Comparison of Different Methods for Control of Gladiolus Bulb Mite Rhizoglyphus echinopus (Fumouze & Robin) (Astigmata: Acaridae) under Greenhouse Conditions

Bulb mites of genus Rhizoglyphus (Acari: Acaridae) have been identified as pest of many crops in storage, greenhouse, and field. The most important hosts are species of family Liliaceae (e.g. Allium spp.) Rhizoglyphus echinopus (Fumouze & Robin) (Astigmata: Acaridae) is one of the most important pest of gladiolus corms in Mahallat. The mites infest bulbs and corms by penetrating through the basal plate or outer skin layers. Bulb mites may establish in the inner layers, which makes control extremely difficult. Feeding wounds created by bulb mites provide entry sites for soil-borne fungal pathogens such as pythium, rhizoctonia and fusarium. Despite their economic importance and broad distribution, the control of R. echinopus remains in a state of confusion and needs a thorough evaluation. In addition, the field biology and ecology of this mite is not well studied, and methods for sampling, monitoring and assessment are limited. Management of bulb mites is complicated because of their short generation time, high reproductive potential, broad food niche, interactions with other pests and pathogens, and unique adaptations for dispersal. Historically, these pests have been controlled by synthetic acaricides and insecticides, which are now limited due to their resistance. Alternative control strategies, including cultural and biological control, have shown limited success, but need to be further developed and implemented. We evaluated the capacity of the soil-dwelling predatory mite, Hypoaspis (Geolaelaps) aculeifer (Canestrini) (Mesostigmata: Laelapidae), as well as disinfestations of corms to control attacking bulbs mite. The experiment was performed in 24 treatments and 3 replicates in randomized complete block design. Each plot was separated with plastic and its soil was sterilized by solarization. In addition, 30 gladiolus corms were cultivated in each plot. Disinfestations treatments (corms were soaked in poison solution for 25 minute) include: 1, 2 & 3- abamectin (0.4, 0.8, 1.2 ml/lit); 4, 5 & 6- ethion (1, 1.5, 2 ml/lit); 7, 8 & 9- fenazaquin (0.5, 1, 1.5 ml/lit); 10, 11 & 12- hot water (45°C for 25, 50 and 75 min); 13, 14 & 15- release of predator mite H. (Gaeolaelaps) aculeifer 10, 20 and 30 predator for every 100 Gladiolus bulb (previously infested with bulb mites); 16, 17 & 18- release of 100, 250 and 500 predator mites in square meter 15 days after planting; 19, 20 & 21- tap water as control treatments (30°C for 25, 50 and 75 min); 22- hot water (45°C for 25 min) and release 10 predator for every 100 gladiolus bulb; 23- hot water (45°C for 25 min) and release of 100 predator mites per square meter; 24- hot water (45°C for 25 min) and release 10 predator for every 100 gladiolus bulb and release of 100 predator mites per square meter 15 day after planting. Significant differences were found among treatments and with control (α= 0.5). In all cases, the population of predatory mites increased as long as bulb mite densities were not too low. Experiments in the greenhouse showed that in the absence of predatory mite, populations of the bulb mite, R. echinopus, on gladiolus corms increased, whereas population growth of bulb mite was slowed down as the predatory mite were released. The highest infestation severity was observed in treatments 19, 20 and 21 (control), while the lowest percentage of corms infestation were recorded in treatments 24, 23 and 22. The highest frequency of corms was produced in treatment 24, also the highest inflorescence length was found in treatments 13 and 24. The height length mean of gladiolus stem was observed in treatments 24, 23 and 13, respectively. The flowers in treatments 7, 14, 17 and 23 lived the greatest. The fastest germination rate was recorded in corms in treatments 24, 23, 22, 14, 15, 13 and 10, respectively. But the number of buds was statistically located in the same group and their differences were not significant. Based on the results and with respect to the gladiolus features, biological and integrated pest control methods could be recommended for reducing R. echinopus infestation.