Evaluation of Trichogramma cacaeciae (Hymenoptera:Trichogrammatidae) and Blattisocius mali (Mesostigmata:Blattisociidae) in the Post-Harvest Biological Control of the Potato Tuber Moth (Lepidoptera: Gelechiidae): Use of Sigmoid Functions

The potato tuber moth (PTM), Phthorimaea operculella, is the main potato pest in the world, having managed to adapt to a wide range of climatic conditions, and causing damage to stored tubers. The effectiveness of a biological control using the parasitoid Trichogramma cacaeciae and the predatory mite Blattisocius mali was evaluated in PTM under conditions that simulated those of tubers in storage. The number of adults found at the end of the trial was significantly higher in the control (181.75 +/- 11.00 adults/container) than in treatments where B. mali (24.50 +/- 7.22) or T. cacaeciae (102.00 +/- 14.61) were released. The biological control's effectiveness using the Abbot formula was 86.52% for the predator and 43.88% for the parasitoid. In addition, the PTM population data was fitted by logistic models, and the best fit was found for the simple logistic function. Using the data generated from these functions, the control efficiencies for the mite and the parasitoid were 94.85% and 73.77%, respectively. B. mali showed greater potential for being incorporated into integrated PTM management programs than T. cacaeciae. Based on logistic functions, a novel way of estimating the effectiveness of predators and parasitoids is also presented and discussed.