Insecticidal activity and antifeedant effect of a new type biocide GCSC-BtA against Plutella xylostella L. (Lep., Plutellidae)

Insecticidal activity and antifeedant effect of a new type biocide GCSC-BtA and its two reactants Bacillus thuringiensis (B.t.) crystal and Abamectin against third instar larvae of Plutella xylostella L. (Lep., Plutellidae) were investigated using bioassays. GCSC-BtA showed significantly higher toxicity to P. xylostella with LC₅₀ of 0.021 mg/ml than B.t. crystal with 0.060 mg/ml and Abamectin with 0.139 mg/ml in leaf-dip bioassay. Net leaf-dip test gave LC₅₀s of 0.073, 0.071 and 0.670 mg/ml for GCSC-BtA, B.t. crystal and Abamectin, respectively. The significant differences of the biocide toxicities between leaf-dip and net leaf-dip methods showed the potential of net leaf-dip method for separating ingestion and contact poisons. Variation in toxicity of the biocide and two reactants in net leaf-dip method and in mortality in topical application bioassay showed that GCSC-BtA possessed a combination of strong stomach as well as contact poison property higher than B.t. or Abamectin. GCSC-BtA indicated no fumigant and systemic toxicities, which the two reactants lacked. In the antifeedant bioassay, GCSC-BtA acted as a strong antifeedant to the larvae of P. xylostella. Leaf consumption by the larvae after GCSC-BtA treatment was 0.04–0.60 mm² with a concentration range of 0.04–4.00 mg/ml, which was lower than 0.26–1.02 and 0.04–6.47 mm² for B.t. crystal and Abamectin, respectively. DC₅₀ (concentration resulting in a deterrence index of 50%) value for GCSC-BtA was 0.089 mg/ml, which was also significantly lower than 0.275 and 0.736 mg/ml for B.t. crystal and Abamectin, respectively.     

Influence of mixed biocide GCSC-BtA on the pupae and adult stages of Apanteles plutellae Kurd. (Hym., Braconidae) and its host. Plutella xylostella (L.) (Lep., Plutellidae)

This paper deals with the influence of the mixed biocide GCSC-BtA on the pupal and adult stages of Apanteles plutellae Kurd. (Hym., Braconidae) and its host, Plutella xylostella (L.) (Lep., Plutellidae). The results show that mortalities of the pupae of P. xylostella in the direct-dip bioassay were 84.67?%, that of the adults in the residue bioassay at 1.2500?mg/ml concentration of GCSC-BtA were 78.00?% which were significantly higher than the mortality values for the pupae with 54.62?% and adults with 48.13?% of A. plutellae. In contrast, cypermethrin showed extremely high toxicity to the pupae with 94.58?% and adults with 86.00?% mortality values of A. plutellae as compared to the low mortality values of 42.14?% for the pupae and 32.11?% for the adults of P. xylostella, with the same concentrations and bioassay methods. The LC₅₀ values of GCSC-BtA were 0.3402, 0.5516 and 1.2405, 1.9480?mg/ml for the pupae and adults of P. xylostella and A. plutellae, respectively, while the LC₅₀ values for cypermethrin were 1.5652, 2.3471 and 0.1096, 0.1152?mg/ml, respectively. GCSC-BtA was found more toxic to the pupae and adults of P. xylostella and safer to the pupae and adults of A. plutellae than cypermethrin. The possibilty of using GCSC-BtA against P. xylostella under partial control by A. plutellae in vegetable fields is discussed.     

Effect of GCSC-BtA biocide on population dynamics of cabbage pests and their natural enemies from fields in southeastern China

