Decay control and fungicide residues in citrus fruits seal-packed in a high-density polyethylene film

The effects of a new packaging method of sealing individual fruits in film of highdensity polyethylene (HDPE), on decay control and the residue levels of various fungicides applied to the fruit, were investigated with four different citrus cultivars. HDPE seal-packaging by itself reduced the decay of Marsh grapefruit but slightly enhanced the decay of Valencia orange fruit in comparison with conventionally handled fruit. Seal-packaging of individual fruit resulted in much less decay than sealing a whole carton of fruit together. The fungicides imazalil, sec-butylamine, 2-phenylphenol, benomyl and thiabendazole markedly reduced the decay of sealed fruit in all cultivars of citrus fruits tested. Residue levels in treated fruit were below the tolerances permitted. The new method of packaging had no effect on the residue levels of benomyl, 2-phenyl-phenol and thiabendazole in the fruit; neither did it affect the extent of absorption of these fungicides into the fruit. Only the volatile fungicide sec-butylamine was found at a higher level (73% higher in the packaged fruit compared with conventionally treated fruit).     

两株橡胶多主棒孢霉对12种杀菌剂原药的敏感性

采用菌落生长速率法测定了两株橡胶多主棒孢霉［Corynespora cassiicola (Berk &; Curt.) Wei］对12种杀菌剂原药的敏感性。结果表明：两个菌株对杀菌剂的敏感性存在一定的差异;供试药剂中多菌灵、甲基硫菌灵、咪鲜胺和抑霉唑的EC50均小于5 μg/mL,抑菌活性高;在加入SHAM后嘧菌酯的抑菌活性也很高,与SHAM具有协同增效作用;其他供试杀菌剂均有较好的抑菌作用,依次为戊唑醇、腈菌唑、异菌脲、溴菌腈、代森锰锌、百菌清和三唑酮。     

Determination and persistence of imazalil in post-harvest-treated apples during cold storage

A method to determine imazalil (allyl 1 -(2, 4-dichlorophenyl)-2-imidazol- 1-ylethyl ether) on apples using high performance liquid chromatography is described. After harvest, fruits were immersed in an aqueous suspension (1 g litre-1) and cold stored (0-2°C) at 85-90% r.h. Samples were taken monthly and imazalil was determined in the peel, outer pulp, inner pulp and on whole fruit. Residues were 3.8-4.9 mg imazalil kg-1 and decreased during storage. Most imazalil was found on the peel and amounts in the pulp decreased toward the core.     

The occurrence of thiabendazole-resistant isolates of Polyscytalum pustulans and Helminthosporium solani on seed potato tubers in relation to fungicide treatment and storage

Tubers infected with thiabendazole-sensitive isolates of Polyscytalum pustulans and Helminthosporium solani were treated annually for 4 years with benomyl, thiabendazole or a formulated mixture of thiabendazole and imazalil, and grown at three farms in Scotland. The proportion of thiabendazole-resistant isolates of H. solani increased, and isolates producing black colonies became more common with successive annual applications of thiabendazole or benomyl. Silver scurf was not reduced after three annual applications. When these fungicides were applied once to untreated seed the incidence of resistant isolates of H. solani was much less in 1988 than in 1991 when tubers had been grown on farms for 3 years from untreated seed.
The proportion of resistant isolates of P. pustulans increased with the number of successive applications of thiabendazole or benomyl but at differing rates on each farm. At one farm, skin spot was not reduced by three annual applications of these fungicides whereas at the other farms it was reduced by 90–100% by four annual applications.
A smaller proportion of resistant isolates of P. pustulans and H. solani was obtained after applying the mixture of thiabendazole and imazalil than after benomyl or thiabendazole alone. Their occurrence was not related to the number of fungicide applications. The mixture also reduced both diseases by more than 75% over the 4 years.
At one farm where resistant isolates of H. solani were present, tubers were infected when stored on trays but not when stored in bags.     

Survey of Fungicide Sensitivity in Colletotrichum gloeosporioides from Different Avocado and Mango Production Areas in South Africa

Pre-harvest fungicidal treatments aimed at reducing inoculum levels in the field include copper oxychloride and benomyl. Pre-harvest applications of benomyl are currently restricted if used on fruit destined for certain export markets. Isolates of Colletotrichum gloeosporioides collected during a three-year market survey were used to determine the incidence of resistance to benomyl, thiabendazole and prochloraz using an in vitro assay. A total of 17.7% of all isolates tested were resistant to benomyl, of which 8.5% were highly and 9.2% moderately resistant. Isolates from certain production areas were less sensitive to benomyl and thiabendazole, and mango isolates were generally more sensitive than avocado isolates. No isolates were resistant to thiabendazole or prochloraz.     

