The Integrated Approach to Disease Management

Fungicides have an important role in the management of foliar diseases of wheat and barley, however they should be used with discretion. Fungicides should not be viewed as the only management strategy available. Best disease management requires a good understanding of the pathogens’ life cycle, and an integration of management strategies targeted at the disease of concern. Integrated management strategies rely on a combination of approaches which, depending on the variety and disease, can include variety selection, crop rotation, control of volunteers, stubble removal, clean seed, seed and/or fertiliser treatments and foliar fungicide applications. See Table 2.6 for the relative importance of the management approach for different diseases.

Resistant varieties need to remain the first line of defence. Resistant varieties not only provide season long control, but also minimise disease carryover to the following season, reduce the use of fungicides which create environmental concerns for consumers and also provide more security of production for growers. An over-reliance on fungicides can lead to more rapid development of new and more virulent strains of the pathogens through mutations and the subsequent loss of resistance in many varieties.

Table 2.6 The effectiveness of various management practices against foliar diseases of wheat and barley

CROP DISEASE CULTIVAR RESISTANCE CROP ROTATION STUBBLE DESTRUCTION ELIMINATE VOLUNTEERS DISEASE FREE SEED TIME

OF SOWING

SEED/ FERTILISER TREATMENT FOLIAR PESTICIDE
WHEAT Stripe rust

1-2A

3 3 2 3 2-3 2 1
Leaf rust 1-2 3 3 2 3 3 2 1
Stem rust 1-2 3 3 2 3 3 3 2
Yellow leaf spot 1-2 1 1 3 3 2 3 2
Septoria tritici blotch 1-2 1 1 3 3 1 2 1
Septoria nodorum blotch 1-2 1 1 3 3 1 3 1
Powdery mildew 1-2 2 2 2 3 2 1 1
Barley yellow dwarf virus 1-2 3 3 2 3 2 2 1
Bunts and smuts 3 3 3 3 1 3 1 3
BARLEY Scald 1-2 1 1 3 2 1 2 1
Net form of net blotch 1-2 2 1 3 2 2 2 2
Spot form of net blotch 1-2 2 1 3 3 2 3 2
Powdery mildew 1-2 3 3 2 3 2 1 1
Leaf rust 1-2 3 3 2 3 2 2 1
Barley yellow dwarf virus 1-2 3 3 2 3 2 2 1
Bunts and smuts - 3 3 3 1 3 1 3

ADepends on the level of resistance (1 = Very Effective, 2 = Moderately Effective , 3 = Not Effective)

 

Correct disease identification is critical when deciding whether to apply foliar fungicides to an infected crop and to aid with selection of the most appropriate fungicide for the disease. It is important to note that not all dis-orders on plant leaves are caused by a fungal pathogen. Disorders on leaves may be caused by viral diseases (e.g. Barley yellow dwarf virus), nutrient deficiency (e.g. Nitrogen) or toxicity (e.g. Boron), or physiological blotching. None of these dis-orders can be controlled with the application of foliar fungicides.

There are a number of guides that are available to help with the effective disease identification. Many of these guides are listed in the reference list below and most are available from the DEDJTR Horsham office, 110 Natimuk Rd, Horsham.

Crop Phenology - The Growth Stages