Safe grain storage

Press, 22 January 1988, Page 10

Safe grain storage

With the harvest starting in some areas, farmers are reminded that grain storage areas should ■ be cleaned thoroughly and last season’s grain should be removed or treated. Spray all surfaces and the ground about with a registered insecticide (Actellic EC, Dichlorvos, Maldison, or Baythion). Do not use' unregistered materials. Thoroughly treat harvesting equipment, especially augers and headers. Residual grain in inaccessible areas in augers and harvesters can act as reservoirs for reinfection of the new grain. Remove residues using a probe, blower or vacuum cleaner or treat with insecticide. Use a residual herbicide to remove surrounding vegetation and make sure stores are weatherproof. Insect infestations will develop rapidly in moist grain under high temperatures. Pasture Porina could be a problem this year so now is the time to prepare for paddock sampling. Pastures most susceptible to porina damage are those that had plenty of growth in the spring and early summer, including hay paddocks, clover and grass seed crops. While overhead irrigation increases populations, porina damage is minimal under flood irrigation. Be prepared to start sampling in February if peak moth flights occurred in your area in October and early November. This will identify infested paddocks while caterpillars are small and before economic damage has occurred. Use the board sampling method (see AgLink FPP 588). Allow 10 boards (32cm x 32cm) per paddock left out overnight • Small grassgrub larvae are present in nonirrigated land but these are not yet causing damage. However, in irrigated situations, including both agriculture and horticulture, populations are further advanced and are causing damage now. This will become more evident in February. More information will

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be given in the next plant health monitor. Lucerne seed crops Check crops at 7 to 10 day intervals with a sweep net until the pods begin to turn brown. Apply an insecticide if an average of one or more sucking bugs per sweep is found. If insecticide application is necessary during flowering, apply Dichlorvos in the evening after bee activity has stopped. Peas and lentils Many growers have used the fungicide Bravo for control of Ascochyta diseases. Although this chemical is not registered for use on peas and lentils it has effectively controlled these diseases. Bravo contains minute quantities of HCB and, therefore, when planning future crop rotations, growers should note the following label precautions: • Do not use. Bravo where grass pasture is an essential part of the crop rotation. • Do not sow grass pasture until at least one crop has followed the last use of Bravo. Coriander As coriander crops reach maturity, some crops are showing symptoms of a bacterial disease which causes flowerstand and petal blight. This disease shows up early in the season as dead, water-soaked areas on leaves. After flowering, petals become brown and fall, with water-soaked lesions on the fruit; the entire inflorescence may shrivel and die. The disease is more common in crops affected by late spring frosts although damage is relatively minor in most crops. However, in dense stands where rain or irrigation has allowed the bacteria to spread within the crop, significant yield losses may occur. Thg only immediate control measure is a pre-

ventative copper spray applied at flowering to protect against infection. A research project has been initiated by the Plant Protection Centre, at Lincoln, to work out an effective control programme for the future. Berryfruit Apply a post-harvest spray of Gusathion or Lorsban to clean up pest caterpillars. Autumn raspberries Maintain bud moth controls, using Gusathion or Lorsban pre-flowering and Carbaryl or Lannate preharvest. Observe witholding periods, and check suitability of chemicals for markets with exporters. Pipfruit Growers should maintain cover sprays for the control of black spot in apples, especially in areas where weather conditions have favoured disease development during the past few days. Growers are reminded to apply calcium sprays as required. Refer to the Apple and Pear Board guidelines for specific recommendations for the various districts and cultivars. Stone fruit Preharvest sprays for the control of brown rot should be maintained, especially where cool wet weather has favoured disease development. Mites Two spotted mite infestations are building up in some horticultural blocks. Mite control may be difficult in pipfruit due to witholding periods, but control could be possible on late varieties using Omite or Peropal. Post-harvest clean up measures can be used on berryfruit crops; Neoron would be suitable. An alternative where populations are not high is to introduce the predator. Phytoseiulus persimilis, and adopt integrated control. Contact P. Workman, Entomology Division. D.5.1.R., Private ,*Bag, Auckland. L