First record of Thrips hawaiiensis (Morgan, 1913) (Thysanoptera: Thripidae), an Asian pest thrips in Spain

Several permanent populations of Thrips hawaiiensis (Morgan, 1913) were discovered outdoors for the first time in Spain in 2010. Captures were made mainly on Rosa flowers, Nerium oleander and Gerbera sp.     

Effectiveness of some plant extracts as surface protectants of cowpea seeds against the pulse beetle,Callosobruchus chinensis

A bioassay procedure for detecting and evaluating pest control agents in plant extracts was developed using the pulse beetle,Callosobruchus chinensis L. Four plant species common in Egypt,Clerodendrum inerme, Nerium oleander, Ipomoea palmata andAtriplex lentiformis, were extracted with petroleum ether. The crude extracts were evaluated as surface protectants for cowpea(Vigna sinensis) seeds againstC. chinensis infestation. All extracts showed some degree of oviposition deterrent effect at one or more of the concentrations applied. The extracts also had conspicuous activity against the eggs ofC. chinensis deposited on treated seeds, leading to a pronounced reduction in F₁ progeny. At 0.5%, theI. palmata extract provided 97% seed protection against insect infestation, followed byN. oleander (94%),C. inerme (93%) andA. lentiformis (89%). Moreover, theI. palmata extract showed good insecticidal activity as a result of contact toxicity. TheC. inerme extract was the least toxic material to the insects.     

Inhibition of Leucoagaricus gongylophorus with Carica papaya: an alternative to control the leaf-cutter ant Acromyrmex octospinosus

Abstract

The symbiotic association of the leaf-cutter ants with the fungus Leucoagaricus gongylophorus implies that the negative impact on the fungi will affect the survival of the ants. After a promising antifungal bioactivity, Carica papaya was studied leading to the bioassay-guided isolation of squalene, 4,5-dihydrohumulen, the flavanol-glycosides quercetin, kaempferol, and rutin, and the alkaloid carpaine. Carpaine and squalene were found to have a moderate individual activity, which increased when evaluated together. Based on the presence of these compounds, standardized extracts were formulated for field tests on nests of Acromyrmex octospinosus. All the nests treated were negatively affected evidencing a promising lead for the integrated management of leaf-cutter ants.     

Influence of caffeine on the survival of leaf-cutting ants Atta sexdens rubropilosa and in vitro growth of their mutualistic fungus

BACKGROUND: Leaf‐cutting ants collect plant fresh material for the cultivation of their mutualistic fungus. Atta sexdens rubropilosa Forel (Hymenoptera: Formicidae) cause great economic losses through their foraging activity, mainly in agriculture. The main control method is the application of granulated toxic baits incorporated with an active ingredient (AI). The present goal is to evaluate the effect of caffeine on in vitro growth of the mutualistic fungus and on the survival of the leaf‐cutting ants, aiming to verify the potential toxicity of this secondary metabolite over these organisms. RESULTS: Three distinct patterns of fungal growth correlated with caffeine concentration were observed: (1) no effect (0.01% caffeine); (2) intermediate growth reduction (0.05% caffeine); (3) drastic growth reduction (0.10 and 0.50% caffeine). The highest caffeine concentration causes fungus death in the first week. As for insect survival, caffeine does not seem to exert any effect. The treatments with diet containing caffeine showed similar values of M50, irrespective of caffeine concentration. CONCLUSION: As caffeine was shown to reduce growth of the mutualistic fungus of Atta sexdens rubropilosa, but with no conclusive effect on insect survival, a hypothetical explanation for the selection of different Coffea species by this leaf‐cutting ant species might be associated with caffeine toxicity to the fungus. Copyright © 2011 Society of Chemical Industry     

Antifeedant effect of commercial chemicals and plant extracts against Schistocerca americana (Orthoptera: Acrididae) and Diaprepes abbreviatus (Coleoptera: Curculionidae)

