Field efficacy and non‐target effects of temephos granules against Culex pipiens (Diptera: Culicidae) and microorganisms in septic tanks,Republic of Korea

A granular formulation of 1.0% temephos (temephos G) was tested for its efficacy in mosquito larval control, residual effects and effects on non‐target microorganisms. Culex pipiens complex in septic tanks in Yangsan, Republic of Korea were used for this study. Microorganisms in the same septic tanks were used for study of non‐target organisms. After the application of temephos G at the rates of 2.0 and 5.0 mg/L to selected septic tanks, mortalities were recorded for 50 days. The effect of temephos G on non‐target organisms was studied by evaluating its effects on the bacterial populations in the treated septic tanks. It was observed that using 1.0% temephos G at a rate of 2.0 mg/L resulted in 100% mortality against Cx. pipiens larvae by the eighth day after treatment. The residual activity of temephos G was observed to continue for a time; for example 29 days after treatment, average larval mortality rates of >68.0% were observed for both concentrations. At the 50th day after treatment, the mortality rates of the Cx. pipiens larvae were observed to decrease to below 42.7% for both concentrations. Application of temephos G did not have significant effects on the bacteria populations in the septic tanks. Since temephos did not seem to have any major effects on the microorganisms, it was concluded that it is a safe and effective larvicide to use in the septic tanks at a rate of 2.0–5.0 mg/L of 1.0% temephos G.     

Effects of a juvenile hormone analogue, pyriproxyfen, on the apterous form of soybean aphid (Aphis glycines)

The soybean aphid, Aphis glycines Matsamura, is an eastern Asian soybean [Glycine max (L.) Merr.] pest which can reduce soybean yield. We determined the effects of pyriproxyfen, a juvenile hormone analogue, on development, mortality, longevity and fecundity of A. glycines under laboratory conditions. Distance Insect Growth Regulator, containing ∼11.2% pyriproxyfen, was applied at two concentrations, 50 and 150 mg/l, to first and fourth instar nymphs. When first or fourth instar A. glycines were treated with pyriproxyfen, some nymphs became supernumerary‐molted nymphs with 1–3 extra molts or were sterilized. Mortality of treated first instar nymphs was >68% greater than the control group and longevity was reduced by >40%. The higher concentration of pyriproxyfen reduced fecundity of first instar nymphs when they reached adulthood by ∼79%. Pyriproxyfen similarly affected fourth instar nymphs. Mortality of treated fourth instar nymphs was ≥15% greater than the control group and longevity was reduced by >24%. Both concentrations of pyriproxyfen lowered the fecundity of fourth instar nymphs by >27%. Pyriproxyfen also had other sublethal effects on fourth instar nymphs which became apparent when they molted to adulthood. In a few instances they developed wing pads and many produced dead, deformed or abnormal neonates that lacked appendages.     

Mosquito Control Evaluations of an Insect Growth Regulator, Pyriproxyfen against Culex pipiens pattens (Diptera, Culicidae) Larvae in Marsh Area, Korea

ABSTRACT Mosquito control evaluations of the granular formulation of 0.5% pyriproxyfen were undertaken in marshes and a pond in Busan during the period of July through September, 2001. In marsh condition where Culex pipiens pattens were predominantly breeding, the treatment of pyriproxyfen produced over an average of 95% mosquito larval reduction at a concentration of 0.05 mg/1 for the first 4 weeks in spite of heavy precipitation (total 274.4 mm) during the period. Reduction rates of 72.6% and 32.3% appeared in the 5th and 7th weeks probably due to heavy input of sewage and flood. However, the reduction rate increased again at the 8th week, showing a 94.5% reduction, probably because of the slow releasing of pyriproxyfen granular formulation. In the second treatment of pyriproxyfen, complete mortality was obtained at the 1st and 3rd weeks. Also, a satisfactory level of Cx. pipiens larval reduction of 96.6% was observed at the 4th week. In a pond assessment, the treatment of pyriproxyfen at a concentration of 0.05 mg/1 produced a complete reduction of Cx. pipiens pattens from the 1st week through the 4th week after treatment. In the second treatment, 100.0% reduction was obtained at the 1st and 2nd weeks in the same sites. The treatment resulted in 84.4% and 97.9% reduction of mosquitoes at the 3rd and 4th weeks, respectively.     

