Organic spraying: a quick case study
While I was in the Dobbin vineyard in Niagara, Canada, a tractor went by with a spray recovery system. I asked Ann Sperling, consultant winemaker here, what was being sprayed. The answer: a mix of Cueva, Regalia, Stargus, Willow Tea and Kelp. These are all organically approved.
Cueva is a copper containing fungicide. It’s copper octanoate combined with a fatty acid, a formulation that means that less copper is needed for protection. The fatty acid helps the copper get into mildew cells and also helps spread the Cueva across plant surfaces. For organic viticulture where there is some growing season rainfall it’s essential to use some copper to combat downy mildew: the other solutions don’t work as well. But by using a formulation like this and combining it with other forms of defence, it’s possible to use less copper and still have protection. This formulation also works with biologicals in the spray mix, whereas some copper formulations are incompatible with biologicals.
Regalia is an example of a biofungicide, and it works by inducing induced systemic resistance. This is a level of defence that falls a little short of full resistance (this is another pathway involving specific resistance genes), but it primes the plant defences, which act to inhibit the growth of fungi and bacteria. This includes cell wall thickening, phytoalexin production, the turning on of PR proteins and increasing the levels of phenolics. The idea is to make the plant more healthy and resistant, rather than targeting the disease organism. Regalia’s active ingredient is an extract of Giant Knotweed (Reynoutria sachalinensis).
Stargus is another biofungicide, but in this case it is a culture of bacteria that are designed to colonize the leaf surface and inhibit the growth of disease-forming organisms. It is a beneficial rhizobacterium (Bacillus amyloliquefaciens strain F727) It protects the plants by inhibiting spore germination, mycelial growth and sporulation of disease-causing fungi.
Willow tea is applied here largely to control leaf hoppers, which are insects that suck sap, and can cause damage when their populations are high enough. It contains salycin (aspirin is salicylic acid) which is toxic to them.
Kelp is an extract from the seaweed kelp, and contains a wide range of micronutrients. It is a foliar nutrient that has some positive effects on growth.
