H.H.M. Helsen

Non-crop plants used as hosts by Drosophila suzukii in Europe

The invasive spotted wing drosophila Drosophila suzukii, a fruit fly of Asian origin, is a major pest of a wide variety of berry and stone fruits in Europe. One of the characteristics of this fly is its wide host range. A better knowledge of its host range outside cultivated areas is essential to develop sustainable integrated pest management strategies. Field surveys were carried out during two years in Italy, the Netherlands and Switzerland. Fruits of 165 potential host plant species were collected, including mostly wild and ornamental plants. Over 24,000 D. suzukii adults emerged from 84 plant species belonging to 19 families, 38 of which being non-native. Forty-two plants were reported for the first time as hosts of D. suzukii. The highest infestations were found in fruits of the genera Cornus, Prunus, Rubus, Sambucus and Vaccinium as well as in Ficus carica, Frangula alnus, Phytolacca americana and Taxus baccata. Based on these data, management methods are suggested. Ornamental and hedge plants in the vicinity of fruit crops and orchards can be selected according to their susceptibility to D. suzukii. However, the widespread availability and abundance of non-crop hosts and the lack of efficient native parasitoids suggest the need for an area-wide control approach.

Phenology of the common earwig Forficula auricularia L. (Dermaptera: Forficulidae) in an apple orchard

Abstract Observational data taken over 13 years, on the phenology and the abundance of the first brood of the common earwig, Forficula auricularia L., in a Dutch apple orchard were analysed. The results are used to indicate a fixed sampling moment for this predator. The fourth instar nymphs emerged between 12 June and 10 July, and the adult stage was reached between 8 and 30 July. The observed phenology, and the number of earwigs in shelter traps, correlated well with the temperature sum in day-degrees above a thermal threshold of 6 C, accumulated from 1 January. Maximum numbers of earwigs could be trapped in the trees when the nymphs of the first brood entered the fourth instar, generally between 600 and 750 day-degrees.

Optimizing biocontrol using phenological day degree models: the European earwig in pipfruit orchards

1 Phenological day degree models are often used as warning systems for the emergence of arthropod pests in agricultural crops or the occurrence of natural enemies of the pest species. In the present study, we report on a case study of the European earwig Forficula auricularia L., which is an important natural enemy in pipfruit orchards, and describe how such a day degree model can be used to avoid negative effects of crucial orchard management, such as spray applications and soil tillage. A precise timing of these interventions in relation to the phenology of natural enemies will enhance biocontrol. 2 Earwig population dynamics are characterized by single‐ and double‐brood populations, each with specific biological characteristics. 3 A day degree model capable of predicting the phenology of local earwig populations of both population types was developed. The model was checked for accuracy by comparing the first field observation dates of various life stages with predicted values using temperature data from the nearest weather station. In addition, variation in development time was assessed using field data. 4 The model was able to make predictions on a global scale. Although single‐ and double‐brood populations differ in phenology, the predictions of first appearance dates were similar. Variation in development time showed that single‐brood populations were more synchronized. 5 Our phenological model provides an accurate tool for predicting and simulating earwig population dynamics, as well as for enhancing the biocontrol of pests in pipfruit orchards.

Diapause termination and thermal requirements for postdiapause development in Aphelinus mali at constant and fluctuating temperatures

Diapause termination under natural and simulated overwintering conditions, the effect of subzero temperature on postdiapause development and the relationship between postdiapause development rate and constant and fluctuating temperatures was studied in a Dutch population of Aphelinus mali Hald. (Hymenoptera: Aphelinidae).

Embryonic development of orchard leafrollers and the forecasting of egg hatch

The development time of eggs of three of the most noxious leafrollers found in Northeuropean orchards, Spilonota ocellana (Denis & Schiffermüller), Archips podana (Scopoli), and Pandemis heparana (Denis & Schiffermüller) (Lepidoptera: Tortricidae) was recorded in the laboratory at five constant temperatures between 14 and 25 °C. In this range, developmental rates of the three species did not differ significantly. While the flight periods of these species overlap largely, a single algorithm could be used to devise optimal spraying time(s) for the three species.

Overwintered Drosophila suzukii Are the Main Source for Infestations of the First Fruit Crops of the Season

The mechanisms allowing the widespread invasive pest Drosophila suzukii to survive from early spring until the availability of the first fruit crops are still unclear. Seasonal biology and population dynamics of D. suzukii were investigated in order to better understand the contribution of the early spring hosts to the infestation of the first fruit crops of the season. We identified hosts available to D. suzukii in early spring and assessed their suitability for the pest oviposition and reproductive success under field and laboratory conditions. The natural infestation rate of one of these hosts, Aucuba japonica, was assessed over springtime and the morphology of the flies that emerged from infested A. japonica fruits was characterized under field conditions. Then, these findings were correlated with long-term monitoring data on seasonal reproductive biology and morphology of the pest, using a cumulative degree-days (DD) analysis. Field sampling revealed that overwintered D. suzukii females were physiologically able to lay eggs at 87 DD which coincided with the detection of the first infested early spring hosts. The latter were continuously and increasingly infested by D. suzukii eggs in nature from early spring until the end of May, in particular Aucuba japonica. Individuals emerged from most of these hosts were characterized by a poor fitness and a rather low success of emergence. In the field, only few summer morphs emerged from naturally infested A. japonica fruits around the end of May-beginning of June. However, field monitoring in orchards revealed that D. suzukii individuals consisted solely of winter morphs until mid-June. These observations indicate that overwintered D. suzukii females are the predominant source for the infestations in the first available fruit crops of the season. We discuss these findings in the context of possible pest control strategies.

Erratum to: Non-crop plants used as hosts by Drosophila suzukii in Europe

The article was originally published Online First without open access. After publication in Volume 89, Issue 3, pp. 735–748 the author decided to opt for Open Choice and to make the article an open access publication. Therefore, the copyright of the article has been changed to The Author(s) [2017] and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons. org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.