Stripe rust showing up

Press, 9 December 1988, Page 30

Stripe rust showing up

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Stripe rust is showing on some of the winter and autumn-sown wheat crops.

Many early crops have moved rapidly through their growth stages this season and growers should be careful to observe the withholding periods when deciding whether to use fungicides. Generally, treatments should only be used up until flowering.

• The spot form of the net blotch fungus has been observed on a number of spring-sown barley crops. It is important to minitor crops and spray where necessary- Impact, Tilt and Sportak are registered for the control of this disease. White clover Monitor seed crops for aphids and, if they can be found easily on the heads, apply Pirimor in the evening. Brassica crops Some aphid problems have been reported in brassica crops. Various chemicals can be used

against aphids on brassicas but most cannot be applied during flowering.

There have been reports of mis-application of insecticides to oilseed rape and other brassica seed crops in flower. Growers are advised to use either Mavrik or Pirimor, the only chemicals registered for use on brassica crops in flower. These must be applied when bees are no longer foraging, during the evening. Bee activity normally ceases shortly after sunset but in calm conditions and where hives are close to crops, bees can- be observed foraging later into the evening. Ryegrass

Stem rust has been noted on a number of ryegrass crops around the region.

The optimum time to control this disease is between stem elongation and flowering. Many crops may now be beyond flowering and care should be taken to observe fungicide withholding periods. Cereous and Tilt are registered for the control of this disease.

If the withholding periods can be observed, a number of chemicals are suitable for preharvest applications to control leafrollers and budmoth., Lannate and carbaryl both have short withholding periods.

Either of the biological insecticides Dipel or Thuracide may be applied during harvest for they have nil withholding periods. In the last issue of the Plant Health Monitor, Dipel was inadvertently omitted from the list of biological insecticides re-

gistered for use on raspberries and brambles during harvest to control leafrollers and budmoth. Berryfruit

Recent damp conditions may favour Botrytis infections on developing fruits. Crops should be carefully monitored for this disease and controls applied where necessary.

Pipfruit Orchards should be carefully monitored for black spot as recent damp conditions will have favoured infection by this disease.

It is important to maintain protective cover sprays. If wet weather

occurs, eradicant fungicides will control newly established infections if applied within four days. @ Fire blight has been observed in a number of orchards in medium to high risk areas this season. To reduce disease inoculum and aid control for next season it is important to remove and burn any infected wood. Stonefruit With harvest approaching it is important to monitor orchards for brown rot infections. Controls should be applied if conditions favour infection or the disease is observed.