Biological activity of clofentezine against egg and motile stages of tetranychid mites

The activity of clofentezine (3,6-bis(2-chlorophenyl)-1,2,4,5-tetrazine) against eggs, immature and adult stages of tetranychid mites has been examined under laboratory and field conditions. The compound has been shown to be active against the eggs and immature stages but does not kill the adults. Eggs become less susceptible to the compound as they mature, and this has been demonstrated both on laboratory cultures ofTetranychus and on the overwintering eggs ofPanonychus ulmi. Control of infestations ofP. ulmi on deciduous fruit is the combined result of direct ovicidal activity and residual activity against the early motile stages.     

Effect of high and low temperatures on the drugstore beetle (Coleoptera: Anobiidae)

The drugstore beetle, Stegobium paniceum (L.) (Coleoptera: Anobiidae), is a pest of stored medicinal and aromatic plants. Generally, mortality of each stage increased with an increase of temperature and exposure time. Heat tolerance for different stages from highest to lowest was young larvae, old larvae, eggs, adult, and pupae. The mortality after 7 h at 42 degrees C for young larvae, old larvae, eggs, adults, and pupae, respectively, was 16 +/- 5, 31 +/- 6, 48 +/- 3, 63 +/- 8, and 86 +/- 2% (mean +/- SEM). Similar trends for stage specific mortality were seen with the lethal time for 90% mortality (LT90) at 42 degrees C; 773, 144, 12, and 11 h for old larvae, eggs, adults, and pupa respectively. Mortality was too low with young larvae to estimate LT90. The LT90 for young larvae at 42, 45, 50, 55, and 60 degrees C was 25, 20, 3.9, 0.18, and 0.08 h, respectively. The cold tolerance of different stages at 0 degree C from highest to lowest was adults, old larvae, young larvae, pupae, and eggs. The LT90 at 0 degrees C was 298, 153, 151, 89, and 53 h, respectively. The LT90 for adults at 5, -5, -10, and -15 degrees C was 792, 58, 2, and 0.8 h, respectively. The supercooling point of adults was -15.2 +/- 2 degrees C; young larvae, -9.0 +/- 0.8 degrees C; old larvae, -6.5 +/- 0.5 degrees C; and pupae, -4.0 +/- 1.4 degrees C. Heat treatments that control young larvae should control all other stages of S. paniceum. Cold treatments that control adults should control all other stages of S. paniceum. Dried plants stored at 5 degrees C for 45 d or 42 degrees C for 30 h and then kept below 18 degrees C throughout the rest of the year, should remain pest-free without any chemical control.     

Molluscicidal activity of various solvent extracts from Solanum nigrum var. villosum L. aerial parts against Galba truncatula

Molluscicidal activity of Solanum nigrum var. villosum (morelle velue) extracts and their fractions were tested against the mollusca gastropoda Galba truncatula intermediate host of Fasciola hepatica. The results indicated that the hydro-methanol (MeOH-H2O) immature fruit extract possess the highest molluscicidal activity (LC50 = 3.96 mg/L) against Galba truncatula compared with other tested compounds. After acido-basic treatment, the methanolic extract fraction isolated from the immature fruits and the richest in alkaloids was the most toxic (LC50 = 1.65 mg/L). The fractions richest in saponosides obtained from the hydromethanolic and methanolic extracts of immature fruits showed interesting molluscicidal activities (LC50 = 6.15 mg/L and LC50 = 7.91 mg/L, respectively). The observed molluscicide activity could be attributed to the presence of alkaloids or saponosides. So, the immature fruits of Solanum nigrum var. villosum could be substrates of choice for molluscicide activity. In addition, total alkaloids and saponosides present in this plant deserve further investigations in order to identify the active principles and demonstrate their activities on mollusks in their natural habitat. According to the World Health Organization's guidelines on screening for plant molluscicides, use of these fractions may add to the arsenal of methods to control snail transmitting fasciolosis in tropical and Third World countries where fasciolosis is a common disease.     

