Fungus gnats, Bradysia spp. (Diptera: Sciaridae), and other arthropods in commercial bagged soilless growing media and rooted plant plugs

Fungus gnats, Bradysia spp., in greenhouses cause economic losses to horticultural producers by damaging young root systems during plant propagation, by spreading soilborne diseases, and by reducing the marketability of the crop. In a greenhouse cage study, our observations suggested that bagged soilless growing media or rooted plant plugs from wholesale distributors may be sources for the introduction of fungus gnats into commercial greenhouse facilities. To evaluate these possibilities, carefully collected samples of bagged soilless growing media stored in the greenhouse, as well as bagged soilless growing media and rooted plant plugs delivered from midwestern wholesale distributors, were incubated under controlled conditions in the laboratory. Fungus gnats emerged from soilless media stored in the greenhouse, soilless media delivered from wholesale distributors, and from rooted plant plugs delivered from wholesale distributors. These results demonstrate that pasteurization of even bagged soilless media may be essential to effectively managing greenhouse populations of fungus gnats. However, pasteurization is not an option for responding to contamination of rooted plant plugs. Preliminary evidence is provided that application of entomopathogenic nematodes may offer potential as a method for managing fungus gnats in plant plugs, so long as treatment is early. Other arthropods found contaminating soilless media and rooted plant plugs included the western flower thrips, Frankliniella occidentalis (Pergande), Collembola, Acari, Formicidae, Staphylinidae, Psychodidae, and other Diptera.     

Method for quantitative sampling of fungus gnat larvae in soilless growing media

A simple method is described for separating fungus gnat larvae from soilless growing media. Samples are first fractionated by water flotation with an inverted flask procedure and then the sediment is degassed under reduced air pressure and fractionated in magnesium sulfate (MgSO4) solution (density of 1.12 g cm(-3)). Fungus gnat larvae with only a small amount of contaminating debris are recovered from the surface of the MgSO4 solution for immediate counting or for preservation in alcohol. In evaluations of different commercial soilless growing media with a range of components, two repetitions of the water flotation step eliminated 20-40% of the dry weight of samples and virtually all of the perlite from further processing. Repeating both the water and MgSO4 flotations a third time only marginally improved the recovery of larval fungus gnats, Bradysia sp. nr. coprophila, added to pasteurized media. Extraction efficiency differed between instars and, to a lesser extent, between different types of media. Across three commercial soilless media tested, recovery was 24-33% for first, 68-85% for second, 85-95% for third, and 98-100% for fourth instars. Within combinations of media and instar, recovery was consistent. With this method, a 400-cm3 sample can be processed and be ready for counting in 1-1.5 h; samples can also be processed in batches or in assembly-line manner to process many samples per day. The method may also prove useful for quantitative recovery of shore fly larvae, thrips pupae, and other arthropods from soilless 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.     

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.     

Potential of temperature, controlled atmospheres, and ozone fumigation to control thrips and mealybugs on ornamental plants for export

Ozone (O3) fumigation is a potential quarantine treatment alternative for controlling stored-product pests and surface insect pests on fresh agricultural commodities. We explored the effects of temperature, treatment time, controlled atmospheres, and vacuum in combination with O3 to control two important pests of ornamental crops: western flower thrips, Frankliniella occidentalis (Pergande), and longtailed mealybug, Pseudococcus longispinus Targioni Tozzetti. Treatment parameters tested were O3 concentrations from 0 to 3,800 ppm, treatment durations were from 30 to 120 min, vacuums were from 0 to 0.41 bar below ambient, temperatures were from 32.2 to 40.6 degrees C, and controlled atmospheres were composed primarily of nitrogen, carbon dioxide, or breathing air [BA]. Treatment efficacy was enhanced by higher O3 concentration and temperature, lower oxygen, and longer treatment times. Reduced pressure was not an important factor. Mealybugs were more difficult to kill than thrips. A 30-min treatment of O3 at approximately 200 ppm in 100% CO2 at 37.8 degrees C killed 47.9 and 98.0% of mealybugs and adult female thrips, respectively. All of the ornamentals tested were damaged to some degree by O3 treatments. However, crops with thick leaves such as orchids exhibited little damage, and the waxy portions of certain flowers were not damaged. The results suggest that O3 has potential as a quarantine treatment to control thrips and mealybugs on selected commodities.     

