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1.
To promote earwigs as natural enemies of pests, or to control their populations if they damage crops, earwigs can be managed during their overwintering period on the ground. Here, we obtained more than a ton of soil to study earwigs' overwintering sites in a citrus grove. We found four species of earwigs: Forficula pubescens, Euborellia annulipes, Euborellia moesta, and Nala lividipes. Surprisingly, and although the European earwig Forficula auricularia is abundant in the citrus canopies the rest of the year, we did not find any F. auricularia, indicating that this species spends the winter outside the citrus grove. Therefore, farmers willing to manage European earwig populations in citrus orchards need to consider the possibility that earwigs may spend the winter outside the field. Earwigs that were overwintering in the citrus grove were more abundant at the south side beneath the canopies than at the north side or between rows, indicating that management practices such as soil tillage can impact overwintering earwigs only beneath the canopies, but not between citrus rows. Overall, our results provide insights into how earwig populations can be successfully managed during winter in citrus orchards.  相似文献   

2.
Field experiments in an apple orchard and in a citrus grove were carried out to evaluate the effect of four commercial pesticides in common use in Israel against apple and citrus pests, on the spider populations inhabiting the trees. The spider populations on apple were markedly suppressed by the pesticides, the order of toxicity being Talstar (biphenate) >Mavrik (fluvalinate) > Smash (fenpropathrin) > Dursban (chlorpyrifos). When grapefruit trees were treated with carbaryl + formothion, 232 spiders were sampled in the unsprayed plot, 55 days after treatment, as compared with only 11 spiders in the treated plot. Two and 7 days after treatment with chlorobenzilate, the sample from the treated plot numbered 68 and 55 spiders, respectively, as compared with 50 spiders collected 24 h before treatment. In addition, laboratory tests were carried out to determine the susceptibility of the spiderChiracanthium mildei L. Koch to 17 pesticides. When the spiders were exposed to grapefruit leaves which had been dipped 1 h previously for 5 sec in the aqueous emulsions of the pesticides, chlorpyrifos, fenpropathrin, fenvalerate, phosphamidon and biphenate caused 100%, and cypermethrin and fluvalinate 60% mortality, whereas all the other pesticides tested - acaricides, fungicides and herbicides - caused about 10-40% mortality.  相似文献   

3.
Citrus black spot (CBS) is a fungal disease, caused by Guignardia citricarpa, that has a high economic impact on citrus. Although G. citricarpa has been associated with black spot of citrus, an adequate pathogenicity test is still not available. Thus, our objective was to develop and evaluate a simple, safe, and practical pathogenicity test. We used fruits from Pera-Rio and Valencia sweet orange trees from two different orchards, located in the State of São Paulo, Brazil. Inoculation was performed by placing six disks colonized by G. citricarpa, onto the peel of healthy fruits, previously bagged. In the Pera-Rio sweet orange grove, initial symptoms of the false melanose type resulting from the inoculations were observed 55 days after inoculation (dai). In the Valencia grove, initial symptoms also of the false melanose type resulting from the inoculations occurred 73 dai. A total of 92.8% and 86.6% of the Pera Rio and Valencia fruits inoculated, respectively, showed symptoms of CBS. Citrus black spot symptoms were not observed in any of the control fruits.  相似文献   

4.
为明确湖南省柑橘黄化症状与柑橘慢衰病和柑橘黄龙病的相关性,应用形态学和分子生物学方法对湖南省永州地区表现黄化症状的柑橘进行了两种病原的鉴定及分布调查。结果表明,造成该地区柑橘黄化现象的主要原因为柑橘半穿刺线虫和黄龙病菌对柑橘的侵染。所检样本中,柑橘慢衰病平均发生率为82.1%,土壤中的半穿刺线虫群体密度最高达到3 077条/100mL。永州地区柑橘黄龙病病菌属于韧皮部杆菌属类细菌亚洲种,平均检出率为64.3%。柑橘半穿刺线虫和黄龙病菌在柑橘园存在混合侵染现象,混合侵染率为53.6%。柑橘半穿刺线虫在永州地区柑橘产区分布广泛,是造成柑橘黄化症状的重要病因,重视并有效防控柑橘半穿刺线虫已迫在眉睫。  相似文献   