BACKGROUND: The deterrent effect of seven commercial compounds against Schistocerca americana (Drury) nymphs and Diaprepes abbreviatus L. adults, two important citrus pests, was investigated. Extracts of three Florida local plants were also tested as deterrents. Antifeedant activity was assayed using a leaf‐disk bioassay in choice and no‐choice tests. The residual activity of the commercial compounds that significantly deterred the insects was assayed by applying them to foliage of citrus plants exposed to three time intervals of sunlight. RESULTS: Sabadilla, azadirachtin and ryanodine effectively deterred S. americana, whereas rotenone, sabadilla and ryanodine reduced the feeding activity of D. abbreviatus. Methanol and methylene chloride extracts of Ceratiola ericoides Michaux deterred D. abbreviatus, but only methylene chloride extract dissuaded S. americana. Methanol extract of Ardisia crenata Sims functioned as a feeding deterrent against both S. americana and D. abbreviatus, but only the latter species was deterred by methylene chloride extract of A. crenata. Extracts of Illicium parviflorum Michaux ex Ventetat only dissuaded the insects in choice bioassays. Rapid loss of effectiveness was observed under field conditions. Sabadilla was the only compound that maintained its antifeedant properties in the field, but only against S. americana. CONCLUSION: Based on their deterrency, some of the commercial products and plant extracts have potential for use as substitute crop protectants against the pest species tested. Copyright © 2011 Society of Chemical Industry     

Ectopic expression of barley constitutively activated ROPs supports susceptibility to powdery mildew and bacterial wildfire in tobacco

ROPs (also called RACs) are RHO-like monomeric G-proteins of plants, well-known as molecular switches in plant signal transduction processes, which are involved in plant development and a variety of biotic and abiotic stress responses. The barley (Hordeum vulgare) ROPs RACB, RAC1 and RAC3 have been shown to be involved in cellular growth, polarity and in susceptibility to the biotrophic barley powdery mildew fungus Blumeria graminis f.sp. hordei. We produced transgenic tobacco (Nicotiana tabacum) plants expressing constitutively activated (CA) mutants of the barley ROPs RACB and RAC3 to monitor the impact of heterologous ROP expression on cell polarity and disease susceptibility of tobacco. CA HvROPs influenced leaf texture, disturbed root hair polarity and induced cell expansion in tobacco. Both barley ROPs induced super-susceptibility to the compatible powdery mildew fungus Golovinomyces cichoracearum but only CA HvRAC3 induced super-susceptibility to the bacterial leaf pathogen Pseudomonas syringae pv. tabaci. Data suggest involvements of ROPs in tobacco cell expansion, polar growth and in response to bacterial and fungal leaf pathogens.     

Insecticidal and repellent properties of nine volatile constituents of essential oils against the American cockroach,Periplaneta americana (L.)

The toxic and repellent properties of nine major constituents of essential oils, comprising benzene derivatives and terpenes, were evaluated against Periplaneta americana (L.). Contact and fumigant toxicities to adult females and repellency to nymphs were determined. The decreasing order of knockdown activity via contact was methyl-eugenol>isosafrole=eugenol>safrole. The killing effect via contact was in the order eugenol=methyl-eugenol=isosafrole>safrole. Fumigant toxicity was only observed for safrole and isosafrole, with safrole being the more potent. Isoeugenol and the tested terpenes had neither contact nor fumigant toxic effect. The decreasing order of repellency to nymphs was safrole>isosafrole>methyl-eugenol=α-pinene> eugenol>isoeugenol. The benzene derivatives were generally more toxic and repellent to P. americana than the terpenes. The distance of the side chain double bond from the aromatic ring and the substitution of a methoxy group to these compounds appeared to be important determinants of their toxicity and repellency. © 1998 Society of Chemical Industry     

Biomolecular relationships among isolates of<Emphasis Type="Italic">Tomato Yellow Leaf Curl Tanzania Virus</Emphasis>

An investigation of the biological properties of the virus causing tomato yellow leaf curl disease in Tanzania was initiated to compare it with other known tomato yellow leaf curl viruses. Properties relating to acquisition and inoculation feeding time, persistence, mechanical inoculation, seed transmission and host range were studied. Results obtained indicate that the virus was transmitted persistently byBemisia tabaci Genn., but it was not mechanically, sap- or seed-transmissible. Minimum acquisition and inoculation feeding time was 30 min.Capsicum annuum, Datura stramonium, Nicotiana glutinosa, N. tabacum andLycopersicon esculentum were found to be hosts of the virus among the plant species tested, whereasPhaseolus vulgaris was not. It is concluded that the properties of the agent causing yellow leaf curl symptoms in tomato plants from different regions in Tanzania are similar to those ofTomato yellow leaf curl Sardinia virus species studied elsewhere. http://www.phytoparasitica.org posting Feb. 20, 2003.     

