Transmission of Pythium aphanidermatum to greenhouse cucumber by the fungus gnat Bradysia impatiens (Diptera: Sciaridae)

The fungus gnat (Bradysia impatiens) was examined for its ability to transmit Pythium aphanidermatum to cucumber plants. Larvae that had ingested oospores and mycelium, and then fed on the roots of young cucumber plants growing in rockwool readily introduced the fungus to them. Trans-stadial transmission of oospores from the larval to the adult stage of B. impatiens was demonstrated, although decreasing to a very low level (1.67%) in adults. However, external transmission of P. aphanidermatum on the surface of adults could not be shown. These results suggest that the larval stages of fungus gnats play a role in the dissemination of the fungus between cucumber plants but that adults probably play only a minor role.     

Insecticidal activity of Brassica juncea seed meal to the fungus gnat Bradysia impatiens Johannsen (Diptera:Sciaridae)

Fungus gnats (Bradysia impatiens) can be a serious pest especially to plants grown in confined areas, and although various methods of control are available, safer and more effective control measures are desirable. Mustard seed meal, a by‐product remaining after oil removal for use as a biodiesel feedstock, contains compounds called glucosinolates that hydrolyse to insecticidal 2‐propenyl isothiocyanate. Our objective was to produce a dose‐response curve for making recommendations of Brassica juncea seed meal applications that will result in fungus gnat larvae control. Twenty colony‐raised fungus gnat larvae were added to 20 g (226 per cm³) of potting media, and adult emergence monitored during 2 weeks using yellow sticky cards. Treatments included without meal, detoxified meal and 19 doses ranging from 0.05 to 3.0 g seed meal. A logistic model was used to predict an LC50 of 0.18 and an LC90 of 0.38 g seed meal for the 20‐g pot. The amounts of seed meal required to produce the observed LC50 and LC90 were predicted to produce 0.08 and 0.17 μmol 2‐propenyl isothiocyanate per cm³ potting medium, respectively. B. juncea seed meal has potential utility for the control of B. impatiens, thus warranting additional studies to determine the seed meal's chronic impact on fungus gnats, phytotoxicity and plant fertility benefits.     

Behavioural response of the fungus gnat,Bradysia impatiens (Diptera: Sciaridae) towards certain edible mushrooms and saprophytic fungi

The fungus gnat Bradysia impatiens (Johannsen) is a worldwide pest inhabiting organic-rich environments, including mushroom-cultivation substrates, which leads to massive production losses of edible mushrooms. To promote a non-insecticidal pest control strategy, we evaluated adult behavioural response towards two saprophytic fungal strains Aspergillus flavus Link and Mucor circinelloides Tiegh., isolated from B. impatiens-inhabiting substrates and six edible mushrooms species. Our results indicated that (a) B. impatiens was most attracted to the oyster mushroom Pleurotus ostreatus among all six edible mushrooms; (b) males and females demonstrated a significant attraction for M. circinelloides over A. flavus and P. ostreatus; (c) adults demonstrated dynamic attraction tendencies that varied with the culture periods of A. flavus and M. circinelloides, wherein females represented most (mean = 78.6%) of the attracted individuals; and (d) larvae that fed on mycelial cultures of M. circinelloides could complete their entire life cycles, but larvae could not survive on a non-fungal or A. flavus diet. These results demonstrate the potential for the development of M. circinelloides in a push-pull strategy to biocontrol this pest in edible mushroom cultivation.     

Egg-laying preference of female fungus gnat Bradysia sp. nr. coprophila (Diptera: Sciaridae) on three different soilless substrates

