Disease monitoring spells success

Disease free vegetables are essential in today’s market. The production of blemish free vegetables requires constant vigilance by the grower in order to apply timely disease control measures to ensure clean wholesome produce. One of the most common diseases in leafy vegetable crops is ringspot. This causes unsightly black spots on the produce which, if severe, can render the crop unmarketable. The disease is spread by airborne spores which infect the plants if weather conditions are conducive to spore germination and development.

It is possible to predict, using weather data and software developed by Warwick Horticultural Research International, when ringspot spores would have optimum conditions to germinate. The disease prediction indicates when control measures should be applied to prevent disease development. The technology has been adopted successfully for the past three years by a number of growers in Northern Ireland, as a follow on from work undertaken by Greenmount Campus demonstrating its effectiveness in local conditions.

However while the model predicts optimum conditions for spore germination it currently does not indicate if spores are actually present. Detecting spores in the air and using this information in conjunction with the weather data will give enhanced control.

Greenmount Campus is currently evaluating a new technique of spore trapping in association with HRI Warwick. Two growers, James Chambers and John Herron both from Comber, are participitating in the project. A spore trap is placed in a brassica field at crop height and is monitored on a weekly basis. The rationale is that if spore numbers do not reach the threshold level for the disease, control measures are not be justified despite suitable conditions for spore germination.

The monitoring has taken place in Comber for the 2005 growing season with the model predicting the need for control measures on four occasions. The growers would normally act on these predictions. However spore numbers exceeded the threshold level on only two of these occasions. This information enabled James and John to make the decision that control measures were therefore only necessary on two of the four occasions. The outcome of this crop management decision was the production of a quality, blemish free crop. Hence this technique of spore trapping shows promise in aiding crop management decisions while reducing disease control measures.

In 2005 the spore trap from the field was sent to a laboratory for counting, however technical advances will allow a rapid “in-field” test, developed by Dr Roy Kennedy, Warwick HRI, to give a positive or negative result depending on the number of spores present. These kits will allow a rapid way of obtaining disease risk data negating the need for laboratory analysis.

Staff from Greenmount Campus will continue with this project next year to further validate the technology.

If anyone wishes further information for disease monitoring for leafy vegetable crops please contact Joan Hamilton, Edible Crops Adviser, Greenmount Campus on 02894426683.

Joan Hamilton, Edible Crops Adviser, Greenmount Campus, John Herron, grower, Colin Alexander, On Farms Team, Greenmount Campus and James Chambers, grower, displaying quality vegetables grown using the spore trap monitoring technology.