Studies on poly(acrylic acid) induced resistance to viral and non-viral plant pathogens

Studies on polymer size, concentration and mode of application, either as foliar spray or soil drench, in relation to the induction of resistance to tobacco mosaic virus (TMV) in Nicotiana tabacum cv xanthi-nc by poly(acrylic acid) (PA) are reported. PA also induced resistance to TMV in N. glutinosa, to pelargonium leaf curl virus in Datura stramonium, to cucumber mosaic virus in Vigna sinensis and to tobacco ring-spot virus in N. tabacum cv White Burley. No TMV was detected in PA-treated tomato cv Virocross 11 days after inoculation; but the susceptible cultivar Craigella became infected. PA treatment had no effect on TMV replication in White Burley tobacco but resistance was induced to Peronospora tabacina, a fungal pathogen of N. tabacum cv xanthi-nc. The potential of PA-induced resistance as a control measure for viruses and fungi is discussed.     

Effects of Irrigation Water in Different Salinity on Yield and Quality Parameters of Tobacco (Nicotiana tabacum L.) Plant

Salinity affects many areas in our country and around the world, resulting in dramatic reductions in plant yields. In this study, the plant yield, some plant quality parameters, and soil salinity in the plant root area were investigated by irrigating tobacco plants (Nicotiana tabacum L.) with different salinity irrigation waters. The experiment was carried out in pots in 4 replicates according to the randomized plot design. Six different salinity of irrigation water applications were applied in the experiment (S0?=?0.38 dS m^?1, S1?=?2 dS m^?1, S2?=?5 dS m^?1, S3?=?8 dS m^?1, S4?=?11 dS m^?1, S5?=?15 dS m^?1). According to the data obtained at the end of the research, as the salinity of irrigation water increased, plant length, leaf width, leaf length, leaf dry weight and leaf number decreased. It was determined that there was a certain increase in nicotine content in the face of the decrease of all examined physical parameters in irrigation water increase. In addition, the salinity values in the plant root zone soils and the salinity values in the outlet (drainage) water have also increased. Salinity threshold value of the tobacco plant was determined to be 2.04 dS m^?1. With an increase in salinity by one unit, there was a 7.1% decrease in leaf dry weight. It was determined that the tobacco plant is vulnerable to salinity based on the data collected.

     

Potential allelopathic effects of Suregada multiflorum and the influence of soil type on its residue's efficacy

This experiment was conducted to determine the potential allelopathic effects of the aqueous extracts and dried leaf powder of Suregada multiflorum and to find the herbicidal effects of its granule on the weed species, barnyardgrass (Echinochloa crus‐galli) and slender amaranth (Amaranthus viridis), in various growth media (germination paper, sand, and soil). Observations in this study demonstrated that the potential and magnitude of their inhibitory effects varied among the plant parts. The leaves and branches possessed the strongest inhibition levels, followed by the bark. The aqueous extract from the leaves of S. multiflorum had a remarkably stronger inhibitory effect on the germination and growth of slender amaranth, compared with barnyardgrass; when applied at the concentration of 100 g L^–1, it completely inhibited the germination and initial seedling growth of slender amaranth. In addition, all the treatments of the dried leaf powder had stronger inhibition effects than the aqueous extract. Interestingly, the inhibitory effects of the dried leaf granule of S. multiflorum were stronger than the effects of the dried leaf powder at equal rates. The degree of inhibitory effect of the S. multiflorum granule, applied in various growing media, can be classified in order of decreasing inhibition as germination paper = sand > clay soil. The present study indicates that the S. multiflorum granule product that was developed in this research has the potential to provide a powerful organic herbicide for controlling slender amaranth.     

