Novel products for disease control in the vineyard

All farmers and growers whether of major or minor crops are facing a continuing loss of agrochemical sprays to fight pests, diseases and weeds as the costs of finding and introducing new chemistry to the market skyrocket and environmental concerns from consumers and lobbyists result in the withdrawal of useful plant protection products. Organic growers have always had to find products that are both at least partly effective and acceptable to organic standards authorities. This includes copper used for centuries in vineyards and although facing a ban for use as a fungicide on other crops is available for vines as Cuprokylt via Certis. 

Novel products are sometimes termed biostimulants or bio-rationals and are often exempt from pesticide regulation – termed ‘out of scope’ as their mode of action is totally physical rather than chemical. Attention to application advice is vital for these products but if used correctly they represent an interesting group of products for both conventional and organic growers. 

Fargro has two of these products of particular interest to vine-growers, SB Plant Invigorator (SBPI) for powdery mildew control and wound coating/paint BloCade. SBPI is a unique blend of plant-safe physical pest and disease control surfactants. It has a non-chemical, non-biological action against powdery mildew and appears to control the disease by physically removing active mildew spores from a leaf surface. Terry Horsman from Fargro describes it as having “a washing action, literally cleaning the leaves of spores.” It is totally safe to vines and to the spray operator and will benefit the vines in other ways by improving leaf colour as it provides valuable nutrition as a foliar feed. To achieve good mildew control, thorough and regular applications of SBPI applied to the whole plant and to the point of run-off are required. Both upper and lower surfaces of leaves must be treated. 

SBPI was invented, trialled and is manufactured on the Channel Island of Guernsey, renowned as a centre of horticultural excellence. A number of independent studies have shown that SBPI can also be highly effective at controlling a number of problem pests like aphids and spider mite as well as powdery mildew. Recent trials at NIAB EMR fruit research station in Kent by plant pathologist Angela Berrie looking for alternative products to control apple powdery mildew demonstrated that SBPI gave very promising results. 

BloCade is an opaque plant wound coating based on acrylic dispersion. It provides a robust physical barrier that prevents fungi and bacteria from infecting plant wounds. This physical coating unlike just acrylic paint which leaves pinhole openings provides a complete seal thus protecting plant wounds against infections caused by bacteria and fungi, such as Eutypa, Botryosphaeria and Nectria (e.g. fruit tree canker and dead arm disease). Once applied BlocCade dries quickly to form a protective shield. It’s exempt from pesticide regulations (EU decision October 2014) and only one application required but with a long life. 

BlocCade is an ideal product for use in viticulture where annual pruning means an ever-present disease threat. Agronomist Julian Searle from Agrii says “BlocCade is now a bit of a standard and is fit for purpose. Partly because there is nothing else legally available but also because users find it goes on well in a range of weather conditions and appears to give a well visible and durable seal to wounds. 

Karma from Certis is a contact fungicide for the control of botrytis and powdery mildew in grapes. It contains potassium hydrogen carbonate with built-in surfactants for maximum efficacy, re-distribution and residual activity. Karma inhibits mycelial growth and causes a total collapse of spores through a combination of dehydration, pH and specific bicarbonate/carbonate ion effects. 

Selchuk Kertev, IPM manager for Certis UK, said: “Karma is one of Certis' biorational products. It’s approved for organic crops and we have an Extensions of Authorisation for Minor Use (EAMU) for wine grapes. This product is based on potassium carbonate, which is also available as a commodity product (in the UK for the control of powdery mildew), which are basic substances. But the regulatory approvals are likely to cease in (August) 2019*." (*Note: According to the HSE, commodity substances are defined as chemicals that have a variety of non-pesticide uses as well as minor uses as pesticides. They have EU approval until August 31 2019). 

Karma has an EAMU until February 28, 2022. The basic substance status disappears in 2019 so having the EAMU is really crucial. Potassium bicarbonate is freely available but there's a risk – a phytotoxicity issue – associated with it and a possible negative impact on the balance of beneficial insects. As Selchuk says, "Because Karma is a formulated, registered product there's a technical team behind it. We [at Certis] know, for example, how the product interacts with the beneficial insects; we can deliver that technical knowledge and expertise to growers. We can help them to understand how the product works and how it will impact their vineyards. 

The potassium carbonate crystals act as the active ingredient – the contact. The molecule is delivered to the fungi, and through a three-way action, it causes the fungi to dehydrate. The fungi are disintegrated very quickly. Because it's got a contact mode of action a good crop cover is really vital." The secret to making sure you get the best from Karma is that you have to apply it when there is a very subtle morning dew. It helps with the spreadability of the active ingredient. As Selchuk says, “We really see a difference when this product is applied in these conditions rather than during the middle of the day." 
By Joanna Wood