Postharvest disease control in mangoes using high humidity hot air and fungicide treatments

The disease control efficacy of quarantine heat treatments developed for fruit fly disinfestation in mangoes cv. Kensington Pride was evaluated in this study. Heat was applied using high humidity (>95% r.h.) hot air (HHHA) at temperatures ranging from 47–49°C. Anthracnose, caused by Colletotrichum gloeosporioides, was well controlled in mangoes heated to a core temperature of 46°C, 47°C or 48°C for 24, 10 or 8 min respectively, prior to ripening at 23°C for 16 days. Stem end rot, caused by Dothiorella dominicana and Lasiodiplodia theobromae, was not satisfactorily controlled by these treatments. In a subsequent experiment, fruit were immersed in a hot benomyl (0.5 g a.i. litre“¹ at 52°C for 5 min) or unheated prochloraz (0.25 ml a.i. litre¹ at 28°C for 30 s) dip before or after the application of HHHA (core temperature of 47°C for 10 min). During storage at 23°C for 15 days, the incidence of stem end rot was reduced by HHHA alone, although immersion in hot benomyl either before or after HHHA treatment greatly improved stem end rot control. HHHA treatment (core temperature of 46.5°C for 10 min) alone reduced the incidence of anthracnose in mangoes stored at 13°C for 14 days prior to ripening at 22°C, although a combination treatment consisting of HHHA and either hot benomyl or unheated prochloraz gave complete control of anthracnose under these storage conditions. HHHA treatment alone gave no control of stem end rot in mangoes stored at 13°C prior to ripening at 22°C. A supplementary hot benomyl treatment was required for acceptable control of this disease in cool-stored mangoes. The development of yellow skin colour in fruit was accelerated by HHHA treatment.     

Physiological responses of mangoes cv. Kensington Pride to gamma irradiation treatment as affected by fruit maturity and ripeness

An investigation was undertaken to examine responses of mangoes cv. Kensington Pride to irradiation treatment.
Gamma irradiation of preclimacteric fruit increased fruit respiration immediately after treatment, delayed the time to attain the climacteric respiratory peak and reduced the magnitude of this peak rate. Fruit softening was unaffected whereas skin colour development was strongly inhibited by irradiation treatment. Inhibition of skin degreening was half-maximal at a dose of 200 Gy. Exposure to ethylene failed to reverse this inhibition. Less mature fruit were more strongly affected by irradiation treatment. Fruit which were partially ripe and in their climacteric rise at time of treatment were largely unaffected by irradiation. These results are discussed in terms of the utility of irradiation technology for commercial disinfestation.     

Susceptibility of eight potato cultivars to tuber infection by Phytophthora erythroseptica and Pythium ultimum and its relationship to mefenoxam-mediated control of pink rot and leak

In addition to cultural practices, the application of the fungicide mefenoxam is an important disease management tactic used to control both pink rot and leak on potato tubers grown in the USA. Mefenoxam resistance has been identified in many of the potato growing regions, and therefore resistance management strategies are very important for retaining this fungicide as a tool to manage these storage rot diseases. The relationship between mefenoxam efficacy and cultivar susceptibility to pink rot and leak was assessed in post‐harvest inoculation studies. Mefenoxam was applied to potato (Solanum tuberosum) cultivars known to express varying levels of susceptibility to pink rot and leak caused by Phytophthora erythroseptica and Pythium ultimum, respectfully. Tubers harvested from plants treated with in‐furrow and foliar applications of mefenoxam were inoculated with isolates sensitive to the fungicide. Incidence and severity of both diseases ranged widely among cultivars. Russet Norkotah was the most susceptible to infection by P. erythroseptica, while cvs Pike and Atlantic were the most resistant. Cultivars Dark Red Norland, Russet Norkotah, Goldrush and Russet Burbank were most susceptible to infection by P. ultimum whereas Snowden was most resistant. Control of pink rot differed significantly among cultivars following mefenoxam treatment, ranging from 28% (cv. Goldrush) to 67% (cv. Snowden) and generally provided the greatest level of disease control on susceptible and moderately susceptible cultivars such as Russet Norkotah and Snowden, respectively. In contrast, the impact of mefenoxam on leak development was minimal and disease control did not differ significantly among the cultivars. The fungicide failed to control leak in the susceptible cvs Atlantic and Pike and control ranged from 1.7% to 5.2% in cvs Goldrush, Russet Norkotah, Dark Red Norland, Russet Burbank and Kennebec. The greatest level of leak control was achieved with the moderately resistant cv., Snowden, at 12.7%. Cultivars most likely to benefit from mefenoxam treatments should be targeted as part of a pink rot management programme. Judicious use of the fungicide, when matched with the level of cultivar susceptibility, may prove to be an efficient and effective approach to reduce infection rates and possibly manage mefenoxam resistance thereby maintaining longevity of the compound.     

