Evaluation of organic insecticides for management of spotted‐wing drosophila (Drosophila suzukii) in berry crops

Spotted‐wing drosophila, Drosophila suzukii (Matsumura), is an invasive pest affecting fruit production in many regions of the world. Insecticides are the primary tactic for controlling D. suzukii in organic as well as conventional production systems. Organic growers have a greater challenge because fewer insecticides are approved for use in organic agriculture. The most effective organically approved product is spinosad, but alternatives are needed because of label restrictions limiting the number of applications per year, toxicity to beneficial arthropods and the risk of developing resistance. We evaluated several organically approved insecticides against D. suzukii in laboratory assays and field trials conducted on organic blueberry and raspberry farms. Spinosad was consistently the most effective insecticide, but a few other insecticides such as azadirachtin + pyrethrins, Chromobacterium subtsugae and sabadilla alkaloids showed moderate activity. None of the treatments had long residual activity. Mortality started to decline by 3 days after treatment, and by 5 days after application, the treatments were not different from the controls. These products may be useful in rotation programmes, necessary for reducing reliance on spinosad and mitigating resistance. Cultural and biological control approaches are needed in fruit production for D. suzukii management, but insecticides will likely continue to be the dominant management tactic while these other approaches are being optimized and adopted.     

Evaluation of adjuvants to improve control of spotted‐wing drosophila in organic fruit production

Spotted‐wing drosophila, Drosophila suzukii (Matsumura), is a key pest of berry crops in the United States. It is managed intensively using insecticides, but organic fruit growers have few effective chemical control options. Spinosad is the most effective organically approved product for control of D. suzukii, while other organic options have not shown high levels of control. Adjuvants are products added to pesticides to improve effectiveness, and these may function as stickers, spreaders or surfactants improving the spray coverage of insecticides on surfaces and thereby increasing the likelihood that pests will contact residues. We conducted experiments evaluating organically approved biopesticides in combination with three adjuvants including poly‐1‐p‐menthene, alcohol ethoxylate and polyether‐polymethylsiloxane‐copolymer polyether to determine whether addition of adjuvants improved efficacy and residual activity of these products. Alcohol ethoxylate and poly‐1‐p‐menthene showed some inherent insecticidal activity against D. suzukii in laboratory assays. Adjuvants increased mortality of some insecticides but not to a level that would provide adequate fruit protection. Poly‐1‐p‐menthene had a negative effect when combined with hydrogen peroxide + PAA and sabadilla alkaloids. Mortality in semi‐field bioassays was quite low except for spinosad. Polyether‐polymethylsiloxane‐copolymer polyether had a negative effect on the efficacy of spinosad. The adjuvants did not extend residual activity of the insecticides. Adjuvants did not provide the expected benefits of increased performance against D. suzukii when combined with organic biopesticides. Other methods for enhancing these insecticides will need to be explored to provide organic growers with more effective chemical control options for this invasive pest.     

Evaluation of non-target effects of OMRI-listed insecticides for management of Drosophila suzukii Matsumura in berry crops

The spotted wing drosophila, Drosophila suzukii Matsumura, is an invasive pest of many fruit crops throughout North America, South America and Europe. The presence of this destructive pest has led to an increase in the number of insecticide applications. While conventional growers have an arsenal of different insecticides at their disposal, organic growers have a limited selection of effective options and rely heavily on applications of Entrust^®, the organic formulation of spinosad. An important part of research is to develop more tools for organic growers and evaluate the effects of insecticides intended to target D. suzukii on natural enemies in the system. The effects of six organic pesticides alone and in combination with three adjuvants and two phagostimulants were tested in laboratory bioassays on three common natural enemies in berry production systems including two predators, Chrysoperla rufilabris and Orius insidiosus, and a parasitoid wasp, Aphidius colemani. Under the IOBC toxicity rating scale, spinosad was rated consistently from slightly harmful to harmful across natural enemy species and residue age (the effects of pesticides over time). Sabadilla alkaloids caused mortality to O. insidiosus equal to that of spinosad. All tested pesticides were at least slightly harmful to A. colemani, and the adjuvant polyether-polymethylsiloxane-copolymer polyether caused mortality that was not significantly different from spinosad. In general, neither the addition of adjuvants nor phagostimulants increased the mortality of the insecticides tested. The exception was polyether-polymethylsiloxane-copolymer polyether, but it is unclear whether it increased the toxicity of the pesticides or was simply toxic itself since it caused high mortality to A. colemani when applied alone. Sublethal effects were measured for two predatory species by measuring eggs laid and % egg hatch. Minimal sublethal effects were observed in C. rufilabris. In contrast, all tested insecticides caused reduced egg hatch in O. insidiosus compared with the control.     

