A flexible drift retardant, specifically designed for use with blight fungicides, could play an important role in keeping potatoes disease free this spring, according to adjuvant and biostimulant experts, Interagro.

Keeping late blight out of potatoes is a season long campaign for growers. It also seems to be getting tougher as the years go by, given resistance to fluazinam and a regular shift in blight populations. So, a robust resistance management strategy, which improves coverage is essential to safeguard crops and chemistry, said Stuart Sutherland, technical manager at Interagro.

“Keeping spray intervals tight is a practice that growers have become familiar with, but it isn’t without its challenges when unfavourable conditions mean spray days are few and far between. Drift is the biggest cause of off-target chemical movement and increases the threat to the crop from late blight where it’s not adequately protected.”

While full crop coverage is vital to prevent scattered infection, the ‘umbrella-like’ structure of the plant canopy – a series of interlocking leaves – makes this difficult to achieve. “Leaves are good collectors of vertical moving spray in the upper canopy but leaves and stems lower down can be very hard to reach – moving the risk of tuber blight to the whole crop,” he said.

So what’s the solution? Developed to help tackle the practical problems growers face, Interagro’s Crusade is a flexible drift retardant specifically designed for use with all blight fungicides to reduce drift and maximise coverage to all parts of the crop canopy.

“It has been specially designed to maximise the performance of blight fungicides in potatoes, by increasing the proportion of spray droplets in the optimum size category for drift reduction and target leaf retention,” said Mr Sutherland. “Research in the field has continually proven that adding Crusade to fungicide sprays helps to maximise coverage to all parts of the canopy, preventing scattered infection and ensuring maximum protection to the whole crop.”

In practical terms, Crusade reduces the fine droplets prone to drift, and optimises droplet size in the upper end of the spectrum that enable the spray droplets to penetrate the canopy lower down and be retained.

“To get the best out of blight protection chemistry, droplets cannot be too big – because they’ll bounce off the leaf and miss the target – or too small, which could mean they may evaporate and drift off-target. They have to be just right.

“Crusade creates droplets more capable of reaching the upper and lower canopy and significantly reduces the number of fine spray droplets, smaller than 100 microns, that are the most susceptible to drift.

“With it, the spray angle (usually 110 degrees) is more closely maintained, improving application, helping to ensure the correct dose is applied to the target. The addition of Crusade to fungicide sprays therefore helps to optimise coverage to all parts of the crop canopy, preventing scattered infection and ensuring maximum protection to the whole crop.”

With a flexible application timing and no growth stage cut-off, the adjuvant can be used throughout the blight control programme with a wide range of fungicides to help maximise blight control.

With an extremely low application rate per ha, it also offers easy handling for spray operators and avoids delayed drying on the leaf, added Mr Sutherland. “We recommend using Crusade at 0.25% of total spray volume. It’s compatible with all common plant protection products and foliar feeds added to the tank-mix, but we do suggest adding Crusade to the spray tank first, before incorporating anything else.