As maize crops approach tassling it is well worth considering the disease risk and likely returns from a fungicide application.
The first consideration is whether the crop can realistically be sprayed, which of course depends on the equipment available and the height of the crop. That said, it is surprising how effective knapsacks can be for even 50 or 100 acres.
Assessing the risk and the likely return depends on a number of factors, including the variety being grown, previous cropping, plant health etc.
Last treatments done on the maize nutrient and disease control trial yesterday🌽✔ pic.twitter.com/Ql9OY7lKnZ
— David Jones (@Cropnuts_agron) July 28, 2019
Our trials last year in the very low risk variety PAN 691 still showed up to a 7% yield increase from the application of a fungicide at Tassling and the R2 stage of grainfill. A yield increase of one and a half bags per acre (140kg/ha) normally covers the cost of the chemical and the application.
The table below gives an indication of a few common varieties from our trials sites across the country. Remember, just because a variety has a poor disease rating does not make it a bad variety. P3812W has a very high yield potential provided the Rust risk is managed, as can Grey Leaf Spot be protected against in H614.
|Low Disease Pressure||Moderate Risk||High Risk|
|PAN 691||DK 9089||P3812W|
|SY 594||4m-19||DK 8031|
|30G19||SC Twiga 83||H614|
|DK 777||H6213||SC 403|
If the site has grown continuous maize for several years, disease inoculum from Grey Leaf Spot and Northern Corn Leaf Blight is likely to be carried over on the previous crop residue. Rust however tends to appear regardless, so I tend to treat DK 8031 regardless of the previous crop (the short stature of 8031 helps spraying operations too).
Weather conditions can form part of the decision process, but we cannot predict the weather a month ahead. That said, a crop flowering in the August rains will highly likely be at a greater risk of Leaf Blight, especially in a continuous maize situation.
If you are going through the crop to spray for Fall Armyworm, the decision to add a fungicide is a lot more straightforward.
Once the decision is made to spray, choose a quality product – for a me a strobilurin is a must – and apply it accurately at a sensible dose to give the persistence of protection. This is also a great opportunity to top-up any late foliar micronutrients after a leaf test.
Farming for the future requires a change of approach. Monoculture, soil degradation and climate change and soil degradation are threats to the futureof how we feed the planet. Agventure Ltd set up the Center of Excellence for Crop Rotation to help farmers diversify cropping systems and introduce techniques which have a long-term outlook to improve soil health. The Center of Excellence for Crop Rotation works extensively with Crop Nutrition Laboratory Services Ltd (CropNuts).
Till next time,
David Jones is the Broad Acre Specialist at Crop Nutrition Laboratory Services Ltd. (CROPNUTS). David has a keen interest in soils and no till farming systems where he has undertaken work looking into weed levels and changes in soil structure, and has extensive experience in field trials and in the development of precision farming techniques. In his spare time he enjoys playing rugby.