Effects of 1-methylcyclopropene alone and in combination with polyethylene bags on the postharvest life of mango fruit

Experiments were conducted to determine how 1‐methylcyclopropene (1‐MCP) treatments influence ethylene‐stimulated ripening of harvested mango cv. Zihua fruit at 20°C. The ripening response of fungicide (prochloraz) treated fruit was characterised following various 1‐MCP treatments in sealed jars followed by storage in polyethylene bags and/or subsequent ethephon (ethylene) exposure. Exposure of fruit to increasing concentrations of 1‐MCP for 12 h resulted in the reduced softening of produce when subsequently held in air for 7 days after ethephon treatment. Application levels of between 1 and 100 μl litre^?1 1‐MCP had increasing impact, while 200 μl litre^?1 1‐MCP apparently began to approach response saturation. Exposure of fruit to 50 or 100 μl litre^?1 concentrations of 1‐MCP for periods from 1 to 24 h subsequently resulted in reduced softening of produce when held in air for 7 days after ethephon treatment. Increasing periods of exposure from 1 to 12 h had increasing impact, while exposure times greater that 12 h appeared to reach saturation. In the absence of ethephon‐stimulation, the natural ripening of mangoes held in polyethylene bags was delayed by prior exposure to 100 μl litre^?1 1‐MCP for 12 h. Extended holding of 1‐MCP treated and non‐1‐MCP treated control fruit in polyethyene bags encouraged physiological and pathological deterioration. Following exposure to 100 μl litre^?1 1‐MCP for 12 h, mango fruit held for 10 days in polyethylene bags showed a delay in the onset of ripening relative to bagged but non‐1‐MCP treated control fruit. Treatment with 1‐MCP allowed storage of mango fruit in plastic bags at 20°C for 30 days. Observations suggest that 1‐MCP treatments do not adversely influence the quality of the post‐storage ethephon‐ripened fruit. Thus, application of 1‐MCP in combination with the use of polyethylene bags can extend the postharvest life of mango fruit at ambient temperature. Treatments that extend postharvest life are important in developing countries, such as China, where the cold chain infrastructure is often lacking.     

Evaluation of an organic treatment for post-harvest control of crown rot of banana

An organic treatment for control of crown rot disease of banana was developed and evaluated at EARTH University in Costa Rica. Studies were conducted to evaluate the efficacy of Biocto 6 (seed extract from citrus) in combination with the wax-based adjuvant Verdiol for control of post-harvest crown rot of banana. The standard commercial fungicide treatment (thiabendazol, imazalil and ammonium sulfate) and an untreated control were included for comparison. Bananas with the various treatments were processed using standard commercial procedures and stored in a refrigerated chamber that was modified to simulate commercial transport, distribution and controlled ripening for exported bananas. Fruit clusters were evaluated for percent weight loss, ripening in storage and crown rot disease severity. At the end of the 28-day storage period, there were no significant differences in percent weight loss between any of the treatments. There was no significant difference in ripening (maturity level) between the organic treatment and the commercial fungicide standard in 2 years of testing. In 2003, the untreated control had a significantly higher maturity rating than the organic or standard fungicide treatment. However, there were no significant differences in any of the treatments in maturity level in 2005. There was no significant difference between the organic and standard fungicide treatment for crown rot control and both treatments had significantly less crown rot than the untreated control. Results indicate that Biocto 6 in combination with Verdiol wax provides a new organic alternative for control of post-harvest crown rot of banana.     

