Control of postharvest diseases of rambutan using controlled atmosphere storage and potassium metabisulphite or<Emphasis Type="Italic">Trichoderma harzianum</Emphasis>

Botryodiplodia theobromae, Colletotrichum gloeosporioides andGliocephalotrichum microchlamydosporum are the causal fungi of three rambutan postharvest diseases, stemend rot, anthracnose and brown spot, respectively. Two different treatments of rambutan fruits to control the diseases were investigated: application of potassium metabisulphite (250 ppm) or culture filtrate ofTrichoderma harzianum (TrH 40) followed by controlled atmosphere storage (CA) at 13.5°C and 95% r.h. Potassium metabisulphite at 250 ppm under CA effectively controlled the incidence and severity of the three postharvest diseases and maintained the eating quality and color of the fruit for 21 days. The greatest effect of this treatment was on brown spot disease, caused byG. microchlamydosporum. Application of TrH 40 was less effective than potassium metabisuphite. http://www.phytoparasitica.org posting July 8, 2002.     

Antagonistic effect ofTrichoderma harzianum on postharvest pathogens of rambutan (Nephelium lappaceum)

Trichoderma harzianum (TrH 40) isolated from soil samples from rambutan orchards (Nephelium lappaceum) had antagonistic effects against three postharvest pathogens of rambutan:Botryodiplodia theobromae, Colletotrichum gloeosporioides andGliocephalotrichum microchlamydosporum, causative fungi of stem end rot, anthracnose and brown spot, respectively. The effects were due to both antibiosis and mycoparasitism.T. harzianum (TrH 40) treatment, while reducing the occurrence of the three postharvest diseases, also retained the overall quality and color of the fruits.     

Effect of GRAS compounds on mycelial growth, pectic enzyme activity and disease severity of postharvest pathogens on rambutan (Nephelium lappaceum)

The GRAS compounds cinnamaldehyde (at 30 ppm), acetaldehyde (at 70 ppm), benzalde-hyde (at 50 ppm) and potassium metabisulphite (at 250 ppm) either completely inhibited or significantly reduced thein vitro mycelial growth ofGliocephalotrichum microchlamydosponim,Colletotrichum gloeosporioides andBotryodiplodia theobromae, the causative fungi of brown spot, anthracnose and stem end rot, respectively, of rambutan fruits,Nephelium lappaceum. The four compounds also significantly reduced the severity of all three diseases and the activity of pectic lyase and polygalacturonase enzymes secreted by the three fungi.     

Bicarbonate solutions control powdery mildew (Leveillula taurica) on sweet red pepper and reduce the development of postharvest fruit rotting

Disease severity of powdery mildew (causal agentLeveillula taurica (Lév.) Arn.) on pepper (Capsicum annuum), defoliation and fruit sunscald rating were significantly reduced (P=0.05) by foliar applications of sodium or potassium bicarbonate solutions, compared with water or penconazole (Ophir). Preharvest application of bicarbonate solutions significantly reduced (P=0.05) postharvest decay development on sweet red pepper fruits.     

马铃薯糖苷生物碱对枸杞镰孢菌果腐病的诱导抗性及相关防御酶活性的影响

为探索马铃薯糖苷生物碱诱导采后枸杞鲜果抗病性的效应,采用菌丝生长速率法测定了离体条件下马铃薯糖苷生物碱对枸杞鲜果采后主要致腐病原菌镰孢菌Fusarium sp.的抑菌活性;采用浸泡处理法测定了马铃薯糖苷生物碱对采后枸杞鲜果发病病情指数及对果实多酚氧化酶(PPO)、过氧化物酶(POD)、苯丙氨酸解氨酶(PAL)和超氧化物歧化酶(SOD)等相关防御酶活性的影响。结果表明:不同浓度马铃薯糖苷生物碱对镰孢菌均具有一定的抑制作用,EC50为0.11 g/mL;0.05～0.25 g/mL(提取原料)的马铃薯糖苷生物碱能显著降低采后枸杞鲜果病情指数,较对照降低了10.18%～38.51%;以0.15 g/mL(提取原料)的马铃薯糖苷生物碱处理后对枸杞鲜果抗果腐病的诱导效果最好,达45.81%;马铃薯糖苷生物碱处理枸杞鲜果后,果实中4种防御酶PPO、POD、PAL、SOD的活性均较对照有不同程度提高,分别于处理后第4、5、2、2天与对照差异达到最大,较对照提高了30.76%、21.34%、31.35%和21.91%。表明马铃薯糖苷生物碱能够诱导枸杞鲜果对采后病害的抗性效应,且采后抗病性可能与枸杞相关防御酶活性的增加有关。     