Fungus gnats, Bradysia spp., are major insect pests in greenhouses. Adult female fungus gnats prefer to lay eggs in growing medium that is microbially active or that contains high amounts of peat moss or hardwood bark. However, egg-laying preference has not been demonstrated quantitatively. This study was designed to determine whether fungus gnat Bradysia sp. nr. coprophila females prefer any of the three soilless growing media provided. The three soilless growing media tested were Metro-Mix 560 with Scott's Coir, Sunshine LC1 Mix, and Universal SB 300 Mix. Initially, the egg-laying potential of the fungus gnat species used in this study was assessed by dissecting mated females after 24, 48, and 72 h. For the egg-laying preference experiment, adults that emerged from pupae were aspirated into a plastic vial, sexed, and then allowed to mate for 24 h. Individual mated females were released into an experimental chamber (15 by 15 by 5-cm plastic container) consisting of four 6-cm petri dishes, three of which contained soilless growing media and one with filter paper (control). In total, there were 50 experimental chambers, with each chamber representing a replication. Females remained in the experimental chambers for 48 h after which the growing media were processed using a flotation/extraction method. The number of eggs laid by female fungus gnats ranged from 21 to 217 with most eggs recovered after 48 h (141.0 +/- 9.3). There were no significant differences among the three soilless growing media in terms of number of eggs laid, although all three growing media were significantly different from the filter paper with higher numbers of eggs laid in the soilless growing media than the filter paper. Despite no significant difference among the growing media in the number of eggs laid, fungus gnat females tended to lay eggs more often, based on the number of petri dishes in which at least one egg was laid, in Metro-Mix 560 (86%) than Sunshine LC1 (66%), Universal SB 300 (52%), or filter paper (18%). Based on the results of this study, female fungus gnats may not prefer a specific growing medium for oviposition. However, fungus gnat females may rely on other factors not tested in this study such as moisture content and volatiles emitted from growing media in their decision where to lay eggs.     

Repellency of naturally occurring volatile alcohols to fungus gnat Bradysia sp. nr. coprophila (Diptera: Sciaridae) adults under laboratory conditions

This study, conducted under laboratory conditions, was designed to determine the repellent activity of 10 naturally occurring volatile alcohol constituents against adults of the fungus gnat, Bradysia sp. nr. coprophila (Lintner) (Diptera: Sciaridae). The essential oil constituents were octanoic acid, furfural, acetophenone, benzaldehyde, dimethoxybenzene, borneol, menthol, 1-octen-3-ol, and 7-hydroxycitronellol, and alpha-terpineol. alpha-Terpineol, octanoic acid and furfural were tested at several concentrations, whereas the remaining seven were tested at only one concentration. The essential oil constituents' menthol, 1-octen-3-ol, and borneol displayed the most repellent activity. The mean percentage of fungus gnat adults recovered from the test compound petri dishes associated with the three essential oil constituents was between 6 and 15% compared with between 36 and 50% for the petri dishes with distilled water. The mean +/- SEM number of fungus gnat adults present in the sample compartments associated with menthol (10.4 +/- 2.6), 1-octen-3-ol (18.8 +/- 2.4), and borneol (23.4 +/- 5.6) was statistically lower than those in the petri dishes containing distilled water (60.9 +/- 7.4, 49.8 +/- 4.0, and 79.7 +/- 13.5), respectively. Only the highest concentration of alpha-terpineol (8.0 micromol) displayed significant repellent activity against fungus gnat adults. The other essential constituents tested, including octanoic acid (all three concentrations), furfural (both concentrations), acetophenone, dimethoxybenzene, and 7-hydroxycitronellol, were not statistically different from the distilled water control. The results of this study indicate that certain essential oil constituents repel fungus gnat adults, which may be useful, from a practical standpoint, in deterring adults from laying eggs into growing media.     

Effect of diatomaceous earth and Trichoderma harzianum T-22 (Rifai strain KRL-AG2) on the fungus gnat Bradysia sp. nr. coprophila (Diptera: Sciaridae)

This study, consisting of three experiments, was designed to assess whether diatomaceous earth, when applied to the surface of growing media, reduces adult fungus gnat Bradysia sp. nr. coprophila (Diptera: Sciaridae) emergence or inhibits the females from laying eggs; and whether fungus gnat adults are attracted to the fungus Trichoderma harzianum T-22 (Rifai strain KRL-AG2) under laboratory conditions. In the first two experiments, diatomaceous earth was applied at two different thicknesses (3.1 and 6.3 mm) and conditions (dry and moist) to the surface of a growing medium (Universal SB 300 Mix) after the growing medium had been artificially inoculated with second or third instars of fungus gnats, or before female fungus gnat adults were released into each deli squat container. In the third experiment, preparations of the fungus T. harzianum at the highest recommended label rate (0.889 kg/m3) were amended into the growing medium and processed 24, 48, or 72 h before use in a series of three two-choice trials with a two-armed experimental arena. In the first two experiments, the dry or moist layers of diatomaceous earth, in general, did not affect fungus gnats in terms of preventing adult emergence or egg laying by the females. During the course of these experiments, we observed that the diatomaceous earth dry treatments expanded as a result of absorbing moisture from the growing medium, creating fissures that allowed the fungus gnat larvae to pupate and females to lay eggs. In the third experiment, fungus gnat adults were not attracted to the T. harzianum treatments in any of the trials.     

