Rust wrap-up

Press, 18 March 1983, Page 21

Rust wrap-up

Stripe rust did not develop in the Canterbury wheat crops this year to become the problem that it was during the 1981-82 season. Although the weather played some part in this, the major factor was the extent to which farmers had reacted to alleviate the problem.

As 90 percent of the wheat acreage was sown with Bay-tan-treated seed, infection was delayed until later in the season when weather conditions were possibly less favourable for the disease.

The majority of crops sown with susceptible cultivars were also sprayed, many of them twice, sothat it was not until late November or early December that infection became widespread in some crops, as the effects of the control programme wore off. The situation in Southland was similar, although a few apparent spray failures were reported which were either the result of spraying just prior to rain, or trying to control established infection on the lower leaves of very dense leafy crops. Concern is also being expressed in Southland about the difficulty of controlling head infection. '

This is a problem which requires urgent attention as head infection leads to shrivelled grain, though not all grains are damaged as happens if leaf infection becomes established.

The one disappointing aspect of this season was the development of a new strain of stripe rust which was collected on crops of Oroua from Waimate to Lincoln. This new race was identified by Dr R. A. Mclntosh of the Plant Breeding Institute, Castle Hill in Australia as 106E139. The extent to which this new race will affect Oroua will be studied in the glasshouse during the coming winter, according to the D.S.I.R.

Although the new race has not substantially affected the Crop Research Division’s autumn wheat breeding programme, two promising breeding lines from the spring wheat programme at Lincoln have been found to be susceptible to the new race and will not now enter Recommended List trials. However the wheat breeders are generally optimistic because most of the material now in the breeding programme has a high level of resistance to many European races of stripe rust.