Partnerships for good hygiene
Nursery managers need to keep a constant watch on crop hygiene, rather than 'fight fires' when problems emerge, argues Dr Martin McPherson of STC
Nursery managers can take one of two approaches to the risks associated 
with plant disease. Firstly, there is the ‘fire brigade’ approach whereby diagnostic action is taken following the appearance of an unexplained crop problem. Secondly, there is the ‘routine monitoring’ approach whereby the grower is aware of the main risks from pests and pathogens in a specific crop and undertakes a routine inspection and testing programme to minimise risk. According to Dr Martin McPherson of Stockbridge Technology Centre in the UK, the latter approach is most advisable as it helps prevent economic loss through early detection. In the former ‘fire-brigade’ situation, it is more a case of identifying cause of loss that has already occurred - with the hope that similar problems can be avoided later.
Minimise risk at every step
‘Growers shouldn’t simply ignore the risks to plant health from serious pathogens until a problem arises. By then, it is often too late to prevent significant loss as many pathogens are capable of rapid spread in advance of visible symptoms and this makes the implementation of control more difficult’, says Dr McPherson. ‘A far better route is to minimise the risk from disease at every step of production, but particularly early, and then to reinforce this with regular monitoring of plants, especially those that show unusual symptoms.’
Stockbridge Technology Centre operates an industry-focused plant diagnostic clinic. With many years of experience in horticulture, Martin and his colleagues provide wide-ranging advice to growers on problems with their crops. ‘All too frequently we see samples in the clinic where a pathogen has caused widespread infection before a decision was made to seek diagnostic advice. Local, on-site testing, backed up with laboratory confirmation, is the ideal situation.’
On-site tests give early indication 
Of course, it is not only pathogens and pests which result in crop loss. Physiological or nutritional imbalances and even crop protection products occasionally can cause crop damage, and the symptoms are often difficult to distinguish. Again, Martin can see value in on-site testing to rule out some pathogens as potential causes for the crop damage. ‘However, it is often only laboratory analysis which will identify the primary problem, but it can be worth on-site testing for Phytophthora or Pythium if the crop is wilting or there is visible evidence of root decay’, continues Martin as this might provide an early indication of cause to help make decisions regarding fungicide application a little quicker.
Maintaining high standards of crop hygiene requires careful planning and well-tried procedures. Trained staff have a role to play in ‘scouting’ to spot unusual or unthrifty plants which might indicate an emerging problem. ‘The grower must take first-line responsibility for crop management and Pocket Diagnostic tests can help him in this task. However, while a test result will give an indication of infection and allow early intervention, laboratory confirmation is advisable to ensure there are no other underlying cultural or chemical problems which have predisposed the plants to infection’, says Martin.