Growing Greener Broccoli

A recent rise in the demand for Broccoli has been good news for local growers.  It appears that the message of health benefits from green vegetables is reaching the public.  More widely, there is now greater emphasis on reduced chemical inputs to edible crop production, which is good news for both consumers and the environment.

The College of Agriculture, Food and Rural Enterprise (CAFRE) is undertaking trials on the ‘biological control’ of club root disease (Plasmodiophora brassicae), a serious soil pathogen affecting all members of the Cruciferae family such as broccoli, cabbage and cauliflower.  In conjunction with Stephen Murdock, a local grower, the CAFRE team will be comparing selected biological controls, which use naturally derived products and even living microorganisms as a substitute for chemicals.

Stephen has planted his 2010 crop in a field near Comber which lies alongside the River Enler and is appropriately called the ‘Long Bog’.  It sometimes floods in winter and this flooding may have introduced the club root disease. Infection causes root cells to multiply and distort severely as the fungus develops. Infected plants can’t take in water and nutrients properly, so they wilt and collapse in dry weather.

Biological control technology has already given positive results elsewhere in the world.  The investigations by CAFRE will determine if the same benefits can be achieved for Northern Ireland produce.  “Biological control often refers to insects eating other insects,” explains Dr. Anne Stone of CAFRE, “but it can also refer to beneficial microbes out-competing those that cause disease, or inhibitory compounds gleaned from natural sources.  Technology work using biological products, including garlic products, may strengthen plants to keep the club root at bay”.

Stephen is very interested in the project, as club root is the single greatest disease threat to his crop.  “Broccoli is quick to grow and there’s not usually time for diseases to establish. Any leaf spots don’t spread onto the broccoli head itself, and we can simply cut them away, but club root affects the growth of the whole plant, so early control is essential.”  He has already noticed an incidental benefit from applying the garlic-based spray.  “I find that spraying seedlings with garlic puts off pigeons and rabbits from eating the young crop; it would be great if it would put off the diseases as well!”

Anne Stone, CAFRE; Stephen Murdock, Comber