In the third of our series on spray application tips for the key winter wheat timings, David Felce, Agrii eastern region technical adviser, gives Martin Rickatson his tips on spraying techniques at T1.
With a multi-task winter wheat role in protecting leaf three from septoria, controlling diseases such as eyespot and mildew in the crop base, possibly regulating plant growth and perhaps addressing nutrition needs and broad-leaved weed development, the T1 spray has a critical influence on crop success, particularly as a well-applied fungicide should safeguard the crop until T2. But, says David Felce, eastern region technical adviser for Agrii, a thicker canopy to penetrate means sprayer set-up and application technique need extra focus for successful results.
“To a certain extent, the success or otherwise of the T0 application in protecting against disease on leaf four will govern the disease status of the crop at T1. However, septoria is likely to be present in the base of the crop, especially with lush growth and dense canopies, even if, in a cooler spring, it may be in its latent phase.
See also: Spraying better in a busy spring
“Protection of leaf 3 is the key aim at T1, but getting the spray to penetrate the greater crop density is important to protect the plant as a whole, and if, for example, adding something to the tank mix to tackle broad-leaved weeds. There are a number of useful tank-mixable herbicides that can be applied at T1, and with bigger farm acreages meaning more must often be done simultaneously to save time, applications at this timing can be multi-layered.
“But it is the disease control element that is most important, particularly as it is not possible to know at this stage what the rest of the season will hold for disease pressure or variety resistance, so it is essential to pick the best possible products and support them with the best application practice. T1 product choices should be sufficiently robust to protect the crop through to T2, especially as the curative capability from azoles is now less than it was. And remember that that multisites such as chlorothalonil only protect the plant area with which they come into contact, and do not move within plants.
“Consider the value of adding an adjuvant to aid application and eventual results. These have two distinct functions – improved physical delivery from more uniform spray, and better application onto the leaf to aid penetration and allow the crop a head start against disease. The latter quality also helps the penetrative action of herbicides where weeds with waxy or hairy leaves are the target. However, it is important to note that not all adjuvants have the same properties, so it is vital to select the one specific to the task in hand.”
Selecting the right nozzle type, keeping accurate boom height 50cm above the canopy, and maintaining a sensible spraying speed are particularly important, he stresses.
“If air induction nozzles are being used, they should be capable of application at the finer end of the spectrum – subject to LERAP requirements – but 80 or 110 degree flat fan nozzles would be the best option. Setting them alternately straight down and at a 30-degree forward angle will provide the best level of canopy penetration and coverage. With 80-degree nozzles there is a little more flexibility in boom height, offering less drift at 75cm than 110-degree units.”
Spraying speed also becomes more critical with the thicker canopy, suggests Mr Felce.
“Set the boom at 50cm above the canopy for accurate delivery, and keep forward speed to a sensible level, both to avoid boom sway and to allow more time for the spray to penetrate the crop. In particularly big or lush canopies and/or where you are trying to target mildew or eyespot in the base of the crop, raising water rates from 100-150 litres/ha will be beneficial.”