Impacts of atmospheric CO<Subscript>2</Subscript> concentrations and soil water on the population dynamics,fecundity and development of the bird cherry-oat aphid<Emphasis Type="Italic">Rhopalosiphum padi</Emphasis>

The impacts of elevated CO₂ and soil water on the population dynamics, adult fecundity and nymphal period of the bird cherry-oat aphidRhopalsiphum padi (Linnaeus) were evaluated in three experiments: (i)Combined effects of CO ₂ and soil water on aphid populations. Spring wheat was grown in pots at three CO₂ concentrations (350, 550 and 700 ppm) and three soil water levels (40%, 60% and 80% of field water capacity, FWC) in field open-top chambers (OTC) and infested with the bird cherry-oat aphid. Aphid population dynamics were recorded throughout the growing season; at the same time, adult fecundity and duration of the nymphal period were recorded. Chemical composition of spring wheat leaves was also analyzed. (ii)Indirect effects of CO ₂ concentrations and soil water on aphid adult fecundity and nymphal period. The experiment was conducted with the leaf discs method in the laboratory. Aphids were reared on leaf discs excised from the treated wheat in OTC with different CO₂ and soil water levels. (iii)Direct effects of CO ₂ concentrations on aphid adult fecundity and nymphal period. Aphids were reared on leaf discs excised from the wheat grown under natural conditions. The experiment was conducted with the leaf disc method in OTC with the three CO₂ concentrations. It was found that the direct effect of CO₂ concentration on aphid population parameters was minor. CO₂ and soil water affected aphid population indirectly through their effects on wheat characteristics. The aphid population under 550 ppm CO₂ was far larger than the one under 350 ppm CO₂, whereas the population under 700 ppm CO₂ was slightly higher than that under 550 ppm CO₂. The largest aphid population was obtained with the 60% soil water treatment, regardless of CO₂ treatment. The effects of CO₂ concentration on aphid population were, however, not significantly correlated with soil water level. Adult fecundity increased with CO₂ concentration, the highest fecundity being achieved under 60% FWC treatments. The nymphal period was not affected by CO₂ concentration. The shortest period occurred under 60% FWC. Atmospheric CO₂ and soil water had significant effects on the chemical composition of the wheat leaves. Aphid population size was positively correlated with leaf water content, concentrations of soluble proteins, soluble carbohydrates and starch, and negatively correlated with DIMBOA and tannins concentrations. http://www.phytoparasitica.org posting Oct. 20, 2003.     

Note: Survey of seedborne fungi of sudanese cultivars of onion,with new records

Through incubation of onion (Allium cepa L.) seed samples on potato dextrose agar and moist filter papers at 28±2°C, 32 species and four varieties belonging to 19 genera of fungi were determined as seedborne in this crop. Among them, 23 species are new reports to the mycoflora of onion seeds.Aspergillus (11 species and three varieties, ∼42.1% of the total colony count of fungi) was the most prevalent genus:A. niger (∼19.7%) was found at the highest rate in the seeds, followed byA. parasiticus (∼17.3%,A. oryzae (∼17.3%) andA. flavus (∼14.5%). The genusAspergillus was followed byPenicillium (∼12.4%),Sclerotium (∼7.1%),Fennellia, Rhizopus, Chaetomium, Drechslera andAlternaria (∼12.4%),Fusarium, Emericella andByssochlamys (∼7.1%), whereas the remaining eight genera displayed a low level of infection (∼10%). Twenty-seven species, three varieties and 12 genera represent Hyphomycetes; four genera, three species and one variety — Ascomycotina; one genus and one species — Zygomycotina; two genera and two species — other Deuteromycotina; and one genus — Oomycetes. Some species, which are known to cause devastating pre- and postharvest diseases to onion crops, were recovered from the seeds of this crop, suggesting the high possibility of their transmission by seed. http://www.phytoparasitica.org posting July 14, 2004.     

