All T3 fungicide applications onto winter wheat should now be planned for application over the next week. Winter wheat crops have moved at exceptional pace during the dry warm period over the last couple of weeks. The cornerstone for the T3 head spray fungicide is a strong triazole that as well as being effective on Septoria is also effective on Fusarium. Prothioconazole & epoxiconazole remain the most effective products to give ongoing Septoria protection. Tebuconazole and metconazole are very strong triazoles for Fusarium and an important contributor at this time. The addition of a strobilurin is also essential to maximise the persistence of the triazole and strengthen activity on Yellow Rust. Good grain fill is totally dependent on retaining green leaf area for as long as possible, and the addition of the strobilurin extends the retention of green leaf tissue. Last years’ HGCA trials show pyraclostrobin (COMET) to be the highest rated strob for use in wheat being the strongest performer on Yellow rust and the late ear diseases. Products containing the active prothioconazole are in short supply this season and therefore an alternative choice may be required. I have seen a lot of physiological tipping on winter wheat and there are a lot of theories as to what may have caused this but most noticeably it seems to be specific to certain varieties. Mildew has been present on most cereal crops this season where the variety has low resistance a mildewicide must be included in the fungicide program. All weed control should now have been carried out on spring barley crops and all should now have received the T1 fungicide application as rhyncho is present on most varieties. Concerto and Waggon both have a very low rating for rhyncho resistance. 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. Where growth regulation has not been carried out it is critical to check crops and apply Cerone onto crops beyond GS32 if required. Moddus can be used on crops which have not yet reached GS32.
All weed and disease control should now be complete on both spring wheat and oats.
Grassland
Attention must now be given to those grass 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 vegetive 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 T is the most effective herbicide on ragwort.
Stock must be kept off until the weeds have rotted away, which can take up to six weeks.
Potatoes
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 that have 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 adhesions 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 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.