Resumen

BERNAL, Liliana et al. Direct sampling plan for Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) in commercial tomato crops. Agron. colomb. [online]. 2008, vol.26, n.2, pp. 266-276. ISSN 0120-9965.

The damages produced by Trialeurodes vaporariorum generate economic losses that decrease yield and can cause an increase in the price of tomato. The control of this pest is carried out by continues applications of insecticides without obtaining satisfactory results. One alternative control is carried out releasing wasps of the parasitoid Encarsia formosa. Nevertheless, the success of this system implies to reckon the pest density through a method of adequate sampling. An economic and viable direct sampling plan by the previous arguments was standardized for nymphs of whitefly in a commercial tomato crop under greenhouse. The incidence of the management practices and phenology was determined in the spatial distribution of nymphs. In general terms, the sampling was divided in three stages: 1) sampling completely random that was carried out between 5th and 7th weeks after sowing (WAS) for plants no divided in thirds, 2) sampling random between 8th and 16th WAS, counts were carried out in leaves from the lower third, 3) sampling in two stages: plant and leaf, counts were carried out between 17th and 24th WAS on leaves from the middle and upper third. It was found that cultural practices as the blunt influenced the spatial distribution of nymphs. The implementation of direct sampling generated an increment in yield equal to 0.06% and reckoned nymph density of T. vaporariorum in tomato crops (with precisions 5%, 10% and 25%) as a criterion to carry out releasing the parasitoid E. formosa.

Palabras llave : whitefly; sample size; population dynamics; tomato.