Influence of abiotic and biotic factors on developmental parameters of Drosophila suzukii (Diptera: Drosophilidae)

Drosophila suzukii (Diptera: Drosophilidae), a pest of thin-skinned fruits, has been detected worldwide recently, with new locations of establishment determined annually since it first became a concern on continental North America in 2008. Drosophila suzukii females are different from most other drosophilids as being one of two known species capable of economic injury in fruit. This is achieved via a serrated ovipositor that pierces the skin of ripening susceptible fruit, depositing eggs that will then hatch into larvae, utilizing the fruit as a food source. Current control methods involve the application of pesticides on a weekly basis upon the coloring of fruit, ending when harvest is complete. To shift back towards IPM, knowledge of D. suzukii development under different environmental factors is necessary to improve upon current management options. The first objective of this research project was to determine the developmental period, longevity, and fecundity of D. suzukii when exposed to seven constant temperatures and separately, five constant relative humidities (RHs) at 22 ± 2 ºC. Temperature had an influence on these parameters, with decreasing developmental periods as temperatures increased from 10 to 28ºC. Developmental period increased above 28ºC. The highest net reproductive rate and intrinsic rate of population increase was 22 ºC. Estimations using linear and nonlinear fit for the minimum, optimal and maximum were 7.2, 28.1, and 42.1 ºC, respectively. The minimal, optimal, and maximal temperatures for intrinsic rate of population increase were 13.4, 21.0, and 29.0 ºC . Relative humidity also had a significant influence on these parameters. The estimated minimum, optimal and maximum development thresholds for RH were 27, 79, and 100% RH, respectively. Fecundity appeared to increase with RH, with a maximum observed at 93%, however ovary dissections indicated that no differences in ovary maturation occurred between 78 and 93% RH. The second objective of this research was conducted to determine the effect of floral resource feeding on nutrient levels in female D. suzukii when provided cherry or blueberry blossoms as well as lifespan over an observed feeding period. When adults were provided cherry blossoms, they had significantly longer lifespans than their water-fed counterparts over a 41-day observation period. Adults provided blueberry blossoms exhibited longer lifespans, however, this observation could not be statistically compared with the cherry and water treatments due to availability of blossoms and a staggered start date. A nutritional assay showed higher levels of glycogen and sugar levels amongst female flies provided either blossom type or sucrose over water-fed flies. Lipid levels tended to be the same across treatments. Overall, this research discovered new information about D. suzukii biology that can be incorporated into future management strategies. The temperature-related development and fecundity study contributed to the development of a population prediction model. The humidity work will be incorporated into the D. suzukii model to refine estimates across different locations. The model will provide a tool for growers to determine management timing. The nutritional work may aide in the development of a bait spray and timing of bait spray application

Impact of floral feeding on adult Drosophila suzukii survival and nutrient status

Drosophila suzukii, spotted wing drosophila, is a serious pest of small fruits and cherries in many regions of the world. While host usage has been well studied at the ovipositional and larval feeding stages, little is known about the feeding ecology and nutrient requirements of adults. This study addressed the impact of feeding on the survival and nutrient reserves of adult D. suzukii in laboratory assays. First, access to cherry blossoms increased survival rates of both adult males and females compared to water only. This suggests that these early spring blossoms may provide a food source for D. suzukii in fields that may be devoid of other food sources. Second, D. suzukii reared on a standard laboratory diet as larvae emerged as adults with minimal glycogen and sugar levels. Adults with continued access to a carbohydrate–protein diet showed rapidly elevated carbohydrate reserves, and adults with continued access to only water showed a decline in total sugars. Third, females with access to cherry or blueberry blossoms showed elevated carbohydrate reserves when compared to those with access to water only. These results illustrate the importance of adult feeding in enhancing survival and carbohydrate reserves among D. suzukii.This is the publisher’s final pdf. The published article is copyrighted by Springer Verlag and can be found at: http://link.springer.com/article/10.1007%2Fs10340-016-0762-7Keywords: Sugar, Lipid, Nectar, Glycoge