Quantitative sampling method for fungus gnat (Diptera: Sciaridae) eggs in soilless growing media

A simple method is described for separating fungus gnat eggs from soilless growing media. The flotation/extraction method primarily involves the use of a MgSO4 solution (density 1.065 g cm(-3)) and a series of sieving procedures. Bradysia sp. nr. coprophila Lintner eggs were collected in an isolation chamber containing adult fungus gnats. Three soilless growing media were used: Metro-Mix 560 with Scott's Coir, Sunshine LC1 Mix, and Universal SB 300 Mix. Each growing medium was inoculated with 100 fungus gnat eggs. Growing medium samples were processed using separatory funnels and a MgSO4 solution. Eggs were washed through a 250-microm sieve and collected on a 53-microm sieve, and then the eggs were rinsed into glass petri dishes. The sieving process separated fungus gnat eggs from the larger growing medium particulates (perlite, bark, and peat), providing a sample consisting of water, eggs, and fine growing medium particulates (peat). Using a vortex for 60 s increased the number of fungus gnat eggs recovered (37.4 +/- 3.7-67.1 +/- 1.9 [mean +/- SEM]) for all three growing media. The mean number of fungus gnat eggs recovered from the three soilless growing media was significantly different, with the growing medium containing coir (Metro-Mix 560) having the highest recovery rate of 61.0 +/- 2.1. For all three growing media, there was > 50% recovery of fungus gnat eggs. In addition to fungus gnat eggs, this method also may prove useful for quantitative recovery of shore fly (Scatella sp.) eggs and the eggs of other arthropods from soilless growing media.     

Transmission of the mycoparasite Coniothyrium minitans by collembolan Folsomia Candida (Collembola: Entomobryidae) and glasshouse sciarid Bradysia sp. (Diptera: Sciaridae)

Folsomia Candida was maintained on potato dextrose agar (PDA) plates precolonised by the mycoparasite Coniothyrium minitans for 3 yr but the sciarid Bradysia sp. survived for a maximum of only three generations. Collembolans and sciarid larvae from these cultures were able to transmit C. minitans to uninoculated PDA plates through the survival of spores in faecal pellets. Adult and larval sciarids also transmitted C. minitans from PDA culture to uninoculated PDA plates by contamination on the cuticle. In soil and sand both sciarids and collembolans were able to transmit C. minitans from C. m/m'tans-inoculated to uninoculated sclerotia of Sclerotinia sclerotiorum. Inoculation of sclerotia with C. minitans enabled greater populations of larger collembolans to develop. In the glasshouse where C. minitans had been applied to the soil, one adult sciarid and four collembolans out of 70 and 101 insects collected respectively yielded C. minitans on placement onto PDA + Aureomycin.     

Field and laboratory observations on the substrates of the mushroom fungus gnat Lycoriella auripila (Diptera: Sciaridae)

The movements of Psila rosae larvae were studied under field and laboratory conditions. In the field, larvae moved up to 60 cm along and between carrot rows, although more larvae moved during the first generation than the second. Sudden increases in soil moisture, and not its prevailing level, stimulated the larvae to move from carrots into the soil surrounding the roots. Up to 50% of the larvae that left their mines in carrots following a sudden increase in soil moisture did not return to the same mine. Evacuation of mines by larvae appears to be a reflex response to the flooding of their mine and might be connected with the production of toxic conditions within the mine following flooding.     

