Clay spray drives wasps away

6 Sep 2016

A close-up of Scott as he inspects a citrus tree

New trial results showing how clay sprays can be used to manage citrus gall wasps (CWG) will feature at a NSW Department of Primary Industries (DPI) field day at SS Citrus Supply, Dareton on Tuesday September 13.

DPI entomologist, Jianhua Mo, said results from Sunraysia trials in 2015-2016 showed spray treatments with calcined kaolin clay could reduce the amount of damaging galls by more than 90 per cent.

“Two applications, one just before and another during CWG emergence, of the commercially available clay reduced the size of large galls, those more than 100 millimetres long, by 99 per cent and average gall size by 35 per cent,” Dr Mo said.

“This product is the only calcined form of kaolin clay available in Australia with 3D structural properties which repel CGW.

“Originally developed to act as a protectant against sunburn and heat stress, it’s a wettable powder which is applied as a spray to form a barrier film on the plant surface.

“The barrier film also appears to deter egg-laying by CGW on citrus shoots, which reduces gall numbers and size in the following season.”

Dr Mo said investigations this season will explore ways to cut treatment costs by reducing application rates with new wetting agents and water rates.

“We have also trialled two new generation pesticides to control CGW larvae – both were effective when applied in the soil, but the level of gall reduction was not as high as the calcined kaolin clay spray,” he said.

CGW has recently emerged as a major pest in southern citrus crops, infesting orchards in the Sunraysia, Riverland and Riverina to impact on plant vigour, fruit size and citrus yields.

A national project led by Dr Mo aims to manage GWG by targeting the pest with its natural enemies, new generation pesticides and environmentally-friendly repellents.

Funded by DPI and Horticulture Innovation Australia, the CGW management project brings South Australia’s Fruit Doctors and Department of Agriculture and Food Western Australia on board as research partners.

The field day will also deliver updates on Queensland fruit fly trapping and district control from the Greater Sunraysia Pest Free Area Committee.

More information is available to growers and industry representatives by contacting DPI citrus development officer, Steven Falivene, 0427 208 611.

Photographs are available from

Media contact: Bernadette York (02) 6938 1664 or 0427 773 785