5.
Peanut pod wart, a relatively new disease to peanut culture, was first reported in Israel in 1988 attacking peanut plants and causing dark warts on the pod. The causal agents are variousStreptomyces spp. Scanning electron microscopy showed a significant difference between healthy and diseased tissues of the exocarp and mesocarp layers of the pod; there were no effects on the endocarp layer. The mesocarp cells of infected tissue were smaller and more compressed than those of healthy tissue. In most cases two cells under the peak of the wart were extremely large and the cells growing from them toward the surface were uneven, forming the shape of a fan. The pathogen could be isolated from the soil and rhizosphere, but in the pod it was found only in the waited tissue. The microorganisms isolated from the warts belong to different groups ofStreptomyces spp.; subsequent pathogenicity tests proved their virulence to a limited host range. In potato, these isolates ofStreptomyces spp. caused deep pitted scab; in peanuts they caused warts. Peanut seeds which developed in infected pods were free of the pathogen if the shell was undamaged. However, the pathogen is surface seedborne, and contaminated seeds during the mechanical cracking process.  相似文献   

6.
Several Phytophthora spp. are known to cause a range of symptoms on citrus, resulting in significant crop losses worldwide. In South Africa, Phytophthora remains a destructive citrus disease, but the species and their distribution have not been well documented. A total of 162 Phytophthora isolates was collected from 60 citrus orchards in seven provinces of South Africa (Eastern Cape, Kwazulu-Natal, Limpopo, Mpumalanga, Northern Cape, North West and Western Cape). Isolates were identified to the species level through PCR-RFLP (restriction fragment length polymorphism) analyses of the internal transcribed spacer region. The identity of a subset of the isolates was confirmed using morphological and sequence analyses. Phytophthora nicotianae was the predominant species (76 % of isolates) and occurred in 80 % of the orchards in all of the provinces, followed by P. citrophthora (22 % of isolates in 28 % of orchards). The P. citrophthora isolates were further subdivided into two previously identified subgroups, G1 and G2, with most (69 %) of the isolates belonging to the G1 subgroup. Other Phytophthora species included P. multivora in the Western Cape Province, and an unknown species in the Eastern Cape Province with high sequence similarity (98 %) to a putative new species submitted to GenBank as Phytophthora taxon Sisuluriver. Phytophthora palmivora, a known citrus pathogen, was not identified. Most of the P. nicotianae isolates (79 %) were of the A1 mating type. The P. citrophthora isolates were mostly sterile (64 %), including most of the G1 isolates (81 %). The remaining G1 isolates (19 %) belonged to the A1 mating type, whereas almost all G2 isolates belonged to the A2 mating type except for one isolate that was sterile.  相似文献   

7.
The occurrence and geographic distribution of powdery mildew on cucurbits was studied in the Czech Republic, Austria, France, Germany, Great Britain, Italy, Slovakia, Slovenia, Spain, Switzerland, the Netherlands, as well as in Turkey and Israel, during the period 1995–2000. In total, 599 leaf samples with powdery mildew symptoms were collected from cucurbits from 166 locations within the Czech Republic; an additional 69 samples were collected from 42 locations elsewhere. Two powdery mildews (Golovinomyces cichoracearum and Podosphaera xanthii) were identified. The host range included the cultivated cucurbits (Cucumis melo, C. sativus, Cucurbita pepo, C. maxima, and Citrullus lanatus) and several other species. P. xanthii was the only powdery mildew pathogen found in Spain, Israel, and Turkey. P. xanthii and G. cichoracearum were detected in the other surveyed countries, occurring in both mixed infections and separately. In the more northerly latitudes and higher elevations, G. cichoracearum is more often the single species. G. cichoracearum was the dominant powdery mildew species in the Czech Republic (detected in 98.8% of the locations there); P. xanthii was found as the lone species in 1.2% of locations. At 28.4% of locations, G. cichoracearum was found with P. xanthii as mixed infections. The hyperparasitic fungus Ampelomyces quisqualis was found in 30% of the samples from the Czech Republic and was also recorded in Austria, Italy, Slovenia, Switzerland, and Great Britain.  相似文献   