Effect of growing media and their constituents on fungus gnat, Bradysia sp, nr, coprophila （Lintner） adults

This study was conducted to determine the attractiveness of two growing media, commonly utilized in greenhouses, to fungus gnat, Bradysia sp. nr. coprophila adults. The constituents of the most attractive growing medium tested were determined by gas chromatography analysis using a steam-distillation procedure. We found that fungus gnat adults were more attracted to the growing medium, SB300 Universal Professional Growing Mix, which contains composted bark, than to another growing medium （Sunshine LC1 Mix） and their components when tested in a series of laboratory experiments using multiple-choice experimental arenas. A higher percentage of fungus gnat adults were attracted to moist SB300 （92%） than SB300 growing medium that had been oven dried （8%）. In addition, fungus gnat adults preferred SB300 although they had been reared on Sunshine LC1 Mix. When comparing the SB300 fresh from the bag to growing medium that had been pasteurized and moistened with water, gas chromatographic-mass spectroscopic data showed there were declines in several terpenoid constituents as well as an increase in fatty acids and cyclosulfur. The results of this study indicate that B. sp. nr. coprophila adults prefer certain growing media, which may assist greenhouse producers in managing fungus gnats in crop production systems.     

Eggshell fine structure of Bradysia aprica (Winnertz) (Diptera : Sciaridae)

The eggshell fine structure of the dark-winged fungus-gnat Bradysia aprica (Winnertz) (Diptera : Sciaridae) was investigated by scanning and transmission electron microscopy. At the anterior pole of the ovoid egg is a single micropyle, centrally located in a well-defined micropylar area. The latter is covered by many long drumstick-like chorionic processes that are longer and more numerous than those of the rest of the egg surface. Cross-sections of the eggshell show 3 concentric envelopes: the vitelline envelope, wax layer and chorion. The chorion consists of 3 components with different morphological features: the inner, intermediate and outer chorion. The latter 2 layers, involved in the organization of the drumstick-like processes, have homogeneous features, whereas the former is crystalline and resembles the innermost chorionic layer of other Diptera.     

Pest species of a fungus gnat genus Bradysia Winnertz (Diptera: Sciaridae) injuring agricultural and forestry products in Japan,with a review on taxonomy of allied species

Agricultural and forestry pest species of the Bradysia tilicola group from Japan were revised taxonomically after examination of the type specimens. A sciarid pest of Welsh onion occurred from northern Saitama, Japan since 2014 and later from south‐eastern Gunma, Japan, was identified as B. odoriphaga Yang & Zhang, 1985, sp. rev. It was removed from synonymy of B. cellarum Frey, 1948, being the first record of the species from Japan. Bradysia agrestis Sasakawa, 1978, was assigned to be a junior synonym of B. impatiens (Johannsen, 1912). Bradysia paupera Tuomikoski, 1960, sp. rev. , was removed from synonymy of B. impatiens and was recognized as a distinct species. We also compiled their host plants and fungi hitherto reported from Japan. Bradysia impatiens was here recorded from an indoor facility of cloud ear fungus, Auricularia polytricha (Montagne) Sacc., for the first time. At least 19 cultural crops belonging to 12 plant and fungal families were reported as actual and potential hosts of B. impatiens. We suggested that B. impatiens and B. paupera might have been confused in studies of mushroom production in Japan. Further survey of distribution of B. paupera in Japan needs to be done.     

韭菜养根期干旱处理对韭菜迟眼蕈蚊种群动态的影响

【目的】本研究旨在明确韭菜养根期干旱处理对韭菜迟眼蕈蚊Bradysia odoriphaga种群动态的影响。【方法】通过控制浇水调控土壤含水量,调查15, 20, 25和30 d干旱胁迫下砂土和壤土栽培的韭菜中韭菜迟眼蕈蚊F1代成虫的发生量,并通过两性生命表方法分析干旱胁迫30 d对韭菜迟眼蕈蚊F₁代种群参数的影响。【结果】研究结果表明,不论砂土还是壤土,干旱胁迫均抑制了韭菜迟眼蕈蚊F1代成虫的发生: 随干旱胁迫时间的增加,韭菜迟眼蕈蚊成虫的数量显著下降;其中干旱胁迫30 d时,韭菜迟眼蕈蚊成虫的发生量最低,壤土或砂土中的F₁代成虫羽化量仅为1头,与其他干旱胁迫时间(15, 20和25 d)相比发生量差异显著。经历30 d干旱胁迫的韭菜迟眼蕈蚊F₁代1, 2, 3和4龄幼虫发育历期、未成熟期、雌成虫产卵前期和总产卵前期较对照组显著延长,分别延长0.82, 253, 2.82, 0.68, 6.32, 1.36和8.69 d,而净生殖率(R₀)、内禀增长率(r_m)以及周限增长率(λ)则显著低于对照组,分别较对照组下降32.38%, 37.50%和5.13%。【结论】在韭菜养根期进行干旱处理可有效抑制韭菜迟眼蕈蚊的发生。     