The present paper deals with the effect of the biocide GCSC-BtA on population dynamics of cabbage pests, i.?e., Plutella xylostella (L.) (Lep., Plutellidae), Brevicoryne brassicae (L.) (Hom., Aphididae), Liriomyza sativae Blanch. (Dip., Agromyzidae), Phyllotreta vittata Fabric. (Col., Chrysomelidae) and their natural enemies, i.?e., Apanteles plutellae Kurdj. (Hym., Braconidae), Erigonidium graminicola (Sundv.) (Araneida, Linyphiidae), Coccinella septempunctata L. (Col., Coccinellidae), in common head cabbage (Brassica oleracea var. capitata) fields in the southeastern China. The experiments were conducted at the experimental farm of Fujian Academy of Agricultural Sciences, Fuzhou, PR China in April?–?June, 2001. The results showed that, at the end of sampling, the pest populations of P. xylostella, B. brassicae and P. vittata reached averages of 39.7, 68.3 and 6.2 ind. / 30 plants in the plot treated with GCSC-BtA, which were about 1.5, 11 and 0.7 times lower than those treated with methomyl, respectively. In contrast, the natural enemy populations were, on average, 23.5 ind./30 plants for A. plutellae, 24.6 ind./30 plants for E. graminicol and 12.2 ind./30 plants for C. septempunctata in the plot treated with GCSC-BtA, about 6, 5 and 3 times higher than for those treated with methomyl, respectively. The GCSC-BtA biocide demonstrated greater effectiveness in controlling the cabbage pests, e.?g., P. xylostella, B. brassicae and P. vittata, having final decreasing ratios of 83.60, 97.05 and 53.67?% compared to 57.63, 64.89 and 30.88?% with the methomyl insecticide. However, it was less toxic to natural enemies, e.?g., A. plutellae, E. graminicola and C. septempunctata, final decreasing ratios being 47.68, 17.84, 27.81?%, than methomyl, with 90.94, 80.80, 74.55?%, in comparison to the populations in the control plots, respectively. So, because of the low toxicity of GCSC-BtA to the natural enemies, it is recommended that, on one hand, its application should be carried out after mass migration of the pests to the fields, on the other hand, the alternative agent GCSC-BtA should be used with the aim of minimizing the harmfulness to the natural enemies in the whole program of integrated pest management in cabbage fields.     

Efficiency of the mixed biocide GCSC-BtA against vegetable pests of different arthropod orders in the south-eastern China

The present paper deals with the efficiency of the mixed biocide GCSC-BtA against vegetable pests of five orders of arthropod insects in the south-eastern China, i.?e., diamondback moth, Plutella xylostella (L.); green peach aphid, Myzus persicae (Sulzer); yellow-fanded flea beetle, Phyllotreta vittata Fabricius; vegetable leaf miner, Phytomyza nigricornis Macquart; and vegetable spider mite, Tetranychus neocaledonicus Andre. The results show that the mixed biocide GCSC-BtA has a higher efficacy of control against all of the five pests than the commercial biocide B.t. and insecticide Diazinon. GCSC-BtA gave a higher mortality value of 92.18?% against P. xylostella as compared to the biocide B.t. with a value of 64.70?% and Diazinon with a value of 50.00?%. Similar mortalities were obtained with the other four pests regarding the efficacy of the three products tested against them. The concentration-mortality regression equations were calculated by the probit analysis, from which the average mortalities were calculated. The values calculated for GCSC-BtA were 81.13?% for P. xylostella, 75?% for M. persicae and T. neocaledonicus, 69.23?% for P. vittata, and 61.03?% for P. nigricornis as compared to those caused by Diazinon: 33.33?%, 27.42?%, 66.31?%, 44.54?%, 19.65?% for P. xylostella, M. persicae, P. vittata, P. nigricornis, and T. neocaledonicus, respectively. Based on LC₅₀, P. xylostella was most susceptible to GCSC-BtA with a LC₅₀ value of 0.3445, followed by B.t. with a value of 0.8404 and Diazinon with a value of 1.3160. The LC₅₀ value of GCSC-BtA for M. persicae was 0.4660 which was about three times less than that of Diazinon. LC₅₀ value of GCSC-BtA for P. vittata was 0.3954 which was about the same as that of Diazinon. P. nigricornis and T. neocaledonicus were also much more susceptible to GCSC-BtA than to B.t. and Diazinon. It is concluded that GCSC-BtA kills more target pests than B.t. and is more effective than Diazinon in controlling the vegetable pests.     

