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1.
Aenasius arizonensis (Girault) (Hymenoptera: Encyrtidae) is an important solitary endoparasitoid of mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae). Studies on seasonal and biological interactions between host and parasitoid are important to optimize the mass production and field release of high-quality females. We investigated the influence of different crop seasons viz., pre-monsoon, monsoon and post-monsoon and host stages viz., three nymphal instars (1st, 2nd and 3rd) and adult stage of P. solenopsis on the development, longevity, fecundity and sex ratio of its parasitoid, A. arizonensis. A. arizonensis female parasitized all life stages of its host except the 1st instar nymphs. Only males emerged from parasitized 2nd instar nymphs, while the sex ratio in the later host instars was strongly female-biased. The adult host stage was most suitable for A. arizonensis in terms of shorter development time, while the 3rd instar nymphal stage was most suitable with respect to higher fecundity, proportion of adults emerged and more females in the progeny. Among different seasons, post-monsoon season (September–October) with temperature (25 to 29 °C) and relative humidity (68 to 73%) was most suitable for the overall fitness of the parasitoid. The findings of this study have implications in designing mass rearing of this parasitoid and devising an effective biological control strategy for P. solenopsis on cotton.  相似文献   

2.
The study aimed to find the possible differences, existing between the cuticular waxes of cotton and mealybug insects, using advanced analytical studies. The biochemical composition of the leaf wax of upland cotton (Gossypium hirsutum L.) and the cuticular wax of the different mealybug species, including Phenacoccus solenopsis Tinsley, Ferrisia virgata Cockerell, Paracoccus marginatus Williams and Granara de Willink, and Drosicha mangiferae Green were analyzed in detail by Gas Chromatography-Mass Spectrometry (GC-MS). The results clearly confirmed that the cotton wax is dominated by the six-carbon alkanes, while the mealybug wax is a mixture of both the five-carbon alkanes and the six-carbon alkanes. Apart from these differences, the common hydrocarbons such as hexadecane, icosane, and heneicosane, the uncommon hydrocarbons such as ethane, cyclobutanone, decane, and cyclododecane, the species-specific compounds of mealybugs such as myristyl alcohol, quinoline, hexacosane, and pentacosane were also identified and their retention times (RT) were listed out in detail. The outcome of this study will be useful to develop pest management techniques targeting the waxy cuticle of mealybugs without obstructing the normal physiology and growth of the cotton crop.  相似文献   

3.
The development, reproduction and life table parameters of the cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) on four ornamental plants (Hibiscus rosa-sinensis L., H. syriacus L. (Malvaceae), Brugmansia aurea Lagerh., Cestrum nocturnum L. (Solanaceae)) were studied at 25 ± 2 °C, 60% ± 10% r.h., and 16 hours daily artificial light. Life table data were analyzed by using an age-stage, two-sex life table. The highest intrinsic rate of increase (0.2911 d-1), finite rate of increase (1.3380 d-1), net reproductive rate (258.0 nymphs/female) and gross reproduction rate (342.6 nymphs/female), as well as the shortest mean generation times (19.1 days) were obtained when the mealybug was reared on H. syriacus.  相似文献   

4.
Control of the invasive vine mealybug Planococcus ficus (Signoret) can be achieved through integration of different management strategies such as the application of chemical treatments and biological control. However, compatibility between these control methods is considered crucial when adopting integrated pest management (IPM) programs against this insect pest. The recently used insecticides Prev-Am®, a contact biopesticide, and spirotetramat, a systemic tetramic acid insecticide, were assessed in laboratory conditions for their side effects on the vine mealybug parasitoid Anagyrus sp. near pseudococci with reference to chlorpyriphos-methyl, an organophosphate insecticide conventionally used for mealybug control in vineyards. Regarding contact toxicity, chlorpyriphos-methyl caused 100% parasitoid mortality 24 h after treatment, but parasitoid mortality from Prev-Am® or spirotetramat was almost absent. Neither the total parasitoid offspring/female nor the sex ratio of the progeny was negatively affected by Prev-Am® or spirotetramat relative to the untreated control. According to the IOBC classification for laboratory trials, both Prev-Am® and spirotetramat were rated harmless (IOBC category 1), whereas chlorpyriphos-methyl was categorized as harmful (IOBC category 4) to A. sp. near pseudococci. None of the insecticides adversely affected the development of the parasitoid pupal stage inside mealybug mummies or the survival of the emerged parasitoids. The practical implications of the results for implementing mealybug IPM programs in vineyards are emphasized and discussed.  相似文献   