芒果、香蕉采后病害生物防治的研究进展

芒果、香蕉采后主要病害为炭疽病、蒂腐病、冠腐病、黑腐病、黑星病.生物防治是当前芒果、香蕉采后病害控制的重要研究方向.概述了生物防治芒果、香蕉采后病害的方法,包括诱抗剂、植物提取物、拮抗微生物在芒果、香蕉采后病害防治上的研究与应用.     

Sensitivity of mango anthracnose pathogen, Colletotrichum gloeosporioides, to the fungicide prochloraz in Taiwan

In order to monitor the sensitivity of the mango anthracnose fungus, Colletotricthum gloeosporioides, to the eradicative imidazole fungicide prochloraz, a total of 43 mango orchards were surveyed throughout the Tainan area, covering a 4000 ha region of mango plantations. These orchards were recognized as having undergone higher prochloraz application. A subpopulation, 55 isolates in total, collected from Wufeng, Taichung, served as a baseline population since no fungicide was ever used in this mango plantation. A total of 545 isolates were surveyed, and it was found that the IC50s (50% inhibitory concentration) fell within a range of 0.009-0.1554 microg/ml. No significant resistance was found in the field even with higher frequency of prochloraz application. One orchard (Yujing (Wu)) located in the Yujing area known had a higher frequency of prochloraz application, the IC50s were between 0.0204 - 0.1554 microg/ml. The average IC50 was 0. 0766 microg/ml, which was about five times higher than the baseline population (0.015 microg/ml). A significant t test indicated that these two sub-populations were different at p = 0.01. The results indicated that the dose-response of C. gloeosporioides to prochloraz shifted slightly toward higher IC50 over time. A further survey using 10 microg/ml as the threshold dosage was conducted, and the results of 1375 isolates collected throughout this region showed that no isolate could survive at this dosage. Knowing that the registered dosage for field use is 83.3 microg/ml, based on above results, the author concluded that there was no sign of prochloraz resistance in mango plantations 13 years after prochloraz registration in Taiwan.     

芒果炭疽菌研究进展

芒果炭疽病是芒果生长期和采后贮藏期的主要病害之一,严重影响芒果的产量和品质。本文从芒果炭疽病的症状、病原菌分类鉴定、生物学特性、侵染特性及致病机理等方面进行综述;针对芒果炭疽病症状复杂、我国芒果炭疽病病原菌未获详细而系统的研究,指出全面了解我国芒果炭疽病的病原菌种类及优势种群,明确我国芒果炭疽菌的致病力强弱,有助于研究该病的发生流行规律,为抗病材料的选育和抗病品种在田间的合理布局提供参考。提出对我国芒果炭疽菌的抗药性进行系统监测分析,可防止或减缓芒果炭疽菌对杀菌剂抗药性的产生,从而有效减少化学农药的用量,为研究芒果炭疽病绿色防控新策略、新方法和新药剂奠定基础。     

Physical postharvest treatments in the control of stem‐end rot of mango

Botryosphaeria dothidea is the major pathogen of mango in Brazil, causing stem‐end rot, which causes significant losses during transportation and storage. The current strategy to control this particular disease using synthetic fungicides has been ineffective, leaving residues in the fruit. The objective of the research was to study the effect of physical treatments, with hot water rinse brushing (HWRB) and ultraviolet C irradiation (UV‐C), individually and in combination, to control stem‐end rot of mango. Physicochemical parameters, respiration and resistance induction of the fruit were also analysed. The in vitro trials demonstrated that B. dothidea is a thermoresistant fungus. The individual treatments with HWRB at 65°C for 15 s and 2.5 kJ/m² of UV‐C presented the best results, showing less symptoms of the disease during 18 days of storage. The combination of HWRB with UV‐C did not improve the control of the disease when compared to the treatments applied individually. The physicochemical parameters and the consumer acceptance evaluation showed that both physical treatments preserved the appearance of the fruit and delayed the ripening–senescence process. The induction of defence‐related enzymes revealed that induced resistance was an important mechanism involved in the control of stem‐end rot of mango.     

