Macadamia growers watch out for flower bug
Note: This content is stored on an archive website and may not be current or accurate. Contact us to clarify.
North coast macadamia growers are being advised to monitor their crop now for damaging lace bug activity in emerging flower racemes.
The pest, which attacks macadamia flowers with devastating results, is the target of new research being conducted by NSW Department of Primary Industries (DPI) entomologists at Alstonville.
"Lace bug has been responsible for increased levels of damage to macadamia crops over the last few seasons," said DPI entomologist Ruth Huwer.
"In some of the worst effected orchards, we are seeing up to 85 per cent of flowers with lace bugs present, and at Alstonville we have measured a 40pc reduction in nut yield due to this pest."
Dr Huwer said growers should monitor closely for lace bug damage early during the flowering season, before opening of the flowers and time control treatments on affected trees before populations get to a damaging level.
"Adult lace bugs are just 3 to 4 mm in size, slender in shape and light to dark brown in colour with red eyes.
"The wingless nymphs have an oval shape and are yellow green in colour in the early instar and reddish brown in the later instar."
According to Dr Huwer, both adult bugs and nymphs attack flowers and suck sap from the buds.
"Black withered florets on the bottom tip and middle of a flower raceme are signs of lace bug damage," she said.
"There is currently no threshold level established for spray decisions to control this pest, but in high damage areas we have observed 85 per cent of flowers with live insects present.
"The current recommendation is to spot spray affected trees with an appropriate registered insecticide.
"Because the insect attacks flowers, insecticide application to control the pest and timing of the application is a bit of a dilemma, as spraying during flowering is adverse to pollination and pollen viability."
Dr Huwer explained that the future challenge for research is to better understand the biology and ecology of the lace bug, including life-cycle, and host plants.
"We don’t know how many eggs they can lay, but number and damage can increase rapidly in some affected areas.
"Observations suggest that their life-cycle is possibly as short as two weeks from egg to adult," she said.
"We are setting up a small trial at Alstonville to test the efficacy of a number of insecticides."
Further reading
Macadamia problem solver and bug identifier - a field guide (book)
Email: