Hull rot a key target in almond disease management programs

Image: Kim Honey (left) and Riverland Agronomist Matt Ward (middle), both of Elders, check out the development of a young almond tree with Bayer Commercial Sales Representative Darren Alexander (right).
Matt said prune rust, blossom blight, bacterial spot (in certain varieties), shot hole, anthracnose and certain root pathogens were other diseases that needed to be managed in almonds, with hull rot becoming more of a problem over the last five to six years.

 

“Hull rot can be extremely damaging, as it comes in late season. In the 2016-2017 season, it caused a lot of damage to nuts and shoots – and the fruiting wood for the last season,’’ Matt said.

 

“Some growers had hull rot infections that bad during the 2016-2017 season that we estimated crop loss up to 20%. The following year it could have been another 20% due to shoot death and with the hail on certain orchards in November 2016, damage was up to 50%.’’

 

He said the disease had also become more prevalent in almonds due to higher fertiliser inputs.

 

“N (nitrogen) applications have increased significantly, up to 280-320 units/ha over the period that hull rot has increased.’’

 

“This has resulted in higher nitrate levels plus more vigour, and if you’ve got hull rot pathogens present and wet conditions, the disease can develop rapidly.’’

 

Matt said the theories being employed to help protect crops from the disease included changing away from high nitrate applications late, better irrigation management, and employing different fungicide strategies.

 

Luna^® Sensation fungicide from Bayer is the only product registered in Australia for suppression of hull rot. It combines the active ingredient, fluopyram, a novel chemical within the SDHI family, with trifloxystrobin.

 

Already well established in the Californian almond industry, Luna Sensation is also highly effective against blossom blight, shot hole and stone fruit rust in almonds.

 

Importantly, Luna Sensation provides another fungicide option for growers, helping to reduce the reliance on older fungicides and assisting in more sustainable disease management.

 

“If you get any level of hull rot, yields can be significantly impacted, so Luna Sensation is a great tool to have in helping reduce this. Everyone in the industry looks at yield, but quality is also very important. You only have to get hit once with hull rot and you won’t underestimate it again,’’ Matt said.

 

He advised one grower with bad hull rot in the 2016-2017 season to treat his almonds with a Luna Sensation spray. It was applied at high volumes (3000 L/ha) via an engine drive Air-O-Fan^® unit at a rate of 1.2 L/ha (40 mL/100 L). Outstanding coverage was achieved to the point of run-off and penetration onto the nuts/hulls was excellent. No further hull rot development was observed in the treated areas on either nuts or shoots after application.

 

A number of highly respected almond industry representatives also assessed the site and came to the same conclusion.

 

Matt said Luna Sensation should ideally be applied in high disease pressure years and while growers could spray the product up to three times, with a maximum application of 2 L/ha over the year, he recommended only two applications.

 

He said a lower applied volume and rate applied as a dilute application could be used during flowering (800 mL/ha of Luna Sensation at 2000 L/ha applied volumes (40 mL/100 L)), however good coverage during the hull split application was critical and volumes around 3000 L/ha (1.2 L/ha of Luna Sensation) were necessary in most cases in mature trees.

 

“We advise growers to put out a Luna Sensation application at full bloom and to keep another up their sleeve for early hull split. We don’t recommend a second application unless the conditions favour hull rot infection. If they do, the application at hull split is good insurance.’’

 

Matt said there were some concerns over the price of Luna Sensation, but it only equated to a cost of around 20-30 kg/ha of kernel, based on an almond price of $7/kg and application rates of 800 mL-1.2 L/ha.

 

“The bigger the tree, the higher the potential yields, so you need spray equipment with good power to spray larger almond trees.’’

 

He said some growers planned to rotate fungicides according to conditions, with wet conditions not expected every year.

 

“I don’t think the hull split application is needed every year – but the full bloom application should be considered depending on conditions.’’