Foliar persistence and residual activity of methoxyfenozide against beet armyworm (Lepidoptera: Noctuidae)

A greenhouse study was conducted to investigate the persistence of methoxyfenozide in pepper (Capsicum annuum L.) foliage. An aqueous suspension of methoxyfenozide was sprayed on pepper plants at concentrations of 72 and 144 mg of active ingredient (a.i.)/L. Foliage was collected at different intervals of time (0, 3, 5, 10, 20, 30, 40, and 50 days) after the treatment, and the methoxyfenozide residue was measured by high‐performance liquid chromatography. The foliage was also used in bioassays to determine the residual toxicity on and the consumption rate of the third‐instar larvae of the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). The methoxyfenozide concentrations observed after 50 days had decreased to 19 and 69 μg/g per sample, corresponding to a loss of 61% and 28% from the application concentrations of 72 and 144 mg a.i./L, respectively. When fitting a first‐order kinetics degradation model, the half‐life (DT₅₀) of this compound was 76 days. Both application concentrations of methoxyfenozide caused a high mortality rate (≥97%) when the larvae were fed the pepper foliage collected at all of the time intervals. Lastly, at all of the time points, the consumption rate by the larvae was reduced to between 57% and 92% for both concentrations that were bioassayed. Our results indicate that, under the present greenhouse conditions, the degradation of methoxyfenozide was slower than that reported by other authors and that its residues were highly toxic to S. exigua larvae. The implications of these results for the management programs of this pest are discussed.     

Mycelia and spent fermentation broth of Beauveria bassiana incorporated into synthetic diets affect mortality,growth and development of larval Helicoverpa zea (Lepidoptera: Noctuidae)

Beauveria bassiana endophytically colonises corn (Zea mays) reducing tunneling from European corn borer (Ostrinia nubilalis). Endophytic colonisation of other plants by B. bassiana has been reported, and potentially, may reduce insect feeding on these plants. We evaluated the effects on larval growth and development, and mortality of different rates of dried, ground mycelia and water-soluble metabolites from fermentation broth culture of different isolates of B. bassiana incorporated into a synthetic diet and fed to neonate bollworm, Helicoverpa zea larvae. Development was delayed, weights of larvae were lower, and mortality was high for larvae fed the highest rates (1.0 and 5.0%, w/v) of mycelia incorporated diet compared to control. Insects fed diets containing mycelia of B. bassiana isolate 11-98 had the greatest mortality. Mortality was 100% for larvae fed 5% (w/v) mycelia incorporated diet of isolate 11-98, and 61% for isolate 3-00. For insects fed low rates (0.1 to 0.5%, w/v) of mycelia incorporated diet, mortality was lower, approximately 5% for isolate 11-98, and 5 to 14% for isolate 3-00. At the 0.1% (w/v) rate of mycelia incorporated diet, development occurred at an accelerated rate, compared to fungus-free controls, indicating increased nutrition in the lowest rate fungal diet. Mortality was low for all larvae fed diets containing spent fermentation broth of B. bassiana; however, development was delayed. Insects fed the highest rate (0.5%, v/v) of spent fermentation broth-amended diet had lower pupal weights, and a greater number of days to pupation than insects fed the lowest (0.1%, v/v) rate. Insects fed the 5% (v/v) rate of spent fermentation broth of isolates 11-98 and 3-00 had the longest days to pupation.     