Effects of temperature and molecular oxygen on the use of atmospheric pressure plasma as a novel method for insect control

Helium atmospheric pressure plasma discharge (APPD) was previously shown to have insecticidal activity with a possible site of action on the insect nervous, neuromuscular system, or both. In the current study, methods to increase the insecticidal activity of plasma by using increased APPD temperature and the introduction of molecular oxygen were investigated for the first time. An increase in the helium plasma temperature from 37 to 50 degrees C increased the insecticidal activity of plasma for the control of the German cockroach, Blattella germanica (L.); western flower thrips, Frankliniella occidentalis (Pergande); and citrus mealybug, Planococcus citri (Risso). This increase in activity could not be explained by the increase in air temperature alone, and it suggests that the enhanced insecticidal activity resulted from increased ionization of the APPD and ion bombardment of the insect. Emission spectroscopy showed that the introduction of 0.5% oxygen into helium plasma produced ionic molecular oxygen at 559.7 and 597.3 nm. The introduction of oxygen to the APPD greatly increased the insecticidal activity of plasma for the citrus mealybug but not the German cockroach or western flower thrips. For the mealybug as an example, the mortality of a 60-s exposure of 37 degrees C helium plasma was 0% at 1 h after exposure and 100% under the same conditions after the introduction of oxygen. It seems that increases in temperature and the introduction of oxygen even at low levels can increase the insecticidal activity of plasma to varying degrees depending on the insect species. The symptomology of cockroach death for both hot plasma and plasma containing trace amounts of molecular oxygen continued to suggest that the site of action of APPD is the insect nervous system, neuromuscular system, or both.     

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.     

Insecticidal properties of a Chenopodium-based botanical

The emulsifiable concentrate UDA-245 based on an essential oil extract from Chenopodium ambrosioides variety near ambrosioides, a North American herbaceous plant, was compared with commercially available pesticides for their effectiveness to control green peach aphid, Myzus persicae (Sulzer) (Homoptera: Aphididae), western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), and greenhouse whitefly, Trialeurodes vaporariorium (Westwood) (Homoptera: Aleyrodidae). Side effects on the whitefly parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae) also were determined. With green peach aphid, UDA-245 at 0.5% concentration was significantly more effective than the control (water) treatment in a laboratory bioassay and significantly more effective than neem oil and the control treatment and as effective as insecticidal soap in a greenhouse assay. With the western flower thrips, UDA-245 at 0.5% was significantly more effective than neem oil, insecticidal soap and the control treatment in a laboratory bioassay, whereas in a greenhouse assay, UDA-245 at 1.0% was the only treatment that maintained control of the western flower thrips 2 wk after the last treatment period. UDA-245 at 0.5% (laboratory bioassay) was significantly more effective in managing greenhouse whitefly than neem oil, endosulfan, and the control treatment and as effective as insecticidal soap. Insecticidal soap proved to be toxic to the parasitoid E. formosa (71.9% mortality), whereas UDA-245 at 0.5% was not significantly more toxic than the control (11.2 and 4.6% mortality, respectively). Our results suggest that a greenhouse integrated pest management (IPM) program using a botanical such as UDA-245 could effectively control infestations of major pests present while having a negligible effect on biological control agents.     

Modified atmosphere treatments as a potential disinfestation technique for arthropod pests in greenhouses

Incidental transport of arthropods on plant material can be a significant mode of pest entry into greenhouses. We evaluated the use of controlled atmosphere treatments as a potential way to eliminate arthropod pests on plant propagules (i.e., cuttings or small rooted plants). Lethal exposures to CO2 or N2 were determined for common greenhouse pests including fungus gnat larvae, Bradysia sp.; green peach aphid, Myzus persicae (Sulzer); sweetpotato whitefly, Bemisia sp.; twospotted spider mite, Tetranychus urticae Koch; and western flower thrips, Frankliniella occidentalis (Pergande). We also studied the effect of pest species, life stage, and presence or absence of plants on efficacy of modified atmosphere treatments. Finally, effects of modified atmospheres on plant quality were evaluated for several bedding plant species including begonia, Begonia semperflorens-cultorum Hort. 'Cocktail Series', chrysanthemum, Dendranthema grandiflora Tzvelev., geranium, Pelargonium X hortorum L.H. Bailey, and impatiens, Impatiens wallerana Hook f., and among cultivars of geranium and chrysanthemum. Exposure for 12-18 h to >99% N2 or CO2 caused complete mortality of aphids, mites, thrips, and whiteflies. Fungus gnat larvae were more tolerant of hypoxic conditions. Adult mites and eggs were equally susceptible. For most pests, there was no difference in response to atmospheres modified by CO2 or N2. However, there was variation in response among plant species and cultivars, with effects ranging from delayed flowering to mortality. Despite the possibility of adverse effects on some plants, this work indicates that use of modified atmospheres has potential to eliminate arthropod pests on plant propagules before they are introduced into greenhouses.     