5.
The cotton mealybug, Phenacoccus solenopsis Tinsley (Homoptera: Pseudococcidae) is a devastating pest that cause rigorous damage to the number of crops through feeding, managed by using various insecticides. To assess the risk of resistance and design a strategy for resistance management, a field collected population of P. solenopsis was selected with deltamethrin in the laboratory for six generations to investigate the cost to its fitness and to examine cross resistance to different insecticides. Bioassay results at G8 showed that the deltamethrin selected population (Delta-SEL) developed a resistance ratio of 100-fold compared to that of the unselected population (UNSEL). The deltamethrin resistance population exhibited strong cross-resistance to acetamiprid and lambda-cyhalothrin, but no cross-resistance to profenofos when compared to that of the UNSEL. The relative fitness of the Delta-SEL population was 0.37, with considerably lower survival rates from crawler to second instar, fecundity, hatchability, number of next generation nymphs, net reproductive rate and biotic potential compared with that of the UNSEL. The cost of fitness associated with deltamethrin resistance was evident in the Delta-SEL population. The present study provided useful information for management strategies to overcome development of resistance.  相似文献   

6.
A new species of Anagyrus Howard (Hymenoptera: Encyrtidae), A. pseudofuscus Zu sp. nov., is described from China as a parasitoid of the mealybug, Phenacoccus solani Ferris (Hemiptera: Pseudococcidae).  相似文献   

7.
Leaves of durum wheat infested with mines of the cereal leaf miner Syringopais temperatella Lederer (Lepidoptera: Scythridae) were collected from fields in Israel in spring 2016 and 2017. The parasitoids and moths reared from the leaf mines in the lab were identified and counted according to sex. The sex ratios of S. temperatella were 1:0.73 (♀ :♂) in 2016 and 1:0.41 in 2017. A cross-correlation analysis revealed that males appeared three days ahead of females (p<0.05). The following parasitoids were reared: Eulophidae (Cirrospilus vittatus Walker, Diglyphus chabrias (Walker), D. isaea (Walker), D. sensilis Yefremova, D. pusztensis (Erd?s & Novicky), Necremnus tidius (Walker), Neochrysocharis formosus (Westwood), Pnigalio gyamiensis Myartseva & Kurashev, P. pectinicornis Linnaeus), Pteromalidae (Norbanus sp.) and Braconidae (Habrobracon stabilis (Wesmail), Apanteles sp.); and Icheumonidae (Campoplex sp.). In all cases, the parasitoids emerged substantially prior to the mass appearance of the moths. The hatching dynamics of ecto- and endoparasitoids were also asynchronous. Most species of ectoparasitoids hatched three days ahead of the endoparasitoids (p<0.05). Syringopais temperatella recorded on clover revealed a similar dynamics of male appearance ahead of female, with a of female-to-male ratio of 1:0.25, and fewer parasitoid species.  相似文献   

8.
Severe outbreaks of Alternaria leaf blotch and fruit spot were recently observed in cv. Pink Lady apples in northern Israel, especially on fruit. Such severe outbreaks have not been reported from other countries. Symptoms involved cracks and rot around the calyx and external rot of the fruit body. Up to 80 % of the fruit in some orchards were affected by the disease. Microscopic examinations, fulfillment of Koch’s postulates and molecular (genetic) analyses confirmed the causal agent as Alternaria alternata f. sp. mali. The incidence of Alternaria increased as the degree of calyx cracking increased, or if fruit were both cracked and rotted. Injecting spore suspensions into the fruit produced typical rot symptoms. Injection assays of detached fruit of eight apple cultivars showed that cvs. Pink Lady and Golden Delicious were susceptible whereas cv. Jonathan was resistant. Pink Lady and Golden Delicious produced more fruit rot as the inoculum concentration increased. Rot in all three cultivars was moderate close to the skin but more severe close to the seed locule. Aqueous extracts taken from Jonathan fruit peel inhibited germ tube elongation of A. alternata f. sp. mali in vitro. This is the first report on heavy infection of Pink Lady fruit in Israel caused by A. alternata f. sp. mali.  相似文献   

