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1.
The susceptibility of adults of the cabbage aphid,Brevicoryne brassicae and two of the most important predators,Coccinella undecimpunctata andChrysopa carnea to pesticides was assessed. Most of the organophosphorus and carbamate compounds tested were toxic to the aphids. Profenophos was highly toxic to the adult virginoparous aphid at Lc50 level. Malathion demonstrated the highest toxicity to, the aphids. The application of profenophos for the cabbage aphid at Lc50 level exhibited no toxicity forCoccinella but was highly toxic forChrysopa. Pirimicarb proved to be the most selective of the compounds tested for the control of aphids when it was used at a concentration that caused 50% mortality as it was found to be unharmful to bothChrysopa andCoccinella. Dimethoate, on the other hand, was found to be very harmful and highly toxic to bothCoccinella andChrysopa adults and would probably be destructive to those natural enemies in the field. Laboratory evaluation indicates that both pirimicarb and malathion have potentials for use, in IPM program for vegetable pest control.  相似文献   

2.
Studies were conducted in cucumber fields to evaluate the standard and reduced dosage rates of 5 insecticides for control the cotton whiteflyBemisia tabaci (Genn.) and melon aphidAphis gossypii Glov. and effect of insecticide application on associated parasites and predators. Eggs of whitefly appeared to be less susceptibility to all treatments (max. 66% reduction) than larval and pupal stages. Populations of larval and pupal stages of whitefly were significantly reduced in all treated plots. For example (larvae on day 10 after treatment with ethiofencarb, diafenthiuron, and chlorpyrifos methyl 67, 50, and 68% pupae 68, 69, and 75%). Two aphelinid parasitoids,Eretmocerus mundus Mercet andProspaltella lutea Masi, were the most primary important parasitoids of the whitefly pupae in all test plots. Percent parasitism, in most treated plots, were slightly affected as a result of insecticide application. However, all tested insecticides and dosage rates caused severe suppression of emergence of adult parasitoids. Moreover, longevity of adult parasitoids were highly decreased. Populations of the melon aphid were extremely reduced, especially by ethiofencarb and diafenthiuron. Populations of predator species (Chrysopa carnea Steph.,Coccinella undecimpunctata Reiche andSyrphus spp.) were reduced in all treated plots. However, ethiofencarb applied at rates as low as 208.4g a.i./1001 provided equally effective aphid control and conserved numbers of insect predators in the treated plots. Also, the prothiofos and chlorpyrifos methyl applications at rates as low as 166.7 g a.i./1001 kept aphid numbers below than those in control and caused a smaller reduction in the combined populations of insect predators.  相似文献   

3.
The anti-hormone compounds, precocene-2 (anti-juvenile hormone) and fenarimol (anti-ecdysone) were evaluated against the green cabbbage aphid,Brevicoryne brassicae (L.) alone and for their compatibility with the endoparasiteDiaeretiella rapae (M'Intosh). The results revealed that precocene-2 provided more than 90% control ofB. brassicae acted on larvae within 72 h after the treatment, while fenarimol was less effective. Moreover, either precocene-2 or fenarimol extremely reduced the reproductive potentiality ofB. brassicae surviving adults. Both anti-hormone compounds demonstrated compatibility withD. rapae, a parasitoid ofB. brassicae. No considerable difference was detected when parasite emergence was compared from treated and untreated individuals.  相似文献   

4.
During 1996 and 1997, populations of aphids and whiteflies and their parasites were studied in plastic greenhouses under a chemical control program and in those free of pesticides. In the greenhouses free of pesticides, the parasite A. colemani destroyed 14.7?% of the aphids. B. tabaci had no effect on the cucumbers during the spring cultivation. However, it attacked the autumn cultivation. The parasite E. mundus killed 30?% of these nymphs. The parasite A. colemani parasitized up to 10?% of aphids on tomato plants in greenhouses free of chemical pesticides. The parasite E. mundus killed 15.7?% of whitefly nymphs. In greenhouses under a chemical pesticides program, aphids and whiteflies were found on the plants at the end of the plantation season, after the pesticide spraying had stopped. Although the pest population was low, the parasite A. colemani parasitized 8?% of the aphid population. Whiteflies were not found on tomato plants in greenhouses under extensive pesticides use.  相似文献   

