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1.
A quick and easy method for estimating the number of surviving nymphs of the tobacco whitefly (TWF),Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae), after spray applications was developed in the laboratory. The method is based on the number of honeydew droplets ejected by TWF immatures during 30 minutes. Since the nymphs ofB. tabaci feed on the lower leaf surfaces, the honeydew excreted falls downward. In this study infested cotton leaves were placed with their lower side up, forcing the nymphs to eject the honeydew droplet upwards. Inverted plastic petri dish covers were placed over infested cotton leaves and after 30 minutes the droplets deposited on the inner side of each cover were counted and the average number of droplets per nymph was calculated. To estimate the number of live nymphs on an infested cotton leaf, the number of droplets ejected during 30 minutes was divided by the average number of droplets per nymph (factor of 1.23).  相似文献   

2.
Over 20 insecticides were screened against the tobacco whitefly,Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae), on cotton. AsB. tabaci feeds only on live plants, a suitable laboratory test method incorporating young cotton plants was developed. Both cover sprays and systemic insecticides applied to the soil were tested. Triazophos, pyridaphenthion, azinphos-methyl, bendiocarb and flucythrinate were found to be effective and persistent. The best of the systemic insecticides was aldicarb, followed by butocarboxim.  相似文献   

3.
A method was developed for estimating the number of surviving tobacco whitefly (TWF),Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae), nymphs after insecticide applications, based on the number of honeydew droplets ejected by TWF nymphs in 30 minutes. Honeydew droplets excreted by live TWF nymphs on a water-sensitive paper (Ciba-Geigy) stained blue and could easily be observed and counted. To estimate the number of live nymphs on an infested cotton leaf, the number of droplets ejected during 30 min was divided by a factor of 1.29.  相似文献   

4.
Cotton leaf curl virus (CLCuV) (Geminiviridae : Begomovirus), the causative agent of leaf curl disease in cotton plants (Gossypium hirsutum), is exclusively transmitted by whitefly species Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). CLCuV transmission occurs in Sriganganagar (Rajasthan), an area endemic with cotton leaf curl disease. The relationships between plant viruses, their herbivore vectors and host plants can be beneficial, neutral, or antagonistic, depending on the species involved. To further understand these relationships, fecundity and life history parameters of an indigenous non- b (Asia II genetic group) biotype whitefly, B. tabaci, were compared on 10, 25, and 40 days post-inoculation (DPI), in CLCuV-infected and healthy cotton plants to determine the effect of virus on its vector. The development time of the immature stages of whiteflies was significantly reduced on CLCuV-infected plants. The development time of the immature stages did not change with severity of symptoms at 25 and 40 DPI (45- and 60-d-old plants). Cotton leaf curl virus infection increased percent egg viability of B. tabaci. Whiteflies deposited significantly fewer eggs on virus-infected plants than on healthy plants. Whiteflies had better egg viability on younger plants than older plants, whereas plant age did not affect the fecundity. Male and female whiteflies had shorter longevity on CLCuV-infected plants than on healthy plants.  相似文献   

5.
D. Gerling 《Phytoparasitica》1984,12(2):109-118
Wild and cultivated plants in the vicinity of Kibbutz Nahshon and a few additional locations in Israel were sampled for the presence ofBemisia tabaci Genna-dius (Homoptera: Aleyrodidae). The whiteflies, together with their parasites,Eretmocerus mundus andEncarsia lutea, were found to develop on numerous host species throughout the winter. Especially high levels were reached onLan-tana camara, Abutilon grandifolium andIpomoea batatas. During late winter and spring the population on these hosts declined. From April onwards the populations increased on potatoes and sunflowers.  相似文献   

6.
Techniques of staining the honeydew droplets excreted by nymphs of the tobacco whitefly,Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae), were screened to select an effective means of estimating the number of nymphs on an infested cotton leaf. Indicators of pH and redox potential, absorbed on a cellulose acetate strip and on a water-sensitive paper (Ciba-Geigy), were used to stain the droplets. The water-sensitive paper provided the most practical means for rapid counting of the stained droplets for nymph estimation.  相似文献   