8.
Alternaria spp. cause leaf spot of almond and Alternaria late blight of pistachio in California, and azoxystrobin is a strobilurin fungicide that has been registered for the control of these diseases. To date, only a single point mutation of G143A in cytochrome b resulting to azoxystrobin resistance in Alternaria spp. was found in California. Based on this single point mutation, a real-time PCR assay was developed to quantify the frequency of the resistant allele G143A (FA) in pathogen samples taken from orchards. Forty-one almond and pistachio orchards were arbitrarily selected in eight counties of California. Fifty leaf lesions caused by Alternaria spp. per orchard were cut to extract the fungal DNA for a real-time PCR assay to determine the FA. About 88% of 41 surveyed orchards had Alternaria spp. with FA > 0.90, while six pistachio orchards showed a FA < 0.90. Therefore, azoxystrobin-resistant Alternaria populations are predominant in almond and pistachio orchards in California, and sprays of azoxystrobin to control Alternaria diseases are not recommended in these orchards. This study shows a potential use of a real-time PCR assay to efficiently quantify the frequency of azoxystrobin-resistant Alternaria spp. from large number of samples.  相似文献   

9.
Postbloom fruit drop (PFD), an important disease caused by Colletotrichum spp., affects citrus yields in Brazil. PFD is characterised by the presence of necrotic lesions on the petals and stigmas of citrus flowers and by the subsequent abscission of young fruit. PFD epidemics have high disease progress rates, which is unusual for a pathogen that produces acervuli and is dispersed by rain. It is possible that other dispersal agents, such as insects and pollen, are involved in the spread of this disease. The objective of this work was to test whether citrus pollen grains can be colonised by Colletotrichum acutatum. Studies using light and electron microscopy showed that the pollen of Citrus sinensis can be infected by C. acutatum. This pathogen can penetrate and colonise citrus pollen grains 24 h after inoculation with the pathogen. The germ tube of conidia either penetrates the pollen sporodermis directly or passes through pollen germ pores. A single hypha can colonise more than one pollen grain. On the surface of the stigma, conidium formation can be observed. This study shows that Citrus sinensis pollen may, in fact, play a role in the spread of C. acutatum in citrus orchards.  相似文献   

10.
The vesicular arbuscular fungusGlomus mosseae (Nicol. & Gerd.) Gerd. & Trappe was retrieved from citrus trees growing in loess soil in the Negev region of Israel. Inoculation of citrus seedlings with the mycorrhizal fungus greatly increased the growth of plants in soil low in phosphorus. Rough lemon responded more than Sour orange. Vesicular arbuscular mycorrhiza caused higher concentrations of P and Cu and lower concentrations of N, K and Ca in leaves of inoculated plants.  相似文献   

11.
Out of 208 isolates ofF. oxysporum, 158 produced toxic reactions when applied to rabbit skin. This fungus, ubiquitous in the soils of Israel, was the most prevalent component of theFusarium flora in the unirrigated (but not in the irrigated) soils sampled.F. oxysporum var.redolens was common only on unfertilized plots of heavy, unirrigated soils.F. oxysporum was a major constituent of theFusarium flora isolated from most of the 450 samples of 20 field and garden crops, but less common in 98 samples of citrus, avocado and mango fruits. It ranks among the most destructive pathogens of cucurbits (exceptCucurbita pepo), tomatoes, onions, and gladioli in Israel, but causes almost no damage to Brassicae, peas or cotton. In pathogenicity tests with 207 isolates from nine field and two fruit crops, numerous isolates caused seedling mortality, with watermelon, onion, cucumber, tomato and eggplant being the most susceptible. Spore measurements on 160 isolates from plants and 355 from soils, showed that spore size was not markedly affected by plant source or by irrigation, but did differ between soil samples taken at 5 and 20 cm depth, and from manured or unfertilized soils.  相似文献   

