Seasonal population dynamics of Rhizoglyphus robini Claparède (Acari: Acaridae) affected by some environmental factors in the saffron fields of Northestern Iran

Saffron, Crocus sativus L. (Iridaceae), is known as the most expensive spice in the world and the saffron mite (R hizoglyphus robini Claparède, 1869) causes direct and indirect damage by feeding on healthy or damaged saffron corms and is known as the most important pest of this crop. In this study, the effect of certain environmental factors including temperature, some soil parameters and altitude, on the population of saffron mite (adults and nymphs) and its dominant predatory mite Gaeolaelaps aculeifer (Canestrini, 1884) (Acari: Laelapidae) was evaluated in 5-year-old saffron fields in Iran (Mashhad, Gonabad, Torbat Heydariyeh, Dargaz, and Quchan). The relationship between the population growth rate (PGR) of adult and nymphal stages of bulb mite and predatory mite throughout the year was fitted by non-linear regression. Based on this model, the PGR of adult bulb mite was lowest on June 24 and highest on December 3. For the nymphal bulb mite, the PGR was lowest on August 5 and highest on December 12. The PGR of the predator of bulb mite was maximally fitted with the model, with a coefficient of determination (R2) of 0.612. In this model, the PGR of predatory mite reached its lowest point on August 9 and its highest on January 3. The effect of temperature and soil moisture on the nymphs/adult population ratio (NAPR) of bulb mites was fitted to a multiple linear model, and according to the results, the NAPR increased with increasing temperature and decreasing soil moisture. The results of this study can play an important role in predicting and placing the development of saffron cultivation.