9.
The role of the self-sown shrubsDittrichia viscosa (L.) W. Greuter andRubus ulmifolius Schott as reservoirs of aphid parasitoids was investigated. In the field studies conducted,D. viscosa grew adjacent to crops of durum wheat and barley andR. ulmifolius grew adjacent to cotton. The relative abundance of the parasitoids of(a) Capitophorus inulae (Passerini) onD. viscosa, (b) Rhopalosiphum padi (Linnaeus) on durum wheat and barley,(c) Aphis ruborum (Börner) onR. ulmifolius, and(d) Aphis gossypii Glover on cotton in various parts of Greece, was assessed during the years 1996–2000. In 2000, the fluctuation of parasitization of the above four aphid species was recorded and the action of the aphidophagous predators of the family Coccinellidae was studied. It was observed thatAphidius matricariae Haliday predominated onC. inulae andR. padi in all sampling cases. In contrast,Lysiphlebus fabarum (Marshall) was the dominant species parasitizingA. ruborum onR. ulmifolius andA. gossypii on cotton in Thessaly (central Greece) and Macedonia (northern Greece), whereasLysiphlebus confusus Tremblay et Eady andBinodoxys acalephae (Marshall) were the dominant parasitoid species in Thrace (northern Greece).Coccinella septempunctata Linnaeus was the most abundant coccinellid species on durum wheat, whereasAdonia variegata (Goeze) predominated on cotton. However, coccinellid individuals were scarce on bothD. viscosa andR. ulmifolius. The present study indicated that these two shrubs can be regarded as useful reservoirs of aphid parasitoids.  相似文献   

10.
Phytophthora capsici infection of chili pepper seedlings can cause substantial losses due to damping-off and collar rot diseases. Chemical control is no longer effective due to reported resistance development, on top of the related environmental concerns and the consumer demands for reduced use of fungicides. Biological control is a sustainable option, with several agents having been reported to be effective against this pathogen. This research focused on optimizing the application of strain THSW13 of Trichoderma hamatum and a bacterial isolate BJ10–86 with the objectives of improving chili pepper seed germination, reduce damping-off disease incidence, and improve the growth of the seedlings. Bacterial isolate BJ10–86 was subjected to molecular identification and found to be Pseudomonas aeruginosa. Chili pepper seeds treated with the biocontrol agents, individually or in combination, were seeded into commercial nursery media that had been pre-inoculated with P. capsici zoospores. Over a period of 35 days the chili pepper seed treatments significantly (P = 0.008) reduced the disease incidence of seedlings damping-off. Combined application of T. hamatum and P. aeruginosa was the best biocontrol treatment with an area under disease curve of only 36.61 units compared to 92.87 units for the control treatment. Similar results were observed in vitro where T. hamatum and P. aeruginosa synergistically inhibited P. capsici growth by 73.2 %. The inhibition activity of this treatment was similar to mefenoxam treatment, which implies that it is an effective and sustainable alternative for chili pepper seed treatment. The biocontrol seed treatment had no effect on seed germination and seedling growth.  相似文献   

11.
Gut microbes play an important role in insect morphogenesis, nutrition, development of resistance against parasitoids and detoxification of toxic compounds. A culture-based approach is therefore an useful tool for the characterization of cultivable microbial communities associated with the insect gut. In the present study an attempt was made to decipher the gender specificity of gut bacterial communities of two major fruit fly species of India viz., Bactrocera dorsalis (Hendel) and Bactrocera cucurbitae (Conquillett) (Diptera: Tephritidae). Based on molecular identification, B. dorsalis females were found to predominantly harbor the bacterial species Enterobacter cloacae, Enterobacter asburiae and Citrobacter freundii, while B. dorsalis males were found to harbor Providencia rettgerii, Klebsiella oxytoca, Enterococcus faecalis and Pseudomonas aeruginosa The cultivable diversity from females of B. cucurbitae comprised mainly of Morganella morganii and Bacillus pumilis while B.cucurbitae males were predominantly colonized by aerobic endospore formers viz., Bacillus cereus, B. licheniformis and B. subtilis. The above findings have thrown light on a distinct pattern of gender specific gut bacterial colonization in fruit flies, which have to be factored in for the formulation of fruit fly management strategies.  相似文献   

