Eastern Tent Caterpillar

eastern_tent_caterpillarOMSPA has been apprised that insect infestations are occurring in sugar bushes, primarily from Eastern Tent Caterpillar but there are others as well. Todd Leuty was kind enough to share the following information. We have only heard of issues is the Eastern part of Ontario. If there are other areas please let Todd and OMSPA know. 

From Todd Leuty:

Pest activity can be different for each region.  For sugar bush and woodlot health situations, I work with the Forest Health Specialists with MNRF for the designated region. Vanessa Chaimbrone Vanessa.chaimbrone@ontario.ca is the Forest Health Specialist for the eastern region.  Vanessa works directly with the lead forest entomologist Dr. Taylor Scarr, MNRF (Canadian Forest Service after June 17).  They would be familiar with private aerial applicators that operate in their regions.  For example, in southwest Ontario Zimmer Air Services coordinates many of the insecticide applications for sugar bushes and managed woodlots.    

The forest health specialist usually will know hot spot activity and stages of development of forest pests in their area.  For example, forest tent caterpillar larvae would be in an advanced development stage by now so insecticide treatment would be less effective.  Severe defoliation in a sugar bush is rather alarming when it occurs.  Fortunately, we know that sugar maples have evolved with these native defoliators and can survive most outbreaks, where trees aren’t stressed by other additional factors at the same time. 
Foray and Dipel are Bt insecticides.  Bacillus thuringiensis (Bt) is a naturally occurring bacterium which produces a toxin, that is commonly used as a biological insecticide.  Bt insecticides are usually approved for use by organic certification, but check with your certifying organization to confirm this.  I’m not sure whether the Forest Stewardship Council (FSC certification) approves the use of Bt insecticide in its sugar bushes, check with them. 

Many overwintering egg masses can be laid during heavy outbreaks, which will set up a sugar bush or deciduous woodlot for heavy defoliation to occur again the following season.  If left alone, the population will eventually decline after two or three seasons due to natural predation and natural disease, which brings the outbreak to an end.  However, sugar production, annual sapwood growth and tap hole healing can be affected.

Where a heavy outbreak is expected to occur again the following year, sugar bush operators can contact an aerial applicator in advance of spring to arrange an insecticide application to be applied shortly after egg-hatch.  The Forest Health Specialists can assist with locating an aerial applicator and providing ideal spray timing.  Each producer can decide the appropriate management decision for their own operation. Some producers prefer to let nature take its course and not apply insecticides for forest tent caterpillar. 

Tapping considerations following defoliation Sugar bushes that are severely defoliated by tent caterpillar will leaf out again after a few weeks, although the new canopy will appear sparse compared to the original canopy.  Maple researchers have found that re-growth of the second canopy will allow the trees to photosynthesize sugar again, however, the effort of growing more leaves will drain the trees of much of the starch energy that was on reserve in the trees.  Syrup producers have found sap sugar concentrations are considerably low following severe defoliation since trees have been depleted of stored starch and sugar. Previously in Grey Bruce counties, sap sugar concentration remained less than 1.5 Brix following severe defoliation by forest tent caterpillar.

Syrup producers can consider reduced tapping (no more than one tap per tree), or no tapping following severe defoliation, to protect the long-term health of their sugar bush.  Reduced tapping may be necessary for two consecutive seasons, or until heavy outbreaks subside.  Any other stress factors, such as summer drought, should also be taken into consideration when determining the health of the trees this coming winter.

There may be some consideration of lowering the vacuum pressure in sap collection tubing along with reduced tapping, but we can consult with maple researchers for this question.  Dr. Abby van den Berg from University of Vermont will be speaking at the maple summer tour on sustainable management practices and this would be a good question for Abby and other maple researchers.

Where an insecticide has been applied at the correct timing and severe defoliation is prevented, normal tapping can resume the next tapping season, assuming the sugar bush has had a normal healthy summer season to replenish starch and sucrose storage.  
Feedback and comments from experienced producers are always welcome.   


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