An investigation of apple sawfly (Hoplocampa testudinea Klug 1816) (Hymenoptera: Symphyta: Tenthredinidae) populations was conducted in conventionally and organically managed apple orchards
An investigation of black plum sawfly (Hoplocampa minuta Christ, 1791) and yellow plum sawfly (Hoplocampa flava Linnaeus, 1761) populations using white sticky traps Rebell ® bianco was carried out in a plum orchard of Institute of Horticulture of Lithuanian Research Centre for Agriculture and Forestry from 2010 to 2012. A possibility to predict spring emergence of H. minuta and H. flava using temperature sum method, species ratio, main population parameters and relation between trap catches and infestation levels were investigated. H. minuta appeared to be more dominant in the complex of two plum sawfly species during the study overall, building up to 62% of individuals in comparison to H. flava and, considering various population parameters (emergence and flight dynamics, population density, sex ratio) being more significant contributor to fruit damage. Population density and flight dynamics were driving factors in determining potential damage to crop. Coincidence between mass flight and flowering periods was one of the major factors influencing fruit damage caused by plum sawflies. When mass flight coincided with flowering phase, vulnerable to sawfly attack of plum cv. 'Stanley', a high damage level of 27.8% was observed. When mass flight was strongly shifted towards the end of flowering, a relatively low damage of 7.0% was recorded. Based on the results of the correlation analysis, trap catch data could be reliably used to predict the magnitude of fruit damage level only when mass flight coincides with susceptible flowering phase. Further studies are needed to establish reliable damage thresholds for different plum cultivars. Temperature sum model to predict emergence of first plum sawfly adults was proposed. The model was based on soil temperature at 10 cm depth and two different starting dates to begin calculation. Temperature sums of 86 and 84 degree-days were calculated. Provisionary date at a temperature sum of 60 degree-days is proposed for trap placement in the orchards.
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.
An investigation on spatial distribution of apple sawfly (Hoplocampa testudinea Klug, 1816) populations was conducted in organically and conventionally managed apple orchards of Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry in 2010-2013. The aim of this study was to examine population density patterns of within orchard spatial distribution of apple sawfly. White sticky traps Rebell ® bianco (Andermatt Biocontrol, Switzerland) were used to monitor apple sawfly population density. In order to determine aggregation extent in sawfly populations, coefficient k of the negative binomial distribution, serving as aggregation index, was computed using maximum-likelihood method. Additionally, in order to accurately evaluate distribution patterns of apple sawfly within orchards, spatial analysis using Kernel density function was performed. Spatial analysis was performed using program package ARCGIS 10. Results of the study on spatial distribution patterns of apple sawfly imagoes demonstrated strong tendency for aggregation of adult sawflies across the orchard area. Localisation of clumps was quite constant despite the size of the orchard. Such knowledge could be applied for optimization of apple sawfly control strategies, especially in large orchards. The highest infestation levels were recorded exactly in the aggregations of sawflies over the course of the study. Moreover, knowing exact locations of such aggregations could be useful for optimization of positioning of traps in the orchards and, ultimately, restricting insecticide applications only to places where it is really necessary.
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