Effects of Selected Chemical Pesticides on Agamermis unka (Nematoda: Mermithidae), a Parasite of the Brown Plant Hopper,Nilaparvata lugens

Selected commercial and technical grade pesticides were tested against the egg, preparasite and adult stages of Agamermis unka , a nematode parasite of the brown planthopper, Nilaparvata lugens . The commercial insecticide, diazinon (LC = 0.37 ppm), was most toxic to the 50 preparasites, followed by phenthoate (LC = 0.43 ppm), BPMC (LC = 0.44 ppm), IBP 50 50 (LC = 0.46 ppm), cartap hydrochloride (LC = 0.82 ppm) and buprofezin + isoprocarb 50 50 (LC = 1.11 ppm). The least toxic commercial pesticide tested was the fungicide, pencycuron 50 (LC = 2.19 ppm). Out of 12 technical grade insecticides tested, phenthoate, monocrotophos, 50 diazinon and carbofuran (LC = 0.37-0.46 ppm) were highly toxic to the preparasites, followed by 50 buprofezin, BPMC and fenitrothion (LC = 0.74-0.86 ppm). Fenthion, etofenprox, chlorpyrifos, 50 imidacloprid and MIPC (LC = 1.11-2.19 ppm) were the technical grade insecticides least toxic 50 to the preparasites. Most preparasites survived for up to 24 h at the low insecticide concentrations (0.63 and 0.31 ppm). Preparasites that were exposed to BPMC for 24 h at concentrations as high as 5.0 ppm and survived the treatments infected brown planthopper nymphs. Four selected insecticides-chlorpyrifos, BPMC, imidacloprid and carbofuran-had significant adverse effects on A. unka egg hatching. Eggs that were in the insecticide solution for 168 h fared poorly with imidacloprid having the best survival ( > 2% of the eggs hatching at 0.04 ppm). No eggs hatched from the other insecticide treatments. Three selected insecticides, BPMC, imidacloprid and chlorpyrifos, tested against adult A. unka showed that most adults survived the exposure to the insecticides between 0.31 and 2.5 ppm. At 5.0 ppm of BPMC or chlorpyrifos none of the adults survived, whereas with imidacloprid 70% of the adults survived. Egg deposition by the surviving adults was greatly reduced in those treated with the insecticides compared with those in the controls. Imidacloprid had some negative impact on the preparasites' ability to infect BPH nymphs, but it had the least detrimental effect of the insecticides tested on preparasite survival and on the eggs and adults of A. unka .     

茚虫威和六伏隆对小菜蛾卵、幼虫和成虫的药效（英文）

化学防治是世界各地防治小菜蛾Plutella xylostella (L.)的主要方法。选择对小菜蛾各发育阶段高效的杀虫剂有助于很好地控制这一害虫。本研究用浸叶法测定了茚虫威和六伏隆对小菜蛾卵、幼虫和成虫的毒性。茚虫威和六伏隆对小菜蛾卵的LC₅₀值分别为201.40 和 37.32 mg/L。茚虫威和六伏隆对3龄幼虫也有很好的毒性（茚虫威的LC₅₀ 为 4.82 mg/L; 六伏隆的LC₅₀ 为1.48 mg/L)。对成虫的毒性结果表明, 这两种杀虫剂对成虫均没有理想的毒性（茚虫威的LC₅₀ 为845.20 mg/L; 六伏隆的LC₅₀ 为3 438 mg/L)。根据计算的LC₅₀值, 六伏隆对小菜蛾卵和幼虫的毒性比茚虫威高, 但是茚虫威对成虫的毒性更高。     

Plagiorchis elegans (Digenea: Plagiorchiidae) infections in Stagnicola elodes (Pulmonata: Lymnaeidae): host susceptibility, growth, reproduction, mortality, and cercarial production.

