Close monitoring of crops supports biological success

Close monitoring of crops supports biological success

Bayer used the Fruit Focus theatre to emphasise the finer points of biological fungicides and insecticides and how growers should adapt practices to get the most from what they have to offer.

Getting the most from any plant protection product requires an understanding of its mode of action, the disease or pest to be targeted and the environment in which the product is to be applied. This applies as much if not more to biologicals as many are live cultures and performance can be heavily affected by conditions at application, explained Jack Hill, Bayer roots and horticulture commercial manager.

“There are many positive benefits to fungicides that extend far beyond their performance, and many are considered more socially acceptable than conventional means of protection. Despite these favourable characteristics, biologicals are required to complete the same regulatory requirements as other forms of crop protection,” explained Mr Hill.

To illustrate how the performance of a biological fungicide differs from that of a conventional product, Mr Hill juxtaposed the mode of action for Luna Sensation (fluopyram + trifloxystrobin) and Sonata (Bacillus pumilis QST2808).

“The mode of action is significantly different and in the case of biologicals can be influenced by the micro-climate within the canopy, among other factors. Sonata has a physical mode of action that actively penetrates the enzymes to gain the upper hand, while Serenade ASO seeks to build a protective layer that repels pathogens. These are both surface-acting products but appreciating the finer points that separate otherwise similar products is central to making the most of their potential,” he said.

By working with these performance differences, Bayer investigated how to maintain control under high pressure while reducing applications of Luna Sensation needed to maintain protection.

“Biologicals work best in the shadow of conventional products. By following the first application of Luna Sensation with two to three sprays of Sonata or Serenade ASO (Bacillus amyloliquefaciens (formerly subtilis) strain QST 713), delivered control of powdery mildew close to that of two applications of Luna Sensation (roughly 88% control). This was in a high-pressure situation where there were 25% losses in the untreated control,” said Mr Hill.

“This is because Luna Sensation reduces the level of disease inoculum within the crop to a level that allows Sonata or Serenade to work in a protective capacity where the disease spores are controlled before they have the opportunity grow on and penetrate the plant’s cells,” he said.

This approach encapsulates what is the central difference between biologicals and conventional products, he said. “Biologicals need to be applied before the disease or pest has the opportunity to become established if they are to have any chance of success.”

Insecticides are different again

At an insecticide trial near East Malling Research (EMR) where the aphid pressure was regarded to be ‘high’ at 120-170 per plant, the performance of the biological insecticide Flipper (fatty acids C7-C20) was investigated in a programme with Batavia (spirotetramat). The importance of a preventative approach was again emphasised.

“Where Batavia was followed with two applications of Flipper, we saw a dramatic reduction in numbers. It was evident that the knockdown of Flipper served to complement the systemicity of Batavia. Such an approach also favours the beneficials within the crop,” said Mr Hill.

The importance of water quality in supporting the spray solution was highlighted by Richard Prankerd, Bayer commercial technical manager for horticulture.

“Water pH and hardness are the most important factors. pH is often less of a concern as most supplies, be they tap or rainwater, are close to neutral and therefore not less than the minimum required value of 6.5. Water hardness is a separate issue that is the greater concern. Growers should be mindful of the effect that high concentrations of dissolved salts, such as calcium and magnesium, can have on performance,” said Mr Prankerd.

Many growers will already be familiar with the issues of hard water given its significance to herbicide performance, but where the status is unknown, Mr Prankerd encouraged growers to have their water tested. Where necessary, the water should be conditioned with a non-acidifying treatment before mixing.

Application dose and the interval between sprays were another important detail that was integral to performance, he said.

“We see that with bio-insecticides such as Flipper it is important to maintain a concentration in the spray solution of not less than 1% and the first application should be repeated after seven days. It’s also prudent to monitor populations three-days post-application to gauge success,” he said.

Making the most of biological pesticides and insecticides first involves a sound understanding of the pressure facing the crop.

“Effective timing relies on knowing when to apply for optimum results. This is hard to achieve without close monitoring of crops to understand when the pest is most active, but also when conditions are likely to be most conducive to supporting performance,” said Mr Prankerd.