Evaluation of isolates and a new granular formulation of Bacillus sphaericus Neide for control of mosquitoes

Nineteen Bacillus sphaericus Neide strains obtained in Brazil were evaluated in addition to a standard strain (2362) supplied by Pasteur Institute. Most strains were more efficient than the standard, and seven of them caused mortality equal to or higher than 80%, at a low concentration (7 x 10(2) spores/ml). Strain ESALQ MS6 was selected for formulation, since it showed better yield in liquid culture medium (3 x 10(9) CFU/ml). The G4 granular formulation was tested in artificial rearing sites, consisting ofplastic buckets containing 10 L water and twenty 3rd-instar larvae of Culex quinquefasciatus Say (Diptera: Culicidae). The efficiency of formulation was compared against a commercial product, at three different concentrations. Evaluations were taken every 24h, at seven and 18 days after inoculation, with subsequent replacement of larvae in the bucket. The G4 formulation was similar to the commercial product, and controlled 100% of the larvae at the concentrations tested; however, the granules remained at the surface for a longer period. In tannery effluent treatment ponds, the G4 formulation at a concentration of 2 kg/ha reduced the number of larvae by 21%, 47%, 85%, and 94%, after 1, 3, 7, and 15 days, respectively.     

Insecticidal activity of garlic juice in two dipteran pests

Abstract

• 1 Botanical products excluding pyrethroids constitute a small, but growing portion of the U.K. pesticides market. With increasing legislative pressure upon chemical pesticides such as organophosphates, interest in this sector is increasing steadily.
• 2 Garlic Allium sativum L. juices and extracts form the basis of several commercially available pest control products, but the performance of these products is variable, possibly due to lack of quality control upon batches of materials in the manufacturing process.
• 3 Some garlic products designed for use in the food industry are subjected to rigorous batch‐control to ensure organoleptic consistency. We studied the insecticidal efficacy of a commercially produced food grade garlic juice using two target dipteran pests, Delia radicum (L.) and Musca domestica L.
• 4 Exposure of the two species to different concentrations of garlic juice revealed variability in insecticidal effect across life stages. LC₅₀ values recorded for D. radicum were: eggs (7‐day exposure) 0.8%; larvae (24‐h exposure) 26.4%; larvae (48‐h exposure) 6.8%; and adults (24‐h exposure) 0.4%. LC₅₀ values recorded for M. domestica were: eggs (7‐day exposure) 1.6%; larvae (24‐h exposure) 10.1%; larvae (24‐h exposure) 4.5%; and adults (24‐h exposure) 2.2%.
• 5 Mortality rates caused by the garlic juice were comparable with those obtained with the organophosphate pesticide Birlane^®, indicating parity of effect at various concentrations depending on life stage.
• 6 We conclude that this product may provide an effective, naturally‐derived insecticide for use in agricultural systems against dipteran pests.

     

Effects of inoculation method on efficacy of wettable powder and oil dispersion formulations of Beauveria bassiana against Colorado potato beetle larvae under low-humidity conditions

The effects of inoculation method on efficacy of two formulations of Beauveria bassiana strain GHA against Colorado potato beetle larvae were investigated. Under dry greenhouse conditions, ca. 58% mortality was observed among second-instar larvae exposed directly to sprays of B. bassiana conidia, whereas mortality among larvae exposed to similarly treated foliage (either leaf dorsal or ventral surfaces) was <10%. Mortality was ca. 64% among larvae exposed to both direct sprays and foliar spray deposits. Equivalent rates of mortality were observed among larvae treated with a clay-based wettable powder versus an emulsifiable oil-based formulation of B. bassiana conidia; however, this was observed despite application of an approximately 40% greater dose of WP-formulated conidia, indicating greater efficacy of the emulsifiable oil formulation. These results suggest that, under dry conditions, potato beetle larvae do not readily acquire an effective dose of conidia from treated foliage and that development of improved application technologies to more effectively target the larvae may ultimately prove more beneficial than development of formulations with greater foliar persistence.     

Marking otoliths of Baltic cod (Gadus morhua Linnaeus, 1758) with tetracycline and strontium chloride

