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1.
The effect of Margosan-O, a formulation of a natural insecticide obtained from the neem (Azadirachta indica A. Juss) tree, on the development of the leafhopperAsymmetrasca decedens (Paoli), was investigated by testing insect performance (i) on cotyledons ofGossypium hirsutum cotton seedlings treated with different concentrations; (ii) on cotton seedlings stood with their petioles in different aqueous
dilutions of Margosan-O and recording mortality until the adult stage; and (iii) determining the repellent effect on adults
by recording their location on treatedvs untreated cotyledons in choice and no-choice situations. In foliar and in systemic treatments with 2% Margosan-O, practically
none of the leafhoppers reached the adult stage. As the concentrations were lowered there was a gradual rise in the percentage
of adults emerging; on untreated cotyledons 60-80% of the adults emerged. Feeding was zero or very low at high Margosan-O
concentrations. Adult leafhoppers settled in significantly higher numbers on untreated than on treated cotyledons in both
choice and no-choice experiments. 相似文献
2.
Bemisia tabaci (Gennadius), the sweetpotato whitefly, has only one known entomophthoralean pathogen,Erynia radicans (Entomophthoraceae). Two new pathogens have been isolated recently from a glasshouse population of this pest:Conidiobolus coronatus and another, undescribed species ofConidiobolus (Entomophthorales: Ancylistaceae). Artificial inoculation experiments revealed that eggs ofB. tabaci are practically immune to infection by either species. Second-instar larvae are highly resistant, only high doses of conidia
causing between <1% and 4.6% mortality. Adults were found to be much more susceptible. Doses of 60 conidia/mm2 ofC. coronatus caused average mortalities ofca 95%. The maximum mortality of adults caused byConidiobolus sp. was much lower,ca 30%, at a dose of 210 conidia/mm2. The incubation period (inoculation to death) for both species, under our experimental conditions, is very short: 18–24 h
forC. coronatus and 30 h forConidiobolus sp. Both fungi produced loricoconidia (conidia metamorphosed into resting spores) on cotton leaves and other dry surfaces.
This ability allowedConidiobolus sp. to remain viable for 17–21 days on cotton leaves, in glasshouse conditions and in the absence of hosts, whileC. coronatus persisted for 10–14 days. 相似文献
3.
Ekrem Atakan 《Phytoparasitica》2006,34(3):221-234
The distribution of theFrankliniella speciesF. occidentalis (Pergande) andF. intonsa (Trybom) (Thysanoptera: Thripidae), and of the predatory bugOrius niger (Wolff) (Hemiptera: Anthocoridae), in various organs of the cotton plant, as well as prey — predator interactions between
thrips andO. niger, were investigated over 6 years in cotton fields in the eastern Mediterranean region of Turkey. The highest number of larvae
ofFrankliniella spp. were found inhabiting bolls, whereas the adults colonized mainly flowers. The majority of predatory bug nymphs were
present on leaves, followed by bolls, whereasO. niger adults visited mostly flowers. The thrips larvae were most likely preyed upon on flowers and squares, and bolls were safe
plant parts for thrips, with a low predation rate. An intermediate but relatively high predation rate occurred on cotton leaves.
In further field experiments, the effects of insecticide treatment on the relationships betweenO. niger andFrankliniella spp. were investigated. These trials revealed that a higher correlation existed between the numbers of adultO. niger in flowers andFrankliniella spp. in non-treated cotton fields than in insecticide-treated fields. The proportions of prey/predator in flowers ranged
from 1.53 to 19.28 and were below four thrips per predator at most sampling dates in some of the non-treated cotton fields.
It is concluded thatO. niger is an effective predator that can play an important role in suppressing population increase ofFrankliniella spp. in cotton.
http://www.phytoparasitica.org posting May 12, 2006. 相似文献
4.