Toxicity of biocide GCSC-BtA on arthropod pests under different temperature conditions

The present research dealt with the toxicity of GCSC-BtA (Germany–China Scientific Cooperation-Bacillus thuringiensis-Abamectin), a new type biocide developed by conjugating a toxin from Bacillus thuringiensis (B.t.) with Abamectin from Streptomyces avermitilis, on arthropod pests under different temperature conditions. The results showed that GCSC-BtA possessed higher toxicity than B.t. crystal, Abamectin or Cypermethrin, with pest mortalities of 97.9, 93.7, 96.4, 82.3 and 96.7% for Tetranychus cinnabarinus (Boisd.) (Acari, Tetranychidae), Frankliniella occidentalis Pergande (Thys., Thripidae), Aphis fabae Scopoli (Hom., Aphididae), Plutella xylostella (L.) (Lep., Plutellidae) and Cameraria ohridella Deschka et Dimić (Lep., Gracillariidae), respectively. Toxicities of GCSC-BtA to T. cinnabarinus and P. xylostella decreased significantly at the older developmental stage with an exception that egg stage had the highest tolerance, in which LC₅₀s of GCSC-BtA were 0.0001, 0.0019 and 0.0708 mg/ml for nymph, adult and egg of T. cinnabarinus, and that 0.0399, 0.2035 and 0.9033 mg/ml for the 2nd instar larvae, 4th instar larvae and egg of P. xylostella, respectively. Also, the biocide was more effective to the lower stage of A. fabae than the higher one with LC₅₀s of 0.0023, 0.0086 and 0.0171 mg/ml against 1st instar nymph, 3rd instar nymph and adult, respectively. In general, toxicity of the new type of biocide was positively related to temperature against all the tested pests, except against T. cinnabarinus, where it was almost similar at the three temperature conditions. GCSC-BtA displayed significantly lower toxicities at 15/20°C than 20/25°C or 25/30°C against F. occidentalis, A. fabae, P. xylostella and C. ohridella. However, no significant difference was found in the toxicities against F. occidentalis, A. fabae and C. ohridella above 20°C, whereas toxicity against P. xylostella increased as temperature raised. Therefore, to achieve higher efficacy in the field, application rate and time should be devised according to these factors.     

Conjugation of δ-endotoxin from <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> with abamectin of <Emphasis Type="Italic">Streptomyces avermitilis</Emphasis> as a new type of biocide,GCSC-BtA,for control of agricultural insect pests

Conjugation of δ-endotoxin from Bacillus thuringiensis with abamectin, a toxin of Streptomyces avermitilis, was carried out to form a new type of biocide, GCSC-BtA based on “Germany-China Scientific Cooperation” research, for the control of agricultural insect pests. The strategy for biochemical linkage was designed by conjugating an amino group in B.t. protoxin with a carboxyl group in carboxylated abamectin under the treatment of conjugator EDC [1-Ethyl-3-(3-dimethylaminopropyl carbodiimide Hydrochloride)]. The formation of B.t. protoxin was processed by solubilizing B.t. crystal in 25?mM dithiothreitol (DTT) at 37?°C for 2?h. The carboxylated abamectin was formed by carboxylating the NaH-activated abamectin with 10?mg/ml butyric anhydride at 111?°C in a water-circumfluent condensation device for 2?h. The conjugating reaction, consisting of 5?mg/ml B.t. protoxin, 10?mg/ml carboxylated abamectin and 19.17?mg/ml EDC, was successfully conducted at room temperature for 24?h. Significant differences were found between pure abamectin, carboxylated abamectin and the conjugated BtA by means of UV-photo absorptions recorded at wavelengths 354, 438, 518, 600?nm (P?<?0.01). LT₅₀ of the conjugated GCSC-BtA to the 3^rd instar larvae of Plutella xylostella (L.) (Lep., Plutellidae) was 35.27 μg a.i./ml, about 62?% and 76?% of that caused by the B.t. protoxin and the caxboxylated abamectin, respectively. The conjugated GCSC-BtA caused 87.14?% mortalities in larvae of P. xylostella, 93.75?% in adult Myzus persicae (Sulzer) (Hom., Aphididae) and 89.33?% in adult Phyllotreta vittata Fabricius (Col., Chrysomelidae) as compared to 48.33?% by the B.t. crystal only in P. xylostella. The symptoms caused by conjugated GCSC-BtA in the 3^rd instar of P. xylostella were black color in the head part and white-yellow in the abdomen of dead larvae, which differed from the black color or the white-yellow all along the body caused by either the B.t. crystal or the abamectin, respectively. It was concluded that the conjugated GCSC-BtA biocide had a broader host spectrum and a faster killing speed than either the B.t. crystal or abamectin alone for the control of agricultural pests.     

