Dispersal of First Instar Larvae of the Felted Beech Scale, Cryptococcus fagisuga

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Abstract
Dispersal of C. fagisuga in a beech forest was studied using suction traps and sticky traps. First instar larvae and eggs of C. fagisuga had mean terminal velocities of about 27 cm s-1 and 40 cm s-1, respectively. The larvae were the main dispersive stage and were carried passively downwind from infested trees. In mean windspeeds of < 1 m s-1 larvae dispersed a mean distance of .apprx. 10 m from a source tree which was infested from near ground level to the lower canopy. The distance dispersed was proportional to height of takeoff and windspeed. In suction traps sited from 1 m above the ground to 6 m above the canopy (18 m above the ground) most larvae were trapped at 1 and 3.2 m above the ground. About 0.7% were trapped at or above the top of the canopy. The larvae dispersed along a short-range steep gradient under the canopy and a potentially long-range shallow gradient above the canopy.

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