Efficacy of commercially available predators,nematodes and fungal entomopathogens for augmentative control of Drosophila suzukii

The recent arrival of Drosophila suzukii, an invasive pest of soft‐skinned fruit with a wide host range, has resulted in increased production costs for growers and the need for additional insecticide applications each growing season. There are few effective organic insecticides for D. suzukii, and insecticide use in conventional farms may be disruptive to natural enemies, suggesting a need for effective biological control to combat D. suzukii. Commercially available natural enemies were evaluated for their potential use in augmentative releases, including: the predators Orius insidiosus and Dalotia coriaria; the entomopathogenic fungi Metarhizium anisopliae, Beauveria bassiana and Paecilomyces fumosoroseus; and the entomopathogenic nematodes Heterorhabditis bacteriophora, Steinernema feltiae and S. carpocapsae. This suite of natural enemies was chosen to target D. suzukii adults as well as larvae in hanging or dropped fruit. Of the cultured fungal strains tested, only M. anisopliae significantly decreased D. suzukii survival, but it had low residual activity and no effect on D. suzukii fecundity. O. insidiosus decreased D. suzukii survival in simple laboratory arenas but not on potted blueberries or bagged blueberry branches outdoors. D. coriaria did not decrease D. suzukii survival in infested blueberries in simple laboratory arenas. The nematodes tested showed low infection rates and were not able to affect D. suzukii survival. Although this suite of natural enemies showed limited ability to suppress D. suzukii under the tested conditions, these and related natural enemies are present as part of the endemic natural enemy community in agricultural fields, where they may contribute to D. suzukii suppression.     

Minimizing insecticides for control of spotted wing drosophila (Drosophila suzukii) in soft fruit using bait sprays

Drosophila suzukii is a major pest of soft fruits, laying eggs in fruit before it is harvested. Control remains dependent on routine applications of insecticides. In semi-field experiments, we tested the possibility of reducing the amount of insecticide needed to control D. suzukii by combining lower rates, volumes and area of application, in combination with phagostimulant baits in comparison with full field rates of the insecticides and an untreated control. The baits were (1) Combi-protec—a proprietary mixture of plant extract, proteins and sugars, (2) a suspension of the yeast Hanseniaspora uvarum and (3) molasses. Low insecticide rates were 4% of the full rates and were attained by diluting the insecticide concentration in the spray and reducing the sprayed volume. The low rate was applied as a coarse quality spray in a swath across the middle of the strawberry or raspberry crop. The full rate was applied as fine droplets to the entire crop canopy. In strawberry, the Combi-protec with a low rate of cyantraniliprole resulted in the same level of control of D. suzukii as the full rate. Combi-protec was a more effective bait than the H. uvarum suspension. In raspberry, the average spray deposit coverage on the crop was approximately eight times higher with the full rate application compared with the low rate application. However, low rates of cyantraniliprole and spinosad with Combi-protec or molasses baits were equally effective in D. suzukii control compared with the full rates of insecticides. In raspberry, the cost of the four full rate sprays of insecticides was £74 ha^-1 or £314 ha^-1 more than the four low rate insecticide sprays with Combi-protec or molasses, respectively. The low rates of application resulted in fruit insecticide residues being less than 11% of those from raspberries sprayed with the full rates.     

