Disease monitoring pinpoints fungicide need and timing in brassicas

Brassica growers must monitor disease risk accurately and be prepared to pinpoint when and what type of fungicide to use on their crop to ensure that the produce remains completely disease-free. The integrated use of weather stations and disease monitoring systems to gauge the need for treatment plus the use of appropriate fungicides are essential to prevent the incursion of damaging diseases such as Alternaria, white blister, light leaf spot and ringspot in brassicas, according to independent vegetable consultant, Fred Tyler.

"It has been a strange year weather-wise, but pest and disease control in brassicas has been relatively easy up until recently. This is probably because brassicas have been smaller than normal and the soil has dried out, leading to much lower humidity within the crop canopy and so less disease risk. A blessing in disguise! But more recently decision support systems such as weather stations and spore traps have indicated an increasing disease risk," says Fred.

"Because of the continuing and relentless pressure from retailers, there is a heavy reliance on justifying the need for fungicides. I use a number of different systems to monitor risk and to help in decision-making, including Brassica Spot and the new spore trapping systems. The former was developed by Dr. Roy Kennedy of Warwick HRI and is an accurate monitoring system using environmental and host information to indicate conditions for disease development. The risk of disease is calculated on a daily basis and is displayed on the internet as a bar chart over time," explains Fred.

"Lateral flow detection devices, rather like home pregnancy kits, are also available and measure the level of airborne spores from the field, providing fast, accurate estimates of the actual risk of disease development in a specific area. Lateral flow devices are now available for Alternaria, light leaf spot and ringspot, and are proving to be very useful tools. The experts are also working on a new device to detect soil inoculum for clubroot which will be valuable not just for brassica growers but also for oilseed rape growers. Decision support systems ensure that growers are fully justified in their use of fungicides and that these products are only used when absolutely necessary and at precisely the right time."

"As an advisor I need to make sure that the crop is well protected from diseases and ensure that there is no over-use of treatments," explains Fred.

"The brassica grower now has a reasonable choice of fungicides and Signum is just one of the excellent protectant fungicides available. As a protectant, it is best used in advance of disease, hence the need for accurate and local disease monitoring systems. It is also a good product to use when there is more than one disease present, as it controls a wide range of brassica diseases, including Alternaria, white blister and ring spot. It has also been used for light leaf spot which is prevalent north of the border, and this usage is particularly important as there is significant concern about this disease becoming less sensitive to the standard treatment of tebuconazole. Monitoring disease risk and timings will make sure that Signum and other fungicides are used only when there is a proven need," reports Mr. Tyler.

Fred has also noticed the positive physiological effects that Signum has on the crop and the combination of disease control and stimulant particularly at establishment mean that he intends to use a lot more next year.

Simon Townsend, Agronomy Manager for BASF advises that Signum should be applied to brassicas before signs of disease when the monitoring systems indicate that disease is likely. It is recommended at a dose rate of 1 kg/ha in a minimum water volume of 200 litres. Sprays can be made at 3 to 4 week intervals, alternating with products from a different chemical group.

Signum has label recommendations in Brussels sprouts, cabbages and cauliflowers for the prevention of dark leaf spot and white blister plus useful control of ringspot. Both actives in the product, boscalid and pyraclostrobin, also have activity on powdery mildew. There are also a number of SOLA's, including protected and outdoor leafy brassica crops grown for baby leaf production, outdoor and protected Chinese cabbage, outdoor collards including spring greens and outdoor kale.

Background Notes - Signum contains 267g/kg boscalid and 67g/kg pyraclostrobin, formulated as a WDG. It is a protectant and systemic fungicide. It is recommended in Brussels sprouts for the control of white blister (Albugo candida) and ringspot (Mycosphaerella brassicola) and in cabbage and cauliflower for the control of dark leaf spot (Alternaria brassicae) and ringspot. Signum is applied as a protectant spray or at first signs of disease at a dose rate of 1 kg/ha in a minimum of 200 litres of water. Further sprays can be made at 3 to 4 week intervals. It is subject to LERAP B and has a harvest interval of 14 days for brassicas.

For further comment and information please contact;

1) Matthew Blaken, BASF on 0161 488 5902 or 07748 932555 (mobile)

2) BASF technical services hotline 0845 6022553

3) Jo Palmer of Prime Contact Communications on 01760 724469 or 07836 584034

Signum contains boscalid + pyraclostrobin.

Signum is a registered trademark of BASF.

ALWAYS READ THE LABEL. USE PESTICIDES SAFELY.

www.agriCentre.basf.co.uk

BASF is the world's leading chemical company: The Chemical Company. Its portfolio ranges from chemicals, plastics, performance products, agricultural products and fine chemicals to crude oil and natural gas. As a reliable partner to virtually all industries, BASF's high-value products and intelligent system solutions help its customers to be more successful. BASF develops new technologies and uses them to meet the challenges of the future and open up additional market opportunities. It combines economic success with environmental protection and social responsibility, thus contributing to a better future. BASF has approximately 95,000 employees and posted sales of €52.6 billion (approximately $66.1 billion) in 2006. Further information on BASF is available on the Internet at www.basf.com.