Researchers at the University of Hawaii’s College of Tropical Agriculture and Human Resources are working with local growers to combat an introduced insect that damages macadamia trees. ADVERTISING Researchers at the University of Hawaii’s College of Tropical Agriculture and Human
Researchers at the University of Hawaii’s College of Tropical Agriculture and Human Resources are working with local growers to combat an introduced insect that damages macadamia trees.
During a workshop held Tuesday in Hilo and attended by macadamia farmers as well as representatives from the state Department of Agriculture, CTAHR professor Mark Wright and junior researcher Rosemary Gutierrez presented findings from a series of studies focused on controlling the spread of macadamia felted coccid.
The insect first appeared on Hawaii Island in February 2005, when an infestation was found on a South Kona farm. It is unclear how it arrived, but during the ensuing years the coccid spread around the island, and has been identified at sites from South Point to Waimea.
Like the macadamia tree itself, the coccid is native to Australia. It is found only on the smooth and rough-shelled varieties of macadamia, and feeds on tree sap. When there are macadamia felted coccid infestations on a tree, they cause dieback of both branches and leaves, reducing yield.
Wright described methods of sampling trees to determine the extent of an infestation — typical infestations are patchy clumps of coccid colonies — and provided an overview of how best to control an outbreak.
Work in South Kona found that a horticultural oil now known as Tritek had a “highly significant” impact on killing off the adult coccid population, while a type of insect growth regulator called Applaud could control the juveniles.
One way of managing infestations is fighting back with help from natural predators.
“We need to find a way to increase the effectiveness of biocontrol,” Wright said.
Macadamia growers can create environments attractive to predators like ladybugs by incorporating flowering plants nearby and trimming back tree canopies. This provides additional food sources for predators in addition to choice environments.