Eggs of Plagiorchis elegans were readily ingested by Stagnicola elodes of all ages, but were more infective to immature than mature snails. Infection enhanced the growth of the host in a dose-dependent manner. The number of cercariae released by immature snails increased with the age of the snail host; mature snails yielded fewer cercariae. Heavily infected snails tended to die prematurely, thereby reducing their total production of cercariae to levels below those of more lightly infected individuals. Even light infections castrated the snail host. Snails that acquired the infection as juveniles never produced eggs. Actively reproducing snails ceased egg laying within days of infection and never recovered. All parasite effects on the growth and reproduction of the snail host first manifested themselves during the early stages of infection, long before the development of daughter sporocysts and cercariae, and are therefore attributable to the effects of mother sporocysts. The study provides insight into how this natural enemy of mosquito larvae may be established in natural snail populations by means of strategically timed introductions of parasite eggs, with a goal of maximizing cercarial production for the biological control of sympatric mosquito larvae.     

Interaction of treatment of both adult and immature Coleoptera with a chitin synthesis inhibitor affects mortality and development time of their progeny

Chitin synthesis inhibitors, like many other insect growth regulating insecticides, do not kill adult insects but cause mortality of the immature stages. Pre-exposure of adult stored grain Coleoptera, Rhyzopertha dominica (F.) (Bostrichidae) and Sitophilus oryzae (L.) (Curculionidae) and development of their progeny in grain treated with the chitin synthesis inhibitor, chlorfluazuron, influenced the mortality and development rate of the progeny. Hatch rate of eggs from R. dominica adults that had both developed and laid on wheat treated with 0.75 mg kg–1 chlorfluazuron was reduced by almost 50% compared with untreated eggs, with an LC50 of 0.84 mg kg–1 . Eggs laid on treated wheat by R. dominica adults that had been exposed only to treated wheat for 2 weeks before oviposition showed greater reduction in hatch: 75% reduction of normal hatch rate at 0.25 mg kg–1 and almost 100% reduction at 2 mg kg–1 chlorfluazuron, with an LC50 of 0.19 mg kg–1 chlorfluazuron. X-rays were used to monitor the development and mortality of the immature stages of S. oryzae that developed within the wheat grains. Numbers of eggs laid were not affected by chlorfluazuron treatment. The combination of pre-exposure of adults and chlorfluazuron concentration had an additive effect on mortality of immature S. oryzae. Pre-exposure of adults caused most mortality in the first three weeks of development (eggs and larvae), whereas development in treated wheat caused mortality from weeks 3 to 8 (pupae and adults); higher concentrations of chlorfluazuron caused higher mortality. Development in wheat treated with 1 mg kg–1 chlorfluazuron caused 12% corrected overall mortality of progeny while pre-exposure to the same concentration and development in untreated wheat caused 29% corrected mortality. Pre-exposure combined with development in wheat treated with 1 mg kg–1 caused 30% corrected mortality. Thus, pre-exposure of adults appears to have a greater effect on mortality of S. oryzae progeny than development of immature stages in treated grain. Development on treated grain had no effect on development rate. Pre-exposure of adults did not appear to affect the rate of immature development, as assessed by X-rays, but did slow the emergence of adults, lengthening development time by about 2 days. This significant, additive effect of pre-exposure of adults on the mortality of their progeny will enhance the toxicity of chitin synthesis inhibitors such as chlorfluazuron, since most adults receive treatment when the immature stages are treated in crops either before they are harvested or in storage. Assessing the proportion of eggs that hatch from pre-exposed adults would be a simpler bioassay for CSIs.     

Gonadal maturation,fecundity, spawning,and timing of reproduction in the mud snail,Cerithidea cingulata,a pest in milkfish ponds in the Philippines