Untersuchungen zur Wirkung verschiedener Insektizide auf Prädatoren von Getreideblattläusen unter Freilandbedingungen

Zusammenfassung Mit Hilfe von Freilandversuchen wurde die Wirkung der Insektizide E 605 f, Metasystox R und Pirimor Granulat auf die PrädatorenCoccinella septempunctata L.,Chrysopa carnea Steph. undSyrphus corollae F. untersucht. Dazu wurden in einem Winterweizenfeld Regenrinnen ausgelegt, um nach Insektizidapplikation die geschädigten bzw. abgetöteten Versuchstiere aufzufangen. E 605 f wirkte sehr stark auf alle 3 untersuchten Nützlinge. Im Freiland wurden die meisten toten Tiere in der Regel in den E 605 f-Varianten gefunden. Aber auch Metasystox R war gegenüber den Coccinelliden und Syrphiden toxisch. Chrysopiden wurden dagegen zu einem großen Teil geschont. Von den getesteten Präparaten war Pirimor Granulat das selektivste. Es schonte die Larven vonC. septempunctata undCh. carnea. Larven vonS. corollae wurden dagegen zum Teil abgetötet. Die Mortalität der Schwebfliegen war allerdings bei Pirimor Granulat etwas geringer als bei den anderen Insektiziden.

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Field-studies on the effect of three pesticides on predators of cereal aphids

In field tests the toxicity of three insecticides to the predatorsCoccinella septempunctata L.,Chrysopa carnea Steph., andSyrphus corollae F. was investigated. Small pieces of plastic troughs were placed in winterwheat fields to collect dead an diseased predators after pesticide applications. E 605 forte proved to be the most toxic of all the compounds tested. It caused high mortality to all three beneficial arthropod species. Metasystox R was highly toxic to coccinellids and syrphids but showed only a slight, insignificant toxicity to chrysopids. Pirimor Granulate was the most selective of the compounds tested. It had no effects on larvae ofC. septempunctata andCh. carnea but some larvae ofS. corollae were killed. However, the mortality of syrphid larvae was somewhat lower in comparison with E 605 f and Metasystox R.

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Mit einer Tabelle     

Attractiveness of three weed species to polyphagous predators and their influence on aphid populations in adjacent lettuce cultivations

The utilization of olfactory responses of predators and ­parasitoids to the allelochemicals emitted by phytophagous arthropods and their host plants is becoming more important in biological pest control. The effects of three weed ­species, i.?e. wormwood Artemisia vulgaris L., tansy Tanacetum vulgare L. and stinging nettle Urtica dioica L., which were planted as accompanying vegetations into a lettuce field, were examined for the predatory species Coccinella septempunctata L., Adalia bipunctata (L.), Propylea quatuordecimpunctata (L.) (Coleoptera, Coccinellidae) and Chrysoperla carnea (Steph.) (Neuroptera, Chrysopidae), as well as for aphids during the summer of 2000. The presence of weeds significantly increased the density of adults and larvae of the predators on the lettuce plants in relation to the control (lettuce field without weeds). However, the differences remained smaller for eggs and pupae. C. septempunctata tended to be the most abundant species, followed by P. quatuordecimpunctata. Remarkable differences among the attractiveness levels of the weeds in the 3 treatments were not observed. The increased populations of predators were accompanied by significantly reduced infestation rates with aphids in the treatments in relation to the control. Myzus persicae Sulzer was in general the most abundant aphid species followed by Nasonovia ribisnigri Mosley and Macrosiphum euphorbiae Thomas. The results of the present study are discussed with respect to the management of agroecosystems and the use of weeds in biological control.     

Entwicklung,Lebensdauer, Fruchtbarkeit und Geschlechtsverhältnis der RaubmilbeAmblyseius longispinosus (Evans) mitTetranychus cinnabarinus (Boisd.) als Beute

The development, longevity, fecundity and sex ratio of the predatory miteAmblyseius longispinosus (Evans) were studied at different constant and alternating temperatures withTetranychus cinnabarinus as prey. Alternating temperatures had no significant effect on the developmental times, in comparison with optimal constant temperature. At the alternating temperature of 33/23°C the mean duration of the life cycle from egg to adult was obvious longer with 5.0 and 4.4 days forA. longispinosus females and males than at alternating temperature of 30/20°C with 4.2 and 4.1 days for females and males. At 25°C constantly the egg stage was the longest during development and required a mean of 2.2 days.A. longispinosus females and males remained in larval stage for 0.5 and 0.6 days. The protonymphal and deutonymphal stage lasted for 0.7 and 1.1 for females and for 0.7 days for males, respectively. At all temperatures the development of females required significantly longer than of males. Longevity ofA. longispinosus adults was variable to tested temperatures: At 25°C females lived for 33.1 days, at 30/20°C for 30.6 days and at 33/23°C for 29.9 days. At 25°CA. longispinosus females produced a mean total progeny of 48.8 eggs and the mean duration of oviposition period was 21 days; at 30/20°C and at 33/23°C a mean number of 49.1 and 48.2 eggs was laid during an oviposition period of 20 days. Temperature had no effect on the sex ratio of predatory mites, about 70% of mites became females at all temperatures.     