Development and reproduction of Stratiolaelaps scimitus (Acari: Laelapidae) with fungus gnat larvae (Diptera: Sciaridae), potworms (Oligochaeta: Enchytraeidae) or Sancassania aff. sphaerogaster (Acari: Acaridae) as the sole food source

Stratiolaelaps ( = Hypoaspis) miles (Berlese) (Acari: Mesostigmata: Laelapidae) is a polyphagous soil-dwelling predatory mite that is widely marketed for use in greenhouse production systems to manage populations of dark-winged fungus gnats, Bradysia spp. (Diptera: Sciaridae) and for supplemental control of thrips. The suggestion by Walter and Campbell (2003, Biol. Control 26: 253–269) that North American commercial cultures of S. miles may actually be S. scimitus was confirmed. The development and reproduction at 21–23 °C of S. scimitus provided ad libidum with one of three different prey – the fungus gnat Bradysia aff. coprophila (Lintner), potworms (Enchytraeidae), or Sancassania aff. sphaerogaster (Zachvatkin, 1937) (Acari: Astigmata: Acaridae) – were compared. Developmental duration of the egg and non-feeding larval stages were 2.47 and 1.11 days, respectively; mortalities were 8.3 and 5.5%. Stratiolaelaps scimitus failed to develop beyond the protonymphal stage when provided with S. aff. sphaerogaster alone, although some feeding was observed. Development and reproduction of S. scimitus was successful on both fungus gnat larvae and enchytraeids, with no influence of prey on protonymphal duration (4.70 days) and mortality (8.3%), or on deutonymphal duration (4.61 days) and mortality (6.1%). Adult female S. scimitus feeding on potworms, compared to those feeding on fungus gnat larvae, had a significantly shorter pre-oviposition period (2.69 vs. 4.59 days). However, diet did not influence other adult female developmental or reproductive characteristics (oviposition period, 18.6 days; post-oviposition period, 6.2 days; total adult longevity, 27.3 days; total number of eggs, 26.5). S. scimitus reared on potworms tended (p = 0.06) to have a higher intrinsic rate of increase, a higher finite rate of increase and a shorter doubling time (r _m = 0.142 day⁻¹, λ = 1.153, Dt = 4.85 days) than those reared on fungus gnat larvae (r _m = 0.105 day⁻¹, λ = 1.110, Dt = 6.58 days), but differences in net reproductive rate (R ₀) and generation time (G) were not significant.     

环境颜色对韭菜迟眼蕈蚊生物学特性的影响

【目的】明确环境颜色对韭菜迟眼蕈蚊Bradysia odoriphaga Yang et Zhang生长发育及繁殖能力等生物学特征的影响。【方法】在室内条件下,利用黑、棕、绿、红和橙5种颜色卡纸模拟自然环境颜色,比较研究了其对韭菜迟眼蕈蚊生长发育和繁殖的影响。【结果】韭菜迟眼蕈蚊发育历期在橙色环境下最长,为26.15 d,黑色环境下最短,为22.35 d;世代存活率在黑色环境下最高,为43.88%,橙色环境下最低,为28.88%;性比在各颜色环境下无显著差异;雌雄成虫寿命均在棕色环境下最长,分别为2.06 d和2.99 d,橙色环境下最短,分别为1.58 d和2.57 d;单雌产卵量在棕色环境下最多,为62.99粒,橙色环境下最少,为45.64粒;种群趋势指数由高到低依次为:黑色(15.90)棕色(15.07)透明色对照(12.93)红色(11.69)绿色(11.67)橙色(8.50)。【结论】环境颜色影响韭菜迟眼蕈蚊生物学特性,黑色及棕色环境有利于其生长发育及繁殖,橙色环境可抑制其生长发育及繁殖。     

Molecular phylogeny of the Paleogene fungus gnat tribe Exechiini (Diptera: Mycetophilidae) revisited: Monophyly of genera established and rapid radiation confirmed

