The fate of sodium 2-phenylphenate and biphenyl applied to citrus fruit in wax coatings

The fate of the fungicide in stored citrus fruit treated with wax coatings containing either sodium 2-phenylphenate (SOPP) or biphenyl was studied. The 2-phenylphenol content of SOPP—treated fruits was virtually unchanged during storage, was localised in the peel and could not be detected in the vapour phase. The persistence of this fungicide on fruit is in accord with the satisfactory results obtained with SOPP waxes. Biphenyl volatilised from biphenyl-waxed fruit at rates reflecting the conditions of storage. The volatilisation of biphenyl accounts for the protective action of biphenyl-waxes and their time limited effect.     

Treatment of citrus fruit with sodium o-phenylphenate foam

The treatment conditions for reducing the incidence of rot in stored citrus fruit with sodium o-phenylphenate (SOPP) foam and the possibility of improving the efficiency of the treatment were examined. Marked differences were noted among different packing houses with regard to ambient temperature temperature of the fruit surface, duration of treatment, SOPP content and pH of the solution, quantities of foam and of SOPP dispersed on the fruit, and between the o-phenylphenol (OPP) residues in fruit treated simultaneously. It should be possible to prolong the duration of treatment without increasing the OPP residues in the fruit above the tolerance limits of 10 ppm OPP in the whole fruit and without causing injury to the fruit.     

Antifungal activity of sodium propylparaben alone or in combination with low doses of imazalil against Penicillium decay on citrus fruit

The performance of postharvest treatments with sodium propylparaben (SPP), alone or combined with low doses of the fungicide imazalil (IMZ), against citrus green (GM) and blue (BM) molds was evaluated on several citrus species and cultivars artificially inoculated with Penicillium digitatum and P. italicum, respectively, and incubated at 20 °C or cold-stored at 5 °C. Effectiveness of 100 mM SPP dips at 20 °C for 60 s was higher on oranges than on mandarins, with GM and BM incidence reductions of up to 60–90 % after 7 days at 20 °C. Irrespective of citrus cultivar and storage condition, SPP generally improved the curative action of 25 μl l^?1 IMZ to control Penicillium molds. In additional tests, 100 mM SPP dips at 20 °C for 60 s only prevented GM on ‘Valencia’ oranges inoculated 24 h after treatment when combined with IMZ. It can be concluded that postharvest SPP treatments show promise as an effective alternative to be considered in citrus postharvest disease control programs.     

柑橘果实壳梭孢腐烂病的鉴定

 柑橘果实腐烂病引起伦晚脐橙果皮褐化、坚硬、缩水,严重影响果实商品价值。2017年对湖北宜昌采集的伦晚脐橙病果进行了组织分离、柯赫氏法则验证和病原菌鉴定,明确病原菌为小新壳梭孢Neofusicoccum parvum,该病菌也可侵染柑橘叶片、枝干和果实,引起腐烂。这是关于小新壳梭孢N. parvum侵染柑橘果实的首次报道。     

柑橘检疫除害处理的现状及发展趋势初探

柑橘是全球重要的国际贸易农产品之一,对柑橘有害生物的检疫处理措施成为全球主要贸易国柑橘检疫研究的热点话题,目前柑橘检疫除害主要有物理和化学以及生物药剂等处理方法。本文就柑橘有害生物除害处理方法现状作综述,并对其发展趋势进行了探讨。     

Effect of 2,4-dichlorophenoxyacetic acid applied as a herbicide on fruit shedding and coffee yield

The aim of this study was to evaluate the effect of 2,4-dichlorophenoxyacetic acid (2,4-D) applied as a herbicide at two timings after coffee blossoming, on fruit shedding from lower or upper plagiotropic branches on the canopy, as well as on crop yield. 2,4-D was sprayed between the rows on a 0.75 m-wide strip of land, starting on the border of canopy projection. Toxicity to the plants, final crop yield per plant and fruit shedding (FS) were assessed. The identical FS was observed for both application timings. Control plots showed an FS 13% lower than those where the highest 2,4-D dose was employed. FS was greater on the lower branches (46.8%) than on the upper ones (39.4%). This was probably due to injury to the lower plant canopy caused by the 2,4-D drift. Ripe or dried cherries and coffee bean yield per plant were not affected. It was concluded that despite the increased FS in the lower plant canopy, final coffee production was not significantly affected in response to 2,4-D application.     

