Due to safety concerns, in 2006 carbendazim underwent review by the Australian Pesticides and Veterinary Medicines Authority (APVMA) and by 2014 its use was withdrawn in a variety of crops. Whilst old broad-spectrum chemistries like carbendazim have proven to be effective at controlling husk spot, macadamia growers are aware that carbendazim has a limited future.
Anticipating the eventual phase-out of older chemistries, industry bodies have been searching for alternative, IPM friendly, husk spot controls. Now, Corteva Agriscience has obtained the registration of Fontelis for control of husk spot in macadamia.
“Corteva Agriscience, with the help of Dr Femi Akinsanmi from the University of Queensland, obtained registration for Fontelis, a Group 7 fungicide, for the control of husk spot in macadamia,” said Nicholas Koch, marketing lead at Corteva Agriscience.
Fontelis is a single mode of action fungicide which makes it an ideal rotational partner as it has no cross resistance with any other fungicides. It is the only SDHI for the treatment of husk spot. The active ingredient, penthiopyrad, works by blocking respiration, depriving the fungus of the energy needed to survive.
“The registration of Fontelis provides protection from a major disease and aids growers who want an IPM friendly husk spot fungicide,” said Mr Koch.
Fontelis has minimal impact on key beneficial insect species such as honey bees, lacewings, parasitoid wasps, predatory mites, and predatory bugs.
Husk spot is a persistent disease that can remain in old husks (sticktights) for up to two years. Spores from the disease are rain-splashed onto nearby green husks where they infect and cause the nut to prematurely drop from the tree.
“Infections that occur during the match-head stage of the crop can have a significant impact on yield. This is when we recommend first applying Fontelis to the crop,” said Mr Koch.
The second application should follow 14 to 28 days later. Fontelis has a 14-day withholding period for domestic markets; however, import tolerances may vary for export markets so it is best to check with processors for the latest information on withholding periods.
“Corteva Agriscience are happy to provide another IPM friendly control option to macadamia growers that coincides with our other IPM friendly products such as Transform, which was just recently registered for the control of fruit-spotting bug.”
Macadamia’s aren’t the only nut crop that can reap the benefits of Fontelis. It is registered for use to treat blossom blight in stone-fruit crops as well as chestnut and almond crops.
“It has both translaminar action and local systemic activity which aids in its movement through the plant to protect against disease.”
Although Fontelis is locally systemic, thorough spray coverage is still essential to control husk spot. The label recommends using a sprayer fitted with a high flow rate nozzle and to use a minimum of 110 L/ha of water to obtain thorough spray coverage (refer to the label for application rates as they vary from crop to crop).
“Fontelis is soft on beneficials, it treats a variety of diseases across a wide range of crops, and now macadamia growers have a safe control option for husk spot that is effective and reliable,” said Mr Koch.