7.
Populations of the sweetpotato whitefly,Bemisia tabaci (Gennadius), were sampled late in the cotton-growing seasons of 1990, 1991 and 1992, in commercial ‘Acala’ cotton fields in southwestern Israel. In mid summer, when populations ofB. tabaci started to build up, cotton fields were commercially treated with a single application of an IGR (insect growth regulator). The experimental plots were then treated in September with conventional adulticides or with the novel insecticides buprofezin and pyriproxyfen (IGR), and diafenthiuron (a thiourea derivative). The effects of the insecticides onB. tabaci larval and adult populations, and the amount of damage to the cotton lint, were recorded. Untreated populations of larvae and pupae ofB. tabaci in the three end-of-season studies, had the tendency to build up toward the defoliation treatment. However, the level of theB. tabaci populations observed in the experimental fields and the short period of exposure of the open cotton bolls to the whiteflies, did not result in lint damage, probably because the whitefly numbers had been reduced considerably after the defoliation treatment. At the end of the 1991 and 1992 cotton seasons, a high level of parasitism, ranging between 50% and 80%, was recorded. The shift in chemical applications toward the novel IGRs during the season, along with the reduction in insecticide use in general, probably contributed to the propagation of parasitoids, thereby improving whitefly control.  相似文献   

8.
F. Mansour 《Phytoparasitica》1984,12(3-4):163-166
Chiracanthium mildei L. Koch (Araneae: Clubionidae) spiders, from two populations, were collected and reared in the laboratory. One originated from a citrus grove at Kibbutz Afeq and the other from an experimental cotton field at the Newe Ya’ar Experiment Station. Laboratory evaluation indicated that the Afeq strain was more tolerant to malathion than the Newe Ya’ar strain (resistance factor of x3.3). When spiders of the Afeq strain were exposed to chlorypyrifos (Dursban) and malathion residues, chlorpyrifos was much more toxic.  相似文献   

9.
A new boll rot disease of cotton (Gossypium hirsutum L.) cv. MCU 9 was observed in Tamil Nadu, India, in 1988. The causal organism was isolated in pure culture and identified asCorynespora cassiicola (Berk. & Curt.) Wei. The isolate, which on cotton is pathogenic only to bolls, is considered to be different from a strain ofC. Cassiicola known elsewhere causing leaf spot of cotton. The pathogenicity of this fungus on several other important crops was also tested. The fungus produced leaf spot and stem rot diseases on, respectively, eight and six host plants. Root rot, after inoculation, was observed only inVigna sinensis, Arachis hypogaea andSesamum indicium.  相似文献   

10.
Insecticides commonly used in cotton fields in Israel against lepidopterous pests were tested against eggs, as well as against 2nd-instar larvae and adults raised from eggs ofSpodoptera littoralis (Boisduval) collected in cotton fields in the Bet She’an Valley. Methomyl, chlorpyrifos, methidathion, monocrotophos, ethyl parathion, and methyl parathion were effective against eggs even at low doses, profenofos and phosfolan were less active, and azinphos-methyl was ineffective. The doses needed for 90% kill (LD 90 ) of the 2nd-instar larvae were 8.5, 35, 280, 1300 and 3400 g a.i./1000 m 2 for chlorpyrifos, methomyl, profenofos, methyl parathion and ethyl parathion, respectively; monocrotophos was inactive against 2nd-instar larvae even at relatively high doses. The LD 90 of adults was reached with 16, 32, 1700 and 6100 ga.i./l000 m2 of chlorpyrifos, methomyl, ethyl parathion and profenofos, respectively. Only chlorpyrifos and methomyl gave successful control of all three stages of the insect tested, at doses close to those generally used with aerial applications.  相似文献   

11.
The effect of azadirachtin and salannin, two triterpenoids isolated from seeds of neem (Azadirachta indica A. Juss), on the feeding response ofSpodoptera littoralis (Boisd.) andEarias insulana (Boisd.) larvae, was investigated. Styropor (foamed polystyrene) lamellae were painted on both sides with a mixture of 5% sucrose with different concentrations of either azadirachtin or salannin dissoled in methanol-water (3∶7). Azadirachtin strongly suppressed feeding inS. littoralis larvae even at 0.001%, whereas salannin showed some antifeedant activity at 0.005% and above. Larvae ofE. insulana were deterred from feeding on azadirachtin-treated lamellae even at 0.005%, whereas salannin was effective only at 0.01% and above. Azadirachtin applied on cotton leaves deterred larvae ofS. littoralis from feeding at all concentrations ranging between 0.001 and 0.02%.  相似文献   