Laboratory evaluation of the effectiveness of the entomopathogen; <Emphasis Type="Italic">Isaria farinosa,</Emphasis> on citrus mealybug, <Emphasis Type="Italic">Planococcus citri</Emphasis>

Citrus mealybug Planococcus citri (Risso) (Hemiptera: Pseudococcidae) is one of the main pests on citrus trees. Biological control of the pest is based on the release of hymenopterous parasitoids and coccinellid predators at present. The effectiveness of entomopathogen fungus Isaria farinosa (Holmsk.) Fries ([Sordariomycetes: Hypocreales] (Syn: Paecilomyces farinosus), as an alternative biological control agent on citrus mealybug, was investigated using four different inoculum densities and different relative humidities (RH). The entomopathogen caused 89.39% mortality in ovisacs, 84.07% mortality in second larval stage, 84.53% mortality in adult females, and 78.71% mortality in first larval stage at 95% RH and at 1 × 10⁸ conidia ml⁻¹ inoculum concentration. Percent mortalities were between 50 and 60 in ovisac, first and second larval stage at 95% RH and at 1 × 10⁷ conidia ml⁻¹. Percent mortality was decreased parallel to the decrease in humidity level and inoculum densities; however, the fungus caused significant infection in 70% and 80% RH. These results demonstrated that the effectiveness of the entomopathogen is promising for biocontrol of citrus mealybug.     

Side effects of botanical insecticides on predatory mite Amblyseius andersoni (Chant)

The effects of the botanical insecticides Biopiren plus, Piresan plus and Neemazal T/S on the predatory mite Amblyseius andersoni (Chant) were tested under laboratory, semi-field, and field conditions. The tests carried out in the laboratory allowed detection of the direct toxicity on eggs and females as well as the effects on fecundity, whereas semi-field trials assessed their residual toxicity. In laboratory and semi-field tests, pyrethrins, particularly Piresan plus, proved to have the highest toxicity with E value, concerning both female mortality and fecundity, of 100?% and 45?%, respectively. The same product tested in the field only caused a significant reduction in the phytoseiid population shortly after the treatment. The relevant escape rate registered in semi-field tests could explain the lack of phytoseiid eradication in the field after treatment with pyrethrins.     

The effects of cold pre-treatment on the toxicity of several contact insecticides on adults of three Sitophilus granarius (L.) populations

As very little is known about the impact of cold pre-treatments on insecticidal toxicity to the surviving stored-product insects, we examined the effects of cooling (?5 °C) on the toxicity of five contact insecticides to Sitophilus granarius adults from three populations (laboratory, field and selected). We determined: (a) weevil lethal time after exposure to ?5 °C, (b) the effects of two cold pre-treatments (LT₂₀ and LT₅₀—lethal time for 20 and 50 % of exposed adults) on 24 and 72 h recovery rates of laboratory adults after exposure to five insecticides and (c) deltamethrin, dichlorvos and malathion toxicity to two weevil populations with altered insecticide susceptibility after exposure to the LT₂₀ and LT₅₀ pre-treatments. The tested S. granarius populations showed no significant differences in their susceptibility to cooling. All insecticides except dichlorvos were more toxic to the laboratory weevils after 24 h than after 72 h recovery from the LT₂₀ pre-treatment. Dichlorvos and deltamethrin were more toxic to the other two populations after 72 h of recovery. Comparing the effects of cold pre-treatment and non-treatment on the laboratory strain, no significant increase in the toxicity of insecticides was detected, while only deltamethrin was significantly more toxic to the field and selected populations recovering for 24 h (12.1 and 11.0 times, respectively) and 72 h (6.9 and 36.6 times) from the LT₂₀ pre-treatment. In conclusion, only the shorter of the two cold pre-treatments was found effective in terms of increasing the insecticidal toxicity, especially against the populations with altered susceptibility to insecticides.     

