MONITORING OF SAWFLY POPULATIONS (Hymenoptera, Symphyta: Hoplocampa spp.) IN PLUM AND APPLE ORCHARDS USING VISUAL TRAPS

The investigation of Hoplocampa minuta (Christ, 1791) (black plum sawfly), Hoplocampa flava (Linné, 1760) (yellow plum sawfly) and Hoplocampa testudinea (Klug, 1816) (apple sawfly) populations using white sticky traps Rebell®bianco was carried out in conventionally and organically managed apple and conventionally managed plum orchards of the Institute of Horticulture of Lithuanian Research Centre for Agriculture and Forestry in 2010 and 2011. Temperature sums for predicting sawfly spring emergence were determined: 120 ± 5 degree-days for apple sawfly, 85 ± 26 degree-days for black plum sawfly and 95 ± 28 degree-days for yellow plum sawfly. However, more years of the study are needed to confirm these temperature sums. The average densities of sawflies during the flight period were: H. minuta — 14.8 ± 7.3 sawfly trap-1 in 2010 and 54.2 ± 35.9 sawfly trap-1 in 2011; H. flava — 13.3 ± 5.2 sawfly trap-1 in 2010,and 16.6 ± 6.9 sawfly trap-1 in 2011; and H. testudinea in organic orchard — 38.3 ± 26.2 sawfly trap-1 in 2010 and 5.0 ± 2.8 sawfly trap-1 in 2011, in conventional orchard — 14.8 ± 8.1 sawfly trap-1 in 2010 and 9.3 ± 4.3 sawfly trap-1 in 2011. Conditions for development of both plum sawfly species were better in 2011, when abundance nearly reached the economic threshold. Population density, cumulative trap catches during the flight period, and damage caused by apple sawfly varied significantly between the study years and apple cultivars. In 2010, apple sawfly was more abundant and caused more serious damage than in 2011. The economic threshold of 30–40 individuals per trap was reached in 2010 due to the better conditions of development. The various apple cultivars suffered different damage levels: cv. ‘Aldas’, ‘Vitos’ and ‘Rubinola’ suffered the highest damage in the organic orchard, but no significant differences were observed. In the conventional garden, cv. ‘Auksis’ had the most damaged fruits.