Interactions of light intensity, insecticide concentration, and time on the efficacy of systemic insecticides in suppressing populations of the sweetpotato whitefly (Hemiptera: Aleyrodidae) and the citrus mealybug (Hemiptera: Pseudococcidae)

The impact of light intensity on the uptake and persistence of the systemic neonicotinoid insecticides, imidacloprid and dinotefuran, were evaluated in poinsettia (Euphorbia pulcherrima Willd.) and yellow sage (Lantana camara L.). Insecticide residues were measured in leaves sampled from the treated plants at four time intervals after treatment to determine the relationship between insecticide concentration and efficacy against two insect pests: sweetpotato whitefly, Bemisia tabaci Gennadius, and the citrus mealybug, Planococcus citri Risso. The insecticides were evaluated at their respective label rate and at the comparable label rate of the other insecticide under two different light environments: ambient and shade. The uptake of dinotefuran into yellow sage was more rapid at both treatment rates than both rates of imidacloprid, resulting in higher percent mortality of whitefly nymphs (89.8-100) compared with imidacloprid (14.1-89.2) across all 4 wk. Additionally, plants that received both rates of dinotefuran had fewer whitefly pupae (< 1.0) at week 4 compared with imidacloprid-treated plants (23.7-25.3). The uptake of dinotefuran into poinsettia plants was also more rapid and resulted in quicker and higher percent mortality of whitefly nymphs (89.5-99.6) compared with imidacloprid (14.1-89.2) across all 4 wk. However, despite efficient uptake, the efficacy of both systemic insecticides was less for citrus mealybug where percent mortality values were <50% among all the treatments across the 4 wk. The use of the two systemic insecticides evaluated in regards to pest management in horticultural cropping systems is discussed.     

The toxicity and synergistic effects of alkyl-succinate oil on the first nymphal instars of the citrus cottony scale,Pulvinaria aurantii Cock. (Hem.: Coccidae)

The citrus cottony scale, Pulvinaria aurantii Cock. (Hem.: Coccidae) is one of the most important citrus pests in Iran. This study investigated the toxicity and synergistic effects of organophosphorous insecticides (Malathion, Chlorpyrifos, Buprofezin and DG oil) on first nymphal instars of P. aurantii in the laboratory conditions (25?±?1?°C, 75?±?5% RH and 16L:8D photoperiod). The values of LC₅₀ for Malathion, Chlorpyrifos and Buprofezin insecticides on the first nymphal instars were calculated as 76.90, 105.25 and 24.70?ppm, respectively. Also, results indicated that Buprofezin and Pyriproxifen are the most effective insecticides on first nymphal instars of P. aurantii. The values of LC₅₀ for each insecticide without oil and in half dose along with DG oil were equal. This was an indication for synergism role of DG oil combination. The results of this study showed that DG oil not only decreases the consumption of insecticides, but also increases their efficacy.     

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.     

