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

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.

A review of West Palaearctic Hoplocampa species, focussing on Sweden (Hymenoptera, Tenthredinidae)

“…60.7°N) (Lindblom 1938). In recent years, testudinea has caused serious damage to organically-grown apple crops in many countries, including Sweden (Sjöberg et al 2015).…”

Pest Control in Organic Systems

“…Traditionally, in organic fruit growing, the apple sawfly Hoplocampa testudinea Klug is controlled by the use of extracts of bitter wood of 6 g/ha/in 500 l. For a good efficiency, the bitter extract can be mixed with Nemmazal T/S® [52,53]. Table 11.…”

Soil application ofBeauveria bassianaGHA against apple sawfly,Hoplocampa testudinea(Hymenoptera: Tenthredinidae): Field mortality and fungal persistence

“…Apple sawflies are known to be controlled by natural enemies, that is, parasitiods, nematodes and entomopathogenic fungi (Babendreier, 1996;Jaworska, 1992). Apple sawfly control in Swedish conventional orchards relies on the use of nonselective synthetic insecticides at the time of egg hatch (Manduric, 2014;Sjöberg et al, 2014), while control in European organic orchards commonly has relied on the use of a commercial or homemade extract from the shrub Quassia amara L. (Simaroubaceae) (Ascard & Juhlin, 2011). Another control opportunity, with soil application of entomopathogenic fungi (EPF) or nematodes, appears at the time of larval descent to the soil for hibernation.…”

“…To the best of our knowledge, no previous study has investigated the potential for apple sawfly control or EPF persistence using a formulated product at the highest recommended field dose and common organic orchard practices. It is important to identify the short-term persistence of the fungal biocontrol agent throughout the first week after soil application during the critical peak larval descent to the soil (Sjöberg et al, 2014). Furthermore, an assessment of indigenous EPF levels, the persistence of the applied EPF by the end of the field season and the long-term persistence a year after application would be valuable information for decision makers in the regulation of biocontrol products.…”