Identified were suitable dosages of tetracycline hydrochloride (TET) in three single treatments and three combined treatments of TET with 2 mg/kg strontium chloride (STR) in wild western Baltic cod (Gadus morhua), in terms of (a) obtainable mark qualities (visibility of fluorescent bands), (b) growth assessment, and (c) induced mortality rates. Isotonic NaCl solution was injected in a control group (25 cod per treatment). The results provide the basis for imperative age validation studies of Baltic Sea cod. Cod originating from pound nets near Fehmarn Island were kept in swimming net cages at the harbor of Warnemünde for 1.5 months. Mean initial total length was 28(±3) cm (salinity: 13, water temperature: 13 to 8°C). Overall average growth of surviving cod was 0.8 mm/day. In single TET treatments, lowest mortality rates and best mark quality were observed for TET concentrations of 100 compared to 50 and 25 mg/kg wet mass. Mortality rates of the 100 mg/kg treatment group were remarkably lower than in the control group emphasizing the antibiotic effect of TET. By contrast, the double treatment in the TET‐STR groups resulted in a binding interaction between both markers in the fish body causing either the antibiotic potency being inhibited or TET and STR forming a non‐beneficial chelate (increased mortality), and decreased incorporation of TET in the otolith (reduced visibility of TET bands). Consequently, TET (short‐term marker) and STR (long‐term marker) should not be injected together. Our results demonstrate that the binding interactions between these substances known from homoiotherm animals also apply for poikilotherms such as fish.     

Field tests with insecticides and insect growth regulators to control insect pests of cowpea and its effects on certain beneficial insects

A small‐plot tests were conducted on cowpea, Vigna ungiculata (L.) Walp, to determine the effectiveness of 14 selected insecticides representing four insecticide classes (organophosphates, carbamates, pyrethroids, and insect growth regulators, IGRs), and four insecticide/IGR mixtures on cowpea insect pests and its effects on certain beneficial insects. By day 3 after treatement, the insecticides phenthoate, isoxathion, cyanophos, carbaryl, and cypermethrin used at sub‐recommended rates reduced the leafhopper, Empoasca spp., populations by >83% than those in the control. On that day, all insecticide treatments significantly reduced the cowpea aphid, Aphis craccivora, numbers below that of the control. The prothiofos, isoxathion, pirimicarb, and fenpropathrin treatments provided continuing control to both leafhoppers and aphids through day 21 after spraying. It seems that most insecticide treatments were not effective in whitefly, Bemisia tabaci, control. The best control of the whitefly immatures was obtained by day 3 after spraying in plots received thiodicarb (76%) and fenpropathrin (60%). All selected insecticides and rates used had very low residual effect against B. tabaci immatures. By day 3 posttreatment, the carbaryl (2.02 kg/ha) caused completely protection for cowpea pods frMw blue pea butterfly, Lampides boeticus, larvae. The IGRs, flufenoxuron and Dowco‐439, applied alone and those applied in mixtures with insecticides, carbaryl/teflubenzuron, chlorpyrifos/XRD‐473, and methomyl/ flufenoxuron, exhibited satisfactory control (>81%) to butterfly larvae on day 7 posttreatment. All treatments did not exhibit a considerable residual activity against L. boeticus larvae through 2–3 weeks followed spray. Most insecticides applied at the higher rates used significantly reduced the numbers of limabean pod borer, Etiella zinckenella, larvae found in cowpea pods collected on day 7 after application. The IGRs, flufenoxuron and Dowco‐439, applied alone, at 0.119 kg/ha, or in mixtures, methomyl/flufenoxuron (0.167 kg/ha) and chlorpyrifos/Dowco‐439 (0.911 kg/ha) caused >73% control of E. zinckenella larvae through day 21 posttreatment. The best control of cowpea weevil, Callosobru‐chus spp., adults (>83%), on day 3 after spraying, was obtained in treatments of cyanophos (1.19 kg/ha), prothiofos (1.43 kg/ha), flufenoxuron (0.119 kg/ha), and chlorpyrifos/Dowco‐439 (0.911 kg/ha). The IGR flufenoxuron applied alone or in mixture, methomyl/flufenoxuron (0.164 kg/ ha) exhibited satisfactory residual activity against Callosobruchus adults through day 21 posttreatment. Percentage seed damage by the larvae of cowpea weevils was significantly lower in most treatments than that of control. Populations of insect predators found in all treated plots were extremely reduced than those found in untreated plots. By day 21 after spraying, the IGRs flufenoxuron, XRD‐473, and Dowco‐439, applied at the low rate of 0.071 kg/ha, seemed to be less effect against insect predators than other insecticides used.     