12.
Four Bt cotton hybrids, each with one of four different events, viz., MRC 6301 Bt (cry1Ac gene), JKCH 1947 Bt (modified cry1Ac gene), NCEH 6R Bt (fusion cry1Ac/cry1Ab gene) and MRC 7017 Bollgard II (cry1Ac and cry2Ab genes) were compared for survival and development of Earias vittella (Fabricius) along with their isogenic non-Bt genotypes. None of the neonates were able to complete the larval period and reach pupal stage on squares of 90, 120 and 150 days old crop of all Bt hybrids. Likewise, on bolls also, zero per cent larval survival was observed in all Bt hybrids except JKCH 1947 Bt where 0.67 per cent larvae could manage to reach pre-pupal stage at 120 and 150 days old crop but failed to form cocoon and enter pupal stage. The surviving larva took more development time (3.7 to 5.4 days) as compared to larvae fed on bolls of JKCH 1947 non-Bt. The average survival period (ASP) of larvae was in order of 150 > 120 > 90 days old crop among the crop ages; JKCH 1947 Bt > MRC 6301 Bt > NCEH 6 R Bt > MRC 7017 Bollgard II among Bt hybrids; and bolls > squares between fruiting bodies. However, reverse was true for speed index of toxic effect. The concentration of Cry toxin varied significantly in squares and bolls and also among the crop ages. The amount of Cry toxin in squares and bolls had significant negative correlation with ASP of the E. vittella larvae.  相似文献   

13.
A 4-year study of parasitoids attackingChrysoperla carnea (Stephens) in the cotton fields of Çukurova, Turkey, revealed the activities of three principal taxa:Telenomus sp. nr.suvae attacks the eggs ofC. carnea: Catolaccus sp. andBaryscapus sp. are larval and pupal parasitoids, respectively. In general, percent egg parasitism increased starting from the second half of June and into July, then decreased until the beginning of August before rising again at the end of growing season. During the early season, weekly parasitism was found to be as high as 94%. Overall, seasonal egg parasitism varied between 13.6% and 62.0% among all study sites. According to the results of a one-year field study at Hac?ali, total larval and pupal parasitism was found to be 12.5% and 55.6%, respectively. Therefore, different factors influencing the effectiveness of the generalist predatorC. carnea against cotton pests, and the differential effects of cotton treatments on both host and parasitoids, need to be evaluated.  相似文献   

14.
The green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), is a major pest of pepper. In this study, we collected data on the development, survival, fecundity, and proportion of apterous and alate forms of green peach aphid reared on five commercial pepper cultivars (Amiral, Erciyes, Mert, Mertcan, and Naz) at 25?±?1°C, 60?±?5% RH, and a photoperiod of 16:8 (L:D) h. We analyzed the life history raw data by using the age-stage, two-sex life table. The shortest development time (6.66 days) and highest fecundity (62.68 individuals) occurred on the Erciyes cultivar. The highest intrinsic rate of increase (r?=?0.332 d?1), finite rate of increase (λ?=?1.394 d?1), net reproductive rate (R0?=?62.7 offspring) and shortest mean generation time (T?=?12.45 d) also occurred on the Erciyes cultivar; while the lower fitness occurred on the Amiral, Mertcan and Naz cultivars. Our results compared differences in the population growth rate of M. persicae on different pepper cultivars. This information will be useful to individuals working in pest management programs particularly those involving M. persicae.  相似文献   

15.
Verticillium wilt is a devastating disease caused by the soil-borne fungus Verticillium dahliae that causes severe wilt symptoms in more than 400 plant species, including economically important cotton. However, the molecular mechanism of plant resistance to Verticillium remains unclear. In this study, we identified an Arabidopsis mutant, vsad1 (verticillium sensitive and anthocyanin deficient 1), which showed more serious disease symptoms such as discoloration and chlorosis than wild-type Arabidopsis. vsad1 is a previously identified allele of the transparent testa 4 gene (tt4), which encodes chalcone synthase (CHS), a key enzyme involved in the biosynthesis of flavonoids. Our results showed that VSAD1 expression was induced in response to Verticillium dahliae infection. Overexpression of VSAD1 partially recovered the anthocyanin accumulation phenotype of the vsad1–1 mutant. The concentration of V. dahliae increased and ROS accumulation decreased in the vsad1 mutant after infection with V. dahliae. Knockdown of the homologous gene GhCHS in cotton plants increased their susceptibility to V. dahliae infection. Thus, we conclude that VSAD1 is involved in the regulation of plant resistance to Verticillium wilt.  相似文献   

