth bulbs, onions, and other crops. The “wheat eel-, worm,” which attacks wheat only, and gives rise to “cockles” or “peppercorns” instead of grains in the ear, has nothing to do with the present outbreak. The “stem eelworm” is microscopic in size, being less than two millimetres in length and extremely thin, and can not be seen with the naked eye. Many farmers have noted small worm-iikt-creatures in the decaying grain some time after the seed has gerrmnated. These are the maggots of a hind of i y which feed on decaying vegetable matter, and they bear ■ no relationsnip to the damage observed. The stem eelworm” invades the gr»wmg plant, and may be found in the tissues at tn base of the stem near to the penn where the roots arise, and also netween the stem and the leaves, at higher levels. Eelworm infested plants are usually .stunted, and very often show a twisting a buckling of the stem and leaves, wnne

many seedlings remain below the surface of the soil, become white or yellow in colour, and are dwarfed and malformed. There is still much to be learnt about this species of eelworm, particularly on such obscure matters as its apparently sporadic attacks on agricultural crops. In the present oubreak instances have occurred where the damaged crop has been resown in wheat. and this has again been attacked, while in other instances the resown wheat is doing well. Since oats are particularly susceptible to attack, it would not appear to be a wise policy to sow oats after affected wheat. It is, however, possible that the more rapid germination and growth secured with spring sowing as compared with autumn sowing would tend to overcome the effects of the eelworm attack. The present outbreak, in view of the comparatively small number of affected crops, and also in view of the fact that similar damage has never been previously observed in New Zealand, and that it is extremely sporadic m its occurrence, can in no way be considered of a serious consequence to the wheat industry as a whole. All the same, it must be carefully watched, and all useful data collected m order to assist in the working out of a solution to the problem. Farmers wm> suspect similar damage m their wheat crops are requested to report the ciri cumstance.