Saffron ( Crocus sativus : Iridaceae) is a fall-blooming perennial plant and its dried stigma is the priciest spice and a key non-oil export for Iran's economy. The bulb mite, Rhizoglyphus robini , is a polyandrous and multivoltine species and its damage to saffron corms directly and indirectly causes lower yields of saffron crops. Environmental conditions and abiotic factors, such as temperature, humidity, density, and diet affect the morphological traits of living organisms and subsequently affect biological abilities. In this study, changes in temperature, soil moisture, density (nymphs + adults), time, and corm weight on the morphological traits of the saffron bulb mite, including body length and width, and leg sizes of adult females were investigated in a saffron field in the Dargaz County of Iran during 2022. The results of variance analysis of the morphometrical parameters of the mite species, including body length, body width, and four pairs of legs in different months were significant. Based on simple and multiple linear regression models as well as non-linear regression, the effect of temperature and density (nymphs + adults) was reversed and the effect of soil moisture and corm weight was direct on morphometrical parameters of this species. Based on our results, soil moisture has a strong relation with female body size traits (body length, width, and leg lengths). This indicates that irrigation cycle management might be an important factor in bulb mite management in saffron agroecosystems.

The bulb mite, Rhizoglyphus robini Clapar & eacute;d & egrave; has been identified as a common pest attacking saffron corms. This mite is also a saprophytic species that is able to feed on fungi (mycelium). It has also been demonstrated that some soilborn fungi can attack and establish on saffron corms. After related fungi were isolated and identified either in saffron corms and mite bodies, the fungus Fusarium oxysporum Schlecht was the most abundant species in both samples; subsequently, it was used in the experiments. For studying the role of soil-borne fungi on life-table parameters of the mite, an even-aged cohort of eggs was obtained and transferred to experimental units to feed on saffron corm sections in two groups (fungal-infected and non-infected corms) in laboratory conditions. A total of 36 individuals were used for each treatment. The life-history data were analyzed according to the age-stage, two-sex life table model. Results showed that total pre-adult development of R. robini was significantly faster on Fusarium-infected rather than healthy corms (10.91 and 11.48 days respectively, P < 0.05). Adult pre-oviposition period (APOP) was significantly shorter when females were reared on fungal-infested than non-infested corms (1.84 and 2.88 days, respectively, P < 0.05). In addition, survivorship and fecundity of the mite on the two diets indicated higher rates and consequently, the net reproductive rate (R-0) and intrinsic rate of increase (r) were significantly higher (P < 0.05 for both parameters) (202.07 and 351.13 offspring for R(0 )and 0.218 and 0.251 day(-1) for r respectively on non-infested and infested diets). According to the results obtained, the soil-borne fungus affected demographic parameters of the bulb mite and it supports the hypothesis that the mite prefers plant tissues infected with soil-borne fungi because these are more suitable hosts.