Fungicide programmes for wheat and barley

This web page covers fungicide programmes for winter wheat, winter barley and spring barley. Focused on the main spray timings, it also outlines the implications for fungicide resistance management and provides basic information for other cereal crops.

Fungicide programmes are an essential component of many disease management strategies. Generally, the T1 and T2 fungicide timings give a yield response in winter wheat and winter barley. The T0 and T3 timings give a much smaller or no yield response, although a T3 can be important for protecting grain quality.

• Exploit all practical, non-chemical control options
• Use varieties with resistance to the main diseases of concern*
• Minimise the number of applications – only use fungicides when the risk or presence of disease warrants treatment, but treat before the infection becomes well established
• Use the minimum dose required to effectively control the target disease
• Include a multisite fungicide, where available, in both the early and late-season sprays
• Make full use of effective fungicides with different modes of action in alternate sprays or mixtures. Where possible, make sure the mixture is balanced (i.e. use mixing partners at doses that give similar efficacy and persistence)
• Avoid repeat applications of the same mode of action

Note: The most resistant-prone diseases are septoria tritici in wheat and ramularia in barley.

Yield responses to fungicides, between the most and the least resistant varieties, can vary as much as 3 t/ha. A variety with a treated yield benefit of 0.5 t/ha will only justify having the value of 0.5 t/ha of grain spent on it.

Disease-resistant varieties also offer greater flexibility within a spray programme, including the omission of sprays, especially where disease pressure is low. For example, in wheat, a T0 can help insure against a weather-delayed T1 for septoria tritici control. However, there is considerably less need for this practice in a resistant variety because disease progression is much slower. At the T1 timing, varieties with a high septoria tritici disease resistance rating are also unlikely to need a succinate dehydrogenase inhibitor (SDHI) fungicide, especially for later-sown crops (i.e. after late October). Omitting the T0 altogether and the SDHI at T1 not only reduces costs, but also lessens the resistance selection pressure on fungicides.

• The cost of a fungicide application rises as dose increases
• Yield loss is proportional to the amount of disease present
• The appropriate fungicide dose is the point at which margin is maximised
• Doses lower than the appropriate dose reduce profit through inadequate disease control
• Doses higher than the appropriate dose reduce profit because the cost of additional fungicide outweighs the value of the extra yield
• Selection for fungicide resistance is also more likely with increasing dose – resistance management guidance states to use the minimum dose required to effectively control the target disease
• Appropriate dose can be estimated by considering disease risk factors (e.g. weather, varietal resistance, drilling date and previous cropping), grain price, fungicide cost and efficacy
• The appropriate dose varies more with disease pressure and varietal resistance than with grain price

A plant biostimulant contains substances and/or microorganisms that stimulate natural plant processes. The use of biostimulants may increase plant growth and yield. Some biostimulants are associated with increased crop nutrient uptake and tolerance to environmental and pathogen stresses. There is, however, limited evidence on how to use biostimulants to achieve consistent benefits in the UK.

A biopesticide (bioprotectant) is a crop protection agent based on microorganisms or natural products that can be used to reduce or eliminate pests, diseases or weeds. In cereals, very few biofungicides are available, but there are several in development.

Cereal chemistry changes demand a new approach to disease management. Fiona Burnett (FRAG and SRUC) describes how to weave fungicide options into programmes to protect efficacy and maintain sufficient disease control.