Plant health monitor

Press, 22 January 1982, Page 9

Plant health monitor

Information

Harvesting of cereal crops has begun as dry weather has accelerated grain maturation. particularly in earlier sown crops.

Farmers should be taking steps to avert potential damage associated with bulk storage of grain. Action to be taken is detailed m an accompanying article by farm advisory officer Dr Ray French and scientist Dr Ken Somerfield.

Although pathogens and pests have declined in importance now that harvest is underway, farmers should note those diseases and pests that have been present. This knowledge will assist in planning rotations to control future outbreaaks.

GRASSES • Grass seed sown before March as new pasture or for winter green-feed (e g. Tama), is liable to severe attack by Argentine stem weevil. Add phorate to the seed to help prevent this. LICERNE

• Insect damage is still possible in lucerne seed crops. Spraying is worth while if insect numbers are high. Use only trichlorfon or bromophos to minimise mortality of leaf-cutter and other pollinating bees. • Spraying for sitona weevil is not recommended. Most adults are now seeking hibernation sites for the summer. CEREALS

• Farmers should note any diseases and pests present at, or before, har-

vest, especially take-all. eye-spot, hessian fly. etc. so that crop hygiene measures and rotations can be planned. For example. burning stubble will reduce hessian fly and eye-spot in subsequent crops. Widespread lake-all or root rots should signal rotation out of cereals for one or more vears. isee AgLink EPP 551). POTATOES

• Potato tuber moth could become a problem, especially under present dry conditions. Ensure the crop is well moulded to prevent caterpillars infesting tubers. Check leaves for blistering as an indication of a potential problem. © Some crops are showing a little leaf curl. This is associated with the dry conditions and wind damage. © Primary leaf roll caused by aphids has been noted. Though crops may have had Thimet at sowing, its limited life (six weeks) means that a systemic insecticide (metasystox) is now necessary to continue aphid protection. The possibility of re-rogu-ing should also be consid-

ered. • Pre-harvest forking for potato cyst nematode is continuing. Most of the Canterbury region will be covered, particularly the high risk areas.

BLACKCURRANTS • Leaf spot will be a problem for most growers. Immediate post-harvest sprays should be applied to prevent disease carryover. • Mite populations have increased dramatically since December. Any late variety blackcurrants not already treated, must be sprayed with a miticide. BRASSICAS

• In paddocks being prepared for sowing winter green feed and turnips, cloddv seed beds or litter left bn the soil surface increase the risk of weevil attack. • Damping-off or wire-stem disease, caused by Rhizoctonia. is often a problem in brassicas following pasture, lucerne, beei or previous brassicas. Seed treatment with a mixture of benomyl plus captan could be used to good effect.

• In export stonefruit crops, control of thrips and brown rot needs constant attention. • Pipfruit growers should watch for a build-up of mite populations. • At this time of the year prolonged periods of intense heat will cause sunburn in pipfruit. This problem can be reduced by use of overhead sprinklers.