Despite all the resources that 21st Century science has to offer, Phytophthora infestans, the organism responsible for potato late blight, remains one of the potato grower’s toughest challenges. One particular strain – ‘Blue 13’ has come to dominate UK blight populations following its emergence in European potato crops back in 2005, explains Certis’ sales manager Peter Shakespeare. “This particular strain belongs to the A2 genotype of potato late blight which is capable of sexual reproduction and has the potential to reproduce further and develop new strains. “Blue 13 is a ‘fitter’ more aggressive strain,” explains Peter. “It’s capable of reproducing very quickly and at lower temperatures than before, which is probably why it’s so successful.” With the reproductive cycle completing in only four to five days under optimum conditions, it can spread very rapidly – producing a seemingly endless number of spores able to cause further infection. “Blue 13 has almost certainly driven the tightening of blight spray intervals with seven days now the basis of most strategies,” comments Peter. “Appropriate fungicides selection is critical,” he advises. “It’s important to know your products and their key strengths and attributes to ensure you’re best equipped to prevent the spread of infection,” believes Peter. Fungicide selection should reflect the variety and stage of growth and applications should be timed accordingly to effectively delay the onset of blight. “Growers should be looking to inhibit the pathogen before it has any chance of penetrating the leaf. ‘Kick-back’ activity assists with this, offering retrospective control over infection that comes into the crop in the past 24 hours. “Fungicides providing systemic activity will also help protect new growth with complete spray coverage often impossible.” Valbon (benthiavalicarb-isopropyl + mancozeb) is one option, giving growers not only strong persistence and protection against leaf penetration but also important ‘kick-back’ action preventing the disease from penetrating the leaf, explains Peter, noting that getting the timing right is all important to make the most of this ‘kick-back.’ “With additional translaminar activity Valbon can move from the upper leaf surface to the lower – vital during that rapid canopy growth period and within dense canopies. “The benthiavalicarb component provides activity actually controlling the disease, preventing sporulation and germination and inhibiting the mycelial growth that can invade tissue,” explains Peter. “And the inclusion of mancozeb, has a proven benefit of preventing blight, stopping the release of spores and also eliminating the risk of disease resistance,” he adds. “In trials Valbon has also shown activity against early blight (Alternaria spp.) – an increasingly serious problem for growers.” |