Vegetable News September 2006

Development of downy mildew is favoured by high humidity especially in autumn when night temperatures are low.

The incidence of mildew in brassicas this season has been high. This disease causes affected areas on leaves to become yellowed with black speckling in most brassica crops. However in sprouts it is often confined to the buttons which show the black speckling. They may also show yellowing and in severe cases may be unmarketable.

Products used to control white blister will also control downy mildew.

Downy mildew is a serious disease on scallions spreading rapidly from initial infection. Typically mildew starts in several locations in the field and spreads to surrounding plants. Wet conditions coupled with high plant populations provide the perfect environment for disease spread and crops can be entirely destroyed.

Downy mildew is difficult to control once in the crop so prevention is very important. A SOLA has just been issued for Invader (dimethomorph + mancozeb) for control of mildew on scallions. Invader is a systemic and protectant fungicide with a 14 days harvest interval.

This now offers growers the option of five fungicides for mildew control. The others are Amistar (SOLA 1687/02), Fubol Gold (SOLA 2324/03) SL567A(SOLA 1515/05) and Aliette (SOLA 0548/05).

It is good practice to use chemicals with different modes of action to help prevent resistance of the disease to the chemical developing.

The disease can survive on crop debris so prompt destruction of this

is essential to reduce disease spread.

The Carbon Trust is holding a seminar on Renewable Energy Opportuntiies for Businesses on 25 October 2006 at the Tullyglass House, Ballymena.

This will cover areas such as Building Regulation, Wind Energy, Energy from Waste, Biomass Energy, and Solar Energy Technology

For information or to register your interest in the workshop phone The Carbon Trust 028 9073 7913 or log on to http://www.carbontrust.co.uk/Events

The SOLA No 0729/06 for Hallmark on carrots and parsley which originally only allowed a rate of 100ml with four applications has been amended to allow 150ml per ha with four applications

Leek growers have a greater choice of products for control of white tip. Elvaron Multi and Signum have both recently received off label approval. Up to five sprays of Elvaron and two of Signum can be used. This will reduce growers’ reliance on Folio for control of this disease.

Nativo 75WG (tebuconazole + trifloxystrobin) has received provisional approval for use on Brussels sprouts, cauliflower, calabrese, carrots and leeks. Tebuconazole (the active ingredient in Folicur) is a systemic conazole fungicide with activity against a number of diseases. Trifloxystrobin is a protectant strobilurin fungicide.

The combination has activity against a number of fungal pathogens including white blister, ringspot, powdery mildew, alternaria, rust and white tip.

Note that Amistar is also a strobilurin and to prevent resistance developing these chemicals should be used with other fungicides with a different mode of action. No more than half total applications to a crop in any season should be strobilurins.

The following SOLAs have been issued since the last Vegetable news

Joan Hamilton

Edible Crops Development Adviser

Greenmount Campus, College of Agriculture, Food and Rural Enterprise

Telephone (office) 028 9442 6683

Mobile number 077 7575 7251