Insecticidal and antifeedant effects of two alkaloids from Cynanchum komarovii against larvae of Plutella xylostella L

A bioassay‐guided fractionation of Cynanchum komarovii crude alkaloid extract led to the isolation of two alkaloids. The isolated alkaloids were identified as 7‐demethoxytylophorine (1) and 6‐hydroxyl‐2,3‐dimethoxy phenanthroindolizidine (2) based on the comparison of their spectroscopic characteristics with the literature data. Insecticidal, antifeedant and growth inhibitory effects of these two alkaloids against the 3rd instar larvae of Plutella xylostella L. (Lepidoptera: Plutellidae) were examined. The results showed that alkaloid 1 was more toxic than alkaloid 2 against the 3rd instar larvae of Plutella xylostella L., but both alkaloids were less toxic than the total alkaloid fraction. For antifeedant activity, alkaloid 1 showed AFC₅₀ of 1.82 mg/ml at 24 h after treatment, alkaloid 2 showed 3.89 mg/ml, while total alkaloids showed 1.56 mg/ml. In dipping toxicity test, alkaloids 1 and 2 produced 93.3% and 63.3% mortality at 72 h after treatment, respectively, while total alkaloids produced 96.7% mortality. The LC₅₀ values for alkaloids 1, 2 and the total alkaloids were 3.54, 9.21 and 2.63 mg/ml, respectively. The development of larvae was also inhibited, and the growth inhibition rates at the concentration of 15.00 mg/ml were 92.8%, 78.2% and 98.6% for alkaloids 1, 2 and total alkaloids, respectively, at 72 h after treatment. Compared with antifeedant and dipping effect, the alkaloids 1, 2 and total alkaloid fraction revealed weak feeding toxicity, and their corrected mortality rates at the concentration of 15.00 mg/ml were 60.0%, 40.0% and 63.3% at 7 days after treatment. The LC₅₀ values for alkaloids 1, 2 and total alkaloids were 12.58, 32.37 and 8.88 mg/ml, respectively, at 7 days after treatment.     

Effects of insect growth regulators on citrus mealybug parasitoid Leptomastix dactylopii (Hymenoptera: Encyrtidae)

In this study, we measured the effects of three commonly used insecticides classified as insect growth regulators, on the encyrtid parasitoid Leptomastix dactylopii (Howard) when parasitizing citrus mealybug, Planococcus citri (Risso). Kinoprene, pyriproxyfen, and azadirachtin were evaluated in both petri dish and a cage experiment at label-recommended rates to measure their effects on the mortality, parasitization rate, and sex ratio of L. dactylopii. Insecticides were applied to petri dishes and plants either immediately before, 24 h before, or 48 h before release of the parasitoid. Kinoprene applied 24 h before parasitoid release caused 100% mortality of L. dactylopii in petri dishes within 48 h. Mortality rates for L. dactylopii exposed to azadirachtin and pyriproxyfen did not exceed 5% regardless of release time. There were no release time x insecticide interactions on L. dactylopii parasitization rate. The insecticide alone, however, did significantly affect parasitization rates of L. dactylopii on P. citri; the kinoprene treatment significantly reduced L. dactylopii parasitization rates compared with azadirachtin and pyriproxyfen. In a cage experiment with coleus, Solenostemon scutellaroides (L.) Codd, applications of both pyriproxyfen and kinoprene resulted in fewer P. citri parasitized by L. dactylopii than azadirachtin or the control. The sex ratio was equivalent in the petri dish experiment, whereas in the cage experiment the sex ratio was biased toward males, particularly for the kinoprene treatment. Based on the results from this study, we suggest that kinoprene is not compatible with releases of L. dactylopii to control citrus mealybugs.     

