PLANT HEALTH MONITOR

Press, 24 January 1986, Page 11

PLANT HEALTH MONITOR

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As the harvest begins yields and screenings may well reflect problems that have been lurking in the crops over the Christmas and New Year period. Unfortunately there are no control measures now. Glume blotch has advanced into the heads of susceptible wheat crops and will cause some loss. Foot rots and take-all are common in both wheat and barley. Takeall is particularly severe in spring sown barley, but in wheat it is producing white heads and grain shrivelling but little stunting of plants. Black point fungus is abundant in wheat heads and could cause down grading through indexing. There should not be further problems in storage, provided the grain is stored below 15 per cent moisture and below 20 to 25 degrees. Above these values black point fungi can be activated causing considerable damage. STORED PRODUCT PESTS • To guard against stored product pest problems, thoroughly clean out and spray all storage facilities with an appropiate insecticide. It is vital to thoroughly spray both inside and outside, and also an area around each construction. Do not forget about the same treatment for harvesting machinery, especially augers and headers. If residual grain cannot be removed from inaccessible areas, then at least try to spray insecticide into them. Concentrate especially on auger wells which can harbour contaminated grain. PASTURE

• Start preparing now to sample pasture for porina. Make up a number of square boards (preferably marine bonded plywood) of 32x32cm so that they will be ready when you need them. About 50 to 100 should be enough to sample all pasture on an average pastoral farm in about four to six days. Paddocks most at risk and requiring early attention will be those that have been laxly

grazed, clover and grass seed crops and some hay paddocks.

• Preliminary sampling confirms that grass grub populations will be high in Canterbury this year. Watch this monitor for further details but be prepared to sample paddocks early. Chemical control is expensive, so consider cheaper management strategies such as feed budgeting, heavy rolling, winter mob stocking, nitrogen application and direct drilling in spring. If maintaining a pastoral policy, avoid ploughing moderately infested pastures as this will create a severe outbreak three to five years after redrilling pasture. LUCERNE • Spotted alfalfa aphids were found in Canterbury last season. They could damage susceptible cultivars from now on particularly if hot weather is experienced during the late summer and autumn. LUCERNE SEED • Sweep crops once a week to check for sucking bugs. Take five sweeps at four places (20 sweeps total) in each paddock. If an average of one bug per sweep is caught apply in the evening dichlorvos or trichlorfon if available. If crops are not in flower, use metasystox but first check that there are no flowering weeds in the crop. RED CLOVER SEED

• If bumble bees are not present, obtain honey bees for pollination. Requirements are one to three hives per hectare. Ideally crops should not be too vegetative during flowering. Do no let the crop wilt or suffer any moisture stress if possible. OIL SEED RAPE

• Check crops for aphids. Although the best time to control aphids is before flowering, problems can occur during and after. Avoid spraying during flowering but use pirimicarb applied in the evening if necessary. If aphids occur in readily detectable numbers on the pods after flowering,

control may be warranted. Avoid using systemic insecticides if the withholding periods are in excess of harvest dates. FRUIT FLY

• Always be on the alert for fruit fly. They are not present in New Zealand, and we do not want them. M.A.F. has a nationwide monitoring programme in operation using traps and baits to attract and catch flies. The public can assist by sending samples of maggots in fruit to M.A.F. for identification. PIP FRUIT

• Black spot in apples is still a problem in many of the moister areas, especially in South Canterbury. Remember to keep cover sprays up to schedule. STONEFRUIT • Harvest is well underway and growers should be aware of potential brown rot problems. Export crops can be sprayed with Saprol or Rovral up to one day prior to’harvest. • Monitor peaches and nectarines for thrips and apply a clean up spray of carbaryl (withholding period one day) if thrips are present. RASPBERRIES AND BRAMBLES • Raspberry bud moth is flying now. If harvest is complete, apply Gusathion or Lorsban. If still harvesting apply dichlorvos or carbaryl instead, but allow for th,e three day withholding period, and then apply the standard spray, post harvest. For Autumn raspberries apply Gusathion or Lorsban before flowering, or dichlorvos in the evening if flowering has started.