The antagonistic effect and mechanisms of Bacillus amyloliquefaciens DGA14 against anthracnose in mango cv. ‘Carabao’

Bacillus amyloliquefaciens strain DGA14 was tested for in vitro antagonism towards Colletotrichum gloeosporioides, a causal pathogen of anthracnose in mango cv. ‘Carabao’. DGA14 produced extracellular metabolites in solid and liquid media that suppressed the growth of C. gloeosporioides. The cells of DGA14 were often observed adjacent to the pathogen so affecting its spore germination and mycelium development. DGA14 colonised mango fruit 48 h after artificial inoculation and persisted 14 days after storage at 18–20°C. On fruit surfaces, DGA14 attached and produced dents to spores of C. gloeosporioides. Dipping mangoes in aqueous cell suspension (10⁸ mL L^?1) of DGA14 significantly decreased the incidence of anthracnose as compared to untreated fruit.     

Effect of hot water treatment on development of anthracnose (Colletotrichum gloeosporioides) and quality of mango fruit at Jimma southwest Ethiopia

Anthracnose is the major postharvest disease of mango and occurs throughout mango producing areas of the world including Ethiopia. Evaluating effect of hot water treatment on development of anthracnose and quality of mango fruit is imperative. A total of three hot water levels 48, 52 and 56 °C at two time interval (5 and 10 min) were tested with factorial arrangement in completely randomised design. The study indicated that hot water treatment at different temperatures and time interval significantly (p < 0.001) affects disease development and shelf life and postharvest quality of mango fruits. Hot water treatments reduced the incidence and severity of anthracnose disease significantly (p < 0.001) in mango fruits as compared to control. There was a highly significant difference (p < 0.0001) on weight loss, total soluble solids, titratable acidity and fruit firmness of mango fruits due to treatment. The present study reviled that hot water treatment has a potential in reducing the postharvest loss due to anthracnose and improving the shelf life and quality of mango fruits. However, the reduction of disease pressure on fruits was not at applicable level, which call ups future effort on developing on integrated disease management strategies for reduction of postharvest loss of mango fruits.     

葡萄抗病无核胚挽救育种及分子标记辅助选择

以欧洲葡萄无核品种为母本,中国野生葡萄双优、欧山杂种北醇及8个欧洲葡萄品种为父本共进行了16个组合的杂交,通过胚挽救技术获得胚挽救苗55个株系。利用无核基因特异引物GSLP1、抗黑痘病和抗炭疽病基因RAPD标记对杂种株系进行分子检测,杂种中检测出拥有无核基因RAPD标记的22株、拥有抗黑痘病基因RAPD标记的16株、拥有抗炭疽病基因RAPD标记的9株。在这些胚挽救杂种苗中,同时拥有无核、抗黑痘病、抗炭疽病基因RAPD标记的胚挽救苗4株,同时拥有无核和抗黑痘病基因RAPD标记的胚挽救苗9株,同时拥有无核、抗炭疽病基因RAPD标记的胚挽救苗1株。     

广西杧果病虫害调查初报

对广西24个市(县)杧果病虫害进行了系统的调查。发现病害有20种,主要为白粉病、炭疽病、细菌性角斑病、蒂腐病等,其中杧果水泡病、杧果畸型病和杧果红点病为国内新发现的杧果病害;发现害虫94种,隶属于8目38科,主要为杧果小齿螟Pseudonoorda minor Munroe、杧果横线尾夜蛾Chlumetia transversa Walker、杧果茶黄蓟马Scirtothrips dorsalis Hood、桔小实蝇Dacus dorsalis Hendel、杧果扁喙叶蝉Idioscopus incertus Baker等。腹足纲有害生物1种。     

The effect of treating seed potato tubers with benzimidazole, imidazole and phenylpyrrole fungicides on the control of rot and skin blemish diseases

