Bean fly ruins adzuki establishment
From the March 2007 edition of Agriculture Today.
One week after his adzuki beans emerged, leading NSW Northern Rivers organic grain grower, Brett Slater, noticed plants slowly wilting and not recovering.
“When you see runs of plants dying, you know it’s not right,” he said.
Opening up stems, Brett saw minute white larvae feeding on vascular tissue.
Within a week plants had collapsed with the main stem a ginger- brown colour and rotten.
Bean fly, an unexpected pest had destroyed his young crop.
“I spend more time checking adzuki beans than soybeans - and adzukis are only 10 per cent of the area.
“There was no reference to bean fly in my adzuki bean growing book,” Brett said.
Bean fly is a recognised pest of adzuki beans on the Northern Rivers.
Overall bean fly is a minor pest; however, infrequent significant losses can occur in individual crops.
Control by pesticides is available to conventional growers but there is a need to develop and register products for organic bean growers.
Bean fly is a major pest of French beans from the Central Coast of NSW to the Northern Rivers. Soybeans are a host but no economic loss occurs.
The adult is a shining black fly about 3.5 mm in length.
The female lays its eggs in punctures on the upper surface of leaves.
These pin pricks become yellow spots and provide an easy means of determining bean fly activity.
Hatched larvae mine their way into the leaf stalk and some tunnel into the main stem.
When full-grown, larvae pupate just beneath the outer surface of the stem or leaf stalk. The life cycle can be over in 3 weeks.
Bean fly pupae are heavily used by numerous wasp parasites.
Early sown crops are less likely to be damaged by bean fly.
Northern Rivers adzuki growers favour a mid-January to mid- February sowing - potentially a high risk time for bean fly damage.
This sowing period produces a light red coloured bean - most desired by the Japanese market.
On a positive note, Brett Slater’s organic soybeans are magnificent. He works with NSW DPI research agronomist Dr Natalie Moore, who is based at Grafton Agricultural Research Station and a member of the GRDCfunded National Soybean Improvement Program.