Summary

Gonadal maturation, spawning, fecundity and timing of reproduction of the snail Cerithidea cingulata in a brackish water pond in Molo, Iloilo, Philippines, are described. Snails 4–41 mm in shell length were sampled monthly from May 1997 to May 1998; 25% were <25 mm, 67% were 20–30 mm, and 8% were >30 mm. The sexes are separate and could first be distinguished at 15 mm. Males are aphallic, have narrower shells than females of the same length, and have bright yellow-orange testes overlying the digestive gland deep inside the shell. Females have more robust shells, an ovipositor at the right side of the foot, and yellow-green ovaries overlying the digestive gland. The sex ratio was one male to two females in the pond population studied. Gonadal maturation was monitored by means of gonadosomatic index (GSI, gonad weight as a percent of visceral weight); maturation stages were based on the gonad appearance (immature, developing, mature) and histology (immature, developing, mature, redeveloping). GSI increased with snail size, and reached 16% in a 33-mm female. The smallest mature males and females were 18–19 mm, and most snails >20 mm were mature, spawning, or redeveloping. Histological sections showed all stages of gametogenesis in mature male snails. The oocyte size-frequency distributions in mature females showed mostly mature oocytes and secondary oocytes, but also oogonia and primary oocytes. GSI and the frequency of snails at different maturation stages varied over the year. Both GSI and the frequency of mature snails were highest during the summer months, April to August. Nevertheless, mature snails occurred throughout the whole year, as did mating and egg-laying. Fecundity (= number of oocytes >70 pμ) increased with size in mature females 2041 mm; an average 25-mm female produced about 1,500 oocytes and larger females produced a maximum of about 2,500 oocytes. Eggs strings laid on the pond bottom were 45–75 mm long; an average 64-mm string contained 2,000 eggs 210+20 pm in diameter. The density of eggs strings was highest (80–120/m²) during March-September. Eggs hatched after 6–7 d into planktonic veligers, which in turn settle on the pond bottom 11–12 d later as juveniles. Juveniles 2–6-mm long were most abundant in the pond during August-October.     

Factors contributing to the in vitro development of Ascaris suum from second-stage larvae to mature adults

When a three-step roller culture system was used, second-stage larvae of Ascaris suum, artificially hatched from eggs, developed in high numbers to the fourth stage, and a few to young and mature adults. The culture system consisted of (1) Medium KW-2 supplemented with 10 mM L-cysteine for the first 4 days, and with 5 mM L-cysteine for the following 7 days; (2) followed by Medium API-18 for 7 days; and (3) thereafter, by Medium API-1 supplemented with hemin (bovine) at a concentration of 24 micrograms/m1. Cultures were gassed with 95% nitrogen-5% carbon dioxide for the first 4 days and 85% nitrogen-5% oxygen-10% carbon dioxide thereafter, and incubated at 39 C. Two mature females that produced unfertilized eggs and a mature male with spermatozoa were the most advanced stages attained. The mature females were obtained in 67 and 73 days; and the largest female measured 110 mm. The latter produced 1,356,000 unfertilized eggs, from days 67 to 125. The mature male was obtained in 80 days; it measured 77 mm long and had paired spicules that were 1.5 mm long. Development of A. suum in three other culture systems showed that deletion of Medium API-18 or its substitution by Medium KW-2 limited development to late fourth stage and early, young adults, respectively; and the use of Medium API-1 without hemin limited development to early fourth stage.     

Effect of insecticides on Trichogramma exiguum (Trichogrammatidae: Hymenoptera) preimaginal development and adult survival

The effect of insecticides on Trichogramma exiguum Pinto & Platner emergence, adult survival, and fitness parameters was investigated. Insecticides tested were lambda cyhalothrin, cypermethrin, thiodicarb, profenophos, spinosad, methoxyfenozide, and tebufenozide. All insecticides, with the exception of methoxyfenozide and tebufenozide, adversely affected Trichogramma emergence from Helicoverpa zea (Boddie) host eggs when exposed at different preimaginal stages of development (larval, prepupal, or pupal). Regardless of the developmental stage treated, none of the insecticides tested had a significant effect on the sex ratio or frequency of brachyptery of emerged females. However, the mean life span of emerged T. exiguum females significantly varied among insecticide treatments, and was significantly affected by the developmental stage of parasitoid when treated. Based on LC50 values, spinosad and prophenofos were the most toxic compounds to female T. exiguum adults, followed by lambda cyhalothrin, cypermethrin, and thiodicarb. Insecticides field-weathered for four to 6 d on cotton leaves showed no activity against female T. exiguum adults.     