Biology and control of the fruit borer, Conopomorpha sinensis Bradley on litchi （Litchi chinensis Sonn.） in northern Thailand

Fruit and leaf shoot of litchi （Litchi chinensis） infestation by naturally occurring populations of the fruit bprer, Conopomorpha sinensis larvae and C. sinensis parasitization rates were determined in litchi orchards in northern Thailand at high （ca. 1 400 m ASL） and low （ca. 800 m ASL） elevations with different, non-overlapping fruiting seasons. In addition, spray applications of Bacillus thuringiensis var. aizawai, the natural compound spinosad and the chemical pesticide imidacloprid were conducted in the field to test the effects of these agents on C. sinensis fruit infestation rate. Fruit infestation rate and fruit growth, studied in a low elevation orchard, were sigmoidal and showed a highly significant positive correlation （P ≤ 0.01）. Leaf shoot infestation rate in the low elevation orchard decreased in the course of the fruiting season （March until May）, but increased in the high elevation orchard, where no fruits were present within the same period of time. Together, these results indicate that females of C. sinensis clearly prefer fruits over shoots for oviposition. If no fruits are available, which was the case in the high elevation orchard during that time, they are constrained to lay their eggs on shoots. The parasitization rate of C. sinensis larvae in untreated fruits was 54.3%. The parasitoid species were Chelonus chailini （90.8%） and Phanerotoma sp. （9.2%）. In the leaf shoots, C. sinensis was found to be parasitized by Phanerotoma sp. and Apanteles briareus. The applications of the different active agents had no significant effect on C. sinensis fruit infestation compared to the untreated control. Besides the cryptic life of the larvae, this is most probably explained by the fact that C. sinensis has several generations during the fruiting season. Because of the high parasitization rates recorded, an alternative and more effective control measure than the application of pesticides might be the augmentative release of parasitoids.     

Effects of the ecdysteroid agonists RH 5849 an RH 5992, alone and in combination with a juvenile hormone analogue, pyriproxyfen, on larvae ofSpodoptera exigua

Biological activity assays with RH 5849 and RH 5992 indicated that both compounds affected growth and development of last-instar larvae ofSpodoptera exigua (Hübner) (Lepidoptera: Noctuidae) in a dose-dependent manner. Within the first 24 h after treatment by continuously offering leaves dipped in a water solution of ≥50 mg/l RH 5849 and ≥0.5 mg/l RH 5992, symptoms of a prematurely induced larval moult and head capsule apolysis were visible. Intoxicated larvae died shortly afterwards, showing signs of unsuccessful ecdysis. LC₅₀-values of RH 5849 and RH 5992 for fifth-instarS. exigua larvae were 110 and 2.5 mg/l, respectively. Pyriproxyfen alone affected the larval stage and disturbed normal metamorphosis. One supernumerary larval instar occurred occasionally. LC₅₀-value for pyriproxyfen was 1.7 mg/l. Larvae simultaneously treated with RH 5849 or RH 5992 and pyriproxyfen, continued to grow until they attained a size and weight about 2–3 times that of the controls. This growth was accompanied by at least one and sometimes two supernumerary moults. Concerning thein vivo imaginal wing disc growth and development, only in larvae treated with 10 and 50 mg/l RH 5849 or 0.5 mg/l RH 5992, tracheole migration was observed earlier than in the controls. When applying 300 mg/l RH 5849 or 3–7 mg/l RH 5992, the discs remained small and no signs of tracheole migration were observed. In larvae simultaneously treated with RH 5849 or RH 5992 and pyriproxyfen, tracheole migration was not prematurely induced and a pupal cuticle was produced in the discs of larvae, undergoing a supernumerary moult. No clear signs of evagination were observed.     

Contact and residual toxicities of 30 plant extracts to Colorado potato beetle larvae

