Sprouting in some crops

Press, 4 March 1988, Page 22

Sprouting in some crops

Wet weather during the last stages of the harvest has had an adverse effect on many crops.

In i Mid-Canterbury, about: 35 per cent of the wheat crop had not been harvested before the start of the wet spell and this caused sprouting in many cropsi Otane and Oroua crops were among those badly affected, with 90 per cent sprouting in some cases. Wheat with a significant amount of sprouting is not suitable for, milling, but can 'be used for feed, either locally or export. Some firms have set up sprouted wheat pools. Grain with only a small amount of visible sprouting should be tested because it could still be suitable for milling. Crops still jin the ground should not be harvested until the moisture content, is about 14 per cent unless the grower has access to a dryer.

• This will be the last regular Plant Health Monitor this season. During the next few months occasional articles on specific and topical plant disease and pest problems will be published. Berryfruit Integrated mite control has been most successful this season. Implementation involves the release of predators (Phytoseiulus persimilis) and avoiding the use of incompatible pesticides. Plan to adopt integrated mite control next season if i your programme is

based entirely on miticide usage at present. Some blocks where predators have not been used have suffered severe mite outbreaks. A clean-up miticide will be appropriate in these blocks. Neoron will control all stages of the mite population. • Raspberry bud moth is laying eggs now and should be controlled with a spray application of Gusathion to non-fruit bearing brambles. Use approved insecticides with short residual life in autumn raspberries. Bee safety is a concern when plants are in flower. Stone fruit Brown rot has been a problem on stone fruits in recent weeks because of the favourable weather. Inadequate control of the disease early this season could cause potential problems in the future, and growers are ( advised to take the following precautions: • Blighted twigs should be removed now when it is easy to identify them. • All mummified fruit remaining on trees after harvest and those that have fallen to the ground should be removed or destroyed by burning or deep burial. These are the principle source of inoculum for spring infection. • Remove discarded fruit left lying on the ground after harvest. j • In orchards where brown rot has been particularly bad, a broad spectrum clean-up spray may be necessary.

Pip fruit Current weather conditions continue to favour black spot which could cause problems in late season varieties for export. Maintain cover sprays for control of black spot and monitor orchards carefully for this disease. Eradicants may need to be used. Remember to observe withholding periods for export and local market fruits. • Maintain ■ leafroller controls if exporting. Do not reduce the spray programme on late varieties just because picking of early varieties is under way. If it is now too late to apply Gusathion, or if spray drift is likely to cause problems on varieties close to picking, use carbaryl at seven day intervals. Observe the withholding period. Pasture Porina caterpillars resulting from late spring and early summer flights will soon be large enough to cause significant damage. Aim to complete board sampling soon. If treatment of infested paddocks is: left too late, the caterpillars become more difficult to control with insecticide, and returns on control costs are reduced because of the damage that has already been sustained. Refer to AgLink FPP 588 for details or contact your M.A.F. consultant. • Grassgrub larvae are feeding in dryland pastures now. If wet condi-

tions prevail from now on, expect feeding to continue until May and June, with damage evident in autumn and early winter. If dry conditions occur, development will be delayed and feeding will continue until late winter and early spring. If severe drought occurs, a significant proportion of the population may be induced to enter the two-year life cycle. In this case, unusual problems can be expected to occur in crops when numbers of feeding larvae exceed thresholds. Granular insecticide applied down the spout did not prevent late root feeding by twoyear cycle grubs in some crops in inland Mid-Can-terbury this season, and significant damage occurred during grain filling.

Sampling grassgrub populations helps to estimate population size and determine stage of development. Sampling is essential in paddocks where a problem is likely to occur and where management decisions may be influenced by the size and feeding status of the grassgrub population. • Pasture mealy bugs

and root aphids may also be present in easily {detected numbers. Dig up ryegrass plants and look for white, fluffy wax material among the roots and crowns. Little is known about the significance of root aphids. However, when abundant they are likely to cause some damage. Pasture mealy bugs have been implicated in : the death of ryegrass plants during drought in irrigated pastures. Recent information suggests that heavy mealy bug populations may:collapse from the effects of parasites. There are no economic {control measures available for either insect. { Vegetables Expect damage from green looper caterpillars from now on, particularly on tomatoes, beans j and lettuce. Regular insecticide applications are necessary to preVent damage since the moth has several generations over the summer. Use insecticides appropriate to crop and take particular care to observe withholding periods, especially on food crops. j {