The phylogeny of the fungus gnat tribe Exechiini (Diptera: Mycetophilidae) is reconstructed based on the combined analysis of five nuclear (18S, two parts of 28S, CAD, EF1α) and two mitochondrial (12S, COI) gene markers. According to known fossil record, and recent higher‐level phylogenies, the tribe constitutes the most apomorphic, distinctly monophyletic clade of the family Mycetophilidae. The tribe originated in the Paleogene and apparently quickly diversified in the Neogene with an unusual rapid radiation of complex male terminalia. Earlier attempts to reconstruct the phylogeny of the tribe, based on both morphology and molecular methods, have not yielded reliable hypotheses, neither in terms of resolution nor in terms of support for major clades. Increased taxon sampling and wider gene sampling have been suggested to achieve better phylogenetic resolution. Aiming at this, we present new phylogenies, for the first time with all known genera and subgenera of Exechiini represented. While many terminal intergeneric relationships are well supported, both in maximum likelihood and in Bayesian analyses, most of the major, deeper clades remain poorly supported. We suggest that a rapid radiation event close to the root may be causing the low resolution at this level in the phylogeny. This contrasts parallel phylogenies of the older subfamilies and tribes of the family Mycetophilidae, where traditional clades have usually been recovered with high support. Further in‐depth studies into the evolutionary history of the tribe are needed to enlighten and coalesce the specific phenomena driving their unique morphological, genetic and phylogeographic histories.     

Attraction and oviposition responses of the fungus gnat Bradysia impatiens to microbes and microbe‐inoculated seedlings in laboratory bioassays

Laboratory tests were conducted to examine preferences of Bradysia impatiens Johannsen (Diptera: Sciaridae) larvae and adults for various microbes associated with greenhouse crops. Fungus gnat larvae and adults exhibited a preference for cultures of Pythium spp. over the medium used to grow the pathogens. Larvae also exhibited a preference for geranium seedlings infected with pathogenic Pythium spp. [P. aphanidermatum (Edson) Fitz., P. ultimum Trow, and P. irregulare Buis. (Oomycota: Peronosporales)] over non‐inoculated plants. Adult fungus gnats exhibited a strong ovipositional preference for the aforementioned Pythium spp. as well as a variety of other microorganisms, including the pathogenic fungus Thielaviopsis basicola (Berk. & Br.) (Ascomycota: Microascales), the geranium‐infecting bacterium Xanthomonas campestris pv. pelargonii (Brown) Dye (Proteobacteria: Xanthomonadales), the non‐pathogenic species Pythium torulosum Coker & P. Patt. and Pythium graminicola Subramaniam, the pathogen‐suppressive fungus Trichoderma harzianum Rifai (Ascomycota: Hypocreales), and the insect pathogenic fungus Beauveria bassiana (Balsamo) Vuillemin (Ascomycota: Hypocreales). Our study is the first to demonstrate that fungus gnats are attracted to and/or stimulated to oviposit by a wide array of living microorganisms both in pure culture and in association with plant seedlings. These findings have important implications with respect to the potential role of fungus gnats in plant pathogen transmission.     

Steinernema carpocapsae (Rhabditida: Steinernematidae) as a biological control agent against the fungus Gnat Bradysia agrestis (Diptera: Sciaridae) in propagation houses

A recently introduced fungus gnat, Bradysia agrestis, has caused serious problems in Korean propagation houses where vegetable seedlings are produced for transplant into the fields. Although chemical insecticides are available against this pest, alternate control measures are needed. A Korean isolate of the entomopathogenic nematode, Steinernema carpocapsae Pocheon strain, was tested against this insect in the laboratory and propagation house. In the laboratory, S. carpocapsae affected oviposition, with the untreated females laying an average of 121±25 eggs, whereas the treated females averaged 7±2 eggs. The infectivity of S. carpocapsae to the fungus gnat was affected by the developmental stage and temperature, with highest mortality observed with the third and fourth instars and pupal stage. Nematode mortality in the second instar fungus gnat ranged between 23 and 35%, but showed no significant differences among the temperatures tested. The egg and first instar were not infected by the nematode. In nematode dispersal studies, adult female fungus gnats alone dispersed S. carpocapsae from the nematode-treated area to the control area at a higher rate than male and female gnats or male gnats alone. In the propagation house experiments with watermelon seedlings, no significant difference was observed in fungus gnat larval reduction at S. carpocapsae concentrations of 5, 10, or 20 infective juveniles (IJs)/g of soil at 7, 14, and 21 days after treatment. In comparison with the control, the S. carpocapsae treatments significantly reduced B. agrestis larval numbers. When the watermelon seed was treated with S. carpocapsae at sowing, the larval density of B. agrestis was significantly reduced, that is, the number of B. agrestis larvae ranged from four to eight and from five to eight in the nematode-treated plots compared with 26 and 30 in the control plots on the 17th and 34th day post-treatment, respectively. In the chemical insecticide treatments, diflubenzuron and chlorpyrifos were significantly more effective than S. carpocapsae and diazinon in reducing larval populations of the fungus gnat. Our data show that, although some of the chemical insecticides were more effective than S. carpocapsae Pocheon strain, the nematode was still an effective tool for management of the fungus gnat larvae and in protecting seedlings from damage in propagation houses.     