12.
Tomato severe rugose virus (ToSRV) is a serious and prevalent begomovirus that causes severe mosaic and yield loss of tomato plants in Brazil. The virus is transmitted by Bemisia tabaci bitotype B (MEAM1) in a persistent circulative manner. This study evaluated the efficacy of cyantraniliprole foliar spray, cyantraniliprole root drenching, spiromesifen, thiamethoxam, and cartap on the mortality of Bemisia tabaci byotipe B and simulated primary and secondary transmission of ToSRV. None of the insecticides were effective in controlling primary transmission of ToSRV by B. tabaci. Cyantraniliprole root drenching, cartap, and cyantraniliprole foliar spray were effective in controlling secondary transmission of the virus, and infections were reduced by 94.5, 89.6, and 81%, respectively, compared to each of their controls. Thiamethoxam and spiromesifen did not provide effective control of secondary infection. Elimination of external sources of inoculum before starting new plantings and rational use of insecticides to reduce secondary infection may contribute to better disease management of tomato crops.  相似文献   

13.
A total of 80 single–lesion isolates of Phytophthora infestans were collected from tomatoes and potatoes in several locations in Chiang Mai and Tak provinces in 2000–2002. These isolates were analyzed for mating type, metalaxyl sensitivity, mitochondrial DNA (mtDNA) haplotype RFLP pattern as determined by probe RG57, and for microsatellite markers. All isolates were A1 mating type. Isolates from tomato were usually sensitive to metalaxyl, but isolates from potato were usually resistant to metalaxyl. With one exception, all tomato isolates were related to the US-1 clonal lineage. With two exceptions, all potato isolates were related to two European lineages. In these two provinces, the populations of P. infestans on tomatoes are clearly different from those on potatoes.  相似文献   

14.
Synergism of mixtures of pyrethroids with organophosphorus (OP) compounds in insects is reviewed, and the toxicity of such combinations againstSpodoptera littoralis (Boisd.) larvae is reported. Mixtures of one of the pyrethroids cypermethrin, fenvalerate or deltamethrin with one of the OP compounds monocrotophos, profenofos, azinphos-methyl or acephate were assayed at different ratios as 24-h-old dipping residues on alfalfa, which was fed toS. littoralis larvae for 48 h. With most of the binary mixtures containing various OP concentrations in excess of those of the pyrethroids, synergism was demonstrated. In the pairs fenvalerate — azinphos-methyl, deltamethrin — azinphos-methyl and deltamethrin — profenofos, however, no synergism was found. In a detailed investigation with pyrethroid concentrations causing 20% mortality and OP concentrations giving a kill of no higher than ;10%, the above findings on synergism were amply confirmed. A cypermethrinmonocrotophos mixture showed synergism also on cotton leaves sprayed in the field. Synergism could not be demonstrated by topical application of pyrethroid — OP mixtures.  相似文献   

15.
This study was conducted under semi-arid conditions in ?anl?urfa province (Turkey) in 2010–2011. One orchard each of peach, apricot and nectarine was selected for the study. There was less than one mile distance separating the orchards, and therefore climate, soil and topography were similar. Adult emergence, population peaks, number of generations per year and damage of the peach twig borer [PTB] [Anarsia lineatella Zell. (Lepidoptera: Gelechiidae)] on twigs and fruits were determined. Sex pheromone traps were used to determine moth population dynamics. Fruits and twigs were checked to determine damage rate and host preference of the PTB among peach, apricot and nectarine. This study showed that the first adults of the PTB were detected in early May and pest populations peaked four times during both years. The highest numbers of adults captured by the pheromone traps in peach, apricot and nectarine orchards were 115, 86 and 70 adults/trap, respectively. The PTB damage rates on twigs were 38, 18 and 16% (2010) (P < 0.05) and 30, 22 and 14% (2011) (P < 0.05), while damage rates on fruits were 29, 6 and 6% (2010) (P < 0.05) and 14, 8 and 5% (2011) (P < 0.05) in peach, nectarine and apricot, respectively. The results showed that A. lineatella caused greater damage on peaches than on apricots and nectarines.  相似文献   