Dry mycelium (DM) of killedPenicillium chrysogenum and its water extract (DME) were used to induce resistance in cotton plants againstFusarium oxysporum f.sp.vasinfectum (Fov). Results showed that the efficacy of either DM or DME in controlling the disease depends on both the concentration and the
mode of application. DM amended to the soil at 0.25–2% (w/w) provided 32–75% protection againstFov. Soil drench with 2–5% DME (w/v) and pre-sowing seed soakage with 5–10% DME provided 51–77% and 28–35% protection against
the wilt disease, respectively, whereas no protection was obtained with foliar sprays of 1–10% DME. DM and its water extract
had no direct antifungal activity on growth ofFov in vitro, suggesting that disease control with DM or DME resulted from the induction of natural defense mechanisms in the cotton plants.
Soil drench with 5% DME was as effective as 2% DM powder in inducing resistance againstFov, implying that the resistance-inducing substances were mostly water-soluble. Four cotton cultivars with various genetic resistance
levels againstFov were tested at the seedling stage: two resistant ‘Pima’ cultivars and two susceptible ‘Acala’ cultivars. The level of protection
achieved in the two susceptible cultivars with DME was equal to, or higher than, that of the two resistant cultivars treated
with water. Innate and induced peroxidase activity in cotyledons or hypocotyls and roots coincided with the level of genetic
resistance and DME-induced resistance, respectively. Based on our results, an integrated control strategy ofFov with both genetic resistance and induced resistance is suggested. 相似文献
5.
Survival rates of neonate larvae of the spiny bollworm,Earias insulana Boisd., on leaves, flower buds and bolls of ten high-gossypol (HG) [terpenoid-aldehyde] and Acala SJb2 cotton lines were 40-74%, 66-92% and 54-76%, respectively. Partial resistance of leaves of three cotton lines, no resistance of flower buds, and resistance of bolls of one line (HG-BR-8) to larval infestation were observed. Bolls which had their bases and bracts removed were heavily penetrated by larvae and more adults were obtained on them, as compared with intact ones. Complete development on cotton bolls, from hatching to the adult, took 25.6-32.6 days, with significant differences among some of the cotton lines. Growth on bolls of HG lines in the larval stage had no effect on oviposition by the corresponding adults. Fertility of these eggs was not affected. 相似文献
6.
红铃虫Pectinophora!gossypiella(Saunders)的为害可分为直接取食为害和间接诱发病害。两年来每隔5天左右系统剥查吐絮棉铃,分析结果表明,受害棉籽产量损失平均为60.92克籽棉/千粒,每头幼虫平均为害2.03粒棉籽。根据单铃幼虫数估计的每条幼虫为害造成的产量损失是籽棉0.24克,皮棉0.101克,其中直接为害分别是0.133克和0.0467克,间接为害分别是0.11克和0.0543克。棉籽受害后皮棉等级降低4级,单价降低31.6%。百斤皮棉单价损失是9.383元/条/铃,其中直接为害5.559元/条,间接为害3.824元/条。应用皮棉产量损失0.101克/条和百斤皮棉单价损失9.383元/条/铃,推导了估计产值损失的公式,可以在生长期的不同阶段估计当时红铃虫所造成的产值损失。 相似文献
7.
A boll rot of cotton (Gossypium hirsutum L.) was observed for the first time in Greece in August 1993 in Larissa and Volos counties, and in August and September 1995
in Trikala and Phthiotis counties. Fungi of the genusPhytophthora were isolated from diseased plants. Morphological characteristics of the pathogen were recorded on mounts made directly from
the infected tissues or after growth of the isolated fungus on corn meal agar or sterile distilled water. Colony morphology,
growth rates, features of asexual and sexual structures and maximum growth temperatures were examined. APhytophthora species new to Europe,Phytophthora boehmeriae Sawada, attacking cotton bolls, was identified. The pathogenicity of the isolates was confirmed by artificial inoculations
of detached cotton bolls. Analysis of α-esterase isozymes revealed unique banding patterns for isolates ofP. boehmeriae compared with those ofP. cactorum andP. parasitica, which arePhytophthora species with similar morphology. 相似文献
8.
