Leaf blotch on barley

Press, 23 December 1988, Page 22

Leaf blotch on barley

SmoWTTOR

Considerable leaf blotching is showing on some late spring sown barley crops. This has been caused by either net blotch, a fungal disease, or by physiological leaf blotch, a non-pathogenic disorder which does not require chemical control. It is important to identify the cause of leaf blotching before applying control measures.

Rust has also been observed on late barley crops. Crops should be monitored for this disease and if active rust is found on upper leaves, a fungicide could be applied before the end of flowering. Pipfruit

Continue to monitor crops for black spot and powdery mildew. Cover sprays should be maintained for these two diseases. Observe correct withholding periods if eradicant chemicals are used.

Pipfruit and berryfruit Check for two-spotted mites. Control may be required if population levels are high on pipfruit and berryfruit. Peropal, Omite or Torque may be used for control of mite nymphs on apples while an application of Peropal or Torque is suitable for pears.

Note the - withholding periods for pre-harvest miticide applications on export crops. Peropal and

Omite are not appropriate for application if it is less than 35 and 28 days respectively from harvest. ‘

© If mite damage was evident earlier on berryfruit, check carefully for the presence of predator species before making a post-harvest application of either Neoron or Omite. Predaceous mite species and the ladybird, Stethorus might already be providing effective control of two-spotted mite populations. Raspberries and . brambles

For control of budmoth and leafrollers during harvest of main crop raspberries and other brambles, the biological insecticides Dipel or Thuracide can be applied. Both these have nil withholding periods. Pre-har-vest applications of either Lannate or carbaryl will also provide control of budmoth and leafrollers but ensure that the withholding periods are observed.

In autumn raspberries, azinphos-methyl can be applied before flowering for this purpose.

Blackcurrants Early control of currant clearwing will have been provided by a pre-harvest application of the highly toxic chemical methylparathion. It is too late to apply this chemical to counteract recent clearwing flights and a postharvest, clean-up application of azinphos-methyl would be of value. Stonefruit

Early maturing varieties should be carefully checked for brown rot. Chemical controls should be applied if the weather favours infection or the disease is observed. To avoid possible resistance to chemicals it is suggested that only 1 MBC and no more than 3 dicarboximide sprays be applied in any 12 month period. When using these chemicals always observe the withholding periods. • On apricots, nectarines, peaches and plums, thrip populations can be controlled by applications of carbaryl pre-harvest and at seven-day intervals during harvest. ’