Effects of extracts from fruit and leaves ofMelia azedarach L. onLocusta migratoria migratorioides (R. & F.)

Water extracts, methanolic extracts and the petrol ether phase from the fruit and leaves ofMedia azedarach L. were tested against different instar nymphs ofLocusta migratoria migratorioides (R. & F.) under laboratory conditions. Water extracts caused various degrees of mortality and a significant delay in the development and growth of the locusts. Treatments with 3% concn of water extracts from the fruit and leaves at a rate of 40ml/m² gave 93% and 100% mortalities, respectively, of first instars, and a 3% concn of leaf extract resulted in a mortality of 93.2% of third instars. Antifeedant and/or stomach-poison effect(s) played an important role. MeOH extract had the same efficacy as water extracts, but the petrol ether phase did not show much effect on the locusts.     

Winter mortality in sub-corticolous populations of Ips typographus (Coleoptera, Scolytidae) and its parasitoids in the south-eastern Alps

A study concerning the winter mortality of a sub-corticolous population of Ips typographus and its parasitoids has been carried out in the south-eastern Alps (Italy) during the winter 1997/98. Three attacked spruce trees were sampled three times (November, February and April) by collecting infested bark disks (1?dm² each). All insects that emerged from the bark or died in the samples before emergence were counted. The mean number of living Ips typographus occurring under the bark decreases by 49?% from November to April. Winter mortality mainly affects larval stages and young adults. The same trend was observed for the parasitoids Coeloides bostrychorum (48.5?%) and Roptrocerus xylophagorum (47.5?%).     

草履蚧幼虫防治药剂筛选试验初报

草履蚧是危害杨树的重要害虫之一。为了筛选出高效低毒的农药,在室内条件下用喷雾法测定了10种杀虫剂对草履蚧1、2龄幼虫的防治效果。结果表明:供试10种药剂对草履蚧均有防治效果,其中40%杀朴磷乳油、2.5%高效氯氟氰菊酯乳油、20%啶虫脒可溶性粉剂、2.3%甲氨基阿维菌素苯甲酸盐乳油防治效果显著,24 h校正死亡率在85%以上,48h校正死亡率在97%以上。结合药剂毒性和防治成本分析,建议将高效氯氟氰菊酯、啶虫脒作为化学防治的首选药剂。     

Chemical composition and bioactivities of three Chrysanthemum essential oils against Tribolium confusum (du Val) (Coleoptera: Tenebrionidae)

Essential oils from three species of Chrysanthemum growing in Tunisia (C. coronarium, C. fuscatum, and C. grandiflorum) were first analyzed by gas chromatography (GC) and GC/mass spectrometry (MS) and then evaluated for toxicity and antifeeding action against Tribolium confusum. The essential oils obtained from leaves and flowers shared a similar qualitative composition, but the relative proportions of the constituents were quite different. The essential oil of C. grandiflorum was rich in sesquiterpenoids, while those of C. fuscatum and C. coronarium were rich in monoterpenoids. The main common constituents of all the essential oils were ??-pinene, myrcene, ??-humulene, ??-caryophylene, spathulenol, and caryophyllene oxide. The most effective essential oil was obtained from the leaves of C. grandiflorum, that inhibited the relative growth rate (?0.03?mg/mg/d), efficiency of conversion of ingested food (?50.69%), relative consumption rate, caused an antifeeding effect (66.43%) and a high mortality (80%) of T. confusum larvae. Topical application C. grandiflorum essential oil caused a significant insect mortality that attends 27% after 7?days of treatment. While essential oil from C. coronarium flowers has contact and fumigant toxicity with a mortality of 9 and 13%, respectively. Results analysis highlights a relationship between essential oils composition and insecticidal activity against T. confusum. The study showed that each essential oil has specific chemical composition and act differently according to the nature of attributed test. The use of essential oils from different Chrysanthemum species with different methods helps poor farmers who store small amounts of grains to preserve it against pest infestation.     