Screening of 25 different natural crop protection products against Drosophila suzukii

Drosophila suzukii is a major pest of soft‐skinned fruits, and insecticides are often used to prevent fruit damage caused by oviposition. As D. suzukii produces many generations per year, repeated insecticide applications are required. Furthermore, D. suzukii attacks ripening and ripe fruits shortly before harvest. Therefore, the use of synthetic insecticides is limited by long pre‐harvest intervals and maximum residue limits. To be able to offer producers immediate and sustainable solutions, we tested 25 natural crop protection products with three different application methods in a laboratory screening. We show that application method is an important factor for the efficacy of the tested products. Of six natural insecticides, only Spinosad was toxic for D. suzukii and reduced the oviposition on treated blueberries. The tested oil products had no control effect and products based on different entomopathogenic fungi and Bacillus thuringiensis rather enhanced oviposition. Mineral products (Kaolin, CaCO₃, Ca(OH)₂ and clinoptilolith) applied as spray solutions were not toxic, but significantly reduced oviposition on blueberries. We provide the first study in which different application methods have been used to compare numerous, commercially available, natural crop protection products with different modes of action against adult D. suzukii. Our findings provide consultants and producers with important insights for the development of sustainable pest control strategies against D. suzukii.     

The effect of border sprays and between‐row soil tillage on Drosophila suzukii in organic blackberry production

Drosophila suzukii (Matsumura) is a major pest of soft‐skinned fruit. Females have an enlarged serrated ovipositor that is used to cut into ripening fruit and lay their eggs. Larvae develop inside infested fruit, rendering fruit unmarketable. Previous research has indicated that D. suzukii can move from adjacent woodlands into cultivated fields. Furthermore, multiple generations can occur in a single season as a result of fallen, infested fruit in the fields. Our hypothesis was that border sprays and soil tillage of field aisles can reduce D. suzukii presence in commercial blackberry fields (Rubus spp.). To test our hypothesis, we conducted split‐plot field trials in organic blackberry fields for 3 and 4 weeks in 2014 and 2015, respectively. Treatments were border sprays (whole plot, pyrethrins + azadirachtin) and tillage (subplot, ~15 cm). We evaluated adult D. suzukii in both years and berry infestation and natural enemies in 2015 only. We found that plots with border treatments had fewer D. suzukii (larvae and adults) than plots without border sprays. Tilling the soil between rows of blackberry bushes did not have a significant effect on adult captures or larval infestation of fruit. Natural enemies were unaffected by the border spray and tillage treatments. Our results confirmed our hypothesis that border sprays can be utilized to reduce populations of D. suzukii in organic blackberry fields, while maintaining populations of natural enemies. However, the effect of soil tillage is unclear and requires further investigation. Additional research should investigate the timing of border sprays and their effect on high infestations of D. suzukii as well as quantify fruit fall and depth of burial to reduce D. suzukii emergence using soil tillage.     

Variation of within‐crop microhabitat use by Drosophila suzukii (Diptera: Drosophilidae) in blackberry

Drosophila suzukii Matsumara (Diptera: Drosophilidae) is an invasive vinegar fly that infests ripe and ripening soft skinned fruits. In the south‐eastern United States, blackberry (Rubus spp.) crops are heavily impacted by D. suzukii, and current management tactics rely on the use of broad‐spectrum insecticides targeted to adult populations. An improved understanding of D. suzukii biology and ecology are necessary to create sustainable management options. Knowledge of how D. suzukii interacts with resources will enable targeted management actions in the future. In this present study, we monitored larval infestation throughout the blackberry canopy and found that infestation was highest in the inner portion of the canopy and lower in more exposed locations. We also documented higher humidity within the cane canopy relative to the edge of the field. A difference in abiotic conditions may create within‐crop microhabitats that D. suzukii is able to exploit. Future research will explore how to take advantage of these microhabitats in pest management programs.     