16.
The protection of plants against bacterial disease is one of the important issues that need to be studied in agricultural applications. The application of a transgene, such as a gene that encodes plant ferredoxin-like protein (PFLP), to generate resistant plants is one possible strategy. Our previous reports have demonstrated that transgenic plants that express extracellular PFLP (ESF plants) are more resistant to bacterial pathogens. This protein intensifies the hypersensitive response (HR) in plants when they are infiltrated by a pathogen-associated molecular pattern (PAMP), harpin (HrpZ), from Pseudomonas syringae. In addition, this intensified HR is associated with the expression of membrane-bound NADPH oxidase. Thus, we attempted to determine the involvement of PFLP in intensifying PAMP-triggered immunity (PTI) to enhance disease resistance. First, we showed that transgenic Arabidopsis plants with the pflp gene were resistant to bacterial soft rot caused by Pectobacterium carotovorum subsp. carotovorum (Pcc). Then, the fliC gene which encoded flagellin from Pcc was cloned and expressed. The FliC protein was used in the functional study with PFLP in Arabidopsis Col-0 plants. The reactive oxygen species (ROS) generation and HR ratio were induced by the treatment with both PFLP and FliC together, but they were not induced by treatment with PFLP or FliC alone. Similar results were confirmed in ESF plants, where FliC elicited rapid ROS accumulation and callose deposition. Moreover, we demonstrated that the PFLP-intensified ROS generation and HR were related to Ca2+ influx and activation of NADPH oxidase. We concluded that the PFLP-intensified disease resistance is associated with the intensification of PAMP-triggered immunity.  相似文献   

17.
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18.
The efficacy of mixtures of respiration inhibitors and phenylamide fungicides (oxadixyl and metalaxyl) in controlling late blight was investigated using potato tuber disks. Results showed that uncoupling agents(e.g. DNP), inhibitors of ATP formation(e.g. oligomycin), ionophores(e.g, valinomycin) and inhibitors that block specific carriers in the electron transport chain(e.g. rotenone, antimycin A) increased significantly the control efficacy of both metalaxyl and oxadixyl towards populations ofPhytophthora infestons when applied to tuber slices pretreated with sublethal doses of both fungicides. When applied alone at the same doses, respiration inhibitors did not inhibit the development of the late blight fungus. Increased control efficacy of mixtures was not noted against phenylamide-sensitive populations of the fungus.  相似文献   

19.
Anthracnose, caused by Colletotrichum capsici, is a major disease of chilli (Capsicum annuum L.) affecting both fruit and seed quality. The pathogen is both internally and externally seedborne. However, a rapid and sensitive method for detection of this pathogen in seeds is currently limited. In this study, a polymerase chain reaction (PCR) method based on sequence characterized amplified region (SCAR) marker was developed for specific and sensitive detection of C. capsici in chilli seeds and fruits. The developed SCAR primers were highly specific to C. capsici and resulted in the amplification of an expected 250-bp fragment from genomic DNA of all seven of the C. capsici isolates tested. No amplification occurred when the SCAR primers were tested with genomic DNA from three other fungal isolates and four other Colletotrichum species. The SCAR primers successfully amplified similar sized fragments from DNA derived from C. capsici-infected chilli fruits. The molecular detection sensitivity of C. capsici was 1 pg of purified C. capsici DNA template and 25 ng of DNA from C. capsici-infected chilli fruits. A real-time PCR assay was also developed using SYBR Green chemistry for detection of C. capsici in chilli fruits and seeds. The standard curve obtained showed a linear correlation between copy number of the cloned target DNA sequence of C. capsici and cycle threshold (Ct) values, with R2 of 0.98. These PCR-based assays may be highly useful in detection of this important pathogen in chilli seeds and fruits in plant quarantine laboratories.  相似文献   

20.
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