Susceptibility of the Box tree pyralid Cydalima perspectalis Walker (Lepidoptera: Crambidae) to potential biological control agents Neem (NeemAzal®-T/S) and entomopathogenic nematodes (Nemastar®) assessed in laboratory bioassays and field trials

The Box tree pyralid Cydalima perspectalis Walker (Lepidoptera: Crambidae) is one of the accidentally introduced organisms that became invasive and established in Europe within a few years. Thus, eco-friendly preparations are required, which should be accessible, affordable, easy usable and suitable for the application in private and public areas. Therefore, the effects of the plant extract formulation NeemAzal®-T/S (active ingredient Azadirachtin A) and the commercial preparation Nemastar® (entomopathogenic nematode species Steinernema carpocapsae) were investigated on C. perspectalis larvae in laboratory bioassays and field trials. When NeemAzal®-T/S-treated leaf discs were consumed by larvae in the laboratory, a significant effect on mortality and feeding activity was noted after 14 days of exposure. At this time, 47–62% of the larvae had already died and less than 10% of larvae were still feeding. Application of different S. carpocapsae suspensions (10–200 EPN/100 μl, i.e. per larva) demonstrated a high susceptibility of both tested larval instars (2nd: 10–75% and 4th: 45–100% mortality). In field trials neither the application of Nemastar® nor the use of NeemAzal®-T/S caused mortality rates comparable to those generated by the treatment with plant protection products based on Bacillus thuringiensis. In conclusion, there is a higher variability in terms of the effects of the investigated agents compared to the constant effectiveness of B. thuringiensis. But their use would be possible if individual feeding damage and proper surveillance will be considered in order to be capable of repeating the application timely and a combination with further measures ought to take place.