12.
ABSTRACT Epidemics of citrus brown rot from 1994 to 1997 in the south-central and east-coast citrus areas of Florida were characterized and the causal Phytophthora spp. identified. Two species of Phytophthora, P. palmivora and P. nicotianae, were consistently associated with brown rot. Epidemics caused by P. palmivora appeared to be initiated on immature fruit dropped on the orchard floor. The soilborne fungus infected and sporulated on these fruit and was then disseminated to fruit above 1 m in the canopy. In contrast, infection by P. nicotianae, the common cause of root rot, was confined to the lowest 1 m of the canopy. Fruit infected by P. palmivora produced large amounts of ellipsoidal sporangia available for splash dispersal, whereas those infected by P. nicotianae produced far fewer spherical sporangia. Isolates from brown rot epidemics were compared with P. nicotianae from citrus in Florida and Texas, P. citrophthora in California, P. palmivora, and selected Phytophthora spp. from other hosts. Brown rot symptoms produced by the different pathogenic citrus isolates on inoculated fruit were indistinguishable. Morphology, mating behavior, and isozyme patterns of brown rot isolates from 1988 to 1997 matched P. palmivora from citrus roots, other host plants, and other locations, but were different from characterized isolates of P. citrophthora in California and P. nicotianae in Florida and Texas. Cellulose acetate electrophoresis of the isozyme glucose-6-phosphate isomerase rapidly identified the causal citrus pathogen from infected fruit and soil isolation plates. Although P. palmivora is an aggressive pathogen of citrus roots, bark, and fruit, populations in orchard soils were low compared with P. nicotianae.  相似文献   

13.
This work aimed to find out patterns of virulence variability of a Phoma tracheiphila population of 51 isolates, to determine geographic distribution of Mal Secco disease in citrus orchards of six Mediterranean countries and also to establish correlation between geographic distribution and pathotypic distance of P. tr population structure over our sampling spatial scale. Based on unweighted pair-group method with arithmetic averaging clustering and mean disease rating scores, three distinct virulence groups were identified. The 51 isolates were classified into 20 pathotypes. Extensive virulence variability was detected in 51 isolates of P. tr causing MSD of citrus in the Mediterranean basin. Regression plot between pairwise virulence and geographical distance showed that virulence is independent of the geographical origin and that isolates collected from the same country have different degrees of virulence. The lack of significant correlation between virulence and geographic structure confirmed the absence of isolation-by-distance pattern, suggesting non-regular and non-gradual dispersal of the pathogen over this spatial scale.  相似文献   

14.
Samples of onion (Allium cepa L.) seeds were obtained from seven regions in Turkey. The seed coat, embryo and endosperm were cultured, the seedborne fungi were determined and their transmission to onion sets was investigated in both sterile and field soils. Among the fungi determined,Aspergillus alutaceus Berk, and Curt.,Beauveria bassiana (Bals.) Vuill.,Cladosporium cladosporioides (Fres.) de Vries,Geotrichum sp.,Humicola fuscoatra Traaen,Trichoderma harzianum Rifai andT. pseudokoningii Rifai in onion seeds, andFusarium culmorum (W.G.Sm.) Sacc,F. graminearum Schwabe andF. sambucinum Fuckel in onion sets, were recorded for the first time.Aspergillus niger v. Tieghem was found at the highest rate in seed samples (especially in the seed coat), and in bulbs and roots of onion sets that developed from these seeds, whether in sterile or field soil.Fusarium oxysporum Schlecht was isolated at a higher rate from onion sets grown in sterile or field soil, than from seeds.F. acuminatum Ellis and Everhart,F. sambucinum, F. equiseti (Corda) Sacc. andF. graminearum were isolated only from onion sets grown in sterile soil. In dual culture tests, theseFusarium isolates were inhibited byA. niger and thus, exceptfor F. oxysporum, could not develop in agar plate. TheFusarium spp. appeared in onion-sets grown in sterile soil and were inhibited by other fungi in field soil. It was concluded that all fungi were seedborne and thatA. niger andFusarium spp., but not the other fungi, were transmitted from the seeds to onion sets.A. niger andF. oxysporum were also transmitted through the soil.  相似文献   

15.
One hundred and twenty-nine isolates ofRhizoctonia spp. were obtained from soil samples in Israel and from culture collections in the U.S.A. and Japan. The isolates varied in host range and disease severity when tested on six to eleven different host plants. Approximately 30% of the isolates were nonpathogenic to all the host plants tested. Mycelial growth rate of the nonpathogenic strains did not differ significantly from that of the virulent isolates. The 107 Israeli isolates represented anastomosis groups (AG) 1, 2, 3, 4, 5 and 6 ofR, solani, two groups ofR. zeae, and three groups of binucleateRhizoctonia AG: A, F and K.  相似文献   