16.
A new species in the genus Ditylenchus, D. stenurus n. sp. collected from western Iran, is described and illustrated herein based on morphological and molecular studies. The new species is characterised by a body length of 772 (663–863) μm, delicate stylet 6 (5–7) μm long, six lines in the lateral field. Median bulb of pharynx well-developed, muscular with crescentic valve. Post-vulval uterine sac well-developed, 35 (30–45) μm long, female tail elongate-conoid, becoming narrow suddenly with finely rounded terminus. The new species comes close in morphology and morphometrics to five known species of the genus, namely D. arachis, D. caudatus, D. clarus, D. myceliophagus, and D. nanus. DNA sequencing data was obtained on the partial 18S, D2/D3 expansion segments of the 28S rRNA gene and internal transcribed spacer (ITS). The phylogenetic relationships of this species with other Ditylenchus spp. using partial 18S–rDNA and D2/D3 indicated that D. stenurus n. sp. clustered together with several species belongs to the D. triformis-group i. e. D. africanus, D. destructor and D. halictus: all sharing a rounded tail terminus and six lines in lateral fields.  相似文献   

17.
Ramularia ranunculicola sp. nov. (Mycosphaerellaceae) is described from Iran on Ranunculus muricatus and compared with other species reported on Ranunculus spp. Ramularia carletonii on Lactuca tuberosa and R. nagornyi on Centaurea solstitialis are newly reported from Iran, and Picris strigosa is a new host for R. picridis (= R. inaequalis s. lat.).  相似文献   

18.
Rice blast is a devastating fungal disease resulting in major losses to rice crops. Owing to continuous acquisition of resistance by the causal fungus, several fungicide chemicals are no longer effective. Therefore, there is a need to identify natural components and develop new agents to control fungal pathogens. We previously demonstrated that the culture filtrate of Biscogniauxia sp. O821 inhibited infection behavior of Magnaporthe oryzae and subsequent blast lesion formation. In the present study, we isolated a new compound, (3aS,4aR,8aS,9aR)-3a-hydroxy-8a-methyl-3,5-dimethylenedecahydronaphto[2,3-b]furan-2(3H)-one (HDFO), from the culture filtrate of Biscogniauxia sp. O821 and determined its molecular weight as 248. The HDFO structure was determined by electrospray ionization-mass spectrometry and nuclear magnetic resonance spectroscopy after purification with column chromatography and high-performance liquid chromatography. The structure of this antifungal compound was similar to that of alantolactone and isoalantolactone. The growth inhibition zone against M. oryzae in presence of HDFO was observed at Rf 0.5–0.6 on a thin layer chromatography plate. HDFO inhibited conidial germination of M. oryzae in a dose-dependent manner (1–200 ppm). Furthermore, blast lesion formation was significantly suppressed by HDFO at over 5 ppm. These results suggest that HDFO from the culture filtrate of Biscogniauxia sp. O821 can protect rice from rice blast disease caused by M. oryzae. This is the first report that HDFO produced by Biscogniauxia sp. can serve as an antifungal compound against M. oryzae.  相似文献   

19.
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20.
Native Trichoderma spp. were isolated from agricultural fields in several regions of Ecuador. These isolates were characterized via morphological observation as well as molecular phylogenetic analysis based on DNA sequences of the rDNA internal transcribed spacer region, elongation factor-1α gene and RNA polymerase subunit II gene. Fifteen native Trichoderma spp. were identified as T. harzianum, T. asperellum, T. virens and T. reesei. Some of these strains showed strong antagonistic activities against several important pathogens in Ecuador, such as Fusarium oxysporum f. sp. cubense (Panama disease) and Mycosphaerella fijiensis (black Sigatoka) on banana, as well as Moniliophthora roreri (frosty pod rot) and Moniliophthora perniciosa (witches’ broom disease) on cacao. The isolates also showed inhibitory effects on in vitro colony growth tests against Japanese isolates of Fusarium oxysporum f. sp. lycopersici, Alternaria alternata and Rosellinia necatrix. The native Trichoderma strains characterized here are potential biocontrol agents against important pathogens of banana and cacao in Ecuador.  相似文献   

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