Testing For Blind Seed Disease

Press, Volume CVI, Issue 31239, 10 December 1966, Page 10

Testing For Blind Seed Disease

As in past years, the Department of Agriculture’s Seed Testing Station will provide a blind seed testing service to South Island ryegrass seed producers during the current season. This service will again operate from a sub-station established at the Timaru office of the Department of Agriculture, to which all field samples for testing should be forwarded. The service will begin on the afternoon of Wednesday December 21. Advice to this effect has already been circulated to grain, seed and produce merchants. A pamphlet outlining details of the service is normally made available to merchants and growers, but as requirements and procedures of the service have become widely known, no pamphlets are being issued this year. However, one or two reminders may not be out of place. Field samples should be taken and submitted for testing not earlier than one week before the anticipated date of cutting of the crop. Blind seed disease can develop and spread throughout the crop right up to the time the seed

reaches maturity. Hence, early sampling could give a false impression of disease incidence. To ensure that the sample submitted is reasonably representative of conditions throughout the crop, traverse the field from corner to corner, collecting single seed heads every few paces until a sample sheath about as thick as your wrist has been gathered. This sheath, should be trimmed to one foot in length. Avoid gathering the sample when the grass is wet If more than one sample is to be forwarded at any one time, wrap each separately and tightly in several layers of paper. To obtain an accurate assessment of disease incidence at the time of sampling, the samples should reach the testing sub-station with the least possible delay. Samples should be forwarded by the first mail or bus or be handed to your local office of the Department of Agriculture, whichever is likely to ensure the quickest transit to the testing station. Each sample should be accompanied by a note indicating your name, postal address and telephone exchange and number and, in the case of crops entered for certification, the registered number and paddock letter of the certification entry. The name and address of the merchant through whom the cost’ of examining the sample is to be charged should also be indicated on the note. A charge of £1 is made for each sample examined. The test report will indicate the stage of maturity reached by the seed at the time of examination, by appropriate classification into any one of four classes, (a) immature, (b) milky, (c) doughy and (d) ripe. It should be noted that the stage of maturity reported at the time of examination is not to be construed as a definite indication as to whether or not the crop is ready to cut. The reported maturity stage of seed is merely intended as a guide to the sender of the sample to indicate the stage of maturity reached by the seed at the time of examination.

If the seed, as reported, is not “ripe” when examined, it is usually advisable to resample the field as the crop nears maturity to check on any possible developments of disease incidence since the first sample was taken and reported upon. Growers will be advised of the results of the test, initially by telephone- Where this will involve a toll call, the grower concerned should arrange to have “collect” calls from the testing station accepted by whoever is likely to be .mswering his telephone. Blind seed disease can cause very low germination percentages in resultant seed lines. Since this disease first came into prominence in 1932 there have been several seasons when the disease has been widespread and severe. The incidence and severity of the disease is closely associated with the seasonal weather conditions experienced between the time of seed setting and of seed maturity. It is likely to prove most widespread and severe when wet weather prevails during this

critical period in the stage of maturity of the crop. The development and spread of the disease is also likely to be less rapid and least harmful in dense “bottomed” crops and especially those which have lodged. The fungus spores of the causative organism, Phialea temulenta, which infect the ryegrass seed heads, are more readily disseminated in relatively thin, upright, open stands and in the splashing of rain drops during heavy rains. The disease may occur in any of the ryegrass species, but the incidence is usually more prevalent in the perennial species, Ruanui and Ariki, than in the shorterlived Italian and short rotation varieties, Paroa and Manawa. It is difficult accurately to forecast the likely occurrence, distribution and probable severity of this serious disease, so that proharvest testing for blind seed disease is a worthwhile safeguard against possible waste of time, energy and money in harvesting a worthless, low germinating crop.