Abstract

Contact and residual toxicities of 30 plant extracts were investigated on third instar larvae of Colorado potato beetle, Leptinotarsa decemlineata. The plant samples were collected during the spring and summer of 2002 and were dried and ground. The plant samples were treated with methanol and the residue was eluted with distilled water containing 10% acetone, resulting in plant extracts. In contact bioassays, the beetle larvae were treated with 40% (w/w) plant extract using a Potter Spray Tower. The insects were incubated at 28±2°C under a 16 h: 8 h photo regime and the mortality was recorded at 24 h intervals for 7 days. The plant extracts exhibited varying toxicity to the larvae ranging from 0 – 91% after 24 h incubation and Artemisia vulgaris, Hedera helix, Humulus lupulus, Lolium temulentum, Rubia tinctoria, Salvia officinalis, Sambucus nigra, Urtica dioica, Verbascum songaricum, and Xanthium strumarium extracts resulted in significantly higher mortality than the control. Generally, prolonged incubation time did not result in an increase in mortality. After 48 h of incubation, 10 plant extracts yielded a significant mortality and H. lupulus extract, the most toxic extract among those tested, caused 99% mortality which is similar the mortality caused by the chemical standard, imidacloprid. In residual assays, potato leaflets were treated with 20% (w/w) plant-extract concentrations using a Potter Spray Tower. Third instar larvae were added to a glass jar to which treated leaflets were transferred before incubation at the temperature and photo regime described above. Mortality was recorded at 24 h intervals for 7 days. Five plant extracts, H. lupulus, L. temulentum, Reseda lutea and Solanum nigrum, induced significantly higher mortalities compared with controls. Chenopodium album extract was the most toxic, killing 34.9% of exposed larvae, followed by L. temulentum, H. lupulus and S. nigrum after 72 h incubation. The results exhibited that certain plant extracts were toxic to the beetle larvae and may have potential for controlling this destructive pest under field conditions.     

Survival, growth and condition of tench Tinca tinca (L.) larvae fed live food for 12, 18 or 24 h a day under controlled conditions

The present 20‐day trial was performed in order to improve growth of tench Tinca tinca (L.) larvae reared intensively in a controlled environment. Larvae of 4.53 mm initial length, 45 per dm³, were fed each day with live Artemia nauplii for 12, 18 or 24 h at 28°C. Final survival rates were very high in all treatment groups, ranging from 88.9 to 91.8%. Duration of daily feeding significantly affected growth and final condition, expressed by Fulton's coefficient (K) (P ≤ 0.05, Duncan's test). The fastest larval growth (17.6 mm total length, TL; 88.8 mg body weight, BW) and the best condition (K = 1.54) were recorded in the group fed 24 h each day. The second best results were attained with the larvae fed 18 h a day (16.5 mm TL, 67.9 mg BW, K = 1.40) whereas those fed 12 h daily grew the slowest (13.5 mm TL, 31.7 mg BW) and showed the worst condition (K = 1.19). Thus, to maximize growth and condition of tench larvae being reared at the optimal growth temperature, intensive 24 h feeding is necessary.     

Molluscicidal action of the latex of Euphorbia splendens var. hislopii N.E.B. ("Christ's Crown") (Euphorbiaceae) against Lymnaea columella (Say, 1817) (Pulmonata: Lymnaeidae), intermediate host of Fasciola hepatica Linnaeus, 1758 (Trematode: Fasciolidae): 1- test in laboratory

The latex action of Euphorbia splendens var. hislopii (Christ's Crown) against snails Lymnaea columella, intermediate host of Fasciola hepatica, derived from irrigation ditches of the Station of Pisciculture at Universidade Federal Rural do Rio de Janeiro, was studied in the laboratory. Lab bioassays, using aqueous solutions of the latex, varying between 0.1 and 10 mg/l, have proven molluscicidal activity of the product collected on the same day the tests were performed, during the four seasons of the year, finding the following lethal concentrations (LC90): 1.51 mg/l in the spring; 0.55 mg/l in the summer; 0.74 mg/l in the fall and 0.93 mg/l in winter, after 24 h exposure of the snails, showing significant differences among the seasons of the year (ANOVA test, F = 11.01, G.L.= 3/33, p < 0.05), as well as among the concentrations (ANOVA test, F = 27.38, G.L.= 11/33, p < 0.05). In the summer, mortality reached 100% from concentration at 0.6 mg/l, the same during fall and in winter as of 1 mg/l, while in spring it only reached 100% mortality as of 2 mg/l. Mortality in the controls was low, reaching 5% in the summer and winter and 10% in the fall and spring. None of the samples died. During the assay, with an aqueous solution of the latex at a concentration of 5 mg/l, in order to check the time of duration of the product effect, in the laboratory, it was observed that the molluscicidal activity remained stable up to the 15th day after the beginning of the test with 100% mortality of L. columella, gradually losing its effect until the 23rd day, when we no longer observed animal mortality. In the control group, there was a random daily variation in mortality rate ranging 0-50% after 48 h of observation for 30 days.     