Plasticity in oviposition and foraging behavior in the invasive pest Drosophila suzukii across natural and agricultural landscapes

The effects and extent of the impacts of agricultural insect pests in and around cropping systems is a rich field of study. However, little research exists on the presence and consequence of pest insects in undisturbed landscapes distant from crop hosts. Research in such areas may yield novel or key insights on pest behavior or ecology that is not evident from agroecosystem-based studies. Using the invasive fruit pest Drosophila suzukii (Matsumura) as a case study, we investigated the presence and resource use patterns of this agricultural pest in wild blackberries growing within the southern Appalachian Mountain range of North Carolina over 2 years. We found D. suzukii throughout the sampled range with higher levels of infestation (D. suzukii eggs/g fruit) in all ripeness stages in natural areas when compared with cultivated blackberry samples, but especially in under-ripe fruit. We also explored a direct comparison of oviposition preference between wild and cultivated fruit and found higher oviposition in wild berries when equal weights of fruit were offered, but oviposition was higher in cultivated berries when fruit number was equal. Forest populations laid more eggs in unripe wild-grown blackberries throughout the year than populations infesting cultivated berries. This suggests D. suzukii may change its oviposition and foraging behavior in relation to fruit type. Additionally, as D. suzukii exploits a common forest fruit prior to ripeness, further research is needed to explore how this affects wild food web dynamics and spillover to regional agroecosystems.     

Acceptability of Drosophila suzukii as prey for common predators occurring in cherries and berries

The invasive cherry vinegar fly, Drosophila suzukii, has been identified in Europe as a destructive fruit pest since its arrival in 2008. In the present laboratory study, three predatory insects (Orius majusculus, Chrysoperla carnea, and Forficula auricularia) naturally occurring on fruit crops in Europe were investigated for their ability to attack and feed on D. suzukii within and outside fruits. The predators were provided with various D. suzukii life stages (eggs, larvae, pupae or adults) exposed or within infested cherries. The anthocorid bug O. majusculus fed on eggs and larvae, but was not able to attack pupae. Larvae of the lacewing C. carnea preyed upon D. suzukii eggs, larvae and pupae and also captured adult flies. The European earwig F. auricularia was the most voracious predator of these three tested species. Although the earwigs were not able to catch adult flies, they readily preyed upon every other developmental stage. Adult O. majusculus or third instar larvae of C. carnea significantly reduced the offspring of D. suzukii from infested cherries, when these contained the egg stage of the pest. None of the predators were able to attack early larval stages inside the cherries. But pupae that protruded from the fruit epicarp or that had pupated outside the fruit were accessible to lacewing larvae and earwigs and significantly reduced by them. Orius bugs, lacewing larvae and earwigs were able, under laboratory conditions, to capture and prey upon various life stages of the invasive pest, if not completely concealed inside the fruit. Our findings suggest that these generalist predators may have some control capacity on infested fruit in cultivated fruit crops and also in non‐crop habitats.     

Effects of sweet alyssum flowers and their volatile compounds on Drosophila suzukii (Matsumura) in the laboratory

Drosophila suzukii (Matsumura) is a major global pest of soft fruit crops. Based on field observations, we tested in the laboratory whether sweet alyssum (Lobularia maritima (L.)) flower volatiles and their major constituent compounds, acetophenone and benzaldehyde, repelled D. suzukii flies. Volatiles from cut flowers and acetophenone reduced numbers of D. suzukii attracted to raspberries, and acetophenone reduced numbers of larvae in the raspberries. Testing of sweet alyssum plantings or dispensing acetophenone to repel D. suzukii in fields and lower fruit infestation should be conducted.     