Over 6 yr the effectiveness of imazalil, prochloraz and fenpiclonil, applied either alone or in a mixture, in controlling gangrene, dry rot, skin spot and silver scurf on potato tubers in store was compared with that of 2-aminobutane and thiabendazole. An assessment was also made of their efficiency in controlling the development of these diseases on the daughter tubers of seed tubers treated at harvest or before planting. Overall, 2-aminobutane was more effective in controlling gangrene (Phoma foveata) in store than the spray-applied fungicides. Deposits of imazalil, thiabendazole and fenpiclonil were greater when sprays were applied with an electrostatic sprayer than with a hydraulic sprayer. The opposite was found with the mixture of prochloraz Mn and tolclofos-methyl. More effective gangrene control was associated with the highest deposits. Fenpiclonil and the mixture of thiabendazole and imazalil were more effective in controlling dry rot (Fusarium solani var. coeruleum) than imazalil alone. The development of dry rot was, however, increased by 2-aminobutane treatment on eight out of 14 stocks. 2-aminobutane gave the greatest reduction (83%) in the severity of skin spot during storage whereas thiabendazole alone, and the mixture of thiabendazole and imazalil, gave mean reductions of 70% and 65% respectively. This mixture and fenpiclonil gave the greatest reduction in the severity of silver scurf although, in general, reductions in silver scurf with fungicide treatment were less than with skin spot. The type of sprayer used to apply a fungicide did not affect the effectiveness of the fungicides in controlling either skin spot or silver scurf on tubers in store, or on the daughter tubers. The incidence of gangrene and dry rot on daughter tubers was not reduced consistently by fungicide treatment of seed tubers of the six stocks tested. However, the severity of skin spot and silver scurf was reduced by fungicide treatments of all eight stocks but the reduction in disease was greater for skin spot than for silver scurf. All fungicides gave reductions in the severity of skin spot, and fenpiclonil and the mixture of thiabendazole and imazalil were the most effective for silver scurf. The effectiveness of the fungicides in controlling these diseases was similar for seed treated at harvest and that treated before planting.     

热杀菌剂处理对“紫花”和“留香”杧果贮藏品质影响?

52±1℃热杀菌剂苯来特或 TBZ等溶液浸果处理,对“留香”和“紫花”品种杧果采后炭疽病和蒂腐病有显著控制效果,改善果实外观,延长贮藏寿命,提高贮藏品质,减少病害的腐烂损失 60％,获得在常温下贮藏 18d的采后寿命和 100％的商品率。在热杀菌剂处理后,贮藏于低温13±1℃下的 杧果,显著减慢果皮转黄和后熟软化,降低呼吸速率,延长贮藏寿命2～3周以上,并且,显著减少病害和腐烂损失,有利于提高采后杧果的商品率和远途运输及销售。     

Attraction of the West Indian fruit fly to mango fruit volatiles

In this study, we investigated the attraction of West Indian fruit fly, Anastrepha obliqua (Macquart) (Diptera: Tephritidae), to volatiles of three mango [Mangifera indica L. (Anacardiaceae)] cultivars in field cage tests. The number of flies captured with Multilure traps baited with Amate mature green mangoes was significantly higher than that captured in traps baited with Coche and Ataulfo fruits. There was no significant difference between the number of flies captured in traps baited with Coche or Ataulfo mangoes. Gas chromatography‐mass spectrometry analysis of mango fruit volatiles identified 24, 22, and 19 compounds for Amate, Ataulfo, and Coche mango cultivars, respectively. A principal component analysis of the volatiles revealed that the Amate mango was more distant from the Ataulfo mango, and the latter cultivar was closer to the Coche mango. The compounds myrcene, α‐pinene, β‐selinene, and trans‐β‐ocimene were the most abundant in Amate mangoes, whereas 3‐carene, β‐selinene, terpinolene, and α‐pinene were the predominant compounds of Ataulfo cultivars. In the Coche mango, the predominant compounds were 3‐carene, β‐selinene, terpinolene, and limonene. Traps baited with a blend of myrcene, α‐pinene, and trans‐β‐ocimene captured more A. obliqua females and males than control traps. Flies were more attracted to the Super Q volatile extracts of Amate mango than to the three‐component blend formulated in a ratio of 1:1:1. However, there was no significant difference between the number of flies caught by traps baited with Amate mango extracts and that caught by traps baited with the three‐blend component when this was formulated according to the relative proportions in the mango extracts. Traps baited with myrcene, the major component, caught fewer flies than traps baited with Amate mango extracts.     