5.
Coccinella undecimpunctata L. is a euryphagous predator established in Azores that offers interesting potential as a control agent in the context of integrated pest management (IPM). However, to further develop IPM against aphids, it is important to evaluate the effects that insecticides might have on voracity. Thus, we proposed to evaluate the effects of pirimicarb and pymetrozine on the voracity of 4th instar larvae and adults of C. undecimpunctata, under distinct scenarios of exposure to chemicals within a prey/plant system. Voracity of C. undecimpunctata was not significantly affected by pirimicarb or pymetrozine when treatments were directly sprayed on the predator; however, when insecticides were sprayed on the prey/plant system, the predator’s voracity was significantly increased. Results suggest that C. undecimpunctata does not detect the insecticide on the aphids and indicate that the increase in voracity may be due to a decrease in the mobility of insecticide-treated aphids, since their capture should be easier than highly mobile non-treated prey. The consequences of such increase in the voracity for IPM programs are discussed.  相似文献   

6.
Larvae of the common green lacewing, Chrysoperla carnea (Stephens) (Neuroptera :Chrysopidae) were fed with different densities of Hyalopterus pruni (Geoffer) (Homoptera: Aphididae) in Petri dishes under laboratory conditions. Functional response, developmental time, mortality rate and fecundity of the predator were measured. Treatments were carried out at 25±1°C, 65±5% RH and a 16L:8D photoperiod in a controlled temperature cabinet. Prey was given at densities of 5, 10, 20, 40, 80, 160 and 250 aphids per larva per day and the number of consumed prey, developmental time and mortality rate of the predator were recorded daily. Larvae of C. carnea responded to increasing prey densities with increasing food consumption and older larval stages displayed a higher rate of predation than younger ones. The behaviour of each of the three larval stages matched Hollings type II functional response. Larvae were able to complete their development in each of the seven prey densities, although increased prey densities reduced developmental time and mortality rate. Increased prey consumption in immature stages resulted in a higher net reproduction rate (R 0) and the intrinsic rate of increase (r m) of adult females.  相似文献   

7.
The whitefly Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) is a worldwide pest which has become one of the main pests in tomato crops. The predators Macrolophus pygmaeus (Rambur) and Nesidiocoris tenuis Reuter (Hemiptera: Miridae) and the parasitoid Eretmocerus mundus (Mercet) (Hymenoptera: Aphelinidae) have shown their efficacy at controlling B. tabaci populations when used as biological control agents. Intraguild predation (IGP) between natural enemies can affect their effectiveness at controlling pests. In the present study, the interaction of these three natural enemies and their effect on B. tabaci was studied on tomato plants by combining morphological observations and molecular analysis of trophic interactions. Under the conditions used in the present study, no IGP was detected between M. pygmaeus and N. tenuis by either counting dead predators or by PCR using prey-specific cytochrome c oxidase I primers. However, predation on B. tabaci decreased when they coexisted on the same plant, which could compromise the biological control of this pest. Although PCR analyses using E. mundus-specific primers showed predation on B. tabaci-parasitized nymphs in 27 % of M. pygmaeus and 17 % of N. tenuis, B. tabaci control was improved when both predators coexisted on the same plant with the parasitoid. The combined use of E. mundus and M. pygmaeus/N. tenuis is therefore recommended in order to improve B. tabaci control in conservation biological control strategies.  相似文献   

