Ontario Forest Health Review for 2008

November-December 2008

THE ANNUAL FOREST HEALTH REVIEW took place in Orillia this year and members of the forestry, arboriculture and nursery industry gathered to hear about this year’s surveillance activities and research. Traditionally, forest health monitoring has been conducted by forest health specialists from the Ontario Ministry of Natural Resources (OMNR) and the Canadian Forest Service (CFS). Tony Hopkins, CFS, announced that in the future, OMNR will be taking complete control of forest health monitoring. In return, CFS plans to enhance their efforts in diagnostics, systematics and research to support forest health issues.

Reduced Moths Due to Rainy Spring
Gypsy moth populations were on a slight incline this year at 31,000 HA – up from 10,000 HA in 2006. Aerial applications of B.t. (Bacillus thuringiensis, a biological insecticide), have yet again been helpful in reducing populations of these leaf-chewing caterpillars. Because of all the rain during late larval development in June, background populations of pathogenic fungi and viruses were also able to significantly reduce larval populations. You probably noticed the plethora of stretched caterpillar carcasses hanging lifelessly from trunks and branches with their heads down. That’s the work of the entomopathogenic fungus, Entomophaga maimaiga. Just like other pathogenic fungi we know, this fungus thrives in wet conditions. We also see them hanging from their middle in an upside down “V” position. This is usually characteristic for those infected with NPV (a type of viral pathogen). The virus (Gypchek) is not registered for use in Canada, but you’ll be encouraged to know that there is a very progressive company out of New Brunswick (Sylvar Technologies Inc.) that has been conducting efficacy studies at various sites in Canada with an emphasis on spray deposition technology. By inoculating with Gypchek, larval populations crashed much sooner, reducing defoliation significantly from untreated plots.

Jack Pine Budworm News
Taylor Scarr, OMNR, gave an update on the successful jack pine budworm management program. Very similar-looking to the spruce budworm, this caterpillar feeds on the pollen and current season’s growth of pine, especially at the top of the crown. Feeding damage turns foliage red and sometimes, jack pine budworm damage can kill a tree in just one year. Current hot spots include Sudbury and North Bay and a little further north. Traditionally, the industry has dealt with the damage by performing salvage cuts in infested areas. This way, the wood can be harvested before its value is compromised. In the last decade, the area of infestation has become so large that regional sawmills are not able to handle the amount of logs from these salvage operations. In 2006, industry and government decided to combine salvage cuts with an insecticidal spray program using the biocontrol agent Bacillus thuringiensis (B.t., Dipel). An aerial spray program using state-of-the-art GPS technology was able to achieve uniform spray deposit at incredibly low rates (1.5 L B.t. per hectare). Defoliation was reduced to 37% in treated areas (vs. 70% in untreated areas). The spray program was repeated quite successfully in the last couple of years. The team has been able to reduce jack pine budworm infested areas to 166,000 ha in 2008 (down from 740,000 ha in 2006).

Other Insect News
Blow down damage is something we see every year. Once they dry, the toppled trees can pose a significant fire hazard. Where stands of white pine have been subject to blow down, forest health technicians are seeing native white spotted sawyers (a long horned beetle, often confused with the invasive Asian long horned beetle). The white spotted sawyer beetles are reproducing on blowdown and slash piles of white pine. Populations have built up so high in some areas that the white spotted sawyers have been observed attacking healthy pines (something which I’m starting to get more calls about). Except for a pocket near Sudbury, forest tent caterpillar is still at a relatively low level at 42,000 HA. Pine false webworm, cedar leafminer and larch casebearer outbreaks are also few and far between.

Sirex Wood Wasp Update
Surveys for Sirex wood wasp (Sirex noctilio, European wood wasp, EWW) were conducted again in 2008 by the Ontario Ministry of Natural Resources. The purpose was to determine the northern limit for this invasive alien species. In 2006, multiple trap sites across southern Ontario uncovered positive detections of Sirex wood wasps. In 2007, surveys efforts were largely concentrated in the counties outside of the 2006 positive detections. According to OMNR, no positive sites were detected north of the 2007 detections. This wood wasp was first found in New York State in 2004 and consequently detected in Eastern Ontario in 2005. Sirex wood wasp has since been detected in several counties of New York and has also been found in Pennsylvania, Michigan and Vermont. Currently, the Canadian Food Inspection Agency is working on a regulatory document to limit the spread of Sirex host material (Pinus sp.). This directive is due to be released for comment some time soon.

New Research Techniques for EAB Detection
Emerald ash borer (EAB) was a popular topic of discussion. This invasive alien species has been detected at several new locations across Ontario (plus Quebec and several parts of the US) this year. CFIA staff are currently engaged in delimitation surveys in order to determine the extent of these new infested sites. As you know, detecting EAB infestations in ash trees has been the most significant hurdle for surveys. Trees quite often don’t show symptoms until the infestation is quite advanced. Dr. Krysta Ryall from the Canadian Forest Service gave an excellent report regarding her research team’s efforts towards improving sampling techniques.

The team focused their efforts on sampling live trees that were found next to those that were heavily infested. They felled the trees, cut them up and labelled them in order to track samples in relation to their position on the tree. For instance, they tracked N-S-E-W orientation and upper crown, lower crown and general branch diameter groupings. They took 59 trees back to their lab and dissected 938 subsamples – painstakingly shaving back layers of bark and cambium in search of the signs of EAB (can you imagine?).

Early instar EAB larvae are so tiny and flat, they are easy to miss. So to check their level of error, they held all the dissected subsamples in sealed rearing cages and monitored for EAB adult emergence (based on established rearing techniques). And yes, they proved that current sampling techniques produce false negatives: only about 50% of the trees had obvious external signs but it turned out that a whopping 89% were actually infested! They also discovered that 40% of the trees had numerous galleries in the branches of the crown with no galleries in the boll (better get out your step ladder and binoculars this winter). The group determined that most of the infested branches were in the 5-6 cm diameter range (although they found EAB in branches as small as 1.75 cm in diameter). The EAB tunnels often tended to be found under less than 5 mm of bark.

Dr. Barry Lyons, also of CFS, gave a whirlwind overview of some of the EAB biocontrol research going on in North America. CFS and US scientists are screening host tree volatiles to determine if EAB adults respond to certain host chemicals more so than others. They are hoping to use this information to develop more EAB-specific attractants and to facilitate trapping in the field (as you can imagine, bark peeling is extremely cumbersome). They did isolate a few volatiles that attract EAB adults and they also found that males seem more responsive to these compounds than females.

A grad student at the University of Guelph has been working with a parasitic wasp, Cerceris fumipennis. The adult wasp will actually hunt for EAB adults, capture them and take them back to their ground nest to feed their developing maggots. What they did was construct a mobile colony of Cerceris, complete with ground nests, on a trailer. They were able to tow the colony around the province and monitor the nests for EAB adults. So it turns out that Cerceris could actually be used as a biosurveillance tool. The effectiveness of Cerceris compared to other monitoring techniques (e.g. purple prism traps) is currently being investigated.

Contact Information

This column is written by Jen Llewellyn, Ontario Ministry of Agriculture and Food and Rural Affairs (OMAFRA) Nursery Crops Specialist

Email any questions you have directly to Jen and we'll publish her response.

P: 519-824-4120 ext. 52671 • F: 519-767-0755

OMAF website: http://www.omafra.gov.on.ca/scripts/english/crops/agriphone/index.asp

Nursery Landscape Agriphone: 1-888-290-4441

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