Effect of insecticides on mealybug destroyer (Coleoptera: Coccinellidae) and parasitoid Leptomastix dactylopii (Hymenoptera: Encyrtidae), natural enemies of citrus mealybug (Homoptera: Pseudococcidae)

In this study, we measured, under laboratory conditions, the direct and indirect effects of insecticides on mealybug destroyer, Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae), and parasitoid Leptomastix dactylopii Howard (Hymenoptera: Encyrtidae), natural enemies of citrus mealybug, Planococcus citri (Risso) (Homoptera: Pseudococcidae). The adult stages of both natural enemies were exposed to sprays of the insecticides buprofezin, pyriproxyfen, flonicamid, acetamiprid, dinotefuran, and clothianidin at label-recommended rates to assess direct mortality after 24, 48, and 72 h, respectively. The effects of the insecticides on L. dactylopii parasitization rate and percentage of parasitoid emergence also were monitored using the label and 4x the recommended label rate. Dinotefuran was extremely detrimental to the adult parasitoid at the label rate with 100% mortality after 24 h. Buprofezin, pyriproxyfen, and flonicamid were not harmful to L. dactylopii when applied at the label rate. At 4x the recommended label rate, dinotefuran, acetamiprid, and clothianidin were all harmful to the parasitoid with 100% mortality 72 h after application. Both buprofezin and flonicamid were not toxic to L. dactylopii with 100% adult survival after 72 h. Pyriproxyfen and flonicamid, at both the label and 4x the recommended label rate, did not negatively affect L. dactylopii parasitization rate or percentage of parasitoid emergence. Acetamiprid, dinotefuran, and clothianidin were toxic to C. montrouzieri adults with 100% mortality after 48 h, whereas buprofezin, pyriproxyfen, and flonicamid demonstrated minimal (10-20% mortality after 48 h) harmful effects to the predator. Based on the results from our study, the indirect effects of the insect growth regulator (IGR) buprofezin were not decisive; however, the IGR pyriproxyfen and the insecticide flonicamid were not directly or indirectly harmful to the predator C. montrouzieri and parastioid L. dactylopii, indicating that these insecticides are compatible with both natural enemies when used together for control of citrus mealybug in greenhouses and conservatories.     

Toxic effects of some insecticides,herbicides, and plant essential oils against Tribolium confusum Jacquelin du val (Insecta: Coleoptera: Tenebrionidae)

Cereals are staple food for many countries and are grown on millions of hectares of land, but much of the harvest is wasted due to losses by pests. To minimize these losses, many pesticides are used which are damaging to the environment and human health. There are debates to get rid of these chemicals but they are still in use at large scale. An alternative control strategy for insect pests in storage houses is the use of botanicals. In this study, four plant essential oils, two plant extracts, two herbicides, and two insecticides were used against Tribolium confusum and the comparison of toxicity was made by calculating LC₅₀ and LT₅₀ values. LC₅₀ values were higher for abamectin (2.09–10.23 mg/L) and cypermethrin (3.41–11.78 mg/L) insecticides followed by neem essential oil (7.39–19.24 mg/L) and citrus extract (10.14–24.50 mg/L). However, LC₅₀ values were maximum in case of jaman plant extract (22.38–176.42 mg/L) followed by two herbicides, Logran (19.66–39.72 mg/L) and Topik (29.09–47.67 mg/L) However, LC₅₀ values were higher for topic herbicide (24.098 ppm) and jaman essential oil (16.383 ppm) after four days of treatment. Abamectin and cypermethrin insecticides, neem essential oil and citrus plant extract also killed adults of T. confusum quicker as compared other essential oils, extracts and herbicides. Results revealed that botanical formulations being environmentally safe could be used instead of highly hazardous pesticides for stored products’ pests. This study also elaborates the non-host toxicity of herbicides commonly applied in our agroecosystem.     

Automatic greenhouse insect pest detection and recognition based on a cascaded deep learning classification method

Inspection of insect sticky paper traps is an essential task for an effective integrated pest management (IPM) programme. However, identification and counting of the insect pests stuck on the traps is a very cumbersome task. Therefore, an efficient approach is needed to alleviate the problem and to provide timely information on insect pests. In this research, an automatic method for the multi-class recognition of small-size greenhouse insect pests on sticky paper trap images acquired by wireless imaging devices is proposed. The developed algorithm features a cascaded approach that uses a convolutional neural network (CNN) object detector and CNN image classifiers, separately. The object detector was trained for detecting objects in an image, and a CNN classifier was applied to further filter out non-insect objects from the detected objects in the first stage. The obtained insect objects were then further classified into flies (Diptera: Drosophilidae), gnats (Diptera: Sciaridae), thrips (Thysanoptera: Thripidae) and whiteflies (Hemiptera: Aleyrodidae), using a multi-class CNN classifier in the second stage. Advantages of this approach include flexibility in adding more classes to the multi-class insect classifier and sample control strategies to improve classification performance. The algorithm was developed and tested for images taken by multiple wireless imaging devices installed in several greenhouses under natural and variable lighting environments. Based on the testing results from long-term experiments in greenhouses, it was found that the algorithm could achieve average F₁-scores of 0.92 and 0.90 and mean counting accuracies of 0.91 and 0.90, as tested on a separate 6-month image data set and on an image data set from a different greenhouse, respectively. The proposed method in this research resolves important problems for the automated recognition of insect pests and provides instantaneous information of insect pest occurrences in greenhouses, which offers vast potential for developing more efficient IPM strategies in agriculture.     

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.     

Nematophagous fungus <Emphasis Type="Italic">Paecilomyces lilacinus</Emphasis> (Thom) Samson is also a biological agent for control of greenhouse insects and mite pests

Pathogenicity of nematophagous fungus Paecilomyces lilacinus (Thom) Samson in control of the most destructive greenhouse pests such as: greenhouse whitefly, Trialeurodes vaporariorum, glasshouse red spider mite, Tetranychus urticae, the cotton aphid, Aphis gossypii and western flower thrips, Frankliniella occidentalis was examined in laboratory and pot experiments. The fungus showed the greatest efficacy in controlling winged and wingless forms of the cotton aphid. The cotton aphid’s population was almost totally eliminated. In controlling the greenhouse whitefly, P. lilacinus was most successful when applied against nymphal growth stages (L₃-L₄). Control of the western flower thrips was most efficient against prepupal and pupal stages when the fungus was applied as a water spore suspension to the soil. When the fungus was applied at temperatures below 10 °C, it was able to reduce a glasshouse red spider mite population by 60%.     

Greenhouse application of <Emphasis Type="Italic">Steinernema yirgalemense</Emphasis> to control fungus gnats, <Emphasis Type="Italic">Bradysia impatiens</Emphasis>

Bradysia impatiens Johannsen (Diptera: Scaridae) has recently been identified as a pest, in various greenhouse-cultured crops in South Africa. The control potential for different concentrations of a local entomopathogenic nematode (EPN), Steinernema yirgalemense Nguyen, Tesfamariam, Gozel, Gaugler and Adams, on a natural population of B. impatiens was determined in a cucumber greenhouse. Additionally, the effect of potting media on nematode movement to control an artificial population of fungus gnats was tested. Doubling the EPN dosage, from that recommended by a commercial product (5?×?10⁵ IJs m^?2), reduced the fungus gnats significantly after 21 days. The three different types of potting media, consisting of pine sawdust, coco coir, and a mixture of both coir bale and vermiculite, all had a positive effect on the movement of S. yirgalemense. A significant mortality was achieved for the introduced fungus gnat larvae.     

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.     

球孢白僵菌不同分离株对西花蓟马的毒力测定

【背景】西花蓟马是我国重要的一种入侵性害虫,已对多种化学农药产生了抗性。【方法】采用孢子悬浮液喷雾处理生测法,研究了8个球孢白僵菌菌株BbKM030716、BbCG051229、BbJS080625、BbQJ031121、BbXW060615、BbSM090521、BbYY090613和BbMZ051230对西花蓟马成虫的毒力,并用＂时间—剂量—死亡率＂模型进行了分析。【结果】供试球孢白僵菌各菌株对西花蓟马成虫侵染致病的剂量效应参数值分别为1.43、0.87、0.93、0.98、1.23、0.92、1.07和0.86。用1.25×104～1.25×108个·mL-1孢子悬浮液接种后,连续10d内西花蓟马的校正死亡率分别为44.13%～98.49%、12.63%～78.90%、30.36%～96.92%、51.36%～98.74%、26.14%～98.59%、7.27%～78.71%、49.06%～98.74%和27.67%～87.36%。球孢白僵菌对西花蓟马成虫的致死剂量是时间的函数,各菌株对西花蓟马成虫的致死中时随孢子浓度的增大而逐渐减小。【结论与意义】球孢白僵菌菌株BbKM030716、BbJS080625、BbQJ031121和BbXW060615对西花蓟马成虫具有较强毒力,可作为西花蓟马生防制剂开发的潜力菌株。