The comparative toxicity of two non-steroidal ecdysteroid agonists, RH-2485 and RH-5992 (tebufenozide), on development stages,
fecundity and egg viability of a susceptible laboratory strain and a pyrethroid-resistant field strain ofSpodoptera littoralis (Boisduval) was evaluated. Taking the LC50s as the criterion, RH-2485 was 3–7-fold more potent than RH-5992 against the susceptible and 7–14-fold more against the field
strain. The LC50 of RH-2485 in the 1st and 6th instars of the susceptible strain was 0.32 and 0.57 mg a.i./l, respectively. The field strain showed a mild cross-resistance of about threefold to both compounds in 1st instars and to
a lesser extent in 6th instars. A considerable increase in fecundity (~3-fold) and no effect on egg viability was observed
when 6th instars were fed on cotton leaves treated with 0.25 mg a.i./l RH-2485 (~LC40). Our results indicate that both compounds are potentially potent insecticides for controllingS. littoralis larvae, being 10-60-fold more potent than a previous ecdysteroid agonist, RH-5849. 相似文献
9.
Dry mycelium (DM) ofPenicillium chrysogenum and its water extract (DME) were examined for their effects on induced resistance against Verticillium wilt and plant growth
of cotton in the greenhouse. Soil application of 0.1–5% DM or 0.5–5% DME provided significant protection against the wilt,
relative to the control. As neither DM nor DME inhibited mycelial growth ofVerticillium dahliae in vitro, it is suggested that the disease-controlling effects of DM or DME are attributed to induced resistance. DME (5%), as well
as DME treated with chloroform or cold acetone, were as effective as 2% DM in reducing disease severity of Verticillium wilt,
implying that the resistance-inducing substance(s) in DM are mostly water-soluble, with neither proteins nor lipids likely
to be responsible for the induction of resistance. No significant difference in root colonization withV. dahliae was found between control-inoculated and 2% DM- or 5% DME-inoculated plants. However, colonization of hypocotyls and epicotyls
was drastically suppressed by either 2% DM or 5% DME relative to the control. Treatments with 2% DM or 5% DME significantly
increased ionically-bound peroxidase (POX) activity in roots, hypocotyls and the second leaf of cotton plants, with the hypocotyls
expressing the highest increase. Soil application of DM or DME increased plant height, fresh and dry weight of inoculated
and non-inoculated cotton plants, relative to their corresponding controls. It is concluded that DM may be used in cotton
crops to promote plant growth and to induce resistance againstV. dahliae. POX might be associated with the defense against Verticillium wilt.
http://www.phytoparasitica.org posting Jan. 9, 2002. 相似文献
10.
An increase of 11–31% of dry mycelial mass was observed along with a slight decrease (5–10%) in aflatoxin Bi production in
5-day-old aflatoxigenicAspergillus spp. submerged cultures containing either 0.5 ml or 1.0 ml clarified neem oil (CNO) in 0.1 % Triton solution. Fungal growth
and aflatoxin B1 production were also determined in potato-dextrose-agar petri plate cultures inoculated with aflatoxigenicAspergillus spp. containing an atmosphere of volatiles emitted from 0.25 ml, 0.5 ml, and 1.0 ml CNO added to the plates. After 5 days’
incubation, fungal radial growth was reduced by 7–29% and aflatoxin B1 production by 0–67%. GC/MS analysis of the head space volatiles of the CNO indicated that the reduction of fungal growth
and aflatoxin B1 was probably due to low molecular weight hydrocarbons, aldehydes, alcohols, and sulfur compounds emitted at 30°C in the dry
culture. These results suggest that volatiles emitted from CNO at 30° C in plate cultures were more fungistatic and consequently
inhibited aflatoxin production more than neem oil added in liquid cultures. 相似文献
11.
