Evaluation of temperature sum models and timing of Quassia amara (Simaroubaceae) wood-chip extract to control apple sawfly (Hoplocampa testudinea Klug) in Sweden.

P Sjöberg,B Rämert,T Thierfelder,D Neupane,E Lennartsson,M Tasin,W Swiergiel

doi:10.1007/s10340-014-0616-0

Abstract

Apple sawfly (Hoplocampa testudinea Klug) is a serious pest in European organic apple production. They hatch during a short period only, making correct timing of control measures crucial. Swedish organic growers have requested a strategy for optimal timing of the Quassia amara (Simaroubaceae) extract against the apple sawfly. The aim of this study was, therefore, to develop methods to predict the timing of Q. amara control in Sweden. A temperature sum model for timely placement of monitoring or mass-trapping sticky traps was validated for Swedish conditions. The average emergence of sawflies occurred at 169 degree days (SD = 20) counted from March 15 (threshold temperature 4 °C). The difference in emergence from existing first flight model of average and maximum 9 and 39 degree days (1 and 9 calendar days) was found acceptable. Accumulated oviposition of 85 % at full bloom (BBCH 65) suggests that mass trapping and monitoring could stop at this time. This is supported by a tendency of decreased trap catches during that period. Three application times for Q. amara were compared: (A) at petal fall (BBCH 67), (B) at a date calculated using female trap catch numbers and temperature sums, and (C) prior to peak egg hatch observed in the field. All treatments resulted in significantly lower percentage of damaged apples compared to the unsprayed control, with significantly less damage (1.3 %) in plots treated according to method (B). The results provide information on adult phenology and methods that could be used to determine timing of mass trapping and insecticide application against the apple sawfly.

Highlights

Apple sawfly (Hoplocampa testudinea Klug; Hymenoptera: Tenthredinidae) is an important univoltine pest of apple in Europe and North America (Pyenson 1943; Vincent and Mailloux 1988; Cross et al 1999; Velbinger 1939)
There is a link between the reproductive period of the apple sawfly and the phenological flowering stages of apple trees, which can be described by the biologische bundesanstalt, bundessortenamt und chemische industrie (BBCH) scale (Meier et al 1994) and used to time control measures against the pest
Apple sawfly control in Swedish conventional orchards relies on the use of nonselective synthetic insecticides (Manduric 2013), while control in European organic orchards commonly has relied on the use of a commercial or homemade extract from the shrub Quassia amara (Simaroubaceae) (Ascard and Juhlin 2011; Trapman pers. com. 2012)

Summary

Introduction

Apple sawfly (Hoplocampa testudinea Klug; Hymenoptera: Tenthredinidae) is an important univoltine pest of apple in Europe and North America (Pyenson 1943; Vincent and Mailloux 1988; Cross et al 1999; Velbinger 1939). The sawfly hibernates in the soil as pre-pupae and emerges in the flowering period of early and moderately early apple varieties The short persistence of Q. amara extract avoids a negative effect on the later emerging apple sawfly parasitoid Lathrolestes ensator (Zijp and Blommers 2002a, b). The extract is sprayed after flowering to eradicate neonate larvae of the sawfly. Monitoring of adult sawfly emergence, estimation of population density, and mass trapping are possible using white sticky traps (Owens and Prokopy 1978; Wildbolz and Staub 1986; Graf et al 1996a). The common recommendation is to place traps 10 days before bloom, since if they are installed too early they attract other insects and may lose their attractiveness (Graf et al 1996c)

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