Phosphite compounds reduce disease severity in potato seed tubers and foliage

Phosphites (Phi) are alkali metal salts of phosphorous acid, with the ability to protect plants against different pathogens. In this research, the effect of Phi applied to potato plants on severity of three important potato diseases in Argentina was assessed. Seed tubers and foliage of potato cvs Shepody and Kennebec were treated with Phi to assess effects on resistance against Phytophthora infestans, Fusarium solani and Rhizoctonia solani. Protection resulting from Phi treatment in seed tubers was high against P. infestans, intermediate against F. solani, and low against R. solani. In addition, seed tubers treated with calcium or potassium phosphites (CaPhi and KPhi, respectively) at 1% of commercial product emerged earlier than untreated ones. When Phi were foliarly applied two or four times at different doses, high levels of protection against P. infestans were achieved in both cultivars. Higher protection was observed in Kennebec when CaPhi was applied, while in Shepody this was true for KPhi. Expression of β-1,3-glucanases was induced at different times after treatment but no correlation between β-1,3-glucanases expression and foliar protection level was found. On the other hand, Phi positive protection effects did not produce negative effects in plant growth. Leaves from CaPhi-treated plants showed a darker green colour than leaves from control plants; also an increase in Rubisco protein and a delay in crop senescence was observed.     

Antifeedant activity of fruit and seed extracts ofMelia azedarach andazadirachta indica on larvae ofSesamia nonagrioides

Methanolic extracts of seeds and fruits of the chinaberry tree,Melia azedarach L. (Meliaceae), showed strong antifeedant activity against 2nd instar larvae ofSesamia nonagrioides Lefèbvre (Lepidoptera: Noctuidae), a very serious pest of maize(Zea mays L.) in Mediterranean countries. Extracts were applied in an artificial diet at concentrations of 1000 and 2000 ppm. The parameters used to evaluate the activity were larval growth rates; quantity of food ingested; phagodepression/phagostimulation index; quantity of frass produced; quantity of material ingested; duration of larval development; and cumulative mortality. Seed extract showed high bioactivity at both doses, while fruit extract proved to be less active, and only at the higher dose used (2000 ppm) did it display a slight antifeedant activity. The activity of theM. azedarach seed extract at the higher dose (2000 ppm) was comparable to that of pure azadirachtin applied at a dose of 1.25 ppm, or to ‘Mubel’, a commercial extract ofAzadirachta indica A. Juss. (Meliaceae), applied at a dose of 75 ppm.     

Application of <Emphasis Type="Italic">Pantoea agglomerans</Emphasis> CPA-2 in combination with heated sodium bicarbonate solutions to control the major postharvest diseases affecting citrus fruit at several mediterranean locations

We determined the potential of using a formulated product based on Pantoea agglomerans CPA-2, either alone or in combination with heated sodium bicarbonate (SBC) solutions, to control the major postharvest diseases affecting citrus crops in the Mediterranean region. Treatments applied either individually or in combination were tested in semi-commercial and commercial trials carried out with oranges and mandarins from the Algarve, Andalusia and Catalonia. Firstly, several formulations of the biocontrol agents were tested in laboratory trials; one of them, a freeze-dried formulation of P. agglomerans strain CPA-2 called FD10-3, was chosen for combined with SBC. This formulation, applied at 2 × 10⁸cfu ml⁻¹ and the SBC treatment, applied at 3% 50°C for 20–40 s, demonstrated that it was possible to reduce decay development in laboratory trials. Semi-commercial applications of FD10-3 and 3% SBC solution at 50°C for 40 s showed excellent control of decay in unwounded mandarins and oranges artificially inoculated with both Penicillium digitatum and P. italicum. No rind injuries or residues attributable to hot water or SBC were observed on treated fruits. Combined treatment provided better control than the two treatments applied separately. Commercial trials demonstrated an important reduction in natural decay with the treatment of SBC 3% at 50°C for 40 s. Furthermore, bacterial-product formulation treatment significantly reduced the percentage of infected fruit and in some cases this reduction was equal to chemical treatments. Even so, no improvement in efficacy was observed with the combination of FD10-3 and SBC in the commercial test. We also assessed the ability of FD10-3 to grow at the wound site in oranges, whether alone or in the presence of SBC, and also its compatibility with standard citrus packinghouse practices.     

