Some biological aspects and population fluctuations of the white tuberworm Premnotrypes vorax Hustache (Coleoptera:Curculionidae) in Mucuchies, Merida State, Venezuela

Abstract

The white tuberworm, Premnotrypes vorax is one of the main insect pests of potato (Solanum tuberosum L.) crops in the Andean region of Venezuela between 2 850 and 3 600 meters of altitude. This work was carried out at the Experimental Station (Campo Experimental) of Mucuchies. Under laboratory conditions (15.3 °C temperature and 89 % relative humidity) the average life cycle of Premnotrypes vorax from egg to adult in pupal chambers was determined . Under field conditions, at three different depths (0-10, 10-20 and 20-30 cm), population fluctuations of pre-pupas, pupas and adults were determined. We also registered adults emergence. Life cycle from egg to adult in pupal chamber lasted in average 112.00 ± 6.47 days. The incubation period took 32.00 ± 1.98 days, the larval stage (in tubers) 36.43 ± 2.34 days, the prepupal stage 19.35 ± 1.10 days, and the pupal stage 23.52 ± 1.05 days. Pre-pupae and pupae were more frequently observed between November and February, while adults in pupal chambers were more frequent between February and May. The 60.6 % and 22.4 % of individuals were found at depths of 10-20 and 20-30 cm respectively. During the observation period most active adults were noticed in April and May. These results coincide with an increment in precipitation and the beginning of potato planting season in Mucuchies.