The influence of temperature and photoperiod on the reproductive diapause and cold tolerance of spotted‐wing drosophila,Drosophila suzukii

Knowledge regarding the reproductive status of spotted‐wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), is of critical importance in predicting potential infestations of this invasive pest, as eggs are laid in ripe or ripening fruit of several commercially important small‐fruit crops. Token environmental stimuli for the induction of reproductive diapause and improved cold tolerance were identified for D. suzukii. Diapause induction was evaluated by assessing, via dissection, the number of mature eggs carried by field‐captured D. suzukii and laboratory‐reared D. suzukii held under various temperature and photoperiod regimes. Egg load decreased over time in females trapped from July to December at sites in Benton County, OR, and Ontario County, NY, both USA, and reached zero eggs by December at all sites. Photoperiods below 14 h of day length led to reduced egg maturation in laboratory‐reared flies held at moderate temperatures (15 or 20 °C). Whereas very few mature eggs were found in females held at 10 °C under short‐ or long‐day photoperiods for several weeks after eclosion, a spontaneous return to ovarian maturity was observed in short‐day‐entrained females after 7 weeks. Diapause termination was investigated by evaluating fecundity in diapausing females returned to optimal environmental conditions. Whereas long‐day‐entrained flies began producing offspring immediately upon return to optimal conditions, short‐day‐entrained flies returned after 1 and 6 weeks at 10 °C were slower to produce offspring than colony flies or short‐day‐entrained flies returned after 7 weeks. Cold tolerance was evaluated by observing chill coma recovery rates after 24 h exposure to ?1 °C. Cold‐acclimated (diapausing) females recovered from chill coma faster than cold‐hardened or unacclimated females.     

Efficacy of biopesticides on spotted wing drosophila,Drosophila suzukii Matsumura in fall red raspberries

Drosophila suzukii Matsumura is a significant pest of soft‐skinned fruit. Larvae of D. suzukii develop within the fruit making it unmarketable as fresh berries and increasing the risk of rejection by processors. We evaluated selected biopesticides for control of D. suzukii in fall red raspberries, Rubus idaeus L. The trial results highlight a small number of biopesticides with the potential to reduce infestation of Drosophila larvae in raspberries. In addition to the standard biopesticide spinosad, we found that sabadilla alkaloids and Chromobacterium subtsugae both reduced the number of Drosophila larvae in raspberry fruit. Treatments that included corn syrup as a feeding stimulant showed no significant difference in their infestation levels compared to treatments without the syrup. In the final week of the 5‐week trial, treatments with rotations of either spinosad/C. subtsugae or spinosad/sabadilla alkaloids had a 67% and 57% reduction in infestation when compared to untreated raspberries. Treatments of spinosad alone on a 7 day rotation and C. subtsugae alone on a 3–5 day rotation both had a 62% and 61% reduction in larval infestation when compared to untreated raspberries. Third instar larvae, the largest and most damaging, were significantly reduced in plots treated with spinosad only, a rotation of spinosad/sabadilla alkaloids and the rotation of spinosad/C. subtsugae with corn syrup added when compared to untreated plots. This suggests that either of these biopesticides could be used as effective rotation partners along with spinosad for control of D. suzukii. Our results highlight that biopesticides can provide significant reduction in this devastating pest when used alone or in combination, providing options to support resistance management.     

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.     

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.     

Simpler is better: fewer non‐target insects trapped with a four‐component chemical lure vs. a chemically more complex food‐type bait for Drosophila suzukii