Improving Control of Green and Blue Molds of Oranges by Combining Pantoea Agglomerans (CPA-2) and Sodium Bicarbonate

The potential of using Pantoea agglomerans (strain CPA-2) alone, or in combination with sodium bicarbonate or sodium carbonate solutions, for control of Penicillium digitatum (green mold) and Penicillium italicum (blue mold) on oranges was investigated under ambient (20 °C) and cold storage (3 °C) conditions. P. agglomerans controlled both pathogens on oranges at 2 × 10⁸ cfu ml^-1. The biocontrol agent was found to be completely tolerant to 2% sodium bicarbonate at room temperature, although its culturability was reduced by > 1000-fold after 30 min in 2% sodium carbonate. The efficacy of P. agglomerans for control of green mold was improved when combined with sodium bicarbonate, resulting in complete and 97.6% reduction of decay incidence at 3 °C and 20 °C, when compared to untreated controls. Satisfactory results were also obtained with the combined treatment for control of blue mold. P. agglomerans grew well inside wounds on oranges at both 20 °C and 3 °C. In contrast, it showed a reduced growth on the surface of intact fruit. Sodium bicarbonate at 2% concentration did not noticeably affect antagonist population development. Thus, use of bicarbonate treatment at 2% followed by the antagonist P. agglomerans CPA-2 could be an alternative to chemicals for control of postharvest diseases on oranges.     

White rust of <Emphasis Type="Italic">Ipomoea</Emphasis> caused by <Emphasis Type="Italic">Albugo ipomoeae-panduratae</Emphasis> and <Emphasis Type="Italic">A. ipomoeae-hardwickii</Emphasis> and their host specificity

In some areas of Japan, yellow spots with white pustules on leaves, stems, petioles, peduncles and calyces were found on Ipomoea nil, I. triloba, I. lacunosa and I. hederacea var. integriuscula. We demonstrated that the diseases on I. nil, I. triloba and I. lacunosa were caused by host-specific strains of Albugo ipomoeae-panduratae and defined three forma speciales of the fungus, respectively, for the three Ipomoea species: “f. sp. nile”, “f. sp. trilobae” and “f. sp. lacunosae”. Because the diseases were new to Japan, we coined the Japanese name “shirosabi-byo”, which means white rust. We also showed that the disease on I. hederacea var. integriuscula was caused by A. ipomoeae-hardwickii. We named this new disease “white rust (shirosabi-byo in Japanese)”.     

Calcium reducesBotrytis c1nerea damages to plants ofRuscus hypoglossum

Plants ofRuscus hypoglossum L. were grown in containers with perlite, an inert medium, or with soil, under similar-to-commercial conditions, for three winter seasons. Constant fertilization with soluble calcium [Ca(NO₃)₂] through the root zone resulted in a reduction of up to 78% in postharvest rot caused by artificial inoculation withBotrytis cinerea Pers. ex Fr. Control plants were treated by fertilization with N,P,K and all other elements, identical to the fertilizer containing calcium. Foliar application of Ca(NO₃)₂ to ruscus bushes or application of this compound or of CaCl₂ or CaSO₄ to mature cut branches standing in water, resulted also in a significant reduction in postharvest phylloclade rot. Application of CaSO₄ and Ca(H2PO₄)₂ + CaSO₄ to ruscus plants, from fertilizers containing 22% Ca and releasing the cation gradually, effectively reduced the susceptibility of cut branches to infection by_{B. cinerea.}     

Bark-Beetle Parasitoids Population Surveys Following Storm Damage in Spruce Stands in the Vosges Region (France)

This paper presents the results of a long-term study designed to follow the population dynamics of hymenopteran parasitoids associated with Ips typographus L. (Coleoptera: Scolytidae) in northeastern France (Alsace and Vosges) in spruce stands devastated by the December 1999 storms. Population densities were estimated by periodic samplings in the pre-emerging insect populations developing under the bark of attacked trees. Data were collected between July 2000 and October 2001. I. typographus population density (per m²) increased respectively by 28%, 105%, and 212% in one year in the three sites surveyed. Six hymenopteran ectoparasitoids were found: Coeloides bostrichorum Giraud and Dendrosoter middendorffi Ratzeburg (Hymenoptera: Braconidae); Rhopalicus tutela (Walker), Roptrocerus xylophagorum (Ratzeburg), Roptrocerus mirus (Walker) and Dinotiscus eupterus (Walker) (Hymenoptera: Pteromalidae). After two years, the parasitoid populations increased in terms of average density but parasitism rates remained at a relatively low level, ranging from 0% to 40%, with 60% of the trees having a parasitism rate below 5%. Data outlined the recurrent coexistence of competing parasitoid species.     