Involvement of carbon catabolite repression on regulation of endopolygalacturonase gene expression in citrus fruit

 The Acpg1 gene of Alternaria citri encodes an extracellular endopolygalacturonase that is important for virulence in citrus fruits. Expression of Acpg1 is regulated by substrate induction and carbon catabolite repression. A green fluorescent protein (GFP) gene was employed as a reporter gene to define 813 bases upstream of the translation start site comprising the Acpg1 promoter. This upstream sequence contains five putative binding sequences of catabolite repressive element A (CreA), a cis-acting zinc finger repressor involved in carbon catabolite repression. We constructed each CreA-binding site-deleted Acpg1 promoters with GFP reporter gene and transformed them to A. citri. The construct PGPDL4 deleted from −401 to −813 showed both substrate induction and catabolite repression, whereas PGPDL5 additionally deleted from −1 to −84, including one putative CreA-binding site, resulted in a loss of catabolite repression function. Green fluorescence of PGPDL4 was induced by pectin in the peel but was repressed completely in the juice sac area of citrus fruit. However, green fluorescence of PGPDL5 was induced in both the peel and juice sac area, indicating that repression of Acpg1 in the juice sac area is likely accomplished by carbon catabolite repression. Received: October 4, 2002 / Accepted: October 31, 2002 Acknowledgments The authors thank Drs. D. Cullen, A. Van den Wymelenberg, and J. Andrews, University of Wisconsin, for providing pTEFEGFP containing GFP and Dr. T. Tsuge, Nagoya University, for providing transformation vector pSH75. The nucleotide sequence data of Acpg1 promoter region in the DDBJ, EMBL, and GenBank sequence databases is under accession number AB047543. This research was supported in part by grants to K.A. from the Ministry of Education, Culture, Sports, Science, and Technology of Japan.     

The determination of thiabendazole (2-(4-thiazolyl)-benzimidazole) in citrus fruit dips

Methods for analysing the strength of thiabendazole (TBZ) dipping fluids are described. The methods which require only the minimum laboratory facilities and can be used in citrus packing houses, are based upon (i) a titration method utilising the complex formed by TBZ with silver ions, for accurate work, and (ii) a refractive index method after concentration for rapid checking by packing house employees. These methods are compared with a spectrophotometric method.     

Histopathology of postbloom fruit drop caused by Colletotrichum acutatum in citrus flowers

Postbloom fruit drop (PFD) is caused by both Colletotrichum acutatum and C. gloeosporioides and is a potentially serious disease in citrus that occurs when flowering coincides with rainfall. The fungus incites necrotic lesions in petals and stigmas leading to premature fruit drop and reduced yield. The mechanisms of infection and survival of the causal agents remain to be fully elucidated. In the present study, we investigated the histopathology of PFD caused by C. acutatum in the petals and stigmas of sweet oranges using electron and light microscopy. In the petals, pathogen penetration occurred intra and intercellularly and also through the stomata, with intercellular penetration occurring most frequently. The distinct tissues of the petals were colonised, including the vascular system, particularly the xylem. Acervuli were observed on both sides of the petals. Although the fungus did not penetrate through the epidermal cells of the stigma, C. acutatum caused necrosis and an increase of phenolics in this tissue. A protective layer rich in lipophilic and phenolic compounds was formed under the necrotic area and crystals of oxalate were associated with the sites where the pathogen was present.     

A gas-liquid chromatographic method for determining imazalil residues in citrus fruit

An electron capture gas-liquid chromatographic method is described for the analysis of the fungicide imazalil,^a 1-(β-allyloxy-2, 4-dichlorophenethyl)imidazole, in citrus fruit. Recoveries were 80–95% from citrus fruit fortified at 0.50–2.0 mg/kg, with a limit of detection of 0.01 mg/kg.     

