The BASF and ADAS sponsored Sclerotinia monitoring system for carrot growers has started once again and growers and advisors are now able to log-on until August via the carrot Sclerotinia Monitoringlink on www.agriCentre.basf.co.uk to see what is happening out there. The system monitors sclerotial germination of the Sclerotinia pathogen and indicates the extent of disease risk and the need for fungicide treatment. Growers should check published information on the website on a weekly basis and be ready to take the right action at the right time.
Dr Caroline Young from ADAS explains that carrots are vulnerable to Sclerotinia infectionwhen the sclerotia (resting bodies) germinate in the soil, about one month after sowing if conditions are right. Sclerotia produce fruiting bodies, apothecia, which release spores into the air which can infect carrot crops. Sclerotia germinate when the soil is moist and soil temperatures are 10C and above. Already soil temperatures are greater than 10C and the soil is moist enough, particularly in irrigated crops.
The risk of Sclerotinia is based on three key factors working together firstly are there sufficient sclerotia within a few cm of the soil surface in the carrot field? Secondly is there sufficient moisture and soil warmth to encourage their germination? And thirdly is the crop at a vulnerable stage? The vulnerable stage begins when the oldest leaves, the cotyledons and first leaves, start to senesce, she says.
Most carrot growers start their fungicide applications, before the canopy closes over, and they aim get their fungicides, most of which are protectant, right down to the base of the plants. Once Sclerotiniais in the crop, it is almost impossible to control.
The fungus invades diseased, senescing and decaying leaves, particularly those at the base of the plant where infection starts,she explains.
Dr Young reports that normally canopy closure takes place from mid-June to late July, depending on sowing date and growing conditions. Starting the control programme before the canopy closes is important. Most growers apply three fungicides in a programme, alternating products with different modes of action to minimise resistance risk.
Robert Storer, FieldVegetable Product Manager for BASF, says that disease monitoring and fungicide timing are important for the successful prevention of Sclerotinia in carrots. Signum is a protectant fungicide,as are most fungicides in this sector, so it needs to be placed at the base of the plant before infection starts and where old leaves come into contact with the ground. For this reason the first Signum spray is recommended before the crop canopy closes over and the ground is still visible. It should then be alternated with other fungicides that work in a different way as part of an anti-resistance strategy. Signum can be applied twice to any crop.
Signumis fully approved in carrots and provides broad spectrum disease control of Sclerotinia, Alternaria and Powdery Mildew. The physiological, AgCelence,benefits of Signumplay an important role in maintaining the canopy greener for longer, says Rob.