Impact of floral feeding on adult Drosophila suzukii survival and nutrient status

Drosophila suzukii, spotted wing drosophila, is a serious pest of small fruits and cherries in many regions of the world. While host usage has been well studied at the ovipositional and larval feeding stages, little is known about the feeding ecology and nutrient requirements of adults. This study addressed the impact of feeding on the survival and nutrient reserves of adult D. suzukii in laboratory assays. First, access to cherry blossoms increased survival rates of both adult males and females compared to water only. This suggests that these early spring blossoms may provide a food source for D. suzukii in fields that may be devoid of other food sources. Second, D. suzukii reared on a standard laboratory diet as larvae emerged as adults with minimal glycogen and sugar levels. Adults with continued access to a carbohydrate–protein diet showed rapidly elevated carbohydrate reserves, and adults with continued access to only water showed a decline in total sugars. Third, females with access to cherry or blueberry blossoms showed elevated carbohydrate reserves when compared to those with access to water only. These results illustrate the importance of adult feeding in enhancing survival and carbohydrate reserves among D. suzukii.To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf, displayed as an "Author's personal copy." The published article is copyrighted by Springer and can be found at: https://doi.org/10.1007/s10340-016-0762-

Integrating Temperature-Dependent Life Table Data into a Matrix Projection Model for Drosophila suzukii Population Estimation

Temperature-dependent fecundity and survival data was integrated into a matrix population model to describe relative Drosophila suzukii Matsumura (Diptera: Drosophilidae) population increase and age structure based on environmental conditions. This novel modification of the classic Leslie matrix population model is presented as a way to examine how insect populations interact with the environment, and has application as a predictor of population density. For D. suzukii, we examined model implications for pest pressure on crops. As case studies, we examined model predictions in three small fruit production regions in the United States (US) and one in Italy. These production regions have distinctly different climates. In general, patterns of adult D. suzukii trap activity broadly mimicked seasonal population levels predicted by the model using only temperature data. Age structure of estimated populations suggest that trap and fruit infestation data are of limited value and are insufficient for model validation. Thus, we suggest alternative experiments for validation. The model is advantageous in that it provides stage-specific population estimation, which can potentially guide management strategies and provide unique opportunities to simulate stage-specific management effects such as insecticide applications or the effect of biological control on a specific life-stage. The two factors that drive initiation of the model are suitable temperatures (biofix) and availability of a suitable host medium (fruit). Although there are many factors affecting population dynamics of D. suzukii in the field, temperature-dependent survival and reproduction are believed to be the main drivers for D. suzukii populations

Log of estimated <i>Drosophila suzukii</i> populations for each of Parlier (California), Wilmington (North Carolina) and Salem (Oregon), US during 2013.

<p>Log of estimated <i>Drosophila suzukii</i> populations for each of Parlier (California), Wilmington (North Carolina) and Salem (Oregon), US during 2013.</p

Log of estimated <i>Drosophila suzukii</i> populations for Riva del Garda, Pergine and Sant’Orsola, Italy during 2013.

<p>Log of estimated <i>Drosophila suzukii</i> populations for Riva del Garda, Pergine and Sant’Orsola, Italy during 2013.</p

Degree-day estimations using 4°C as a lower threshold for Wilmington (North Carolina), Parlier (California), and Salem (Oregon), US during 2013.

<p>Degree-day estimations using 4°C as a lower threshold for Wilmington (North Carolina), Parlier (California), and Salem (Oregon), US during 2013.</p

Log of estimated <i>Drosophila suzukii</i> populations for Salem (Oregon), US during 2012 and 2013.

<p>Log of estimated <i>Drosophila suzukii</i> populations for Salem (Oregon), US during 2012 and 2013.</p

Log of estimated <i>Drosophila suzukii</i> populations for Pergine, Italy during 2012 and 2013.

<p>Log of estimated <i>Drosophila suzukii</i> populations for Pergine, Italy during 2012 and 2013.</p