Inactivation of soil-borne plant pathogens during small-scale composting of crop residues

Samples of heavily infested crop residues were incorporated in static compost heaps (2.5–4.6 m³) of the Indore type. Temperature increased to 50–70°C within 6 days depending on the type of crop residues used and the location within the heap. The heat phase (>40 °C) lasted 2–3 weeks and was followed by a c. 5-months maturation phase (<40 °c).=" among=" the=" 17=" pathogens=" tested,=">Olpidium brassicae and one of the four formae speciales ofFusarium oxysporum that were tested survived composting, but also their inoculum was greatly reduced.Survival during specific phases of composting was studied by incorporation and retrieval of samples at various stages of the process.F. oxysporum f. sp.melonis was completely inactivated andO. brassicae andPlasmodiophora brassicae were almost completely inactivated during the short heat phase. The three pathogens survived the long-lasting maturation phase without loss of viability. Heat evolved during composting was found to be the most important factor involved with sanitation of crop residues. The possible involvement of fungitoxic conversion products and microbial antagonism is discussed.     

Fenpropimorph: a promising fungicide for postharvest diseases in citrus fruits

Sour rot, green mold and blue mold are postharvest diseases of citrus fruit. Benzimidazole and imidazole fungicides control molds, and guazatine controls sour rot, but strains ofPenicillium spp. resistant to these chemicals have been reported. Aqueous formulations of fenpropimorph, a morpholine fungicide, are very active in controlling fungi attacking postharvest citrus fruits. The fungicidal effect of the chemical in the coating wax was investigated in combined treatments with guazatine in dip or spray applications on various citrus fruit varieties. Fenpropimorph alone was as good as or a better curative and protective treatment than the current commercial treatments applied in packinghouses in Israel for decay control.     

Host status and reaction of <Emphasis Type="Italic">Medicago truncatula</Emphasis> accessions to infection by three major pathogens of pea (<Emphasis Type="Italic">Pisum sativum</Emphasis>) and alfalfa (<Emphasis Type="Italic">Medicago sativa</Emphasis>)

Ditylenchus dipsaci, the stem nematode of alfalfa (Medicago sativa), Mycosphaerella pinodes, cause of Ascochyta blight in pea (Pisum sativum) and Aphanomyces euteiches, cause of pea root rot, result in major yield losses in French alfalfa and pea crops. These diseases are difficult to control and the partial resistances currently available are not effective enough. Medicago truncatula, the barrel medic, is the legume model for genetic studies, which should lead to the identification and characterization of new resistance genes for pathogens. We evaluated a collection of 34 accessions of M. truncatula and nine accessions from three other species (two from M. italica, six from M. littoralis and one from M. polymorpha) for resistance to these three major diseases. We developed screening tests, including standard host references, for each pathogen. Most of the accessions tested were resistant to D. dipsaci, with only three accessions classified as susceptible. A very high level of resistance to M. pinodes was observed among the accessions, none of which was susceptible to this pathogen. Conversely, a high level of variation, from resistant to susceptible accessions, was identified in response to infection by A. euteiches.     