为阐明入侵害虫草地贪夜蛾Spodoptera frugiperda对我国不同农作物的适应性,利用年龄-阶段两性种群生命表技术研究取食玉米粒以及玉米、花生、棉花、大豆、高粱和谷子叶片等7种不同食物对草地贪夜蛾生长发育与繁殖的影响。结果表明,不同食物显著影响草地贪夜蛾种群。整个成虫前期从长到短依次为取食棉花叶>取食大豆叶>取食高粱叶>取食花生叶>取食谷子叶>取食玉米叶>取食玉米粒,取食玉米粒要比取食棉花叶的时间缩短27.95 d。雌雄成虫寿命均以取食玉米粒和高粱叶的最长,以取食玉米叶的较短,且取食棉花叶的雄成虫寿命仅有3.00 d。产卵量以取食玉米粒的最多,为619.27粒,是取食其他食物的6.00倍～61.25倍。取食玉米叶的草地贪夜蛾初孵幼虫个体完成幼虫、蛹和成虫阶段的概率均较高,分别为95.38%、78.46%和78.46%,而取食棉花叶的最低,分别为37.29%、20.34%和20.34%。草地贪夜蛾取食玉米粒的净增值率、内禀增长率、周限增长率均最高,分别为105.59、0.12 d-1、1.13 d-1,平均世代周期最短,为36.91 d,而取... 相似文献
12.
A weed survey conducted in 2004 and 2005 in Aydin province of Turkey showed that Solanum nigrum, Xanthium strumarium, Amaranthus retroflexus, Portulaca oleracea, Sonchus oleraceus and Datura stramonium were the most prevalent weeds in the cotton fields exhibiting Verticillium wilt. Verticillium dahliae Kleb. was recovered from A. retroflexus and X. strumarium in those cotton fields. This is the first report of V. dahliae occurring naturally in A. retroflexus in Turkey. Pathogenicity tests on cotton and weeds showed that the virulence of V. dahliae isolates from weeds was higher on cotton plants than on weeds, with the disease severity ranging from 31.7% to 98.0%. Disease
severity of V. dahliae isolates was 54.7–93.9% on eggplant, 23.7–51.6% on cucumber and 11.0–16.4% on tomato, whereas it did not cause any disease
symptoms, or only low levels, on pepper and bell pepper. Two vegetative compatibility groups (VCGs) were identified among
seven tested weed isolates: VCG2A (two isolates) and VCG2B (three isolates) using international reference strains. 相似文献
13.
棉株施用缩节胺后能减少棉铃虫(Heliothis armigera Habner)在棉株上的落卵量48.8%—88%,田间虫量减少39.5%—77.3%,取食嫩叶、花蕾后的2龄幼虫体重下降、发育历期延长,死亡率增加,化蛹率和羽化率都有下降,总的生存率降低了57.62%。测定表明施用缩节胺后,棉株各部组织内棉酚有增加趋势,以蕾内增加较多,为49%—92.1%,铃壳次之,为13.8%—65.5%,叶内较少,为3.6%—39.7%。而单宁量除大铃壳内有增外,大多下降。施用次数与剂量的增加,与棉酚量的提高有共同趋势。花蕾期施用,棉酚量的增加高于花铃期。 相似文献
14.
