July 15, 2010
By Jen Llewellyn
OMAFRA nursery crops specialist

In May, I was privileged to attend the International Organization for Biological Control in the Americas, held in Niagara Falls, Ont. All the who’s who in the world of biocontrol attended the conference. I made a lot of contacts and gleaned several new ideas and approaches to biocontrol in the greenhouse, nursery and related production systems. I would like to share some of the highlights from the speaker program.    

Ladybird beetles

When it comes to rapid, effective biocontrol options, ladybird beetles are not exactly on the top of the list. They exhibit poor colonization, high levels of cannibalism (yes, they feed on each other), high levels of dispersal and slow reproductive rates.

In nature, ladybird beetles arrive late in the pest lifecycle, when there are already high numbers and plant damage is quite significant. Personally, I have found ladybird beetles a little more organized than their reputation may suggest. These predatory insects have been interfering with the Viburnum leaf beetle trials that I’ve conducted in the last couple of years. In my 2008 trial, various species of ladybird beetles consumed most of the beetle larvae across my entire trial, all within about two weeks.

United States Department of Agriculture researchers discovered an interesting observation of the unfortunate relationship between ladybird beetles and lacewings. An important predator of soft-bodied insects, lacewings will do everything they can to avoid laying their eggs in areas that are occupied by ladybird beetles. Researchers discovered that lacewing adults are actually repelled by the semiochemicals that can be found in the tracks of ladybird beetles.  

Scientists are looking at sprays in food crops to attract the predatory ladybird beetles earlier, so that they are already there when mid-season aphid pests start to build.  

Interestingly, ladybird beetles also have non-predator effects on plant feeding insects:  their presence causes aphids to drop off the plant.  If you have ever looked at ladybird beetle mandibles under a 40 x microscope, you understand the aphid’s response. Obviously, the aphid loses valuable feeding time and in many cases, may not successfully re-colonize the plant. It may even fall victim to another predator.  

Spiders as biocontrol  

Spiders are not well studied in the role as predators of economic plant pests. Researchers at the University of Kentucky discovered that 40 per cent of the spider species he studied in agricultural crops have aphid DNA in their digestive tract. Several species of aphids when alarmed, exhibited significant levels (up to 50 per cent) of dropping from the plant. Remember how those big mandibles must look to them?
Talking to another conference delegate, I learned that greenhouse operators, who have taken the time to monitor arachnid activity, have noticed much lower aphid pressure where spider activity (i.e. webbing) was observed beneath and around the crops.    

Weakest link  

The main strategy for biocontrol is to understand the enemy, and then discover its weakness, so you can enhance the predators, parasites and parasitoids that might best exploit this weakness. For plant pests that lay their eggs in soil, you need to create an environment that will support ground-dwelling predators, such as ground beetles that love to feast on soil-dwelling eggs and larvae.  For plant pests that cannot fly, but must walk to find host plants, you might try inter-row cropping with non-host plants to confuse and complicate their journey. Where beneficial parasitoids need a pollen and nectar source to support their reproductive energy needs, conservation strips of flowering annuals and perennials can significantly increase the success of that biocontrol system.    

Biocontrol products in Canada  

Dr. Michael Brownbridge and Dr. Rose Buitenhuis of the Vineland Research and Innovation Centre gave a summary and some predictions about promoting success with bios in the future. There is no question the Bacillus thuringiensis (B.t.) is probably the most successful example of biocontrol we have for ornamental plant production. Botanigard (Beauveria bassiana Strain GHA) is being touted as a significant solution for the suppression of sucking insect pests in greenhouse crops. Beauveria fungal spores in the spray solution germinate on the cuticle of the insect and penetrate the cuticle to colonize the inner tissue, eventually killing the insect.  

By trialing and observing the performance of biocontrol organisms in various crops and environments, and tweaking the production and formulation, we will be in a much better position to improve the performance.

An example is the current project that looks at the synergy between entomopathogenic nematodes and Met52 (Metarhizium anisopliae strain F52) and the attractiveness of various ornamental host plants for the management of black vine weevil. The granular formulation of Met52 was recently registered and classified for use in container production of ornamentals (outdoor and greenhouse) to be mixed into the growing media at potting to manage black vine weevil and strawberry root weevil.  

Emerald ash borer biocontrol  

According to Nick Mills, University of California, about 30 to 35 per cent parasitism needs to be observed before we can be confident that the invasive pest population will be overcome. Emerald ash borer is an example of a newly-introduced pest where the level of parasitism and predation of the pest is still quite low, but we have great hope that these levels will increase sharply over the next decade.

In Michigan, the natural callusing response of the tree has been credited a 20 to 40 per cent reduction in the successful colonization of the larvae in our native ash trees. In other words, researchers have found signs of early larval feeding under the bark, but the larval tunnel was never completed, with the insect obviously walled-off by overgrowth of callus tissue.

Also in Michigan, woodpeckers have been observed as predators of emerald ash borer larvae and pupae, but at a very small level.  Interestingly enough in Asia, woodpeckers are the most significant predators of emerald ash borer larvae and pupae. North American scientists have been studying this beetle in its native Asian habitat to see if there were some biocontrol organisms that we may be able to introduce here. I guess the importation of Asian woodpeckers was out of the question, since scientists chose three species of Asian wasp parasitoids (insects that lay their eggs inside the body of other insects). These wasp species were mass-reared and small numbers were introduced into Michigan (2008) and in both Michigan and Ontario (2009). So far, things are looking up. The level of wasp parasitism increased from 1.1 per cent in 2008 to 4.2 per cent in 2009.  
Jennifer Llewellyn may be reached at 519-824-4120, ext. 52671, or by email jennifer.llewellyn@ontario.ca. Her Nursery-Landscape Report can be found at  http://apps.omafra.gov.on.ca/scripts/english/crops/agriphone/index.asp.