Byers, J.A. 1993d. Orientation of bark beetles Pityogenes
chalcographus and Ips typographus to pheromone-baited
puddle traps placed in grids: A new trap for control
of scolytids. Journal of Chemical Ecology 19:2297-2316.
Abstract--
A puddle trap was designed that is simple to build and efficient in
catching bark beetles (Coleoptera: Scolytidae). The trap is
insensitive to wind and should be much easier to manufacture than the
more complicated perforated pipe and barrier traps commercially
available. A 7 times 7 grid of 49 puddle traps baited with
aggregation pheromone components of Pityogenes chalcographus
(chalcogran and methyl decadienoate) was placed at either 1.5-, 3-,
6-, or 12-m spacing between traps in the field for two or more
replicates of one day length (June 1989, Torsby, Sweden). The
resulting catches showed that beetles were trapped as they flew into
the grid since the inner square-ring of 24 traps caught less beetles
per trap than the outer square-ring trap average (36 traps) in most
experiments. Ips typographus also landed in puddle traps primarily on
the periphery of the grid (6-m spacing only) when traps were baited
with its pheromone components, (S)-cis-verbenol and methyl butenol.
Computer simulation of flying bark beetles in grids of traps of
various spacings and catch radii estimated that the experimental
pheromone traps had an effective catch radius of 1.3 m or less for P.
chalcographus, depending on the spacing between traps. An effective
catch radius of 2 m for I. typographus was found for the 6-m grid
spacing. P. chalcographus beetles were increasingly disrupted in
their orientation to pheromone at the closer trap spacings since the
effective catch radius declined linearly with closer trap spacing.
However, landing was still precise since unbaited puddle traps within
the grid did not catch any bark beetles.
Diffusion-dilution release of semiochemicals part II:
The diffusion-dilution equation for obtaining predicted semiochemical release rates (Byers, 1988b
) by dilution with solvent:
mls = fws * (gsem / fwsem - fsem * gsem / fwsem) / fsem / gs ___( Equation 1 )
can be simplified:
mls = -fws * gsem * (fsem - 1) / (fsem * fwsem * gs) ___( Equation 1 simplified )
and then solved for the mole fraction of the chemical (equal to the fraction of the
release rate when neat (or pure)):
fsem = 1 / (fwsem * mls * gs / (fws * gsem) + 1) ___( Equation 2 )
where:
fsem = mole fraction of semiochemical or the proportion of the release
rate when neat
fwsem = formula weight of semiochemical
mls = milliliters of solvent
gs = grams solvent per milliliter (density)
fws = formula weight (or molecular weight) of solvent
gsem = grams of semiochemical
For example, if 0.2 g of chalcogran, a pheromone component of the bark beetle Pityogenes
chalcographus is placed in the bottom of a small test-tube (5.25-mm-diam. opening x 32-mm-long)
it is released at about 1 mg/day at room temperature. If 0.05 g of chalcogran is mixed with
1 ml of ethanol and 0.2 g of this solution was placed in the same type of test-tube, then
Equation 2 predicts that about 1.75 percent of the maximum release rate of neat chalcogran will occur,
or the release rate would be 0.0175 mg/day for the diluted solution.
0.0175 = 1 / (156 g/mole * 1 ml * 0.828 g/ml / (46 g/mole * 0.05 g) + 1)
Chemical Ecology