Drosophila suzukii in Michigan vineyards,and the first report of Zaprionus indianus from this region

Drosophila suzukii is a new invasive pest that in recent years has become established in the Great Lakes region of the United States. Understanding the level of infestation in potentially susceptible crops is an important first step for planning appropriate management responses. This study was conducted in 2010–2012 to determine the infestation potential of this pest in native Vitis labrusca, French hybrid and V. vinifera grape cultivars grown in Michigan vineyards. Drosophila suzukii adults were reared out of collected grape samples in all 3 years, comprising a low proportion of all emerged drosophilids in each of the years. This trend was also found in vacuum sampling, conducted in 2011, with the majority of flies collected being non‐D. suzukii drosophilids. Another recently introduced invasive fly species, Zaprionus indianus, was also reared out of grape samples collected in 2012. While the results of this study indicate no immediate threats to commercial grape production from D. suzukii, further research is needed to elucidate possible secondary effects that this species may have on vineyards, such as the introduction of diseases to the fruit.     

Capacity of Japanese Asobara species (Hymenoptera; Braconidae) to parasitize a fruit pest Drosophila suzukii (Diptera; Drosophilidae)

Drosophila suzukii is a pest of soft fruit such as cherry, strawberry or blueberry and recently colonized North America and Europe from Asia. In this study, we assessed the utility of Japanese Asobara species as agents for the biological control of this pest species by examining their host use in nature and their capacity to parasitize this pest species. From Japan, eight Asobara species including putative three undescribed species were found; Asobara japonica was recorded from all over Japan, Asobara tabida from high altitude areas in central and northern Japan, Asobara rossica and Asobara rufescens from central to northern Japan, three undescribed species from central to western or southern Japan and Asobara pleuralis from a subtropical island of Japan. Among them, an undescribed species Asobara sp. TK1 may be useful as an agent for the biological control because it was recorded only from D. suzukii. All of the remaining seven species were generalists mainly using drosophilid species associated with fermenting fruits, and four of them had no or very low abilities to parasitize D. suzukii, indicating that these seven species are not or less appropriate as agents for biological control.     

A rapid LAMP-based colorimetric assay with quick DNA extraction for on-site identification of Drosophila suzukii Matsumura

The spotted wing drosophila, Drosophila suzukii Matsumura (Diptera: Drosophilidae), distributes in most soft-skinned fruit areas in China, is an economically important pest of fresh cherries during Sino-European trade and is considered a quarantine pest in A2 list by European and Mediterranean Plant Protection Organization. Loop-mediated isothermal amplification (LAMP) is an accurate, quick and convenient molecular identification method, applied to distinguish D. suzukii from other fruit flies. This method can be used for inspection in the field, and at the points of entry (POEs), because its results can be detected with the naked eye due to colour changes. In our study, first, we reported a simple and fast LAMP colorimetric detection method for molecular identification of D. suzukii. We designed primer sets for D. suzukii based on mitochondrial cytochrome oxidase I (COI) sequences. The specificity and sensitivity of the primers were tested by using target and non-target fruit flies in the family Drosophilidae and Tephritidae, usually intercepted during the Sino-European cherry trade. Second, for detection in the field and at POEs, the adoption of a quick DNA extraction method could save the total time of LAMP identification to about 90 min. Taken together, this accurate, quick and convenient LAMP-based colorimetric identification assay combined with a quick DNA extraction method could visually detect clearly with just one portable heating device, which will be useful for rapid on-site identification and inspection for D. suzukii by the quarantine department.     

Nutritional geometry and fitness consequences in Drosophila suzukii,the Spotted‐Wing Drosophila

Since its arrival to North America less than a decade ago, the invasive Spotted‐Wing Drosophila (Drosophila suzukii) has inflicted substantial economic losses on soft fruit agriculture due to its ability to oviposit into ripening fruits. More effective management approaches for this species are needed, but little is known about the factors that influence behavioral choices made by D. suzukii when selecting hosts, or the consequences that their offspring experience when developing in different environments. Using a nutritional geometry methodology, we found that the ratio of proteins‐to‐carbohydrates (P:C) present in media greatly influenced adult D. suzukii behavior and subsequent offspring development. Whereas adult flies showed a strong bias in their oviposition and association behaviors toward carbohydrate‐rich foods, larval survival and eclosion rate were strongly dependent on protein availability. Here, we explore the preference–performance hypothesis (PPH), in which females are predicted to oviposit on medias that provide the greatest offspring benefits, in regard to its relevance in D. suzukii behavior and consequences for management. Our results provide valuable insight into the ecology and evolution of this species that may hopefully lead to more effective management strategies.     