Baits – fermented food products – are generally attractive to many types of insects, which makes it difficult to sort through non‐target insects to monitor a pest species of interest. We test the hypothesis that a chemically simpler and more defined attractant developed for a target insect is more specific and attracts fewer non‐target insects than a chemically more complex food‐type bait. A four‐component chemical lure isolated from a food bait and optimized for the spotted wing drosophila (SWD), Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), was compared to the original wine/vinegar bait to assess the relative responses of non‐target insects. In several field experiments in Washington State, USA, it was shown that numbers of pest muscid flies, cutworm and armyworm moths, and pest yellowjackets were reduced in traps baited with the chemical lure compared to the wine/vinegar bait. In other field experiments in the states of Washington, Oregon, and New York, numbers of non‐target drosophilid flies were also reduced in traps baited with the chemical lure relative to wine/vinegar bait. In Washington, numbers of Drosophila melanogaster Meigen and Drosophila obscura Fallen species groups and Drosophila immigrans Sturtevant were reduced in the chemical lure traps, whereas in New York, D. melanogaster and D. obscura species groups, D. immigrans, Drosophila putrida Sturtevant, Drosophila simulans Sturtevant, Drosophila tripunctata Loew, and Chymomyza spp. numbers were reduced. In Oregon, this same effect was observed with the D. melanogaster species group. Taken together, these results indicate that the four‐component SWD chemical lure will be more selective for SWD compared to fermentation baits, which should reduce time and cost involved in trapping in order to monitor SWD.     

The effects of non-crop habitat on spotted wing drosophila (Drosophila suzukii) abundance in fruit systems: A meta-analysis

1. Drosophila suzukii (SWD) poses a threat to soft and stone fruit globally. SWD inhabits non-crop areas adjacent to farms from where it moves into crops to cause damage. Effective IPM control strategies, considering both the crop and non-crop area, are needed to control this economically important pest.
2. We conducted a meta-analysis to quantify the impacts of different non-crop habitats around fruit farms on SWD populations, comparing abundance of SWD trapped in crop and non-crop habitats.
3. Overall, SWD abundance was greater in non-crop habitats than in cropped areas and this difference was greatest in farms adjacent to woodland, or field margins containing known SWD host plants.
4. The difference in SWD abundance between crop and non-crop habitats was not affected by crop type but was greatest in the winter months and in conventional compared to organic farms, indicating conventional approaches can reduce relative SWD abundance.
5. Drosophila suzukii overwinter in non-crop habitats which provide refuge outside the cropping season. However, certain habitats support greater relative abundance of SWD than others and this is also affected by farm management. We discuss what these findings mean for effective control of SWD.

     

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.     

Chemical cues from competitors change the oviposition preference of Drosophila suzukii

Although Drosophila suzukii Matsumura (Diptera: Drosophilidae) infests fresh and ripening fruits, it is attracted to fermented fruits as well. Because fermented fruits attract other flies too, if D. suzukii utilizes fermented fruits as oviposition substrates, competition can be more intense on them. To avoid such competition, D. suzukii may change oviposition preference when particular species of competitor flies are present, but the effect of odor cues associated with competitors on the oviposition preference of D. suzukii is still unknown. To examine such an effect, we investigated the oviposition preference of D. suzukii in the presence of four competitor fly species – Drosophila melanogaster Meigen, Drosophila lutescens Malloch, Drosophila rufa Kikkawa & Peng, and Drosophila auraria Peng – and D. suzukii itself. We prepared artificial substrates with yeast treatment (Y⁺: yeast supplementation, Y⁻: control) and competitor fly treatment (F⁺: pre-inoculated with competitor fly odor, F⁻: control), and performed two-choice experiments using the substrates with various Y and F treatments. Our results showed that D. suzukii oviposited more eggs on Y⁺ substrates than on Y⁻ substrates when no competitor flies were present and the presence of competitor flies influenced D. suzukii’s oviposition preference for yeast-supplemented substrates and its effect changed depending on the competitor fly species. If the presence of competitors around fallen fruits on the ground suppresses D. suzukii’s oviposition on the fallen fruits and facilitates the oviposition on non-fermenting substrates in nature, it may drive D. suzukii to use ripening fruits on the tree. Such selective pressure may facilitate the evolution of morphological traits such as a serrated ovipositor in D. suzukii.     