臭氧水对韭蛆的防治效果及对韭菜生长的影响

【目的】为科学合理地浇灌臭氧(O₃)水防治韭菜迟眼蕈蚊Bradysia odoriphaga幼虫(俗称韭蛆),明确最佳浇灌时期和使用条件。【方法】在平地覆膜环境中浇灌不同浓度(5, 10, 20和30 mg/L)O₃水,调查对韭蛆的防治效果;在平地覆膜环境中不同日光强度、3种不同灌溉环境［平地覆膜、小拱棚和小拱棚+草垫］、2种不同灌溉环境［平地覆膜、小拱棚］的不同浇灌频率等条件下分别浇灌30 mg/L O₃水,调查对韭蛆的防治效果;调查平地覆膜环境中浇灌30 mg/L O₃水对韭菜产量和根系生长的影响;分析日光强度对不同灌溉环境中土壤温度及浇灌O₃水对韭蛆的防治效果的影响。【结果】平地覆膜条件下,O₃水防治韭蛆的最佳浓度为20~30 mg/L。在平地覆膜条件下浇灌30 mg/L O₃水处理中,对韭蛆的防治效果与浇灌当天的日光强度呈正相关;当日光强度超过60 000 lx时,第1天韭蛆的死亡率高达100%;日光强度低于10 000 lx时,对韭蛆无显著的防治效果;日光强度处于中间水平时,前期对韭蛆的防治效果较差,而后期防治效果逐渐增强。土壤升温效果与日光强度呈正相关,也与灌溉环境显著相关,不同灌溉环境下土壤5 cm深处的温度为：平地覆膜>小拱棚＞小拱棚+草垫。小拱棚内浇灌O₃水对韭蛆的防治效果显著高于平地覆膜组和小拱棚+草垫组。采取连续多次浇灌O₃水有利于提高O₃水对韭蛆的防治效果,而且小拱棚内韭蛆的防治效果更显著。浇灌O₃水时,进水口离田埂末端的距离不能超过40 m。平地覆膜环境中浇灌30 mg/L O₃水后,韭菜的株高、重量和须根数量显著高于对照组(浇灌清水);韭菜植株分蘖数与对照组差异不显著。【结论】若能科学合理地浇灌O₃水,既能达到防治韭蛆的理想效果,又能促进韭菜生长。     

A comparison between the larval eyes of the dimly luminescent Keroplatus nipponicus and the brightly luminescent Arachnocampa luminosa (Diptera; Keroplatidae)

Larvae of the weakly blue‐luminescent fungus gnat Keroplatus nipponicus possess on either side of their heads a small black stemmatal eye with a plano‐convex lens approximately 25 μm in diameter. In total, 12–14 retinula cells give rise to a centrally fused rhabdom of up to 8 μm in diameter. The rhabdom's constituent microvilli, approximately 70 nm in width, are roughly orthogonally oriented, a requirement for polarization sensitivity. Screening pigment granules are abundant in the retinula cells and measure at least 1 μm in diameter. In comparison with the stemmatal eye of the brightly luminescent Arachnocampa luminosa, that of K. nipponicus is considerably smaller with a poorer developed lens and a rhabdom that is less voluminous, but possesses wider microvilli. Although the larval eye of K. nipponicus can be expected to be functional, as the larvae react to light with a behavioural response, the eyes are probably mainly involved in the detection of ambient light levels and not, as in A. luminosa, also in responding to the luminescence of nearby conspecifics.