Greetings Uzzz,
I've located some information yet I'm not certain that it exactly
addresses what you want to know, so I'm posting it here in the
Comments section. If it does meet your expectations, let me know and
I'll post it as an answer.
*********************************
"The impact of forest tent caterpillars should not be underestimated.
For comparison purposes, at the peak of a caterpillar outbreak, the
biomass of caterpillars per km2 would be equivalent to 657 caribou per
km2. Similarly, the biomass of the tiny parasitic flies that attack
and feed on these caterpillars would be equivalent to 82 wolves in the
same one km2 area."
http://www.sciencedaily.com/releases/2002/03/020313074748.htm
And from the same article:
"Roland and his team of researchers sampled 127 sites covering an area
of 400 km2 near Ministik Hills, Alberta in aspen stands ranging in six
sizes from as small as .28 hectares to 289 hectares. "What we
determined," said Roland, "is that for the parasites and the viruses
to be most effective, the size of the forest stand should be a minimum
of about 100 hectares. Smaller forest stands served as a caterpillar
refuge because of less effective natural enemies-helping to extend the
length of the infestation by several years."
*********************************
Maps showing infestation that include Forest Tent caterpillars
http://www3.gov.ab.ca/srd/forests/health/aspen_cond.html
*********************************
"The study found it isn't so much what forestry companies take from the
forest, but the size of the stands they leave uncut that counts. "If forest
companies were going to manage specifically for tent caterpillars, one thing
would be to avoid leaving small stands of forest," said Prof. Roland, who
has been studying the impacts of the insect for 11 years. Parasitic flies
and viral infections that keep caterpillars in check are not as effective in
smaller stands, where there is more sunlight and it is hotter and drier, as
they are in thicker, deeper forests that are cooler and damper. Since
forest tent caterpillar infestations can last up to six years, a reduction
of even a year could have a huge impact on Canada's boreal forest -- saving
one to two cubic metres of wood per hectare annually, Prof. Roland said."
http://64.233.179.104/search?q=cache:opegJOXmBhYJ:archives.foodsafetynetwork.ca/agnet/2002/3-2002/agnet_march_13.htm+%22forest+tent+caterpillar%22+%22rate+of+spread%22&hl=en
*********************************
"Edmonton, March 12, 2002 - SFMN Principal Investigator, Dr. Jens
Roland has discovered a correlation between forest tent caterpillar
infestations and the amount of forest left standing after an area has
been harvested. Says Roland, "In larger forest stands, the mortality
factors which cause collapse of the tent caterpillars infestation
(parasites and disease) are more effective than they are in small
stands."
http://64.233.179.104/search?q=cache:x7_SxwacmvAJ:www.nce.gc.ca/media/newsrel/2002/120302_e.htm+Forest+fragmentation+and+colony+performance+of+forest+tent+caterpillar&hl=en
In the citations, there are two studies mentioned - you may be able to
locate these for further information, or by contacting Dr. Jens Roland
(see contact info below citations).
Rothman L. & J. Roland. 1998. Relationships between forest
fragmentation and colony performance in the forest tent caterpillar,
Malacosoma disstria. Ecography 21: 383-391.
Roland, J., B.G. Mackey & B. Cooke. 1998. Effects of climate and
forest structure on duration of forest tent caterpillar outbreaks
across central Ontario, Canada. Canadian Entomologist. 130: 1-12.
Dr. Jens Roland
Room: B 702, Biological Sciences Bldg.
Phone: (780) 492-1180
Fax: (780) 492-9234
Email: jens.roland@ualberta.ca
http://www.biology.ualberta.ca/faculty/jens_roland/index.php
************************************
Text of the abstract "Effect of forest structure on dynamics of forest
tent caterpillar populations" by Jens Roland
http://sfm-1.biology.ualberta.ca/english/pubs/PDF/PR_1999-12.pdf
Interview with Dr. Roland about the Forest Tent caterpillar
"CC: WHY DO THEY GO THROUGH THESE CYCLES? WHY ISN'T IT EVERY YEAR? WHY
DOES IT HAVE TO BE EVERY TWELVE YEARS?