8.
The output of inspection resulted in the following common predators:Orius laevigatus Fieb.,Orius albidipennis Reut. (Hem., Anthocoridae);Chrysoperla carnea Steph. (Neur., Chrysopidae);Coccinella undecimpunctata L.,Scymnus syriacus Mars,Scymnus interruptus Goeze (Col., Coccinellidae). It was found that the 6 insect species appeared on the cotton plants during the last week of April or the first week of May. The population increased gradually during May and the first two weeks of June then decreased during the second two weeks of June and the first week of July.Orius spp. constitutes more than 50% of the inspected species. Data show that application of kelthane-S and methomyl against mites and aphids slightly reduced the population of these predators, percent reduction ranged between 10.6–17.9%. The same species previously inspected during the early season were found during the second half of the season, exceptC. undecimpunetata.
Zusammenfassung Die Untersuchungen umfaßten folgende 6 Predatoren-Arten:Orius laevigatus Fieb.,O. albidipennis Reut. (Hem., Anthocoridae), —Chrysoperla carnea Steph. (Neur., Chrysopidae),—Coccinella undecimpunctata L.,Scymnus syriacus Marsh.,S. interruptus Goeze (Col., Coccinellidae). Es wurde festgestellt, daß diese 6 Insektenarten auf den Baumwolle-Pflanzen während der letzten April- oder ersten Mai-Woche erschienen. Ihre Populationen wuchsen während des Mai bis Mitte Juni und verringerten sich danach bis Ende Juni, Anfang Juli.Orius spp. machte mehr als 50% der Gesamt-Predatorenpopulation aus. Die Daten zeigen, daß die Anwendung von Kelthane-S und Methomyl gegen Milben und Blattläuse die Predatoren-Population um 10,6–17,9% reduzierte. Die gleichen Predatoren-Arten wie in der Frühsaison wurden auch in der Spätsaison festgestellt, mit Ausnahme vonC. undecimpunctata, der in der Spätsaison fehlte.
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9.
The contact and feeding toxicity of NeemAzal T/S (EID Parry, Chennai, India) to the parasitoid Encarsia sophia (Girault & Dodd) was compared with three synthetic insecticides (chlorpyriphos, endosulfan and triazophos) against immatures and adult emergence. NeemAzal T/S (1.0%) at lower dose (200 mg/l) did not cause any effect on the emergence of E. sophia adults, but there was a significant reduction in emergence at higher doses (800 mg/l). Also, it did not show contact toxicity to adults of E. sophia, but there was a significantly high feeding mortality in a dosage dependant manner, whereas chlorpyriphos, endosulfan and triazophos showed high toxicity both by contact and feeding method. Three neem preparations registered in India, NeemAzal T/S, Nimbecidine (T. Stains, Coimbatore) and Godrej Achook (Godrej Agrovet, Mumbai) were tested against egg and larval stages of Chrysoperla carnea (Stephens) at three dosages, using a synthetic insecticide, triazophos 40 EC (200 mg/l), for comparison under laboratory conditions. The three biorationals did not induce any adverse effect on the hatchability of C. carnea eggs. The mortality of the first instars of C. carnea was not affected by any of the azadirachtin enriched formulations; however, at higher dosage of 800 mg/l these neem based products resulted in increased mortality of the first and second instar larvae of C. carnea relative to the untreated controls. Whereas, triazophos induced very high mortality rates (85.0, 89.0 and 81.5%) of all the three larval instars. The neem based insecticides showed a dosage-dependant effect on the larval instars of C. carnea. Thus, these biorationals show that there is a potential to use them in an IPM system, being safe for natural enemies of B. tabaci in cotton.  相似文献   

10.
Efficient use of parasitoids in pest control depend on the knowledge of the biological relationships between host and parasitoid. Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae) is one the most important natural enemies of Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) that is found in fields and greenhouses in Adana, Turkey. Although more studies have been done to determine the relationships between E. mundus and B. tabaci, the differences among strains of E. mundus could have important biological concequences. In this study, biological characteristics of native population of E. mundus parasitization of B. tabaci (Q biotype) were determined using bean plants Phaseolus vulgaris (L.) at a constant temperature of 25 ± 1°C, relative humidity 70 ± 10% and 16:8 (L:D) photoperiod regimen. All B. tabaci nymphal instars were parasitized by E. mundus, but the mean number of daily-parasitized nymphs was highest in the second instars (15.3). In addition, second instar females had the shortest mean development time (15.2 days). Mean development times of parasitoids obtained from first, second, third and fourth B. tabaci instars varied from 15.2 to 16.2 days and 15.2 to 15.9 days for female and male, respectively. Proportion of female (♀/♂+♀) varied from first (0.53) to second (0.34) host instars. Impact of results on potential biological control of B. tabaci was discussed through conservation native natural enemies.  相似文献   