Susceptibility of table grape varieties grown in south‐eastern Italy to Drosophila suzukii

Since 2008, Drosophila suzukii, the spotted wing drosophila, has colonized most of the American and European continents, being able to adapt to very different climates. In Italy, this pest has been captured from northern Alpine to southern Mediterranean regions where it can infest a broad range of fruits, including wine grapes. Studies have shown that oviposition levels and developmental rates of D. suzukii on wine grapes are lower than on other berries, although recent observations indicate that grapes may become a suitable host plant in particular conditions. Here, we report, for the first time, the results of a series of no‐choice oviposition experiments using berries of five table grape varieties sampled in the provinces of Taranto and Bari (Apulia region, south‐eastern Italy) during 2013 from both organic and conventional farming systems. The sugar content (SC) and skin hardness of each sample were analysed to assess the influence of these physiological parameters on the susceptibility of table grapes to D. suzukii infestation. A negative correlation was found between the number of eggs laid and berry skin penetration force, whereas there was a positive one between the number of eggs and Brix values, as well as sampling date. In organic grapes, SC and skin hardness of two varieties (“Crimson” and “Scarlotta”) were measured, respectively, higher and lower than in conventional grapes, thus making them more susceptible to pest infestation. The study hence shows that in laboratory conditions D. suzukii is able to heavily infest and develop on table grapes and that susceptibility to its infestation significantly depends on both variety and farming system.     

Potential host fruits for Drosophila suzukii: olfactory and oviposition preferences and suitability for development

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), the spotted wing drosophila, is a pest endemic to Southeast Asia that invaded the Americas and Europe in 2008. In contrast to most of its congeners, D. suzukii possesses a serrated ovipositor that allows it to lay eggs in unwounded commercial fruits, resulting in severe revenue losses for the industry. The purpose of this study was to determine the susceptibility of known host fruits, including cherry, strawberry, blueberry, and grape, and potential host fruits, such as banana and apple, to attack by D. suzukii. Based on the responses to volatile cues offered in a six‐choice olfactometer, the preference of female D. suzukii was ranked in the following order: strawberry = cherry > banana = apple = blueberry = grape, but in no‐choice and choice oviposition tests, the preferences were ranked as follows: cherry > strawberry = blueberry > grape = banana > apple. Furthermore, we reconfirmed that D. suzukii mainly targets rotten fruit for feeding and ripe fruit for oviposition, and females preferred fruits with intensive mechanical damage. Based on developmental parameters, apple was the least suitable host. This study has implications for the control of D. suzukii, especially in mixed fruit orchards, by providing a promising avenue for exploiting behaviour‐based control tools and emphasizing the importance of phenology in host fruit susceptibility.     

Diet quality mitigates intraspecific larval competition in Drosophila suzukii

The invasive frugivore Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) utilizes a wide range of host plants and damages important fruit crops, including blueberries, cherries, blackberries, raspberries, and strawberries. Field infestations of D. suzukii often exceed one larva per berry, suggesting that intraspecific competition may frequently occur. Because dietary resources are also likely to vary across the host range of D. suzukii, we designed a laboratory assay to measure larval performance across diets of varying quality: a standard artificial diet, a fruit‐based medium, a low‐protein, and a low‐carbohydrate diet. We manipulated egg density across these diets to provide increasing levels of competition and measured larval performance by observing survival to pupation and adulthood, and development times for both life stages. Although increasing density generally negatively impacted D. suzukii performance across diets, the magnitude of these impacts varied by diet type. Drosophila suzukii performance was generally similar in fruit and standard diets, although larval development was more rapid in fruit diets at lower densities. Even at low densities (5 or 10 eggs per arena), survival was reduced and development time increased in low‐protein diets relative to standard and fruit diets. At the two highest larval densities (20 or 40 eggs per arena), survivorship was reduced in low‐carbohydrate diets as compared to standard and fruit diets. There is evidence that larvae compensated in both low‐quality diets by extending development time, which could have consequences for population dynamics. Population models for use in D. suzukii management may need to account for both host nutritional quality and relative competition to accurately predict turnover and geographic expansion.     

