A population growth model of Tetranychus urticae Koch (Acari: Tetranychidae)

Abstract

Two-spotted spider mite, Tetranychus urticae Koch is a serious pest of different crops over the world. Different strategies are used to regulate the population of this mite. To this end, as a first step, a population growth model has been developed for describing the dynamics of T. urticae population growth. In this regard, the population abundance of T. urticae was estimated weekly from 29 June to 29 September 2016 at two bean fields, each field was planted with Goli and Akhtar cultivars, separately. During each sampling period in each field, 30 plants were randomly chosen and a leaf was selected as a sample unit from the middle of a plant, then a simple population growth model was constructed for T. urticae on two bean cultivars. The result showed that T. urticae had a distinct seasonal pattern of abundance but differed between two cultivars. A logistic growth model was developed based on relationship between the cumulative density of T. urticae and time (day) and demonstrated high prediction capability for T. urticae population on Goli (R 2 = 0.99) and Akhtar (R 2 = 0.99) cultivars. According to the logistic equation, carrying capacity was recorded 463.9 ± 9.73 (mite/leaf) and 59.67 ± 8.72 (mite/leaf) on Goli and Akhtar cultivars, respectively. Furthermore, it has been shown that the logistic growth model can be used to make population predictions. The model parameters estimated for two different cultivars, providing a new mathematical tool for ecologists to predict two-spotted spider mite outbreaks, and ultimately to develop effective two-spotted spider mite control strategies.