Phenology of the Florida wax scale,Ceroplastes Floridensis Comstock (Homoptera: Coccidae), on citrus in Israel

The phenology of the Florida wax scale (Ceroplastes floridensis) was studied on grapefruit trees in three citrus-growing regions of Israel — the Jordan Valley, the Coastal Plain, and the Yizre’el Valley. This citrus pest develops two annual generations in, all the regions: a ‘summer generation’ which develops from May-June to August-September, and a ‘winter generation’ which develops from August-September to May-June. The mass appearance of the first instar larvae of each generation occurs in May-June and August-September, respectively.     

Colletotrichum gloeosporioides, a new causal agent of citrus post-bloom fruit drop

Citrus post-bloom fruit drop (caused by Colletotrichum acutatum) frequently occurs in the southwestern region of São Paulo State, Brazil. A survey of Colletotrichum isolates associated with symptoms of post-bloom fruit drop in São Paulo State showed C. gloeosporioides in addition to C. acutatum. The objectives of this study were to confirm the identification of C. gloeosporioides isolated from symptomatic citrus flowers, to test the pathogenicity of C. gloeosporioides isolates, to compare the development of disease caused by C. gloeosporioides and C. acutatum, and to determine the frequency of C. gloeosporioides in a sample of isolates obtained from symptomatic flowers in different regions of São Paulo State. Through the use of species-specific primers by PCR, 17.3% of 139 isolates were C. gloeosporioides, and the remaining 82.7% were C. acutatum. The pathogenicity tests, carried out in 3-year old potted plants of sweet oranges indicated that both species caused typical symptoms of the disease including blossom blight and persistent calyces. Incubation periods (3.5 and 3.9 days, respectively, for C. acutatum and C. gloeosporioides) and fruit sets (6.7 and 8.5%, respectively for C. acutatum and C. gloeosporioides) were similar for both species. The incidences of blossom blight and persistent calyces were higher on plants inoculated with C. acutatum than in those inoculated with C. gloeosporioides. Conidial germination was similar for both species under different temperatures and wetness periods. Under optimal conditions, appressorium formation and melanisation were higher for C. gloeosporioides than for C. acutatum. These results indicated that Colletotrichum gloeosporioides is a new causal agent of post-bloom fruit drop.     

Crop loss and control of Pseudocercospora fruit and leaf spot of citrus in Ghana

Pseudocercospora fruit and leaf spot (PFLS) of citrus, caused by Pseudocercospora angolensis, was recently described in Ghana and has spread in most citrus-growing areas of the country. A survey of PFLS incidence was conducted in the Eastern Region. Orchards were georeferenced and data on altitude, annual mean temperature, and annual precipitation were obtained from the WorldClim database. Fruit drop due to PFLS and other pests and diseases was evaluated in three orchards. Field efficacies of 4-week, 6-week and 8-week schedules with carbendazim + mancozeb were evaluated in the major and minor fruit production seasons. Ordinal logistic regression and generalized linear models were fitted in each case according to the nature of the data and possible overdispersion. Disease incidence in the sweet orange orchards surveyed was 25–100 %, with higher values in higher altitude areas exposed to lower temperatures and higher rainfall. PFLS was the main problem causing yield losses, associated with 84–87 % of fruit dropped on the orchard floor. PFLS severity on shoots and incidence on fruit 12 weeks after full bloom was significantly reduced by all fungicide schedules evaluated. The effects of fungicides on PFLS severity in fruit at harvest were not substantial because of intense fruit drop. The 8-week schedule showed the lowest effectiveness in reducing fruit drop and thus the 6-week schedule is preferred. Further research is needed for an integrated management of PFLS in Ghana.     

