Facial Eczema (FE). Farmer Information. Part 2. Fungicides in FE control.

Agriculture, Farming, animal husbandry, animal health, animal diseases, Facial Eczema, spraying, prevention, fungicides.

By Dr Clive Dalton

Original 1991 information written by Dr Barry Smith and Dr Neale Towers, Ruakura Agricultural Research Station, Hamilton, New Zealand.

Through the microscope, spores of Pithomyces chartarum look like brown hand grenades among the other debris on the slide.

Part 2. Fungicides in FE control.


Background

• Spraying with fungicides in late January or early February reduces the growth of the FE fungus in the pasture base and lowers the numbers of spores formed when weather conditions are dangerous.
• Pastures sprayed early remain safe for 4-6 weeks.
• Fungicides reduce the number of toxic spores produced during a danger period by 55-65 percent. They do not completely eliminate spore production.
• To achieve best control, apply fungicides before spore numbers rise.
• Except in years when conditions are extremely dangerous properly applied fungicides should prevent FE. Under extremely dangerous conditions fungicides will give partial protection markedly reducing the severity and costs of the outbreak.
  

Spraying Strategy
Farmers can spray all or only part of their farms. Individual management options, likelihood of severe outbreaks, economics and the terrain will decide strategy.

1. Spraying total grazing area

• Requires suitable farm contour for ground or aerial application to total area. This method is used on dairy or deer farms where stock managers want unrestricted access to all available grazing on their property.
• This is a relatively high cost but very effective option suited to high producing areas or to protect high value animals.
• Monitor pastures occasionally to check whether they are still safe.
• Respray after 5-6 weeks until all danger of FE has passed.
  

2. Spraying part of grazing area

• Part of the farm (perhaps one third) is sprayed to provide an area of safe pasture for grazing during dangerous conditions.
• When spore counts are high, or danger warnings are issued, stock are moved onto the sprayed pasture.
• It may then be necessary to spray a further area to provide safe pasture for the animals after the finish of the original sprayed pasture.
• This method minimises the initial cost of spraying but requires ongoing monitoring of the pastures the animals are to graze to ensure that it is safe.
• Decisions to spray additional pasture should be made early to ensure the spray is applied before dangerously high spore counts are established.
  

Fungicide sprays currently recommended for controlling FE spores are:

• Benomyl (Benlate)
• Thiophanate methyl (Topsin M4A).
  

DO NOT use orchard type fungicides such as Mancozebs (e.g. Dithane M45). They are excellent on fruit and vegetables but totally ineffective for controlling pasture (FE causing) fungus.

Spraying Techniques

• Complete spray cover is essential. Include stock races, fence lines and under hedges and shelter belts.
• Use clean water and clean equipment.
• Boom spray only. Rosette type applicators are not sufficiently accurate.
• Spray at the rate of 220 litres water/hectare. Avoid fluctuations of vehicle speed.
• Fungicide application rates and costs:

• Spray in settled weather. Rain in excess of 25 mm in a 24 hour period within 3 days of spraying will reduce the efficacy of the fungicide and make respraying necessary.
• Respray pasture after this time, or respray if additional safe pasture is required.
• Allow 5 days for mid-season spraying for pastures to become safe; only graze earlier in emergency.
• Do not spray pasture with spore counts over 200,000. The fungicide will be ineffective and the pasture will remain dangerous to stock.

Disclaimer

This material is provided in good faith for information purposes only, and the author does not accept any liability to any person for actions taken as a result of the information or advice (or the use of such information or advice) provided in these pages.