This season’s pea fungicide work has highlighted again the effectiveness of elemental sulphur for controlling Powdery Mildew. Alternatives with known activity on the disease were tested including metrafenone, triadimefon and azoxystrobin + cyproconazole but while useful, but none were quite as effective as elemental sulphur. All of these products are preventative so must be applied before the disease is becoming established.

2kg/ha of elemental sulphur provides around 3 weeks protection, so if applied at flat pod stage the application will likely need to be repeated to ensure a clean crop at harvest.

Molecular disease diagnosis services to help guide grower decisions

Cropnuts now have a molecular disease diagnosis service, the first of its kind in East Africa, which will allow growers to identify not only the presence of a particular disease but the pathogen race. This will help us better understand the changes in Stem Rust and Blight Races across the country and potential control strategies.

In potatoes for example, Fluazinam insensitivity in Blight is yet to reach Kenya, meaning that for the time being the fluazinam is still a very effective way of controlling Tuber Blight. Virus detection will also be available, helping potato growers make decisions about farm saving seed or purchasing new seed.

Plant pathologist Rose Nyakundi next to an ultra modern molecular diagnosis PCR machine that offers added quality, more accurate plant disease screening at Cropnuts lab facility

Wheat varieties

This season’s variety trials are once again highlighting the susceptibility of the current crop of varieties to Stem Rust. Hawk is equally as bad as Robin, Korongo only slightly better, Eagle showing significant infection, while only Eldo Baraka and Mavuno remain spotlessly clean.

Thankfully many of the new varieties are still very clean – Brambling for example in its fourth season of trials is rated a 7 out of 9 for its resistance to Stem Rust.

No Limits Canola

Given the potential that we know exists across many parts of Kenya for growing very good canola crops, and the fact that we now have several varieties in trials that are showing an improvement of 15-20% in yield over Belinda it leads me to ask; “how would I grow the ultimate crop if I were entering a yield competition”.

Firstly, let us disregard costs. This is an important imperative because in my experience once you have identified a way to meaningfully increase yields, you invariably find a way to do it that covers the additional costs involved.

Take the German Yield Enhancement Network competition for example, in which the highest yielding crop last year was also the most profitable despite the fact that the farmer spent 30% more per hectare than the average entrant.

My greatest priority would be establishment, and accurate seeding. If I could pick any variety that is currently in trials it would be Lexus, and I would establish 10 plants per square meter with a precision planter.

An important consideration is to avoid Group B (sulphonylurea) herbicide residues that may have been applied to the previous crop, and I would absolutely want to have had the soil tested and limed 6 months previously if required.

A site that has not grown brassicas for 6 years too will be a big benefit – this reduces soil borne pathogens such as Clubroot, Verticillium Wilt and Olpidium Brassicae. In-furrow fungicides can help with these to an extent, and improve establishment too.

On a very high fertility site I would apply a tebuconazole or metconazole growth regulator to control the size of the canopy and reduce stem leaning. Remember that stems leaning just 20 degrees at mid seed fill can lose up to 20% of yield.

This can also be helped by managing topdressing, and not applying fertiliser too early. Two doses of nitrogen and sulphur at 5-6 leaf, and the main dose at green to yellow bud stage should be targeted, and on most soils in Kenya, a foliar application of molybdenum and boron at the 4-5 leaf stage with a fungicide.

For a long canopy duration and to minimise yield loss from Sclerotinia, two flowering fungicides would be applied, containing either prothioconazole, boscalid or azoxystrobin.

And the final part of the equation – no desiccation. If the crop is uneven in maturity to the extent that the greater risk to yield is early ripening pods shattering, then of course desiccate. Otherwise, leave the crop to fill the seeds for as long as possible. This keeps recurring in research into high yielding canola crops.

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,


Barley farming in narok kikuyu laikipia eldoretAbout 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.