Effect of juvenile hormone and pyriproxyfen treatments on the production of Spodoptera litura nuclear polyhedrosis virus

Efficient production is essential for developing baculoviruses into marketable bioinsecticides. In this study, we evaluated how juvenile hormone (JH) III and the JH analog pyriproxyfen affected the production efficiency of Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) Nucleopolyhedrovirus (SpltNPV) in SpltNPV‐inoculated early sixth instars. Both the JH III and pyriproxyfen treatments significantly enhanced the body size and weight of S. litura, which resulted in a 1.5‐ to 2‐fold increase in the production of occlusion bodies (OBs). The OBs obtained from JH‐ and pyriproxyfen‐treated larvae were as pathogenic as those produced in untreated larvae. More importantly, JH‐ or pyriproxy‐fen‐treated larvae consumed less than twice the amount of food consumed by two untreated larvae. These results indicate that JH and pyriproxyfen treatments improve the production efficiency of SpltNPV in S. litura. SpltNPV infection affected the development of S. litura not only as larvae, but also during subsequent growth stages and generations.     

Ultralow rates of spinosad in phagostimulant granules provide control of Spodoptera frugiperda (Lepidoptera: Noctuidae) in maize

Field trails in 2002 and 2003 were performed to determine the efficacy of maize flour-based granular formulations with ultralow rates of the naturally derived insecticide spinosad (0.1, 0.3, and 1.0 g [AI]/ha), for control of Spodoptera frugiperda (J.E. Smith) in maize, Zea mays L., in southern Mexico. Spinosad formulations were compared with a chemical standard, a commercial granular formulation of chlorpyrifos (150 g [AI]/ha). In both years, application of spinosad resulted in excellent levels of control, indicated by the number of living S. frugiperda larvae recovered from experimental plots. The efficacy of spinosad applied at 0.3 and 1.0 g (AI)/ha was very similar to that of chlorpyrifos. Natural reinfestation caused S. frugiperda numbers in insecticide treated plots to return to values similar to the control treatmentby 10-15d postapplication. Many spinosad-intoxicated larvae collected in the field died later in the laboratory in 2002, but not in 2003. Percentage mortality due to parasitoid emergence did not differ in any treatment in either field trial. The number of parasitoids that emerged from S. frugiperda collected in each treatment was significantly reduced after application of spinosad (all rates) or chlorpyrifos due to a reduction in the number of host larvae. Parasitoid numbers returned to control values by 9-15 d postapplication in all treatments. The most prevalent parasitoid was the braconid Chelonus insularis Cresson, which represented approximately 80% of emerging parasitoids in both years. We conclude that appropriate formulation technology can greatly enhance the performance of this naturally derived, biorational insecticide.     

Growth and survival of blowfly Lucilia sericata larvae under simulated wound conditions: implications for maggot debridement therapy

Maggot debridement therapy has become a well‐established method of wound debridement. Despite its success, little information is available about the optimum duration of the treatment cycle and larval growth in wounds. This study examines the development of Lucilia sericata (Diptera: Calliphoridae) larvae under two containment conditions (bagged and free range) under simulated wound conditions and assesses the impact of transport and further storage of larvae on their survival and growth. There was no significant difference in size between bagged and free‐range larvae over the 72‐h experimental period. Larvae grew fastest 8–24 h after inoculation and completed their growth at 40–48 h. Mortality rates were similar (0.12–0.23% per hour) in both containment conditions and did not differ significantly (P = 0.3212). Survival of free‐range larvae was on average 16% lower than survival of bagged larvae. Refrigeration of larvae upon simulated delivery for > 1 day reduced their survival to < 50% and caused a reduction in growth of up to 30% at 12 h, but not at 48 h, of incubation. Therefore, it is recommended that free‐range larvae are left in the wound for a maximum of 40–48 h, and bagged larvae for 48–72 h. Larvae should be used within 24 h of delivery to avoid high mortality caused by prolonged refrigeration.