Limited protection of the parasitoid Pachycrepoideus vindemiae from Drosophila suzukii host‐directed spinosad suppression

Laboratory trials were conducted to determine whether the spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), puparium can provide an effective physical barrier to protect immature stages of the pupal parasitoid Pachycrepoideus vindemiae (Rondani) (Hymenoptera: Pteromalidae) from spinosad treatments. Spinosad insecticides are currently an important suppression strategy for D. suzukii in organically managed fruit orchards although they are well known to cause mortality in hymenopteran parasitoids. High adult P. vindemiae female mortality (83%) occurred within 24 h of exposure to D. suzukii pupae treated with 10 mg a.i. l^?1 spinosad and female parasitoids did not avoid the pupae treated with similar low levels of spinosad in choice tests that included untreated pupae. Pachycrepoideus vindemiae develops as an idiobiont ectoparasitoid on host fly pupa within the sclerotized host puparium. Significant P. vindemiae survival and emergence was recorded when parasitized D. suzukii puparia were exposed to field treatment levels of spinosad; however, the parasitoid survival was dependent on the time of the spinosad treatment of the host post‐parasitization. Significant parasitoid survival occurred when the host puparia were treated at 2 weeks when the parasitoid was in the pupal stage but did not occur when the host puparia were treated at 1 week post‐parasitization, when the parasitoids were still in a larval stage. The parasitoid adults consumed or otherwise came in contact with residual degrading spinosad when they exited the treated host, and consequently high and low adult parasitoid mortality occurred when the adults emerged from puparia treated at 2 and 1 week(s), respectively. Our study indicates that generally the integration of P. vindemiae parasitism into a sustainable D. suzukii management program is not compatible with spinosad treatments, although P. vindemiae in the pupal stage inside sclerotized host puparia appear to be minimally impacted by spinosad treatments, provided that the spinosad degrades before parasitoid emergence.     

Seasonal monitoring of Drosophila suzukii and its non-crop hosts in Wuhu,Eastern China

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is a serious pest that prefers fresh fruits and is native to Southeast Asia. In our study, apple cider vinegar bait traps were used to capture and monitor the population dynamics of this native pest in Wuhu City, China, from May/June 2017 to May 2018. The research was conducted at 15 locations in two fruit orchards in Wuhu. Traps caught more adults in general in a Meiling blueberry orchard than in a Xicun mixed orchard, and the highest trap counts occurred near harvest time (October). Females had more mature eggs from September to November, and the number of mature eggs declined thereafter. We found several non-crop hosts, which can provide food and reproductive resources for D. suzukii and are common in forests and field margins. By comparing the number of captured adults in the Meiling and Xicun orchards, we found that blueberry was preferred by D. suzukii among the fruits in our search. Fruit ripening times differed among crops; therefore, fly populations moved between crop and non-crop habitats during the year or had varying population dynamics on different crops in different seasons. The D. suzukii population and the number of mature eggs decreased in summer and winter but increased in spring and autumn. Drosophila suzukii had higher survival rates with blueberry than those with other fruits, and D. suzukii could use four non-crop species growing around the orchards as host plants.     

Evaluating Drosophila suzukii immunomarking for mark‐capture research

Drosophila suzukii Matsumura (Diptera: Drosophilidae) utilizes ‘Himalaya’ blackberry, Rubus armeniacus Focke (Rosaceae), as a host and may invade berry and stone fruit crops from field margins containing this invasive weed. Laboratory and semi‐field studies were conducted to determine (1) the persistence of protein marks including 10% chicken egg whites (egg albumin protein), 20% bovine milk (milk casein protein), and 20% soy milk (soy trypsin inhibitor protein) on topically sprayed D. suzukii, (2) protein retention on blackberry leaves, and (3) D. suzukii acquisition of protein after exposure to marked blackberry leaves for up to 14 days after application. All flies and leaves were assayed for the presence of the protein marks using protein‐specific enzyme‐linked immunosorbent assays. Egg albumin, milk casein, and soy trypsin proteins persisted on 94, 49, and 25% of the topically marked D. suzukii, respectively, throughout the 14‐day study period. Egg albumin was retained on 100% of treated leaves for 14 days, regardless of environmental conditions. At least 50% of flies exposed residually to egg albumin‐treated leaves were marked for 3 days, regardless of exposure time and environmental conditions. However, increasing fly exposure time to treated leaves in April and June appeared to improve protein mark acquisition. Acquisition of protein by flies from treated leaves for milk casein was inconsistent, and poor for soy trypsin, despite detectable levels on treated leaves. Egg albumin had the longest and most consistent persistence on flies, leaves, and flies exposed to leaves in laboratory and semi‐field studies, under a variety of environmental conditions and exposure times.     