"JR: That's a really good question. And this is the area of population
dynamics that I'm particuarly interested in. It's thought that these
kinds of cycles are driven by the natural enemies of the forest tent
caterpillars. And these natural enemies include viral disease,
parasitic insects which attack the tent caterpillar. And also
predatory insects. And because the disease and parasites are so
tightly linked with the tent caterpillar, that's pretty much all they
feed on, they get into this cyclic pattern whereas the tent
caterpillars increase, then a year or so later, the parasites and
disease start to increase. There's a bit of a lag between the two,
sort of a one year lag in their abundance. And it's this lag that
starts to set up the cycle."
http://www.innovationalberta.com/article.php?articleid=172
***************************************
Landscape Crop Advisory Team Alert
Volume 16, No. 11, June 22, 2001
"We have had many reports from people in the UP who are really, really
tired of forest tent caterpillars on their trees, their lawns, the
road, their kids, etc. Forest tent caterpillar feeding continues,
although male caterpillars should be to pupating by now. Aspen
defoliation is very heavy in much of the western UP, areas of the
central UP and even some locations in the eastern UP. The natural
enemies are building up too, however. Parasitic flies are heavy in
areas of the western UP and pathogens, mostly virus, are also flaring
up. That's good news -- it should mean that forest tent caterpillar
populations will be lower in the western UP next year."
http://www.ipm.msu.edu/CAT01_land/L06-22-01.htm
***************************************
Forest Tent caterpillars in Minnesota
Comprehensive text and photos
http://www.extension.umn.edu/distribution/horticulture/DG7563.html
***************************************
Pest-based models
"With BA loss calculated for each risk agent and conflated to the RSAC
forest type map, total loss of BA can now be tallied for each forest
cover type group by summing the BA loss for each species. For example,
a pixel within the Maple-Beech-Birch group contains 10 BA of ash and
90 BA of sugar maple, with a simulated risk for EAB and Forest Tent
Caterpillar (FTC) of 7 and 5, could potentially lose as much as 52 BA
(52% of the total BA) in the next 15 years: 10 * 70% + 90 * 50% = 52
BA or 52% of the total of 100 BA."
http://www.fs.fed.us/foresthealth/mcm/pest_models.htm
*************************************
Lifecycle (illustrated)
"Larvae of the forest tent caterpillar do not spin silken tents, as
their name implies. They spin silken threads for pathways to and from
their feeding sites on the trees, and they also spin silken mats on
which to rest. The eastern tent caterpillar, which prefers cherry and
apple trees, does form a tent and is often confused with the forest
tent caterpillar.Once they are full-size the larvae spin cocoons of
white silk mixed with yellow powder, on trees and other vegetation and
on fences, buildings, and other structures. The larvae moult to the
pupal stage inside the cocoon. About ten days later (usually early
July) the moths emerge. The yellow to brown moths are stout-bodied,
with a wingspan of 3.5-4.5 cm and two dark bands on the forewings.
During July each female deposits 150-200 eggs in a single brown band
1.5-2.0 cm long that encircles a small twig. Within three weeks a
young larva forms in each egg, but it remains dormant until the
following spring."
http://www.foresttentcaterpillar.ca/lifeCycle_printable.htm
**************************************
Facts
"the first outbreak of this insect to be positively identified goes
back to 1791 - records indicate outbreaks with an average of 10?12
years between intervals - although complete defoliation may occur,
typically this does not kill the tree"
http://www.nrcan-rncan.gc.ca/cfs-scf/science/prodserv/pests/f_tent_e.html
*****************************************
Southern region U.S.
"In the South, it heavily defoliates water tupelo, sweetgum, blackgum,
and various oak species. The most persistent and extreme outbreaks in
the South occur in bottomlands, forested wetlands, and riparian areas.
However, when FTC populations reach epidemic levels, the caterpillars
often spread to urban and suburban areas where they defoliate a
variety of shade trees and ornamental plants. Outbreaks in recreation
areas may adversely affect business due to the nuisance created by
migrating caterpillars and the presence of completely defoliated trees
during the tourist season. Outbreaks of the FTC occur in several
Southern States, where well over 500,000 acres can be defoliated in a
single season; FTC defoliation does not cause significant amounts of
tree mortality."
http://www.srs.fs.usda.gov/sustain/draft/hlth2/hlth2.pdf
*******************************************
Hope this helps. I didn't locate a definitive rate of spread but I
hope you find some of this info to be of assistance.
Best regards,
journalist-ga
SEARCH STRATEGY
"forest tent caterpillar" rate of infestation
"forest tent caterpillar" "rate of spread"
"forest tent caterpillar" proliferation
"forest tent caterpillar" life cycle
"forest tent caterpillar" feeding cycle
Forest fragmentation and colony performance of forest tent caterpillar |
