Fusarium head blight fungicide timing

FUSARIUM HEAD BLIGHT

Fusarium Head Blight is a serious risk to wheat, and the risk is greatest after maize when the disease is transferred from the residue of the previous maize crop, to the wheat. So with many farmers having failed to get continuous maize fields planted this year and resorted to wheat instead, there is a real risk of Fusarium head blight impacting on wheat yields and quality.

Fusarium head blight wheat heads scabs on head

Above: The line of wheat varieties at our Nakuru trials site this year had no fungicide applied (for disease assessment purposes) on the left, and 200g of tebuconazole on the right. A very noticeable reduction in Fusarium with the fungicide!

Fusarium Head Blight Fungicide

Fusarium species not only impact yield and quality, but also produce mycotoxins in the ear which are damaging to human health. Thankfully a well-timed fungicide will drastically reduce infection.

As a general rule there are three triazole fungicides which are useful in this respect; tebuconazole which is in-expensive and effective, prothioconazole as in Prosaro and Skyway, which is the very best, and metconazole which is also quite effective.

Do not be tempted to apply low rates. 200g of tebuconazole, or 100g each of prothioconazole and tebuconazole are what you should be aiming to apply if there is any risk. Remember that a good flag leaf fungicide will also reduce the fusarium pressure if it contains prothioconazole.

A dry start to the year as we have experienced in 2019 actually increases spore production, so the risk this year is automatically higher. A lot of wheat crops are after maize this year too which produces a lot of Fusarium on the trash, and a cooler, wet flowering period then raises the risk further.

Secondly, factor in the risk of the variety. White wheats with open glumes such as Korongo and Nduma are a high risk, as is the red variety Tai. Also bear in mind that varieties with protracted flowering such as Kwale also make it very difficult to effectively time an ear fungicide.

In Stem Rust situations I also tend to apply azoxystrobin to my ear sprays – while this will not control true Fusarium and mycotoxins, it is very good at reducing Microdochium ear blights which affect yield and quality severely, and is a solid protectant before the Stem Rust appears.

Ear sprays should be targeted at early anthesis BEFORE the infection event, and Defy 3D nozzles are the best for coating the ear effectively.

fusarium head blight wheat heads scabs on head

Optimum ear spray timings for Fusarium control, Courtesy of the AHDB, UK.

 Fall Armyworm update

Looking at maize crops in Timau, Aberdares, Ol Kalou, Naivasha, Nakuru, Eldoret and Nyahururu last week once again highlighted the very low levels of Fall Armyworm in – most – parts of the country.

Whatever the cause of this, the focus now must be on continuing to monitor crops for signs of infestation and damage. In the most advanced crop I looked at last week there were actually signs of 1st to 2nd instar Fall Armyworm larvae in 50% of all silks, so although the crop may look unaffected the risk is still high.

Remember, there are no good established thresholds and spraying when the larvae are small is crucial. To help with the decision making on what you need to do now, please take a look at the video below in a maize field near Nakuru….

Center of Excellence for Crop Rotation Agventures

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,

Happy farming,

David,

David Jones cropnuts

About David

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.