Monitoring the appearance and possibility for prevention of the apple sawfly in Croatia
The apple sawfly Hoplocampa testudinea Klug has recently become a widespread pest in Croatian apple orchards. It causes severe damage in the blooming period due to the fact that infested fruit fall off.This article shows results collected over three years of field research on trap catches of sawflies, the period of laying eggs, the appearance of larvae and detection of damage. In the climate of northwestern Croatia, adult sawfly appear in April during the blooming period of the early apple variety of Idared.By monitoring temperatures from January 1, adults were detected when the thermal constant reached 210 day-degrees. Our observations showed that the larvae emerged when the sum of thermal constants reached ca. 110 day-degrees.The investigation of effective control strategies with insecticides showed high efficacy of thiametoxam (Actara), imidacloprid (Confidor), thiacloprid (Calypso) and betacyfluthrin + oxydemeton-methyl (Enduro) and lower efficacy of phosalone (Zolone), chlorpyrifos-methyl (Reldan), and lambda cyhalothrin (Karate).
Species ratio, spring emergence, population dynamics and damage of plum sawflies Hoplocampa minuta and H. flava in plum orchard.
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.
A simulation model for the population dynamics of rice leaf-folders (Lepidoptera: Pyralidae) and their interactions with rice
1. A simulation model for the population dynamics of rice leaf-folders (Lepidoptera: Pyralidae) interacting with rice (Oryza sativa L.) is described. It was designed to improve the understanding of the role of rice leaf-folders as elements of the rice ecosystem and to detect crucial knowledge gaps in view of a holistic assessment of their pest status. The model represents a synthesis of experimental results on leaf-folder biology and behaviour. 2. A distributed delay model including attrition was applied to simulate dynamic population changes such as birth, ageing, mortality, migration and growth in terms of numbers and biomass