Wheat diseases and Fusarium head blight: when to spray
Wheat is sprayed against Fusarium head blight at flowering, as soon as about 5% of ears show anthers, and ideally before forecast rain. The best window lasts only a few days. Leaf diseases (powdery mildew, Septoria, rusts) are controlled earlier, from stem elongation. If rain shuts the field right at flowering, the drone sprays as soon as the access road to the field dries.
By Nikola Mojsa, MSc in Agricultural Engineering
The most common wheat diseases and how to recognise them
According to Agrosava, three leaf diseases are controlled from stem elongation, and the table also shows the yield loss each of them can cause. The fourth disease, Fusarium, attacks the ear itself.
| Disease | What it looks like | Yield loss (Agrosava) | When to control it |
|---|---|---|---|
| Powdery mildew | White, powdery coating on the leaves | up to 20% | From stem elongation, preventively or at the first symptoms |
| Septoria leaf blotch | Chlorotic spots with tiny black dots (pycnidia) | 30 to 50%, in wet years | From stem elongation |
| Rusts | Orange pustules on the leaves and stem | up to 70% | From stem elongation |
| Fusarium head blight | Spikelets lose their green colour and turn straw-yellow or white; grains are shrivelled, white to pink (Agrotop, V. Savić) | Yield, plus mycotoxins in the grain (Forecasting and Warning Service, AgroSmart) | At the start of flowering |
These losses show the damage a disease can do in a bad year, not an average. Fusarium symptoms only become visible after flowering, when it is already too late to spray, so the treatment is timed by crop stage, not by symptoms.
Fusarium head blight: why the spraying window is short
Infection happens at flowering, in wet weather above 20 °C, and raindrops spread the spores (PSSS Padinska Skela, Eleonora Onć Jovanović, MSc). The disease appears regularly in warm spells with frequent rain during flowering and grain fill (Agrotop).
The treatment goes on at the start of flowering, when about 5% of ears show anthers, and before forecast rain. The Forecasting and Warning Service (PIS) advises a single treatment at exactly that point, because several days of rain at flowering significantly raises the risk of infection (AgroSmart, PIS). The start of flowering is therefore the key decision point.
After a wet May in 2019, PSSS Padinska Skela recorded 38 to 64% infected ears on the fields it inspected in early June (PSSS). That is why the treatment date should be agreed before flowering starts.
When to spray wheat: from stem elongation to flowering
Disease protection in wheat usually takes two sprays.
The first spray goes on at tillering and the start of stem elongation: a fungicide against leaf diseases, preventively or at the first symptoms (Agrosava). If there are no sensitive crops around the field, a herbicide can go on in the same pass. One of the products Agrosava lists can be applied from stem elongation to full flowering (BBCH 30 to 65); always check the label for the exact stage for your product.
The second spray, at flowering, is the fungicide against Fusarium head blight. The Forecasting and Warning Service lists groups of active ingredients: triazoles (tebuconazole, prothioconazole, difenoconazole), strobilurins (azoxystrobin, trifloxystrobin) and others (AgroSmart, PIS). Your agronomist chooses the product and rate according to the label. If cereal leaf beetle appears late, an insecticide is added to the second spray.
When rain shuts the field: spraying wheat at flowering by drone
The fungicide at flowering is the most important wheat spray we do by drone. The rain that raises the Fusarium risk also soaks the field, so a tractor usually waits 2 to 5 days for the ground to dry, and the window can close in that time. The drone only needs the access road to the field to dry, and if a tarmac road leads to the field, we work the same day after rain.
On fields grouped close together we cover about 20 ha an hour, with 15 to 20 litres of water per hectare. We fly in winds of up to 3 to 5 m/s and don't work in the worst of the heat. The drone flies about 3 m above the crop, and the downdraught from the rotors pushes the droplets down to the lower leaves. Our agronomist Nikola mixes the product at the field; you supply the product and the water.
Before an insecticide spray we notify nearby beekeepers so they can close their hives in time.
What spraying wheat at flowering by drone costs
Drone spraying costs €25, €22 or €20 per hectare for areas up to 20 ha, from 20 to 100 ha and over 100 ha. We don't charge for travel within 50 km of Opovo, and new clients get the first hectare free on a first order of at least 10 ha. For comparison, contract tractor spraying in Banat costs about €30 per hectare. Three treatments on the same field in a season (for example herbicide and fungicide in spring, foliar feeding, and the fungicide at flowering) get 5% off, and five or more get 10%; clients with a package get priority when booking flowering week. Check the price for your field in the calculator.
Frequently asked questions
At the start of flowering, when about 5% of ears show anthers, and ideally before forecast rain. The weather forecast and your agronomist decide the exact day.
Orange pustules on the leaves and stem. Powdery mildew shows as a white, powdery coating, and Septoria as chlorotic spots with tiny black dots (Agrosava).
Yes, the fungicide at flowering is the most important wheat spray we do by drone. We also spray when the field is wet, as soon as the access road to the field dries, and the same day after rain where a tarmac road leads to the field.
- First hectare free
- Free travel up to 50 km
Book a date before flowering
Everyone wants the flowering fungicide in the same few days. Tell us how many hectares of wheat you have, where, and when you expect flowering, and we will book your date in good time.