超敏蛋白对烟草黄瓜花叶病毒的诱导抗性及生长、品质的影响

为明确超敏蛋白对烟草黄瓜花叶病毒(Cucumber mosaic virus,CMV)的诱导抗性及其生长、品质的影响,采用半叶枯斑法和田间试验研究了10%超敏蛋白对枯斑三生烟和普通烟的诱导抗性及促生作用,并分析了对烤烟经济性状和内在质量的影响。结果表明,10%超敏蛋白在活体外对CMV无钝化作用,但预防、治疗效果显著,接种前48 h喷施预防效果达75.70%,接种后24 h喷施治疗效果达65.45%,均显著高于对照;10%超敏蛋白处理后烟草的株高、茎围、最大叶面积均高于其它处理,单位产量比20%吗啉胍·乙铜可湿性粉剂处理增产211.8 kg/hm2,增值3 519.2元/hm2;经10%超敏蛋白处理后的烤烟化学成分均处于优质烟的适宜质量分数范围内。表明超敏蛋白不仅有利于提高烟草抗性和促进烟株生长,且可以明显提高烟叶经济效益和烟叶内在质量。     

Using bioassays with the green peach aphid (Myzus persicae) to determine residual activity of two systemically soil-applied neonicotinoid insecticides in field-grown tobacco

Duration of systemic pesticide activity under field conditions has wide implications for pest management. Our aim was to determine the duration of activity of systemic insecticides commonly used in cultivated tobacco (Nicotiana tabacum) by measuring the levels of insect infestations on field plots and effects on reproduction and survival of the green peach aphid (Myzus persicae) in controlled bioassays using field grown leaves. Plants were treated with different concentrations of two systemic neonicotinoid pesticides, imidacloprid and thiamethoxam, and grown in small field plots. Our results show that these materials are effective under field conditions against aphids for at least 13 weeks after transplant. Pesticides also affected aphid reproduction and nymph survival in bioassays, although some aphids survived on pesticide-treated leaves. We also observed that leaf age affected aphid survival. We showed that neonicotinoids were very effective against M. persicae, aphids are a useful organism to assess pesticide efficacy early in the growing season, but plant characteristics are more important than pesticide concentration in the second half of the growing season.     

Agroinoculation Shows Tobacco leaf curl Yunnan virus is a Monopartite Begomovirus

We demonstrated that only 2 out of 15 isolates of Tobacco leaf curl Yunnan virus (TbLCYNV) were associated with the satellite DNAβ molecules. To investigate the infectivity of this virus, an infectious clone of TbLCYNV isolate Y143 (TbLCYNV-Y143) was agroinoculated or whitefly transmitted into Nicotiana benthamiana, N. glutinasa, Petunia hybrida and N. tabacum. TbLCYNV-Y143 alone was able to induce severe upward leaf curling, vein thickening or stunt symptoms in these plants. Co-inoculation of TbLCYNV-Y143 with DNAβ molecules associated with other begomoviruses induced similar symptom types on these plants. This indicates that TbLCYNV is a monopartite begomovirus. The relevance of results that only two isolates of TbLCYNV were associated with DNAβ molecules is discussed.     

Removal of duvatrienediols from the surface of tobacco leaves increases their susceptibility to blue mold

Dipping leaf strips of greenhouse or field-grown tobacco (Nicotiana tabacum L., cv. Ky-14) plants into acetone for 1 s, prior to inoculation with sporangia of Peronospora tabacina Adam, increased their susceptibility to blue mold. Disease severity and sporangial production on leaf discs from acetone-treated leaves were markedly increased compared to those on discs from untreated leaves. Treatment with acetone also decreased variation in susceptibility of leaves from plants of various ages. Disease severity on discs obtained from attached leaves which were dipped in acetone for 1 s was three times greater up to 15 days after dipping than on discs from leaves that were not dipped. TLC and GLC analyses of the acetone extracts indicated that 95% or more of the major cuticular diterpenoids, α- and β-4,8,13-duvatriene-1,3-diols (DVT), were removed from the surface by dipping for 1 s. These compounds had not reappeared on the leaf surface 15 days after leaves were dipped in acetone for 1 s. Aqueous suspensions of the acetone-soluble constituents as well as authentic DVT, inhibited sporangial germination of P. tabacina (ED₁₀₀ = 25 ppm) and the antifungal activity was accounted for by DVT. When DVT was removed from a leaf surface and added back to the same leaf strip, the resistance of the leaf tissue was restored. As tobacco plants aged, their susceptibility to blue mold decreased and the quantity of DVT on the leaf surface increased. The data support a role for DVT in the resistance of tobacco against blue mold.     