采前灌溉对骏枣落果、裂果及果实品质的影响

以8年生骏枣为材料,采用间隔灌水处理法,研究采前(8月1日至9月9日)不同灌溉次数对骏枣落果率、裂果率、叶片相对含水量及果实品质等指标的影响。结果表明:骏枣叶片相对含水量随着土壤含水量的增加而上升,T3(灌水5次)处理叶片相对含水量比CK高17.64%;随着灌水次数的增多,骏枣采前落果率和裂果率均显著下降,其中T3处理的采前落果率和裂果率分别为7.697%±0.724%、12.393%±0.290%,分别较CK低5.977%、9.987%;灌水次数的增多会导致果实中可溶性糖、可滴定酸、Ca和Zn含量减少,同时会促使其可溶性蛋白、糖酸比、黄酮、N、K、Mn、Fe和Cu含量显著提高,对P和Mg含量影响均不显著。增加采前灌水次数能够明显降低骏枣采前落果率和裂果率,灌水5次处理的效果较为显著。     

Crawler phenology and generation development of the Florida wax scale,ceroplastes floridensis,on citrus planted in two soil types

Appearance of Florida wax scale (FWS) crawlers in citrus groves planted in sandy soil preceded that in groves planted in loam. The duration of crawler presence was longer on citrus in loam than in sandy soil. Mean age, as expressed by weighted developmental stage, yielded a linear regression with time. FWS develops two generations per year, which on sandy soil appear earlier and develop faster to the preovipositional stage than on loam. The size of ovipositing females was in direct correlation with the duration of development.     

Effect of pesticides on spiders occurring on apple and citrus in Israel

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.     

Laboratory and field evaluation of fungicides to control anthracnose stain of citrus fruit

Anthracnose stain on Clementine tangerine and grapefruit, caused byColletotrichum gloeosporioides, is described. Among the fungicides bioassayed against this organism Bordeaux mixture was the most effective copper compound; potent organic compounds were captafol, captan, chlorothalonil, maneb and mancozeb. Bioassay evaluation of fruit treated in the grove revealed that the protection and lasting effect of captafol and Bordeaux mixture were superior to those of chlorothalonil and maneb. Effective field control was achieved even with one prophylactic treatment in July with copper-containing fungicides.     

柑橘大实蝇传入新区后的发生规律及防控方法探讨

柑橘大实蝇[Bactrocera minax(Enderlein)]属双翅目实蝇科,是国际、国内植物检疫对象。此虫于1999年开始传入本县,随即迅速蔓延扩散,2002～2004年形成为害高峰,柑橘虫果率达30%～100%,堆积如山的蛆果,使人触目惊心。通过2005～2006年2年的控防,遏制了蔓延势头,疫区虫果率被控制     

Spatiotemporal characterization of citrus postbloom fruit drop in Brazil and its relationship to pathogen dispersal

Citrus postbloom fruit drop (PFD) is caused by Colletotrichum acutatum and C. gloeosporioides. These pathogens attack the flowers and cause premature fruit drop and the retention of fruit calyces. This study was designed to characterize the spatial and temporal dynamics of PFD in commercial citrus‐growing areas to better understand the disease spread. Experiments were carried out in three young orchards (500 trees each) in two municipalities in Sao Paulo State, Brazil. Symptoms of PFD on the flowers and presence of persistent calyces were assessed in each of three orchards for three years. Logistic, Gompertz and monomolecular models were fitted to the incidence data over time from the trees with symptoms. The spatial pattern of diseased trees was characterized by a dispersion index and by Taylor′s power law. An autologistic model was used for the spatiotemporal analysis. The logistic model provided the best fit to the disease incidence data, which had a fast progress rate of 0·53 per day. During the early epidemic of PFD, the spatial pattern of diseased trees was random, which suggested that inoculum spread was due to mechanisms other than rain splash. As the disease incidence increased (up to 12·6%), the spatial pattern of diseased trees became aggregated. The rapid rate of disease progress and the distribution of PFD suggest that dispersal of the pathogen is possibly related to a mechanism other than splash dispersal, which is more typical of other fruit diseases caused by Colletotrichum spp.