Population ecology and phenology of Diaphorina citri (Hemiptera: Psyllidae) in two Florida citrus groves

Studies were conducted to assess population densities and phenology of the psyllid Diaphorina citri Kuwayama at two citrus groves in east-central Florida. One grove contained young, irrigated grapefruit trees and the other contained mature, nonirrigated orange trees. The two groves were sampled weekly for eggs, nymphs, and adults on flush shoots; for adults on mature leaves; and for adults captured on yellow sticky card traps. Because infestations of immature D. citri develop strictly on young flush, the abundance of flush was assessed weekly. Overall means of 26.5, 16.8, and 0.27 eggs, nymphs, and adults per flush shoot, respectively, were observed in the young grapefruit trees. In the grove of mature orange trees, overall means of 16.0, 12.7, and 0.31 eggs, nymphs, and adults per flush shoot were observed, respectively. Flush abundance was an inconsistent indicator of the mean density of D. citri per flush shoot. Mean density per shoot by itself was an inconsistent indicator of overall population levels of D. citri at each study site because few shoots were sometimes present when mean densities per shoot were high. May, June, and July were periods of time when immature D. citri were consistently present and most abundant at each study site, but the study indicated large infestations could occur at any time of the year depending on environmental factors and flush availability. Yellow sticky traps were effective for both male and female D. citri and useful for gauging adult population trends.     

DIFFERENCES IN THE LIFE HISTORIES OF XEROLENTA OBVIA (MENKE, 1828) (HYGROMIIDAE) IN A COASTAL AND A MOUNTAINOUS AREA OF NORTHERN GREECE

The life cycle of Xerolenta obvia (Menke, 1828) was studiedin two areas, Paleokastro (Chalkidiki), an inland mountainousarea, and Nea Karvali (Kavala), a coastal area in northern Greece.At Paleokastro snails hatch in autumn, become adult the followingJuly, but do not lay eggs until October, after which they die.Clutch sizes are small, but eggs and hatchlings are large comparedwith those at Nea Karvali. Growth is fast in spring, and continuesuntil the end of July. The young hatchlings have dark shell-bands,but by July a quarter of snails appear unbanded. At Nea Karvali,eggs are also laid in October, and young snails emerge fromhibernation in March. Here, however, they do not mature untilApril of the following year. They thus have a 2-year life cycle,with adults dying in their second autumn. Clutches are aboutthree times the size of those at Paleokastro, but eggs and hatchlingsare significantly smaller. A little growth occurs in winter,but the rate of growth is generally much slower than at Paleokastro.Only 1–2% of this population has banded shells; the bandsare less obvious and they become invisible in some individualsas they mature. At both sites population density fluctuatedduring the two study years, but it was always higher at NeaKarvali. These results are discussed in relation to the differingclimates of the sites, and comparisons made with studies onrelated species in the region. (Received 23 July 2004; accepted 30 December 2004)     

Toxicity,persistence, and efficacy of indoxacarb on cabbage looper (Lepidoptera: Noctuidae) on cabbage

Toxicity of indoxacarb was bioassayed against eggs and young (first and second instars) and older larvae (third and fourth instars) of cabbage looper, Trichoplusia ni (Hübner), on cabbage (Brassicae oleracea variety capitata L.), and persistence of field-aged leaf residues of indoxacarb was bioassayed with second and third instars of T. ni on cabbage. Efficacies of indoxacarb and several other newer insecticides to T. ni were tested under field conditions for two seasons in south Texas. LC50 and LC90 values for T. ni eggs were relatively high, indicating that indoxacarb has little ovicidal effects on T. ni eggs. Indoxacarb was highly toxic to T. ni larvae, having low LC50 and LC90 values. Bioassays of field-aged leaf residues of indoxacarb tested in the spring of 1998 (0-, 3-, 5-, and 12-d-old residues) and the fall of 2000 (0-, 3-, 5-, 7-, 9-, and 13-d-old residues) indicated that ingesting indoxacarb was highly toxic to the second and third instars of T. ni, giving 100% mortality for the second instars at 2 d after exposure, and 100% mortality for third instars at 5 d after exposure. Two trials conducted under field conditions show that indoxacarb at 0.072 g (AI) /ha rate was effective against T. ni in cabbage, providing marketable cabbage with three applications per season. In addition, indoxacarb was as effective as spinosad and chlorfenapyr and significantly more effective than tebufenozide and emamectin benzoate.     

