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.

Puddle trap 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 )

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

Pityogenes chalcographus 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)

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Chemical Ecology