Germline transformation of the spotted wing drosophilid, Drosophila suzukii, with a piggyBac transposon vector

Drosophila suzukii is a pest of small fruits in many parts of the world, whose management is limited to cultural practices and the use of insecticides. Here we describe a method to genetically manipulate this species in the first step to create female lethality strains useful for the sterile insect technique method of population suppression. This was achieved by the germ-line transformation of D. suzukii with a piggyBac transposon vector having a female-specific lethality effector construct. This can be used in a tetracycline-suppressible conditional gene expression system, when crossed to a suitable tet-transactivator strain. Transformation occurred efficiently, at a frequency of 16 % per fertile G0 embryo injected with vector and helper transposase plasmids. The vector was marked for transformant selection with the polyubiquitin-regulated EGFP fluorescent protein, and contains the attP landing site and heterospecific lox recombination sites for post-integration modification of the transgene vector. The 3xP3-AmCyan fluorescent protein marker was inserted within the lox sites to follow a possible recombinase-mediated cassette exchange, that would allow subsequent improvement of the transgenic strain by immobilization of the vector and introduction of new marker cassettes.     

Effect of temperature on reproduction,development, and phenotypic plasticity of Drosophila suzukii in Brazil

Temperature is a determining factor for the development and establishment potential of insect pests. The present study describes the impact of temperature (13, 18, 23, 25, 28, 30, and 33 °C) on the life cycle parameters and phenotypic plasticity of South American populations of Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) in the laboratory. Secondary objectives were to determine the lower thermal threshold and thermal constant to estimate the number of annual generations of the insect in small-fruit-producing regions in Brazil. The highest egg-to-adult survival was recorded at 23 and 25 °C. At 30 and 33 °C, no emergence of D. suzukii was observed. The egg-to-adult development time was shortest at 25 and 28 °C (ca. 10 days). The net reproductive rate (R₀), and the intrinsic rate of population increase (r_m) were highest at 23 and 25 °C. In contrast, temperatures of 13 and 28 °C generated largest and smallest body sizes, respectively, and caused reductions of 99 and 93% in R₀. The estimated lower thermal threshold was 7.8 °C for egg-to-adult survival. The estimated thermal constant was 185.8 degree days, and the estimated annual number of generations of D. suzukii ranged from 17.1 in cold regions to 27.2 in warm regions. The results of the present study are important for understanding D. suzukii occurrence in the field, contributing to more informed and precise pest management.     

拱背果蝇属二新种记述(双翅目,果蝇科)

记述了拱背果蝇属Lordiphosa 2新种,毛突拱背果蝇 Lorrdiphosa pilosella sp.nov.和叉拱背果蝇Lordiphosa furcans sp.nov..     

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.     

Insights into the susceptibility of raspberries to Drosophila suzukii oviposition

The spotted wing drosophila (SWD) causes massive losses in red raspberry (Rubus idaeus L.) cultivation by direct oviposition leading to damages of the soft skin fruits. Knowledge of the fly's host preference could help farmers in managing the pest. We used a laboratory-based oviposition assay for screening the germplasm of Rubus to ascertain whether the spotted wing drosophila prefers certain cultivars to others for oviposition and if preference is based on citric acid and Brix content or firmness. Correlation analyses of evaluated characters with no-choice tests results in 3 years obtained no correlation between citric acid, Brix content and oviposition. Primocane raspberries were lower affected by SWD than floricane raspberries. The Rubus hybrid cultivar “Dorman Red” and the primocane cultivar “Pokusa” showed the lowest oviposition rate compared to the other 58 evaluated genotypes. We found that oviposition correlates to firmness of the investigated cultivars, which strongly indicates that host preference is partly connected to that character in raspberries. The results are discussed regarding the use of Rubus genetic resources in breeding and integrated pest management to control spotted wing drosophila in the field.     