Integrating Circadian Activity and Gene Expression Profiles to Predict Chronotoxicity of Drosophila suzukii Response to Insecticides

Native to Southeast Asia, Drosophila suzukii (Matsumura) is a recent invader that infests intact ripe and ripening fruit, leading to significant crop losses in the U.S., Canada, and Europe. Since current D. suzukii management strategies rely heavily on insecticide usage and insecticide detoxification gene expression is under circadian regulation in the closely related Drosophila melanogaster, we set out to determine if integrative analysis of daily activity patterns and detoxification gene expression can predict chronotoxicity of D. suzukii to insecticides. Locomotor assays were performed under conditions that approximate a typical summer or winter day in Watsonville, California, where D. suzukii was first detected in North America. As expected, daily activity patterns of D. suzukii appeared quite different between ‘summer’ and ‘winter’ conditions due to differences in photoperiod and temperature. In the ‘summer’, D. suzukii assumed a more bimodal activity pattern, with maximum activity occurring at dawn and dusk. In the ‘winter’, activity was unimodal and restricted to the warmest part of the circadian cycle. Expression analysis of six detoxification genes and acute contact bioassays were performed at multiple circadian times, but only in conditions approximating Watsonville summer, the cropping season, when most insecticide applications occur. Five of the genes tested exhibited rhythmic expression, with the majority showing peak expression at dawn (ZT0, 6am). We observed significant differences in the chronotoxicity of D. suzukii towards malathion, with highest susceptibility at ZT0 (6am), corresponding to peak expression of cytochrome P450s that may be involved in bioactivation of malathion. High activity levels were not found to correlate with high insecticide susceptibility as initially hypothesized. Chronobiology and chronotoxicity of D. suzukii provide valuable insights for monitoring and control efforts, because insect activity as well as insecticide timing and efficacy are crucial considerations for pest management. However, field research is necessary for extrapolation to agricultural settings.     

A chitinase from Euphorbia characias latex is a novel and powerful plant‐based pesticide against Drosophila suzukii

Drosophila suzukii attacks on developing soft fruits have recently caused important economic losses in Europe. This study explores the effectiveness of a new control strategy against this insect pest that is based on a plant chitinase extracted from the latex of the Mediterranean spurge, Euphorbia characias. The ability of the purified Euphorbia latex chitinase (ELC) to degrade the chitin exoskeleton of D. suzukii was assessed using confocal laser scanning microscopy. ELC treatment caused reduced larval growth, higher mortality and notable degradation of external insect structures. Therefore, the chitinase may induce a double effect on the D. suzukii larvae, a direct injury on the larval bodies and an action as antifeedant. The effects of the ELC treatment were also tested on leaves of the insect's host plants, Fragaria × ananassa and Rubus idaeus, using physiological parameters (chlorophyll concentration, chlorophyll fluorescence, leaf gas exchange and water potential) and defence gene expression (FaPGIP, FaChi2_1 and FaChi2_2) as stress indicators. ELC at concentrations effective against D. suzukii did not damage the host plants. Only plant defence gene expression was somewhat enhanced during the early hours after ELC application. In conclusion, ELC, a natural product, proved to be an effective tool for use in the development of an environmentally friendly integrated management strategy against D. suzukii, a pest whose control by conventional chemical insecticides is problematic.