Effects of Soil Depths on Nymphal Eclosion of Melanoplus sanguinipes (Fabricius)

ABSTRACT

This work reports on the use of cultural practices that influence grasshoppers' nymphal emergence. Grasshop-per eggs were buried at depths of 2, 14, 18, 22, and 26 cm in laboratory arenas. Nymph eclosion ranged from 77.5 to 87.8%. However, nymph emergence, measured as the number of nymphs that reached the soil surface, was estimated at 70.9% when eggs were buried at 2cm, but was reduced to 2.5 % at 18cm depth. No nymphs emerged at depths of 22 cm or more. The relative high percentage of nymphal eclosion and the low or no nymph emergence suggests that the depths tested on this trial do not affect egg development and nymphal eclosion, but affect the ability of the insect to emerge to the soil surface, thus increasing first instar mortality. The addition of sand to the soil reduced nymphal emergence. A signifi-cantly lower percentage of hoppers emerged from sand as compared to soil, vermiculite, or soil mixed with 25, 50 and 75% sand. This suggests that cultural practices, such as plowing can be used as a management tool to control grasshop-pers. Further research should investigate if nymphs died of suffocation at the eclosion site or in the process of emerging to the soil surface.

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