11.
Results of two field experiments, one on SA 1 pigeonpea in rainfed and the other on Co.5 pigeonpea in irrigated conditions revealed thatBacillus thuringiensis var.kurstaki (B.t.k.) (Delfin), its combinations with nuclear polyhedrosis virus ofHeliothis armigera andChrysoperla carnea were as effective as endosulfan in reducing the pod borers,Heliothis armigera andExelastis atomosa. However,B.t.k. 1.25 kg+endosulfan 175 g/ha orB.t.k. 2.5 kg+HaNPV, 250 LE/ha gave better control of damage to flowers and pods thanB.t.k. applied alone on SA 1 pigeonpea. The yield differences between these treatments were not significant. A combination of HaNPV 250 LE/ha+endosulfan 175 g/ha was superior toB.t.k. Similar trend was seen on Co.5 pigeonpea. Release ofC. carnea second instar larvae 1 lakh/ha was not effective in increasing the yield of pigeonpea.  相似文献   

12.
Thrips tabaci Lind. is very difficult to control and thus one of the most important pests of leek in Europe. As an alternative to insecticides biological control may be carried out by making use of beneficial insects, the Coccinellidae being one of the most important predatory families. In the present study laboratory trials were carried out withHippodamia convergens Guer.-Men., one of the polyphagous representatives of the lady birds, to figure out the feeding activity, development and prey preference ofH. convergens against the onion thrips in comparison with two aphid species. H. convergens developed fully when fed exclusivelyT. tabaci larvae, although mortality was considerably higher and development took much longer. When fed thrips the complete development lasted 29,8 days on an average, the mortality reaching 88%. When offeredAcyrthosiphon pisum (Harris)H. convergens took only 24 days for development with a mortality of only 16%. Above all, the fourth larval instar and the pupa suffered from a very high mortality, reaching 45 and 50% respectively. WithA. pisum as a prey mortality decreased to only 6%. The duration of the pupal development was not affected by the prey species. The feeding activity ofH. convergens increased significantly during the development. The larvae of the second and fourth instar predated 28 and 170 thrips larvae respectively per day as a maximum. The adults achieved the highest feeding activity, predating more than 300 thrips larvae in 24 hours. When adding up the number of prey individuals per day for each developmental instar, the L2 larvae predated more than 90 and the L4 larvae more than 1000 thrips larvae. When offered thrips larvae andMyzus persicae (Sulz.) simultaneously, there was an increasing prey preference during the development ofH. convergens from first larval instar to adult. As to the last instars there was 20–25% less predation of thrips larvae compared to the aphids during 24 hours.  相似文献   

13.
Toxicity and repellent activities of aqueous extracts of nine medicinal plants were evaluated on different life stages of the sweet potato whitefly, Bemisia tabaci. Tomato plants infested with whiteflies were dipped in 10% (wt/wt) of each plant extract for toxicity evaluation. Repellency was evaluated in a choice experiment with detached tomato leaves. All extracts evaluated were relatively ineffective against the adult stage. Extracts of Ruta chalepensis, Peganum harmala and Alkanna strigosa were effective in reducing the numbers of B. tabaci immatures similar to the reduction observed in the imidacloprid treatment. These three extracts were not detrimental B. tabaci parasitoid, Eretmocerus mundus. In addition, the plant extracts Urtica pilulifera and T. capita were repellent to B. tabaci adults. These results indicate that the extracts from the plants R. chalepensis, P. harmala and A. strigosa could act as a potential source for natural product developed for B. tabaci management.  相似文献   

14.
The entomopathogenic fungusPaecilomyces tenuipes was isolated from dead noctuid pupae the identification of which was impossible. Some remarks are given on the morphology of this fungus rarely occurring in our regions. Besides the conspicuous synnemata and the oblong oval conidia (6,0–10,0×2,0–3,8 μm from culture, 4,5–7,5 ×2,0–2,5 μm from infected larvae) brown coloured and thick-walled appressoria were formed on glass surfaces. Pathogenicity tests showed thatP. tenuipes can infect as well larvae ofMamestra brassicae andAgrotis segetum as pupae ofM. brassicae andAutographa gamma. The formation of a perfect state was never observed.  相似文献   

