All T2 fungicide applications onto winter wheat should now be complete. Winter wheat crops moved at exceptional pace during the dry warm period a few weeks ago with some crops missing the growth regulator as ears emerged overnight. Aphid numbers had increased significantly during the dry warm spell also, but the recent rain will have washed them down the stem hence slowing their colonisation further up the plant. Growers need to continue checking crops right up to milky ripe stage and spray if present in numbers. Unnecessary insecticide applications should not be applied as most are not bee friendly. Of the aphicides approved for use for this purpose, Sumi-Alpha is the safest to bees.
All weed control should now have been carried out on spring barley crops, and all should now have received the T1 fungicide application. The two most dominant diseases in our climate are powdery mildew and rhynchosporium with ramularia becoming an increasing problem over recent years. Ramularia can be difficult to identify but unlike most other physiological leaf spots which are only visible on the upper side of the leaf ramularia is easily seen both on the upper and lower surface of the leaf and the longitudinal edges of the brown lesions remain enclosed by the leaf ridges. Symptoms appear where crops are subjected to stress from alternating periods of wet weather & sunshine, or man-made as a result of scorching. Chlorothalonil (BRAVO) is very effective when used preventatively, helping to maintain green leaf area when used along with a triazole/strob mixture.
All weed and disease control should now be complete on both spring wheat and oats.
Although it looked very grim a few weeks ago grass crops yielded very well and for most the quality was excellent. Attention must now be given to those fields which were not sprayed prior to first cut. Grassland herbicides use growth function to kill weeds, therefore peak growth periods should be used for herbicide application. There must be sufficient growth to allow herbicides to be effective and vegetative growth is the key time to apply as the chemical then gets drawn down into the roots. Herbicides are less successful once plants have progressed to the reproductive stage and have thrown a stem or began to seed. Once weeds are beyond the ideal growth stage for spraying they should be mown or topped and allowed to regrow again, and a herbicide applied to the fresh young growth.
To optimise efficacy of any herbicide, recommended water volumes should be observed, even when it means more time spent spraying. It is important to note ragwort plants in their second year are now coming close to flower and should be sprayed immediately as flowering ragwort is poorly controlled. The routine herbicide treatments for this weed are full rate MCPA or 2, 4-D, and they are most active on growing rosettes with reduced activity as the stem starts to extend. They are not clover safe. You can use a mixture of both these products as Nufarm Lupo which allows an increased dose herbicide compared with either alone, with a consequent activity benefit. Forefront is also very effective on ragwort.
Stock must be kept off until the weeds have rotted away, which can take up to six weeks.
The protracted planting this spring has meant some potato crops have yet to receive weed control. This task must take priority as to delay until after crop emergence will set the crop back even further in an already late season. Conditions have been ideal for the use of residual products (Afalon,Linurex,Sencorex). Where broad –leaved weed control has yet to be completed and the crop has passed the latest timing for Sencorex a reduced rate of Sencorex tank-mixed with Titus will provide a wider weed spectrum of weed control than Titus used alone and can be used on emerged crops up to 25cm high where the label allows. Scutch, other grasses or volunteer cereals are not controlled by the Titus/Sencorex mix. Where these weeds become a problem in coming weeks the graminicide Shogun can be used. Shogun can cause transient yellowing and is therefore not approved for use on seed crops.
As canopies close, the soil surface will tend to remain damper, encouraging slugs onto the soil surface. Timing is critical for effective control, just before the crop meets across the rows. Take advantage of any rainfall by applying pellets just afterwards, as this will bring slugs up onto the soil surface. Potato varieties particularly susceptible to slug damage include Maris Piper ,Desiree and Kerrs Pinks.
Blight fungicides move through the plant in three different ways contact, translaminar and systemic. Dithane,Ranman Top, Shirlan and Tizca are all contact fungicides. These Products protect only the outer surface of the leaf onto which they are deposited. Translaminar products such as Curzate M, Invader, Resplend and Revus move into the leaf and redistribute throughout the leaf tissue as it increases in size whilst systemic products such as Consento, Fubol Gold and Infinito move in through the leaf surface and upwards into the new growth protecting this from infection also.
Products with zoospore activity are the most effective 1st spray, applied at the rosette stage prior to rapid haulm growth. Shirlan or Tizca will control any zoospores that may be in the soil and provide good protection of the new plant. During the main canopy development phase with the considerable amount of new growth 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 drilled crops, at a time when the level of inoculum in the air is progressively increasing. If spraying during periods of unsettled weather, rainfastness of all products will be further improved with the addition of a sticker to the spray solution. Guard is a latex sticker and will improve the retention of the fungicide onto leaf surface, so improving both adhesion onto the leaf immediately post application and over the following days should rainfall levels remain high. The way the blight product is applied is as important as the product choice. Make sure nozzle type used is correct to ensure sprayer pressure, droplet size and water volume applied, is as directed on the label. Inspect and calibrate nozzles regularly to maintain performance. Never use any blight product at reduced rates. Do not spray when the leaves are wet as this will significantly increase the likelihood of runoff.