Potential for the Postharvest Biological Control of Phthorimaea operculella (Lepidoptera, Gelechiidae) by Blattisocius tarsalis (Mesostigmata, Blattisociidae)

Phthorimaea operculella is one of the most important pests causing damage to stored potatoes. In this work, the effect of temperature (at 10, 20 and 30 °C) on the predation of pest eggs by Blattisocius tarsalis was studied in the laboratory. In addition, the effect of three predatory release rates on two pest densities was studied under microcosm conditions. The results showed that B. tarsalis maintains its predatory capacity at low temperatures (10 °C), obtaining an efficiency of 49.66 ± 5.06% compared to the control. In turn, at 20 °C, a maximum efficacy of 78.17 ± 4.77% was achieved, very similar to that presented at 30 °C (75.57 ± 4.34%). Under microcosm conditions and at low pest density (10 eggs/container), the mortality due to the mite was 96.97 ± 3.03%, 81.82 ± 8.84%, and 84.85 ± 8.30%, respectively, for the three predatory release rates (5, 10 or 20 mites/container). At the high infestation level, the pest control ranged from 61.54 ± 9.21% to 92.31 ± 2.74%, depending on the predatory release rate. The results obtained show that B. tarsalis could be a relevant control agent against P. operculella under non-refrigerated potato storage conditions, as well as in the first stages of their storage under refrigerated conditions.

Selection of Predatory Mites for the Biological Control of Potato Tuber Moth in Stored Potatoes

Worldwide, the potato tuber moth (PTM), Phthorimaea operculella (Zeller), is one of the most severe pests affecting potato (Solanum tuberosum L.), whether in open-air crops or during tuber storage. This work examines the potential control of this pest by two species of predatory mites, Macrocheles robustulus (Berlese) and Blattisocius tarsalis (Berlese), on pest eggs under laboratory conditions. In the two first assays, the acceptance rate of the pest eggs was assessed for each predatory mite. Then, in a third assay, the functional response of B. tarsalis was studied. The results showed that Macrocheles robustulus did not prey on the pest eggs (number of eggs surviving = 4.33 ± 0.38), whereas B. tarsalis did (number of eggs surviving = 0.5 ± 0.5). Likewise, B. tarsalis showed a type II functional response when it killed the eggs. The results showed the potential use of Blattisocius tarsalis as a biological control agent of P. operculella in potato under storage conditions.

Mites in dried figs of Turkey: diversity, species composition and density

This study was conducted to determine mite species in dried figs in Aydin, Turkey between August 2014 and November 2016. A total of 141 dried fig samples were taken from producers’ storage, commercial storages and fig processing factories in Buharkent, Germencik, Incirliova, Kocarli, Kosk, Kuyucak, Merkez, Nazilli, Sultanhisar and Yenipazar districts. In addition, 24 dried fig samples were kept in storage for 8 months and the changes in mite species composition and their densities in stored figs were determined. As a result, 8 mite species belonging to 3 orders and 5 families were identified from the dried figs. Acarus siro L., Carpoglyphus lactis (L.), Glycyphagus destructor (Schrank), G. domesticus (De Geer) and Tyrophagus putrescentiae (Schrank) as pest species, and Blattisocius tarsalis (Berlese), B. mali (Oudemans) and Cheyletus eruditus (Schrank) as predatory mite species were found. Out of 141 samples, 133 were infested with mites and the infestation ratio was 94.3%. Tyrophagus putrescentiae was the most common pest species with an infestation rate of 72.3%, followed by C. lactis with 34.8%, A. siro, G. destructor and G. domesticus with 0.7% contamination, respectively. Carpoglyphus lactis was found to have the highest density with 10,488 individuals/kg in contaminated fig samples. Blattisocius tarsalis was the most common predatory mite species with an infestation rate of 77.3%. Blattisocius mali and C. eruditus were found in 9.2% and 4.3% of dried figs, respectively. This study showed that the dried fig samples kept in storage were always vulnerable to contamination with mites. Mite species composition and their densities also fluctuated over time.

Laboratory studies on the role of an egg predator,Blattisocius tarsalis(Berlese) (Acari: Ascidae), in relation to the natural control ofEphestia Cautella(Walker) (Lepidoptera: Pyralidae) in Warehouses

Effective control ofEphestia cautella(Wlk.) byBlattisocius tarsalis(Berl.) has occasionally been observed in warehouses. It has been postulated that this control is negated by fumigation under sheets, because of differential effects on the moth and its predator, and removal of alternative prey. The biology ofB. tarsaliswas studied at 27°C and 73% RH. On eggs ofE. cautella, development took 5·9 days and there was 7% mortality; on eggs ofTribolium oastaneum(Hbst.), development took 7·4 days and there was 48% mortality. When offered a choice of eggs of the two pest species, the mites very rarely preyed on those ofT. castaneum. The number ofE. cautellaeggs consumed (after correction for partial consumption) was 3·8 (total) by nymphs, 2·4/day by ovipositing females, 1·5/day by non-ovipositing females, and 0·8/day by males. The sex ratio (female: male) was 2·5:1. Adult life-span averaged about 55 days (maximum 153 days), and the oviposition period lasted about 20 days. Females laid up to 5 eggs/day at peak oviposition. The potential rate of increase ofB. tarsalisonE. cautellaeggs was very high, far exceeding that of its prey. These data confirm previous postulates concerning the role ofB. tarsalisin natural control ofE. cautella, and support the hypothesis that fumigation reduces predator-effectiveness. Modification of control regimes might allow greater natural control by the mite and reduce the increasing pest status of the moth.