The influence of the aphid-specific pathogen Conidiobolus obscurus (Entomophthoromycota: Entomophthorales) on the mortality and fecundity of bamboo aphids

Bioassays and scanning electron microscopy of Conidiobolus obscurus for bamboo aphids as well as its effects on the fecundity of bamboo aphids were carried out to estimate bamboo aphid biocontrol potential. Multi-concentration bioassay and fecundity assessment were performed on aphid species of Takecallis taiwanus, Takecallis arundinariae, Melanaphis bambusae, and Metamacropodaphis bambusisucta. C. obscurus can effectively infect four species of bamboo aphids, and most cadavers appeared in the first 2 days after inoculation. The final mortalities reached 74–91 % at high concentrations of conidia among the tested species. Based on the fitted time–concentration–mortality models, the estimates of the median lethal concentration (LC₅₀) of the fungal conidia differed significantly among different aphid species and decreased with observation days. The lowest LC₅₀ was estimated to be 57 conidia mm^?2 for T. taiwanus on day 5 after conidial shower. Moreover, the C. obscurus-infected aphids only produced 3.9–18.2 % progeny of the corresponding healthy aphids, which strongly presented fungal influence on host fecundity. In conclusion, C. obscurus has the ability of restraining the development of bamboo aphid populations, which is suitable for further application in aphid biocontrol in bamboo forests.     

Parasitoids of Saperda populnea (L.) (Coleoptera: Cerambycidae) on aspen (Populus tremula L.) in Bulgaria

The parasitoids of Saperda populnea (L.) (Col.: Cerambycidae) were studied in Bulgaria during the period 1997?–?2001. Galls with pest larvae were collected from young aspen trees at eight locations (Sofia, Kokaliane, Plana, Churek, Gorni Lom, Gintzi, Dolno Kamartzi and Klisura) and examined under laboratory conditions. Four species were reared from 1118 galls containing overwintering pest larvae: Iphiaulax impostor (Scop.) (Hym.: Braconidae), Dolichomitus populneus (Ratz.), Schreineria populnea (Gir.) (Hym.: Ichneumonidae) and Billaea irrorata (Meig.) (Dipt.: Tachinidae). All of the parasitoids were solitary. Schreineria populnea was found as a new parasitoid of the host in Bulgaria. B. irrorata emerged mainly from late-stage S. populnea larvae; the remaining species from both early- and mid-stage larvae. In the parasitoid complex of S. populnea, the most numerous were B. irrorata (59.8?%) and D. populneus (29.4?%). The percentage of host larval parasitism varied from 2.4 to 33.3, with an average of 9.7?%. B. irrorata was the most important in reducing the pest number. The average mortality of S. populnea caused by the tachinid was 5.8?%, and the highest mortality observed in individual study was 20.2?%.     

Impact and control of the cone tortricid Pseudococcyx tessulatana (Staudinger), damaging the cone crop of a selected clone of cypress (Cupressus sempervirens L.) in Italy

The green cypress (Cupressus sempervirens) is of great interest for ornamental, reforestation and windbreak use in the whole Mediterranean basin. In Italy, seed material selected for resistance to the fungus Seiridium cardinale is produced in seed orchards by controlled crosses of parent trees. The insect pest showing the highest impact on seed cone production is Pseudococcyx tessulatana (Lep.; Tortricidae), which attacks cones during the initial growth period as well as full-grown cones. The impact on the seed cone crop of the tortricid was estimated on a clone patented for its resistance to cypress canker (Agrimed 1). The attack was inversely related to the cone crop, as it concerned 36.7?% of cones in 1999 (high crop year) and the 66?% in 2000 (low crop year). In both years, about 90?% of the surveyed branches revealed cones attacked by P. tessulatana by the 1^st life-cycle larvae, whereas only 40?% of branches were also attacked by the larvae of the 2^nd life cycle. The highest attack rate per branch was always observed on branches bearing a low number of cones. The potential of two control methods against P. tessulatana to protect cones which result from crossing a mother tree “Agrimed 1” with selected father trees was also evaluated in 2000. The protection given by a sleeve surrounding the branch was almost complete (0.4?% cone mortality), whereas a cone mortality of 24.3?% was observed on branches treated by the insecticide diflubenzuron. Sleeves appear to be useful to protect branches on which special crosses were done, but are expensive and time-consuming and may favour the attack of the mealybug Planococcus vovae inside the sleeve. The insecticide application may represent a valid alternative, especially when protection should be directed toward a high number of branches.     

Laboratory evaluation of some pesticides on the cabbage aphid,Brevicoryne brassicae L. and their side effects on some important natural enemies

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.