The effect of botanical insecticides and bacterial toxins on gut enzyme activity of larvae of the rice leaffolderCnaphalocrocis medinalis (Guenée) (Insecta: Lepidoptera: Pyralidae) was investigated. Gut enzyme activities were affected by botanical insecticides
and bacterial toxin individually and in combination. When fed a diet of rice leaves treated with botanical insecticides and
bacterial toxins, in bioassays the activities of gut tissue enzymes — acid phosphatases (ACP), alkaline phosphatases (ALP)
and adenosine triphosphatases (ATPase) — of rice leaffolder larvae were affected. When combined, the effect was more severe
at a low concentration. Larvae that were chronically exposed to botanical insecticides and bacterial toxins showed a reduction
in weight (59–89%) and exhibited a significant reduction in ACP, ALP and ATPase activities. The combination ofBacillus thuringiensis kurstaki and botanical insecticides caused a decrease of twofold in enzyme activity even at reduced concentration. A synergistic effect
was found when botanical insecticides and bacterial toxins were combined at low doses. These effects were most pronounced
in early instars. Clear dose-response relationships were established with respect to enzyme activity. In conclusion: (i) biopesticides
are relatively safe and biodegradable; (ii) a synergistic effect of botanical insecticides and bacterial toxins was found;
(iii) less expensive, readily available and naturally occurring biopesticides could be an alternative for organic and inorganic
pesticides in controlling RLF.
http://www.phytoparasitica.org posting Sept. 28, 2004. 相似文献
15.
Diflubenzuron, PH 60-38, PH 6043, penfluron (PH 60-44), PH 6045, triflumuron, chlorfuazuron (IKI-7899), teflubenzuron (CME 134), XRD473 and Dowco 439 were tested for their efficacy against the larvae of the spiny bollworm,Earias insulana (Boisd.), in laboratory experiments. The compounds were incorporated at different concentrations in an artificial diet and 5-day-old larvae were introduced and grown on the treated diets until pupation and adult emergence. Teflubenzuron was active at 0.1 ppm, chlorfuazuron at 0.75 ppm and PH 60-38 at 10 ppm; triflumuron and diflubenzuron were active only at 50 ppm; all the rest of the compounds were even less active. When cotton bolls were dipped in teflubenzuron and offered to 6-day-old larvae in the laboratory, only 4% and 10% of the larvae penetrated inside the bolls treated with 50 and 25 ppm a.i., respectively, whereas 68% penetrated inside untreated bolls. 相似文献
16.
Diets consisting of leaves of cotton and/or water were insufficient to promote the complete development and survival of Podisus nigrispinus (Dallas) to the adult stage. However, nymphs fed leaves lived longer than those provided with only water. Addition of Alabama argillacea (Huebner) larvae to the diet of P. nigrispinus added a substantial increment to the survival during the nymphal stage. The addition of cotton leaves to the diet of P. nigrispinus nymphs promoted an increase in the weight of newly eclosed adults, independent of predator sex. In addition, diets supplemented with cotton leaves promoted an increase in the duration of the oviposition period, the number of egg clutches per female, and the number of eggs per female. No effects were noted on either the duration of the pre-oviposition period, the number of eggs of the first clutch, the number of eggs per clutch, the interval between egg clutches, or sex ratio. Feeding on plant material by P. nigrispinus is a potentially positive attribute in biological control against cotton leafworm. 相似文献
17.
The effect of microclimate variables on development ofClonostachys rosea and biocontrol ofBotrytis cinerea was investigated on rose leaves and crop residues. C.rosea established and sporulated abundantly on inoculated leaflets incubated for 7–35 days at 10°, 20° and 30°C and then placed
on paraquat—chloramphenical agar (PCA) for 15 days at 20°C. On leaflets kept at 10°C, the sporulation after incubation on
PCA increased from 60% to 93% on samples taken 7 to 21 days after inoculation, but decreased to 45% on material sampled after
35 days. A similar pattern was observed on leaves incubated at either 20° or 30°C. The sporulation ofC. rosea on leaf disks on PCA was not affected when the onset of high humidity occurred 0, 4, 8, 12 or 16 h after inoculation. However,
sporulation was reduced to 54–58% on leaflets kept for 20–24 h under dry conditions after inoculation and before being placed
on PCA. The fungus sporulated on 68–74% of the surface of leaf disks kept for up to 24 h at high humidity after inoculation,
but decreased to 40–51% if the high humidity period before transferral to PCA was prolonged to 36–48 h. The growth ofC. rosea on leaflets was reduced at low inoculum concentrations (103 and 104 conidia/ml) because of competition with indigenous microorganisms, but at higher concentrations (105 and 106 conidia/ml) the indigenous fungi were inhibited. Regardless of the time of application ofC. rosea in relation toB. cinerea, the pathogen’s sporulation was reduced by more than 99%. The antagonist was able to parasitize hyphae and conidiophores
ofB. cinerea in the leaf residues. AsC. rosea exhibited flexibility in association with rose leaves under a wide range of microclimatic conditions, and in reducingB. cinerea sporulation on rose leaves and residues, it can be expected to suppress the pathogen effectively in rose production systems. 相似文献
18.