应用A-蛋白诱捕修饰和羊抗兔血清诱捕双修饰法研究马铃薯X病毒

A-蛋白和羊抗兔血清应用于免疫电镜,检测马铃薯X病毒(PVX)粗汁液,灵敏度比诱捕修饰法高;而且加羊抗兔血清后,病毒粒体比诱捕修饰法明显加粗,在电镜放大2500倍时,就能清晰地观察到。用诱捕双修饰法检测PVX,证实在寄主植物的叶、茎和根中均存在,以叶内含量最高。接种在普通烟上第三天,接种叶就能检测到PVX,接种15天后,寄主体内病毒能达到较高浓度,而且高浓度一直可保持2个月以上;PVX在不同寄主中的含量不同,以普通烟中病毒浓度最高,心叶烟、番茄和黄花烟中次之;昆诺阿藜、千日红和大椒中含毒量极抵。用诱捕双修饰法检测马铃薯薯块休眠芽中的病毒获得成功。     

Evidence from nucleic acid hybridization tests for geminivirus infection of ornamental crotons in India

Reduced growth of plants and excessive generalised and spotty yellowing of leaves occurred in ornamental crotons that were infected with a geminivirus, which was detected by spot hybridization tests using a cloned probe derived from DNA-A of acalypha yellow mosaic geminivirus. The croton virus was transmitted by the whitefly,Bemisia tabaci, toNicotiana tabacum andAcalypha indica, in which it caused leaf curl and yellow mosaic, respectively, but it was not transmitted to five other species. Infected crotons may therefore serve as reservoirs of a geminivirus that is able to infect a crop species.     

Movement and metabolic fate of [14C]ethephon in flue-cured tobacco

The absorption, distribution, and metabolic fate of [¹⁴C]ethephon in flue-cured tobacco (Nicotiana tabacum L.) was studied using autoradiography, thin-layer chromatography, high-voltage paper electrophoresis, and liquid scintillation spectrometry. Labeled ethephon penetrated mature leaf tissue easily and was translocated primarily in an acropetal direction. No ¹⁴C activity was detected in any other plant part except the treated leaf. The first day after treatment, most of the translocated ¹⁴C was detected in the midrib, and after 2 days radioactivity was noticed in veinal areas distal to the point of application. Four days later, however, ¹⁴C was detected in slight amounts only in the midrib, indicating that [¹⁴C]ethephon was rapidly degraded by the leaf tissue. Depending on leaf position on the stalk, as much as 92% of the radioactivity had disappeared from the leaf tissue during the first day after treatment, and as little as 5% of the applied radioactivity was recovered 4 days later. Methanol-extracted plant residues contained insignificant amounts of ¹⁴C. All of the ¹⁴C in methanol extracts was present in the form of a labeled compound with an R_f value corresponding to that of ethephon, indicating the absence of any detectable metabolites of the parent compound. Smoke analysis of cigarettes showed that more [¹⁴C]ethylene than ¹⁴CO₂ was recovered in the main stream, whereas the trend was reversed in the case of side stream smoke.     

Toxicity and electrophysiological effects of Spilanthes amella Murr. extracts on Periplaneta americana L.

The potential insecticidal activity of Spilanthes acmella Murr. (Compositae) extracts was assessed in this study. The extracts were shown to be toxic against adults of American cockroach, Periplaneta americana L. The active component in S. acmella extract was isolated and identified as N-isobutyl-2,6,8-decatrienamide (spilanthol). The results from topical application of spilanthol show that it has a high acute toxicity and spilanthol was the most potent compound when compared to three conventional insecticides. The potency was found to be 1.3, 2.6 and 3.8 times more toxic than carbaryl, bioresmethrin and lindane, respectively. Electrophysiological studies indicated immediate hyperexcitation followed by complete inhibition of the cockroach cercal nerve activity.     

Feeding deterrence of northern fowl mites (acari: Macronyssidae) by some naturally occurring plant substances

Eighteen of 21 naturally occurring compounds and plant extracts tested in an in-vitro feeding system deterred northern fowl mites, Ornithonyssus sylviarum (Canestrini and Fanzago), from feeding. At 1.0% (w/v) concentrations in chicken blood, five compounds killed all mites exposed to them. Citronellal and bay extract prevented mite feeding completely at 0.1% concentrations. None of the compounds or extracts had repellent activity when mites were surrounded by a ring of the test material (0–42 mgcm^?2) impregnated in filter paper.