15.
In light of a recent increase in the aphid populations on young canola (Brassica napus) in autumn in Northwestern Europe, we carried out a survey of their parasitoid species during this season. The study was done in France from 1998 to 2001 using different sampling methods. Results highlighted the presence of two main species of Aphidiinae, Aphidius matricariae and Diaeretiella rapae (and to a lesser extent Aphidius ervi) on Myzus persicae, and of D. rapae on Brevicoryne brassicae. Nine other Aphidiinae species were found occasionally as well as some Aphelinidae parasitoids and hyperparasitoids. There was no difference in parasitoid species pattern between fields in Northern and Southern France. The principal parasitoid species found in the fields were reared in the laboratory to confirm their ability to develop on the canola aphids. Aphidius matricariae and D. rapae were reared successfully on M. persicae, but a low parasitism rate was obtained for A. ervi on this aphid. This study showed that A. matricariae and D. rapae could develop on aphids on canola and that they are present naturally in canola in autumn. However, the parasitism rate is low in autumn, so the options could be the use of these parasitoids in augmentative release biological control programs or in an IPM project on canola fields during this time of the year.  相似文献   

16.

The cabbage aphid Brevicoryne brassicae is a notorious agricultural pest that specializes on plants of the Brassicaceae family, which are chemically defended by glucosinolates. By sequestering glucosinolates from its host plants and producing its own activating enzyme (myrosinase), this aphid employs a self-defense system against enemies paralleling that in plants. However, we know little about the metabolic fate of individual glucosinolates during aphid sequestration and activation and about the biochemical effects of this defense on aphid enemies. Here, we probed these questions focusing on B. brassicae and a predatory lacewing, Chrysoperla carnea. We found that distinct glucosinolates were accumulated by B. brassicae at different rates, with aliphatic glucosinolates being taken up more quickly than indolic ones. B. brassicae myrosinase enzymatic activities toward different glucosinolates were strongly correlated to their rates of accumulation in vivo. Surprisingly, after simulated predation, the production of toxic isothiocyanate products (ITCs) was quantitatively outweighed by less toxic products such as nitriles and ITC-conjugates. Nevertheless, the defensive cocktails significantly impaired C. carnea development. Tissue-specific quantification of glucosinolate metabolites revealed that the lacewings employ both conjugation and mobilization to reduce the toxicity of aliphatic ITCs, but these strategies were only partially effective. These results clarify the metabolic fates of glucosinolates after sequestration by an aphid herbivore and further in a higher trophic level, as well as the consequences for predator survival and development, and might be instructive for integrative pest management approaches targeting the cabbage aphid.

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17.
The predacious mite,Agistemus exsertus Gonz. was reared on 4 types of animal egg diets (eggs ofTetranychus urticae Koch,Eutetranychus orientalis Klein,Brevipalpus pulcher [C. & F.] andBemisia tabaci [Genn.]). Life table parameters of each diet (net reproduction rate [Ro], mean generation time [T], intrinsic rate of increase [rm] and finite rate of increase [erm]) were determined. Eggs ofT. urticae were found to be preferred above other egg diets as food byA. exsertus and promoted a higher rate of oviposition. The intrinsic rate of increase was 0.15 individuals//day; the population multiplied 57.91 times in a generation time of 26.21 days. Rearing on eggs ofB. tabaci exhibited more attractive compared withB. pulcher. The average number of eggs consumed daily by female was 17, 12, 9 and 7 eggs ofT. urticae, E. orientalis, B. tabaci andB. pulcher respectively. In the sex ratio of the progeny, predator females fed inT. urticae andB. tabaci gave rise to more females.
Zusammenfassung Die RaubmilbeAgistemus exsertus Gonz. wurde im Labor unter Fütterung mit veschiedenen Milben- und Insekteneiern (Tetranychus urticae, Eutetranychus orientalis, Brevipalpus pulcher, Bemisia tabaci) aufgezogen. Die life table-Parameter bei jeder Nahrung (Netto-Reproduktionsrate Ro, mittlere Generationsdauer T, Innere Zuwachsrate rm sowie Gesamt-Zuwachsrate erm) wurden bestimmt. Die Eier vonT. urticae wurden allen anderen Eiern vorgezogen und bewirkten die höchste Eiablege-Rate der Raubmilbe. Die innere Zuwachsrate betrug 0,15 Indiv.//Tag. Die Population nahm während der Generationszeit von 26,2 Tagen um das 57,9fache zu. Die Eier vonB. tabaci wurden jenen vonB. pulcher vorgezogen. Die durchschnittliche Zahl der täglich von einem Raubmilben-Weibchen verzehrten Eier betrug 17, 12, 9 und 7 Eier vonT. urticae, E. orientalis, B. tabaci undB. pulcher. Bezüglich des Weibchen-Anteils der Nachkommen brachten Raubmilben-Weibchen bei Fütterung mitT. urticae- undB. tabaci-Eiern die meisten Weibchen hervor.

