How to manage a biocontrol program at a production nursery

Woodburn Nursery and Azaleas in Woodburn, Ore., is one of the largest growers of floral azaleas in the U.S. I manage the Integrated Pest Management/Biological Control Program. I have been given latitude over this program that few in the industry experience. This latitude has given me a perspective that is unique and valuable to the industry.

On numerous occasions, I have achieved control, well below damaging thresholds, of harmful insects using an overwhelming number of beneficial insects. I can tell you through personal experience that, yes, beneficial insects work. We have two primary approaches to insect biological control. The first is augmentative and the second is conservation. Augmentative insect control is the purchase and release of beneficial natural enemies to control insect and mite pests. Conservation biological control refers to the conservation of natural enemies by avoiding practices which are harmful to natural enemies and implementing practices which benefit them.

Our biological control program extends outside of our floral azaleas department to other crops. Woodburn Nursery also grows woody ornamentals including Japanese maples and Euonymus fortunei. These crops are grown in unheated greenhouses with roll-up sides that are situated right next to each other. There is about an acre of maples and about two acres of euonymus. Each year in the early spring, the Japanese maples and the euonymus become infested with aphids. And each year native hoverflies lay their eggs among the aphids. For the last four years I have not needed to spray for aphid control on either of these crops. It takes about four to six weeks until the aphids on these crops are destroyed by the hoverflies. Of course, it’s not just the hoverflies, but a ménage of native beneficial insects, including, but not limited to, brown lacewings, lady beetles, parasitizing wasps, predatory midges, and soldier beetles. But it is the hoverflies that do the heavy lifting. Hoverflies require a pollen meal to lay eggs, so I place baskets of candytuft (Iberis) and other early flowering annuals and perennials within the crop. The candytuft is typically set out between February and March, depending on when the hoverflies appear. I also set out barley plants infested with a cereal aphid to feed the hoverflies. The cereal aphid is found only in monocots, such as barley and grass, therefore the aphids do not migrate into our crop. This combination of flowers/pollen and added aphids as food is jokingly referred to as the “Full Meal Deal.”

The late comers to the party always seem to be the lady beetles. Once I find a contingent of lady beetles, I know the end is near for the aphid infestation. I can tell you with high confidence that even though I scout our crops like a bluetick hound on a black-tailed jackrabbit’s trail, I have not found all the actors in this little drama.

Click here to read the full article in our April issue.

Top photo courtesy of IPPS Western Region