Effects of methoxyfenozide, indoxacarb, and other insecticides on the beneficial egg parasitoid Trichogramma nr. brassicae (Hymenoptera: Trichogrammatidae) under laboratory and field conditions

Trichogramma nr. brassicae is a common egg parasitoid of Helicoverpa species in Australian processing tomatoes, but its effectiveness can be severely curtailed by insecticide applications. To identify insecticides that are potentially compatible with this species, the effects of seven insecticides, including newly introduced compounds and a surfactant, were screened in laboratory and glasshouse assays for their toxicity to the wasps. Assays involved direct applications on adults, residual effects on adults, and applications on life stages still inside the host. Methoxyfenozide and indoxacarb were not toxic to Trichogramma in any assay when applied at field rates. Naled and chlorfenapyr caused 100% mortality when directly applied to adults, and 95% mortality when adults were exposed to residues of these chemicals within 24 h of application. The effects of naled residues were short lived (<48 h). Naled and chlorfenapyr were also toxic when applied to Trichogramma developing inside host eggs, reducing emergence of adults by >25%. Imidacloprid, emamectin, and tau-fluvalinate were toxic in some experiments; they caused >97% mortality in adults 1 h after direct application and in residue assays they caused 23-64% mortality during the first 24 h. In field trials, methoxyfenozide had no harmful effects on emergence from sprayed parasitized eggs, whereas indoxacarb had a small impact (<8%) on emergence. Methoxyfenozide and indoxacarb are potentially suitable for inclusion in integrated pest management strategies for management of Helicoverpa because they do not influence adult survival or development of immature stages, whereas other chemicals need to be treated cautiously.     

Comparison of heart rate in embryonic,young and adult Achatina fulica

We have studied the embryonic heart in the gastropod Achatina fulica using eggs soon after their deposition. We also followed the development of organs, with the main emphasis on the heart and its physiology. The embryos were examined at different stages by carefully removing egg shell until hatching. In this context the heart rate (HR) was analysed in embryonic snails and compared with that of young (from hatching) and adults. The HR of embryos dissected from newly deposited eggs was irregular, with a mean frequency of 0.42?±?0.14?Hz. The heartbeat during the ontogeny was more rhythmic and HR increased to 0.82?±?0.12?Hz. The intersystolic intervals (ISI) in real time showed a Gaussian distribution for all animals. The peak ISI from Gaussian fit closely matched the cumulative probability for corresponding data. Although the HR increased after hatching, comparisons yield a weak correlation (R?=?0.56?±?0.27) with the total body weight of embryonic, young and adult snails.     

Sucrose octanoate toxicity to brown citrus aphid (Homoptera: Aphididae) and the parasitoid Lysiphlebus testaceipes (Hymenoptera: Aphidiidae)

We report the toxicological effects of a new biorational, synthetic sucrose octanoate (AVA Chemical Ventures L.L.C., Portsmouth, NH), on brown citrus aphid, Toxoptera citricida (Kirkaldy), nymphs and adults and to its native parasitoid Lysiphlebus testaceipes (Cresson). Sucrose octanoate topically applied was equally toxic to brown citrus aphid adults and nymphs with LC50 and LC90 values ranging from 356 to 514 and 1029 to 1420 ppm, respectively. Mortalities of both stages did not differ significantly over time during the 3-24-h sampling period. Dry residues of sucrose octanoate exhibited similar levels of toxicity to both nymphs and adults. Mortality ranged from 60 to 70% at 6,000 ppm 4 h after exposure. L. testaceipes was not harmed by treatments as high as 4,000 ppm of sucrose octanoate as long as the parasitoid had mummified before treatment. Based on these results, sucrose octanoate would be a useful biorational in citrus integrated pest management programs.     

