Complex mixes do more harm than good
Published 07/06/2011 | 05:00
The recent good weather has helped to reduce the spraying backlog, which for a lot of growers was becoming critical. The problem with mixed weather is that when an opportunity to spray occurs, complex tank mixes are applied, which may not always be best practice.
Multiple product mixes in a tank, with numerous different active ingredients applied in 150 litres of water per hectare, generally is not a great idea. Common combinations on spring barley are sulphonyl ureas and hormone herbicides, triazole, morpholine, chlorothanil fungicides, trace elements and growth regulators.
The composite effect of the various formulations, chemical interactions and general crop bombardment can result in very poor performance and crop damage. I can remember when there were lists of tank mixes available and when a three-way mix was considered adventurous.
Walking through winter wheat crops is particularly nice this year, with heads emerging on the early crops. Crops are well tillered with great canopy cover, have four clean leaves and are a good rich colour. The good crops never got a growth check and were well rooted, which minimised nutrient and moisture stress.
Disease levels are generally at low to moderate levels concentrated on the lower leaves. I have noticed some sharp eyespot on wheat crops, with the eye-shaped lesions 15-20cm up the stem and the fungus evident under the stem sheath.
The comprehensive fungicide applications at T1 control common eyespot and, as a result, sharp eyespot can develop. The disease circles the stem and, depending on the severity, will restrict water and nutrient transport to the developing head.
The recent dry weather will have encouraged the disease, and the first time that growers may notice it is in the white heads dotted around the field.