Effects of fluctuating thermal regimes on cold survival and life history traits of the spotted wing Drosophila(Drosophila suzukii)

Drosophila suzukii is an invasive pest causing severe damages to a large panel of cultivated crops.To facili tate its biocontrol with stratcgies such as sterile or incompatible insect techniques,D.suzukid must be mass-produced and then stored and transported under low temperature.Prolonged cold exposure induces chill injuries that can be mitigated if the cold period is interrupted with short warming intervals,referred to as fluctuating thermal regimes(FTR).In this study,we tested how to optimally use FTR to extend the shelf life of D.suzukii under cold storage.Several FTR parameters were asessed:temperature(15,20,25℃),duration(0.5,1,2,3 h),and frequency(every 12,24,36,48 h)of warming intervals,in two wild-type lines and in two developmental stages(pupac and adults).Generally,FTR improved cold storage tolerance with respect to constant low temperatures(CLT).Cold mortality was lower when recovery temperature was 20℃ or higher,when duration was 2 h per day or longer,and when warming interruptions occurred frequently(every 12 or 24 h).Applying an optimized FTR protocol to adults greatly reduced cold mortality over long-term storage(up to 130 d).Consequences of FTR on fitness-related traits were also investigated.For adults,poststorage survival was unaffected by FTR,as was the case for female fecundity and male mating capacity.On the other hand,when cold storage occurred at pupal stage,postorage survival and male mating capacity were altered under CLT,but not under FTR.After storage of pupae,female fecundity was lower under FTR compared to CLT,suggesting an energy trade-off between repair of chill damages and C22 production.This study provides detailed information on the application and optimization of an FTR-based protocol for cold storage of D.suzuki that could be useful for the biocontrol of this pest.     

中国及周边国家的伏绕眼果蝇属叶芒绕眼果蝇复合种组研究(双翅目,果蝇科)

叶芒伏绕眼果蝇复合种组是Tsacas and Okada,1983建立的,已报告有6种,均出自于东洋区.记述了采自于中国及周边国家的伏绕眼果蝇属叶芒伏绕眼果蝇复合种组的10个种,并附有分种检索表.端尖叶芒伏绕眼果蝇Phortica foliacea(Tsacas et Okada,1983);叶芒伏绕眼果蝇Phortica foliiseta Duda,1923;侦测伏绕眼果蝇Phortica speculum(Máca et Lin,1993);异叶芒伏绕眼果蝇Phortica afoliolata Chen etToda,sp.nov.;短毛伏绕眼果蝇Phrtica brachychaeta Chen etToda,sP.nov.;拟叶芒伏绕眼果蝇Phortica foliisetoides Chenet Toda,sp.nov.;缺毛伏绕眼果蝇Phortica glabra Chen etToda,sp.nov.;刺伏绕眼果蝇Phortica spinosa Chen et Gao,sp.nov.;对称伏绕眼果蝇Phortica symmetria Chen et Toda,sp nov.;田边氏伏绕眼果蝇Phortica tanabei Chen et Toda,sp nov.     

Inhibition of the spoilage yeast Pichia occidentalis in a wheat germ diet for mass rearing of Drosophila suzukii

A wheat germ diet was initiated for the mass rearing of Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) and subsequent production of its parasitoid Trichopria drosophilae Perkins (Hymenoptera: Diapriidae). However, the main problem of the diet was the microbial contamination affecting the batches of good pupae production. Therefore, the concentration of four antimicrobials was optimized through the Taguchi orthogonal array for the inhibition of microbial contamination, identified as Pichia occidentalis (Kurtzman et al.) Kurtzman et al. The optimized Taguchi-selected-antimicrobials concentrations were 1.33 g l⁻¹ of potassium sorbate, 1.33 g l⁻¹ of propyl paraben, 1.33 g l⁻¹ of sodium propionate, and 0.16 g l⁻¹ of triclosan. When the antimicrobials were added to the diet, colony-forming units of P. occidentalis were inhibited by two orders of magnitude. Such inhibition means that the D. suzukii females produced 61.1 and 79.3% more pupae and adults, respectively, than the diet with no antimicrobials. These results increase the potential of the wheat germ diet as an artificial diet for mass rearing of D. suzukii and T. drosophilae.