Among 153 isolates ofRhizoctonia spp. obtained from 95 soil samples collected from different fields in the USA, 42 (27.5%) isolates were hypovirulent or non-pathogenic
on cabbage (tested on tap water agar plus 250 μg/ml chloramphenicol plates). Of these, 14 (33.3% of the np-R) isolates protected
>60% of the cabbage seedlings againstR. solani, and the best eight isolates protected 73–95% of the cucumber seedlings. The np-R isolates RU56-8 (AG-P) and RU89-1 [AG-B(o)]
induced the highest resistance against hypocotyl challenge inoculation with virulentR. solani (38.3–85.7%), whereas most of the challenged control seedlings (85–100%) collapsed. Similarly, isolates RU56-8 and RU89-1
induced the highest resistance (22.2–87.5%) against hypocotyl challenge inoculation withPythium aphanidermatum, whereas most of the challenged control seedlings collapsed (90–100%). Isolates RU56-8 and RU89-1 significantly reduced the
lesion numbers and area/leaf (to 8.9–42.0% of the control) caused by challenge inoculation of the first true leaves withPseudomonas syringae pv.lachrymans. No np-R isolate could be recovered from the upper hypocotyls or from the leaves, indicating that there was no contact between
the inducer and the pathogen. Root colonization with some np-R increased seedling tolerance to low soil moisture levels. 相似文献
19.
红铃虫为害棉铃的损失分析和经济阈值的探讨 总被引：1，自引：0，他引：1
用大田取样调查资料分析了第二代和第三代红铃虫对棉铃的为害损失。被害样本的损失表现在铃重减轻和品级下降。样本单铃活虫数与重量损失率具有幂函数回归关系。二代为y=6.65x~(.9763),三代为y=5.42~(.9575)。虫量与品级具直线回归关系,二代为y’(级别)=1.4x(虫量)+1.3,三代为y’=1.2x+1.3(不计小数)。经济阈值(经济允许虫量)和防治指标是按Chiang,H.C.(1979)模式按照幂函数关系修正为由于棉花产量随时间进程渐增,因而经济阈值和防治指标也呈动态交化。设计了微机运算程序以适应在防治方法、防治次数、产量、价格变化时的运算。 相似文献
20.
AbstractThe aim of this study was to determine whether target-insects selectively feed on transgenic or non-transgenic crops after consecutive cultivation in fields. We sampled leaves from insect-resistant single-transgenic cotton (expressing Cry1Ac gene), pyramided-transgenic (expressing Cry1Ac and CPTI genes) and conventional cotton that were consecutively cultivated for three years in a field. Cotton bollworm (Helicoverpa armigera) collected from the cotton field was reared and its next-generation larvae were fed the three types of cotton leaves in a laboratory. The leaf area damaged by the cotton bollworm larvae was not significantly different among single-transgenic, pyramided transgenic and conventional cotton leaves. There was no significant difference found in the leaf damage among the combination groups of the three cotton types. The survival rate of the bollworms was comparable among the combination groups. The results demonstrated that the cotton bollworms did not selectively feed on transgenic or non-transgenic cotton leaves after consecutive cultivation, which may be due to the resistance evolution of the target-insects and decreased Bt content in transgenic cotton leaves. 相似文献