Treating cereal seed

Press, 8 September 1989, Page 18

Treating cereal seed

SmOIIITOR

This is the first issue of the plant health monitor for the 1989-90 season. The monitor, published fortnightly, will provide up-to-date information and management advice on plant health problems in arable and horticultural crops. The monitor is compiled by the Lincoln Plant Protection Centre from information provided by M.A.F. and D.S.I.R. staff throughout the South Island. Cereal seed treatment Whether to treat cereal seed or not can be an important decision for cereal growers at this time of year. Benefits of treatment include the control of seed and seedling rots, control of seed-borne diseases such as smuts, net blotch and protection against rusts (such as stripe rust) •in the early stages of crop growth. Seed treatment with either Baytan IM or Vincit should give up to six weeks protection against stripe rust infection. If growing wheat cultivars which are seedling resistant to stripe rust, Vitaflo 200 or Benlate are alternative seed treatment options. Vitaflo 200 offers protection against seed and seedling rots and seed-borne diseases on wheat, barley and oats. The decision not to treat seed could be a viable option for wheat cultivars with seedling resistance to stripe rust or if your seedline is known to be free of, or have a negligible risk of, smut diseases. If growing a wheat cultivar susceptible to stripe rust in the seedling stage, and the decision has been made not to treat seed with either Baytan IM or Vincit, then crops should be carefully monitored for disease. In such crops, stripe rust infection can occur two weeks earlier. Growers using their own seed should treat it

at least every second season, as there is a risk of smuts building up in the line. Weed control in cereals Weeds in cereal crops should not be left uncontrolled. Application of a medium-priced herbicide to a crop of wheat with a yield potential of 4.5 tonnes/ha will generate a positive net return 80 per cent of the time. According to Dr Graeme Bourdot, a M.A.F. weed scientist, yield losses in wheat crops can range from 7 per cent to 55 per cent for broadleaved weeds and from 5 per cent to 33 per cent for wild oats. However, it is important to choose the correct herbicide to maximise profitability. This can be best achieved by accurately identifying the weeds present in a crop. Staff at local M.A.F. offices and the Plant Protection Centre, Lincoln, can help with weed identification and herbicide choice. Stone fruit Apricots are now at various stages of bloom and some of the early nectarines and peach varieties are approaching pink. Flowering is an important time to protect against brown rot infection. Octave can be applied for brown rot control up until petal fall and Saprol, Baycor, and Bravo can be used up until shuck fall. Check withholding periods for Saprol, which can be used pre-harvest for some markets. To minimise potential resistant problems:— 1. Only use MBC fungicides (Benlate, Bavistin

FL, Topsin M 4A) where resistant strains of the brown rot fungus are not known to occur. They are useful over the blossom period because of their anti-sporulant activity. 2. Limit the application of DMI fungicides (Octave, Baycor, Saprol) to no more than three in a 12 month period. 3. We suggest the dicarboximide fungicides (Ronilan, Rovral) be restricted to pre-harvest sprays to control brown rot. Leaf curl can be particularly troublesome on some orchards. If the critical copper sprays have been missed or control has not been satisfactory in other seasons then Bravo over the blossom period can offer additional control. Pre-blossom application of oil and Chlorpyrifos WP (also Lorsban 50W and Jolt 50WP) should provide aphid control. Lindane is no longer permitted to be used. Mavrik can be applied during flowering and up to shuckfall for control of aphids and thrips. Consult your export summer-fruit spray programme/diary for conditions applying to particular stonefruit to various countries. Pipfruit A late dormant application of oil will control over-wintering European red mite (E.R.M.) populations. Alternatively, an application of Chlorpyrifos WP (also Lorsban and Jolt) and oil at greentip should provide control of overwintering E.R.M. as well as woolly aphids and scale insects.