CROP CRACK - 02.06.07
By WENDY FEARON
Clarendon Agricare - Blight Check

The low night time temperatures coupled with the localised thundery showers have hindered spray opportunities over the past week. Many spring cereal crops are suffering from stress and it important to be aware of this when applying agrochemicals. It is essential to apply a good balance foliar feed immediately to encourage crops to go forward and minimize the effect of uneven development. Foliar feeds are fast acting and will have extra benefits over fertilizer applications. It is advisable to apply both a foliar feed and fertilizer application to ensure healthy plant development.

Spring Barley

There is a wide variation in the growth of spring barley due to stress. Some crops are now at stem elongation with most just at or beyond second node. Manganese deficiency is showing up in some crops as is lack of potash and many other nutrients.BYDV is showing in many crops and may be confused with manganese deficiency. Weed control should now be complete as crops race through the growth stages. Both mildew and rhyncho are appearing on crops and will spread rapidly with the current climate. Any crops which have not yet received a T1 should do so now. Where two fungicide applications will be made Colstar or Midas+Talius should be applied as T1 and followed up with either Mobius or Mantra at T2.If only one fungicide is going to be applied and a strob is preferred Mobius or Mantra may be used or alternatively Colstar,Opus Team or Midas+Talius which are triazole mixes should be applied. Attention should be given to growth regulation at this time as many crops will require Cerone.The optimum timing is onto the emerging flag leaf GS37-39.

Spring Wheat

Spring wheat’s are generally more advanced than the barley’s and again weed control should now be complete. Spring wheat’s will benefit from at least two fungicide applications and all crops should now have received a T1. Any crop which has not been treated should receive both Foil and Talius or Opus Team with Bravo immediately, followed up with either Prosaro or Mantra at T2.

Winter Barley

Most winter barley crops are now at the flowering stage (GS61-69) and should now have received a T2 fungicide treatment. It is essential to include chemistry which will control both mildew and Rhynco as levels of both diseases have spread rapidly over the last few weeks. As most crops will not begin to ripen until July there is the need to keep the head clean for another 6 weeks. Choice of fungicide will depend on varietal resistance and disease level.

Winter Wheat

The ear has emerged in most winter wheat crops and all T2 fungicide applications should be complete. The excellent weather in April and early May allowed all T1 applications to be on time although the change in weather has delayed T2 applications. Yellow rust and mildew have been seen on some more susceptible varieties and it is important to use products which will control these diseases. Aphid numbers are extremely high and it is essential to use products such as Hallmark, Decis or Sumi-Alpha.

Potatoes

With record temperatures and dry weather during April, planting in excellent conditions and then followed up by the recent rain; most crops have had an almost perfect start.The low night time temperatures experienced recently will slow down growth but it is important to emphasise we have had a half Smiths period two weeks ago (16/17th May).

The ideal growing conditions has also effectively shortened the spray-window for weed control, with crop and weeds both growing past cut-offs sooner than might be expected, and in such circumstances alternative weed control strategies must be considered.

Due to the considerable amount of new growth being produced during the canopy development phase, it is essential the product being used is fully systemic to properly protect the new leaves being put on between applications. Later planted crops are higher risk as they produce more new growth between applications than earlier planted crops, at a time when the level of inoculum in the air is progressively increasing.

Shirlan is an optional first blight spray. Although it has no systemic activity, it controls any zoospores that may be in the soil, either from ground keepers or infected seed, and therefore is ideal when the bulk of the product is landing on bare soil rather than foliage. This should be followed up with a systemic product such as Tattoo.

With damp soils and canopies now closing, slugs will be coming up onto the soil surface, so providing the ideal opportunity for good control. An application of slug pellets is recommended before the crop canopy meets. Take advantage of any rainfall by applying pellets just after rain, as this will bring slugs up onto the soil surface,

Potato varieties susceptible to slug damage include Maris Piper, Desiree and Kerrs Pinks.

Grassland

There is still a bit of first cut silage to be lifted but most of the acreage is now in. Fertilizer should be applied as soon as possible after cutting to ensure quick uptake by the regrowing plant. Where first cuts will be later there may still be time to spray docks. Products such as Pastor, Forefront and Doxstar have little or no effect on the growth of grass. Squire may be used on leys with clover to control docks.Allistell can be used on new leys to control chickweed up to 15cm.
Spot control of nettles, thistles and docks can be achieved using Grazon 90 or Nushot.