Natural plant volatiles as an alternative approach to control stem‐end rot in avocado cultivars

Stem‐end rot is a postharvest disease associated with multiple important fungal pathogens including Lasiodiplodia theobromae. The incidence of stem‐end rot in avocado during postharvest storage affects the shelf life, quality and marketability of the fruit. This study is aimed at the investigation of the antifungal activities of selected natural plant volatiles (vapour phase): citral, octanal, hexanal and thymol against L. theobromae (causal pathogen of stem‐end rot) in vitro and in vivo in “Hass” and “Fuerte” avocados. Hexanal showed a lower inhibitory effect on the radial mycelial growth of L. theobromae in vitro. However, citral at a minimum concentration of 4 μl/L revealed fungicidal activity and completely inhibited the spore germination of L. theobromae. Artificially inoculated “Hass” and “Fuerte” avocados with L. theobromae were exposed to citral (768 μl) and commercial fungicide prochloraz and stored for 6 days at 20°C and 14 days at 10°C separately and thereafter held at 20°C for 3 days to simulate the retail shelf conditions. Although citral in a volatile phase effectively reduced the development of stem‐end rot in both cultivars, its effect was significant in “Fuerte” with 75% reduction in the incidence of stem‐end rot. The biochemical analysis demonstrated an increase in total phenol contents, phenylalanine ammonia‐lyase, chitinase and β‐1, 3 glucanase activity in fruit exposed to citral when compared to the reference treatment prochloraz and the untreated control for both cultivars. Furthermore, fruits exposed to citral retained the ready‐to‐eat firmness and therefore could be considered a potential alternative treatment to control stem‐end rot at the postharvest stage.     

Comparison of cross inoculation potential of South African avocado and mango isolates of Colletotrichum gloeosporioides

Three hundred and eighteen Colletotrichum gloeosporioides isolates from stem-end rot and anthracnose infected avocados as well as from stem-end rot/anthracnose and soft brown rot on mango, were compared using fruit inoculations. Isolates could be categorised according to lesion size and both avocado and mango isolates produced larger lesions when inoculated on their own hosts. Cross-inoculation potential of these isolates was also compared on strawberries, peppers, guavas, papayas and citrus. All isolates produced lesions on all hosts except citrus. Factors such as area of origin and symptom type from which original isolations were made, could not be correlated with lesion development on these hosts.     

Fungicidal drenches for control of root rot in subterranean clover

Fungicide drenches of benomyl, metalaxyl, iprodione, propamocarb, or thiram were applied to intact soil cores taken from known root rot affected fields in Western Australia, to control subterranean clover root rot. Metalaxyl was the most effective in reducing seedling damping-off. The most effective fungicide for reducing the level of rotting of both tap and lateral root systems of survixing plants varied from season to season at one site and varied between different sites in any one season with each fungicide giving a significant reduction in root disease on at least one occasion. Results suggest that different individuals or complexes of root pathogens were operative between seasons in any one site, and between sites for any one season. In some instances it appears that different individual root pathogens or pathogen complexes were operative on tap roots compared to lateral roots.     

STUDIES ON GLOEOSPORIUM MUSARUM CKE. AND MASSEE CAUSING STORAGE ROTS OF JAMAICAN BANANAS

Experimental inoculations indicate that several factors may influence the extent to which anthracnose, caused by Gloeosporium musarum , develops on bananas following wound-infection. Severity of disease increases with increasing 'grade' of maturity, 'full' fruit being more seriously affected than 'thin' fruit. The evidence suggests that Gros Michel fruit is less susceptible to this form of rot than fruit of the Lacatan or Robusta varieties. The amount of Gloeosporium -rot on fruit imported into the United Kingdom undergoes marked seasonal variation, being greatest during autumn and winter.
The presence of perforated 'Polythene' bags during cold storage (55° F.) appears to favour slightly the development of disease. Bagging had no significant effect on rotting during the subsequent ripening period. After wound-inoculation, disease incidence and severity decreased appreciably with increasing periods of storage at tropical temperatures (76–87° F.). Such a decrease was evident even when the humidity at the surface of the fruit was maintained at a high level (92–100%).
In several shipping trials, a post-harvest fruit-dip treatment with nystatin (200–400 p.p.m.) effected 40–70% control of anthracnose.