With one table  相似文献   

18.
Exposure to standard solution S extract ofPunica granatum, Thymus vulgaris andArtemisia absinthium for 72 h reduced the numbers of active nematodes by 100% forMeloidogyne incognita and by 95.7%, 71.4% and 42.9% forHelicotylenchus dihystera, respectively. Exposure to S/2 dilutions for 72 h reduced nematode motility by 100%, 77.3 and 72.7% forM. incognita, and by 92.9%, 37,1%, and 37,1% forH. dihystera, respectively. As exposure to S and S/2 extracts ofCitrullus colosynthis andRicinus communis reduced nematode motility by less than 32% forM. incognita and by less than 30% forH. dihystera. WhenM. incognita andH. dihystera were transfered to water for 72h, more than 85% of the individuals resumed normal movement at all extract dilutions except S ofA. absinthium andT. vulgaris and S and S/2 ofP. granatum. However, recovery ofM. incognita was more less than that ofH. dihystera. Exposure to S extracts ofP. granatum andT. vulgaris for 30 days reduced egg-hatching ofM. incognita by 100% and by 98.7% for S/2 dilutions. Also, 98.7% reduction in the egg-hatching was obtained by S ofA. absinthium. Extracts ofC. colosynthsis andR. communis gave less egg-hatching inhibition. Acetylcholinesterase (AChE) activity was suppressed by more than 75% inH. dihystera treated with S of each ofP. granatum, T. vulgaris andA. absinthium. However, the former extract gave the highest AChE inhibition (98.7%). When nematodes were treated with oxamyl (Vydate 24%), AChE activity was suppressed by 53.3%. The other extract dilutions suppressed AChE activity by less than 50%.  相似文献   

19.
Two bacterial insecticides,Bacillus thuringiensis H-14 andB. sphaericus 1593 were evaluated for larvicidal potency against mosquito larvae ofAedes aegypti. LC50 values showed thatB.thuringiensis H-14 (4×105 spores/ml) had a higher pathogenicity against fourth larval instars ofA. aegypti thanB. sphaericus (3.1×106 spores/ml) by about 7.75 times. Larval selection with LC90 of both pathogens for 8 successive generations caused a decrease in the susceptibility levels of selected strains ofA. aegypti as compared with the original strain. Moreover, the results indicated that the effect of larval selection with the above bioinsecticides led to an obvious reduction in the egg production and hatchability of eggs produced by mosquito adults that developed from surviving larvae.  相似文献   

20.
A new technique was performed to simulate exposure of the host Pieris rapae larvae to both botanical treatment and the parasitoid Hyposoter eheninus in different sequences. It was found that: host larvae subjected to both parasitoid and 1?% neem treatment showed significant or insignificant reductions both in pupal formation as well as adult emergence percentages when treatment preceded or followed parasitism, respectively. Both neem treatments revealed significant prolongation in the development of unparasitized and parasitized larvae (on average 4 to 5 days delay), whereas chinaberry caused significant prolongation only among parasitized larvae (on average 2.7 days delay in egg-larval duration). Fate of parasitism among untreated hosts was found to be faster than among neem-treated ones. Parasitism percentages among 1 and 0.5?% neem-treated third instar host larvae held 7 days before parasitism reached 3 and 2 times that achieved among those reared on untreated diet for the same period, ­respectively. It was concluded that prolongation of the preferred target instars of the host, due to neem treatments, increased the chance for parasitism. Nevertheless, treatment with neem at the LC50 level exhibited a great reduction in parasitoid progeny. However, a lower concentration (LC25) could reasonably potentiate parasitism without drastic losses in parasitoid emergence.  相似文献   

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