Evaluation of the Egg Predator Blattisocius tarsalis (Mesostigmata: Blattisociidae) for the Biological Control of the Potato Tuber Moth Tecia solanivora under Storage Conditions

Tecia solanivora is the most prevalent pest causing damage to potato crops in fields in the Canary Islands, but even more so in the postharvest storage period. However, currently, there are no authorised chemical insecticides for potato storage facilities. Analysis of the viability of the predator mite Blattisocius tarsalis as a biological control agent for this moth was carried out. A study of the temperature effect showed B. tarsalis maintains predatory capacity in the range of 10-27 degrees C. Though predatory activity increases with temperature, no differences in mortality rates were observed between 10 and 20 degrees C (33.52 +/- 2.44 and 40.14 +/- 3.54% efficacy rate, respectively), nor between 25 and 27 degrees C (59.26 +/- 4.59 and 75.19 +/- 4.64% efficacy rate, respectively). Under microcosm conditions, at low pest infestation (10 eggs), B. tarsalis achieved the highest mortality of eggs at a density of 5 mites, with an efficacy rate of 91.67 +/- 8.33%. At high infestation levels (50 eggs), maximum mortality was achieved with a density of 10 mites and efficacy of 98.52 +/- 1.48%. The choice-assay showed no preference of B. tarsalis between T. solanivora and Phthorimaea operculella, suggesting this mite could be useful in mixed infestations of potato moths. The results show B. tarsalis is a very good candidate as a control agent in storage conditions and even in mixed infestations of T. solanivora and P. operculella.