Original scientific paper

Biology and natural enemies of spotted ash looper, Abraxas pantaria (Lepidoptera, Geometridae) in Krka National Park

MILAN PERNEK orcid.org/0000-0001-8200-6913 ; Croatian Forest Research Institute, Cvjetno naselje 41, 10450 Jastrebarsko, Croatia
DINKA MATOŠEVIĆ orcid.org/0000-0001-7380-688X ; Croatian Forest Research Institute, Cvjetno naselje 41, 10450 Jastrebarsko, Croatia

Abstract

Background and Purpose: Spotted ash looper (Abraxas pantaria) is a
forest present in Krka National Park, Croatia with occasional mass occurrence. The caterpillars of this pest have completely defoliated leaves of Narrow-leafed ash (Fraxinus angustifolia) in the upper flow of river Krka in the period from 2008–2010. We have researched the biology of spotted ash looper which is first comprehensive study of this pest in Croatia.

Materials and Methods: The research of spotted ash looper included
field trials through all the years and laboratory experiments. Caterpillars
were reared and daily weighted in laboratory. Fresh and dry Narrow-leafed ash leaves have beenweighted and factor of drymatter in leaves defined. For each individual sex, moment of onset of particular larval instar, prepupa, pupa and butterfly was noted in order to identify the duration of each stage and possible differences. Duration of larval stages and consummation of food were analysed separately by gender. A total of 200 pupae of spotted ash looperwere transferred to the laboratory for the identification of natural enemies. Each pupa was placed in a separate glass tube and incubated in laboratory.

Results and Conclusions: Our results show biology of this pest in
Croatia. Caterpillars feed on Narrow-leafed ash and have not been found on Manna ash (Fraxinus ornus). They have moulted only 3 times and pass through 4 larval instars in laboratory conditions. Average caterpillars of 4th larval instar gained their maximum growth on the 4th day from the beginning of that stage andmaximumweight on the 8th day, three days before entering the prepupal stage. The difference betweenmales and females starts to develop during the 4th larval instar when females consume significantly more food, gain significantly more weight and form significantly heavier pupae. The average 4th larval instar consumes between 0.3329 and 0.3673 g of fresh leaf. Research shows that number of pupae diapauses during the winter,while some of themhave no diapause. This indicates that the pest has at least two generations a year, which was also shown by observations in the
field. Pathogen fungus Beauveria bassiana, parasitoids Pales pavida, Cratichneumon cf. fabricator F. and unidentified species from the genus
Coelichneumon were natural enemies found in pupae. Beauveria bassiana as a pupal pathogen plays an important role as the most important natural enemy and the existence of its alternative host, ash weevil (Stereonychus fraxini)which occupies the same overwintering niche is also important.

Keywords

Hrčak ID:

110876

URI

https://hrcak.srce.hr/110876

Publication date:

30.9.2013.

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