Lace Bug and Groundcovers
Groundcovers not only help with erosion control, organic matter and water penetration but are also a potential source of beneficial insects. GVB and BFC do have some plant hosts that can occasionally grow in the interior but the major pests of macadamias do not breed in the inter row.
This provides opportunities to build up natural enemies. Good ground cover growth and diversity including flowering and high pollen grasses provide a home for a myriad of insects that are not pests of macadamias. These insects are in turn, food for various predatory insects which will also have some impact on our in-tree pests and can help the farm be more resistant to pest incursions. They also give you more time to make spray decisions.
For example, there are strong indications that lacewing larvae can significantly suppress lace bug. Lace bug get from one season to the next on out-of-season flower so its important to have good natural enemy populations during harvest through to flowering. To aid this process, we are now rearing and supplying adult green lacewings to help restock farms with lacewing after the spraying season.
So, can we also better manage the interrow to increase these natural enemies? What practices can we adopt and what should we avoid? We want to try answer these questions. Some growers have even started planting other species in the inter row.
We also want to develop better ways of measuring insect and beneficial activity in order to measure changes through the season and to compare farms.
At this stage, our recommendations are:
Reduce mowing when you can. Try and allow grasses and weed to get to pollen and flowering stage before mowing.
Alternate row mowing - enable insects to move into the next row and means food sources and pollen and nectar more evenly available to insects
Leave a "Mohawk" down the centre of interrow during harvest if rows wide enough. This will keep some pollen available - its better than none.
Consider planting flowering plants down every third or fourth row. The more nectar available to parasitoids, lacewings, adult beetles and hoverflies, the longer they will live and the more offspring they will produce.
Lace bug get from one season to the next on out of season flower.
Flowering plants will provife nectar sources for adult lacewing allowing them to live longer and lay more eggs.
Spiders are also likely important predators of lace bugs