16.
Detection and quantitative estimation ofXanthomonas campestris pv.campestris (XCC) from soils were done on Kritzman’s selective medium (KSM). The composition of KSM, its selectivity and the recovery of 64 isolates ofXCC obtained from Israel, Holland, Taiwan, the USA, and Germany are given in detail.XCC was isolated from soil in Israel 22 months after infected cauliflower residues were incorporated into the soil. Metham-sodium (MES) at 16 ml/kg (32.7% active compound) of air-dried soil killed more than 99.9% and 99% ofXCC in soil in laboratory and field tests, respectively. MES applied at this ratevia the irrigation system in a field infested withXCC, significantly reduced counts of the pathogen in stems, siliques and seeds, and the incidence of plants with black rot symptoms. The treatment was more successful in reducing disease incidence when applied to the soil at a depth of 30 or 40 cm rather than 20 cm. It is recommended that a seed treatment be combined with fumigation of soil with MES for the production of seeds free ofXCC.  相似文献   

17.
A fruit rot, similar to brown rot, occurred on extremely early ripening Satsumas in Saga Prefecture in the early autumn of 1999. A single species of Phytophthora was isolated from the affected fruit. After nonwounding inoculation of healthy fruits of Citrus spp. including Satsuma with the isolated fungus, the fungus was reisolated from fruit with symptoms similar to those in nature. On the basis of its morphology and molecular analysis of the rDNA-internal transcribed spacer regions, the pathogen was identified as P. palmivora. This is the first report of P. palmivora as a causal pathogen of citrus brown rot in Japan.  相似文献   

18.
The major nematode pests of cultivated plants in Greece include root-knot nematodes Meloidogyne spp. (in almost all plants except citrus), cyst-forming nematodes Globodera rostochiensis, G. pallida (in potato), Heterodera avenae (in cereals), Ditylenchus dipsaci (in vegetables and ornamental plants) and Tylenchulus semipenetrans (in citrus). Based on observations made on samples examined at Benaki Phytopathological Institute, it was confirmed that serious infestation of new kiwi orchards with Meloidogyne spp. originated from seedlings infested at the nursery. Also the wide distribution of the nematode Tylenchulus semipenetrans in citrus orchards was mainly attributed to infested seedlings. The above observations led us, in 1985, to the decision to study the nematological fauna of nurseries in Greece.  相似文献   

19.
为了确定生防菌新月弯孢菌Culvularia lunata菌株J15(2)的安全性及防除稗草的潜力,研究了该菌株的寄主范围,接种孢子时稗草叶龄、接种后保湿时间、接种浓度对该菌株致病力的影响,土壤带菌对稗草出苗的影响,以及与化学除草剂的相互作用.结果显示,菌株J15(2)只能在稗草上侵染并扩展;接种孢子后保湿24 h,对2叶期稗草抑制率可达55.6%,对1.5叶期稗草抑制率可达100%;保&48h,对2叶期稗草防效提高至91.6%;接种孢子量需达1012孢子/hm2才能较好地抑制稗草生长;土壤带菌亦可抑制稗草生长.该菌与化学除草剂精噁唑禾草灵或二氯喹啉酸混用能显著提高除稗效果,菌株J15(2) 3.3 × 1012孢子//hm2分别与精噁唑禾草灵有效剂量3.83g/hm2二氯喹啉酸有效剂量250.00g/hm2混用,对稗草防效分别为99.5%和88.6%,远高于这两个除草剂单用时的药效.该试验结果表明,菌株J15(2)具有作为微生物除草剂的开发潜力.  相似文献   

20.
Rhizoctonia cerealis E.P. van der Hoeven (anamorph of Ceratobasidium cereale D.I. Murray and Burpee), which causes sharp eyespot in wheat, is a major soilborne fungal pathogen that severely impairs yield and quality of winter wheat in China. Because the pathogen is difficult to identify and quantify in soil using conventional methods, a rapid and reliable method is needed to detect and quantify the fungus. In this study, we developed an SYBR Green-based quantitative real-time polymerase chain reaction assay for specific, sensitive detection and quantification of R. cerealis in soil samples. Using a specific primer pair based on the β-tubulin gene of the fungal DNA sequence, we could specifically detect R. cerealis at quantities as low as 100?fg of purified pathogen DNA. Using the real-time PCR assays, we were able to quantify R. cerealis in artificially and naturally infested soil samples. This new technique to quantify R. cerealis is rapid and accurate and will be a useful tool for future studies of pathogenic R. cerealis.  相似文献   

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