Histopathological Changes in Tissues of Bithynia siamensis goniomphalos Incubated in Crude Extracts of Camellia Seed and Mangosteen Pericarp

The present study was performed to observe histopathological changes in tissues of Bithynia siamensis goniomphalos (Gastropoda, Bithyniidae) incubated in crude extract solutions of camellia (Camellia oleifera) seed and mangosteen (Garcinia mangostana) pericarp, and furthermore to estimate the molluscicidal effects of 2 plant substances. Substantial numbers of bithyniid snails were incubated in various concentrations of 2 plant solution for 24 hr. As the positive control, snails incubated in various concentrations of niclosamide, a chemical molluscicide, were used. The histopathological findings were observed in sectioned snail specimens of each experimental and control groups. The results showed that both camellia and mangosteen extracts had molluscicidal effects at 24 hr with 50% lethal concentration (LC₅₀) at concentrations of 0.003 and 0.002 g/ml, respectively, while niclosamide had LC₅₀ at concentrations 0.599 ppm. B. siamensis goniomphalos snail tissues (foot, gill, and digestive system) showed disruption of columnar muscle fibers of the foot, reduction of the length and number of gill cilia, numerous mucous vacuoles, and irregularly shaped of epithelial cells. Irregular apical and calciferous cells, dilatation of the digestive gland tubule, and large hemolymphatic spaces, and irregular apical surfaces, detachment of cilia, and enlargement of lysosomal vacuoles of epidermis were also shown in all groups. By the present study, it is confirmed that 2 plants, camellia and mangosteen, are keeping some substance having molluscicidal effects, and histopathological findings obtained in this study will provide some clues in further studies on their action mechanisms to use them as natural molluscicides.     

Susceptibility of immature stages of Chrysoperla rufilabris (Neurop., Chrysopidae) to pyriproxyfen, a juvenile hormone analog

Effects of pyriproxyfen (Knack), a juvenile analog, at three concentrations (10, 50 and100 mg [AI]/l), on survival and development of all immature stages of Chrysoperla rufilabris (Burmeister), were determined in the laboratory. Pyriproxyfen significantly reduced the survival rates when eggs, first and third instars were treated, but not when the second instars and pupae were treated. When eggs were treated, the two higher concentrations reduced the eggs viability by 33.3–50%, and only 0.0–6.7% developed to adults. The lowest concentration of pyriproxyfen (10 mg [AI]/l) caused high mortality on third instars, not on other stages, indicating the third instar was the most vulnerable stage. Pyriproxyfen had significant effects on development for all immature C. rufilabris that successfully developed to adults with variations among the developmental stages and concentrations. The overall developmental duration from eggs to adults when eggs, first, and third instars were treated were 2.6–4.2, 2.4–4.1 respectively, and 6.0–7.1 d longer than those in water control, respectively. However, the overall developmental durations from eggs to adults were 0.5–1.2 d shorter than in water control when the second instars were treated with pyriproxyfen. The compatibility of pyriproxyfen with natural enemies in integrated pest management programs is discussed.     

储藏物害虫嗜卷书虱对DDVP熏蒸的行为反应与致死剂量

1 引言 嗜卷书虱(Liposcelis bostrychophila)属啮虫目虱啮科。其体形微小,食性复杂,栖息场地多在粮食仓库及食品加工厂、图书馆、标本馆等地。大量发生时可造成严重损失,传播微生物,并以其尸体、排泄物等污染储藏的粮食和其它储藏物品。王进军等调查发现,在我国“双低”和“三低”贮粮的粮仓中,书虱已成为优势种群,对贮粮安全构成了威胁。使用病原真菌和细菌来防治嗜卷书虱,很难达到理想效果,即使采用菊酯类杀虫剂也难以奏效,贮粮熏蒸中普遍使用的溴甲烷(CH_3Br)和磷化氢(PH_3)对嗜卷书虱的防治效果也不很理想。利用昆虫生长调节剂防治嗜卷书虱的研究已有一些报道,但在具体应用上还存在着一些问题。气调措施可应用于控制书虱种群的增长,但书虱的抗气性发展很快,