高效氯氰菊酯亚致死浓度对桃小食心虫成虫体内解毒酶活性的影响

为研究高效氯氰菊酯亚致死浓度对桃小食心虫Carposina sasakii Matsumura雌、雄蛾体内解毒酶活性的影响,采用药膜法,以LC10、LC20和LC40浓度的高效氯氰菊酯处理桃小食心虫成虫24 h,分别测定药剂压力解除后0、6、12和24 h桃小食心虫雌、雄蛾体内细胞色素P450单加氧酶7-乙氧基香豆素-O-脱乙基酶（ECOD）、羧酸酯酶（CarE）和谷胱甘肽S-转移酶（GSTs）的活性,并分析其动态变化。结果表明:与对照相比,高效氯氰菊酯LC10浓度处理能抑制桃小食心虫成虫的ECOD比活力,且随处理浓度增加,高效氯氰菊酯对ECOD活性的诱导作用逐渐体现,LC40浓度处理组ECOD活性显著高于对照;此外,LC20和LC40浓度处理组可诱导桃小食心虫雄蛾CarE和GSTs比活力的增加,但对于雌蛾则结果相反。当药剂压力解除后,随着处理时间的延长,成虫体内ECOD、CarE和GSTs活性总体表现为先增加后降低,而药剂浓度越高对其解毒酶的诱导或抑制作用越显著,且存在一定性别差异。研究显示,从短期响应来看,桃小食心虫雌、雄蛾体内的3种解毒酶在高效氯氰菊酯亚致死浓度胁迫后均表现较为活跃,酶活性呈现出先增加后降低的动态变化。由于雌、雄蛾个体的生理机能以及对药剂敏感性的差异,这种生理响应机制存在一定的剂量和性别差异。     

两种蚜小蜂对烟粉虱MED隐种的田间笼罩控效评价

为明确烟粉虱Bemisia tabaci MED隐种优势寄生蜂海氏桨角蚜小蜂Eretmocerus hayati ZolnerowichRose与浅黄恩蚜小蜂Encarsia sophia GiraultDodd对其控制效果的影响,在棉田尼龙纱网笼罩中释放烟粉虱之后,再分别单独释放海氏桨角蚜小蜂、浅黄恩蚜小蜂以及二者以不同比例组合(1∶1、1∶3、3∶1)释放,定期调查统计2种蚜小蜂对烟粉虱的寄生量和烟粉虱的种群动态。结果表明,相对于不放蜂对照,自首次放蜂后40 d开始,所有放蜂处理均能显著降低烟粉虱若虫种群密度,每100 cm~2叶片上均少于1.00头,但各处理间的烟粉虱种群密度无显著差异;海氏桨角蚜小蜂和浅黄恩蚜小蜂以3∶1比例组合释放的处理中对烟粉虱的寄生量最高,每100 cm~2棉花叶片上能达到4.25头。表明在棉田中对烟粉虱进行生物防治时,以初级寄生蜂海氏桨角蚜小蜂与复寄生蜂浅黄恩蚜小蜂为3∶1的比例释放,可以到达较好的控制效果。     

Concentrations of constitutive alk(en)ylresorcinols in peel of commercial mango varieties and resistance to postharvest anthracnose

Mature green mango fruits of commercially important varieties were screened to investigate the levels of constitutive antifungal compounds in peel and to assess anthracnose disease after inoculation with Colletotrichum gloeosporioides. High-pressure liquid chromatography was used to quantify the levels of 5-n-heptadecenylresorcinol and 5-n-pentadecylresorcinol in the peel extracts. The fruit peel of the varieties ‘Kensington Pride’ and ‘Keitt’ were observed to have the highest levels of both 5-n-heptadecenylresorcinol (107.3–123.7 and 49.9–61.4 μg/g FW, respectively) and 5-n-pentadecylresorcinol (6.32–7.99 and 3.30–6.05 μg/g FW, respectively), and the fruits of the two varieties were found to have some resistance to postharvest anthracnose. The varieties ‘Kent’, ‘R2E2’, ‘Nam Doc Mai’, ‘Calypso’ and ‘Honey Gold’ contained much lower concentrations of resorcinols in their peel and three of these varieties were found to be more susceptible to anthracnose. Concentrations of 5-n-heptadecenylresorcinol were significantly lower at the ‘sprung’ and ‘eating ripe’ stages of ripening compared to levels at harvest. Concentrations of 5-n-pentadecylresorcinol did not differ significantly across the three stages of ripening. The levels of these two resorcinols were found to be strongly inter-correlated (P<0.01, r²=0.71), with concentrations of 5-n-heptadecenylresorcinol being an average 18 times higher than those of 5-n-pentadecylresorcinol. At the ‘eating ripe’ stage, significant relationships were observed between the concentrations of each type of alk(en)ylresorcinol and anthracnose lesion areas following postharvest inoculation, P<0.001, r²= 0.69 for 5-n-pentadecylresorcinol, and P<0.001, r²= 0.44 for 5-n-heptadecenylresorcinol.