South Africa's River Bioscience has launched a new product which offers growers a key alternative to be included in their citrus black spot (CBS) spray programs to reduce the chance of resistance occurring. 

The company, which is owned by the Citrus Growers' Association of Southern Africa (CGA), has developed a contact fungicide called RB1, which is described as being unique for having active ingredient dipotassium phosphate.

CBS, caused by the fungus Guignardia citricarpa, is important as a fruit disease and all commercial cultivars are susceptible. The disease is severe and found mostly in hot, humid, low-lying tropical regions, but can occur sporadically in lower summer rainfall regions such as the Eastern Cape, according to the CGA.

European regulations require 100% control of CBS on export fruit to the EU, and CGA CEO Justin Chadwick said commercially acceptable levels of control can only be achieved through the use of plant protection products. 

"Citrus fruit is susceptible to infection from the point of fruit set until natural resistance against the disease develops in the rind by the end of January while some types, like lemons, are still susceptible until the end of March," he said in a newsletter.

"As a result of the extended period fruit is vulnerable to CBS, growers rely on a 4 – 5 month long spray programme to protect their crops."

He went on to say there were currently very few active ingredients registered for CBS control on the market, and that repeated applications of the same products can result in the development of resistance. 

"Most of these products are also detrimental to beneficial insects, which results in secondary pest outbreaks leading to further use of synthetic chemistry," Chadwick said.

"This pesticide treadmill makes farming with Integrated Pest Management (IPM) principles and practices almost impossible. River Bioscience is proud to announce the registration of a new CBS control product: RB1™^.

"RB1™ is a systemic and contact fungicide with the active ingredient being Dipotassium phosphate. There are no other products with this active ingredient for CBS on the market and this offers growers a key alternative to be included in their CBS spray programmes to reduce the chance of resistance occurring."

Another key attribute of the product is that it is compatible with IPM, he added, saying that unlike other products on the market, RB1 can be considered a “soft” product, allowing growers to once again use beneficial insects for the control of other key pests.

"RB1™ is yet another demonstration of the CGA group benefitting its growers by conceptualising new possibilities in the research arm, CRI, and River Bioscience (Pty) Ltd following through with successful commercialisation of this promising innovation to benefit the citrus industry as a whole," Chadwick said.

"For advice and assistance on how to add this to a spray programme or to obtain RB1™ please contact the agent in your area or River Bioscience directly."

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