Pre- and post-harvest control of mango anthracnose in the Philippines

Two field trials were conducted in the Philippines in successive years to compare the effectiveness of different pre- and post-harvest treatments on the development of anthracnose on mango fruits caused by Colletoirichum gloeosporioides. In one experiment, the pre-harvest application of benomyl (250 mg/l a.i.) significantly reduced the number of conidia sampled in tree canopies compared with control trees (no fungicide) and was associated with a significant reduction in the post-harvest development of anthracnose on fruits. A hot-benomyl dip (850 mg/l a.i. at 52 55 C for 10 min) completely eradicated anthracnose on fruit treated on the day of harvest. In a second experiment, pre-harvest applications of prochloraz (500 mg/l a.i.) either within a pre-planned spray schedule or applied strategically (when 18 h or more continual leaf wetness was recorded by a sensor placed within a tree canopy) gave the best control of anthracnose on fruits. A hot-benomyl dip was again the most effective post-harvest treatment for fruit treated on the day of harvest and on the day after. There was no significant difference, however, between hot-benomyl dips or prochloraz dips (500 mg/l a.i. for 10 min) at ambient temperatures when fruit were treated on the third day after harvest. The implications of these results for the production and treatment of Carabao mangoes in the Philippines are discussed.     

The effect of temperature before or after inoculation with Phoma exigua var. foveata on the development of gangrene in potato tubers

Potato tubers of five cultivais were incubated at five temperatures between 2 and 20°C for 1 month and then inoculated with Phoma exigua var. foveata and stored at 5°C. Larger rots usually developed on tubers previously incubated at the higher temperatures but cultivar differences were greatest where tubers had been incubated at 2°C. In another experiment, rot size was related to the duration of incubation at 20°C before inoculation.
In a series of experiments, tubers were stored at different temperatures after inoculation; other factors (e.g. wound type or r.h.) were also investigated in some of these. Combining the results of all experiments a linear decrease of % wounds infected (logit transformation) with storage temperature was demonstrated. The size of rots was not simply related to temperature, but tended to increase over the range 2–10°C and then stabilized or declined at higher temperatures. Relative humidity treatments of 75% v. 95% did not consistently affect either the incidence of rotting or rot size. The other factors investigated did not usually interact significantly with temperature.
The relevance of the results for resistance testing is discussed and a simple equation relating disease incidence to inoculum levels, type of damage and temperature is proposed.     

Fungitoxicity of plant growth regulators (PGRs) and PGR/fungicide mixtures in soak treatments to Septoria apiicola pycnidiospores

Mixtures of the plant growth regulators (PGRs) gibberellins A4 and A7 (GA 4/7) and ethephon (2-chloroethylphosphonic acid), applied as soak treatments at 20° C for 24 h, were toxic to pycnidiospores of Septoria apiicola on agar, apparently as a result of low pH of their solutions. Ultraviolet spectroscopy showed that the aqueous solubility of the fungicides benomyl and carbendazim increased significantly when buffered at low pH or mixed with aqueous solutions of GA 4/7 and ethephon. This resulted in greater quantities of ¹⁴C-labelled fungicides entering celery seeds imbibed in PGR/fungicide mixtures in comparison with fungicides alone.
A 24-h seed soak at 20° C in a mixture of aqueous benomyl, GA 4/7 and ethephon eliminated S. apiicola in infected celery seeds. A thiram soak was also effective but PGR mixtures alone did not completely eliminate the pathogen.     

A mini-bag technique for evaluation of fungicide effects on Trichoderma spp in mushroom compost

An in vivo technique was developed to observe colonisation of mushroom compost by Trichoderma spp. Isolates of T. harzianum (Th2), T. harzianum (Th1), T. koningii (Tk) and T. viride (Tv) were artificially introduced into compost using a mini-bag system. Wheat grains, colonised by Trichoderma spp, were placed centrally on a layer of compost at the bottom of 1-litre polythene bags which were then filled with 350 g of spawned or un-spawned compost, and partially sealed. After 14 and 21 days incubation at 27 degrees C, the bags were assessed for recovery of Trichoderma from middle and top zones using a needle stab re-isolation technique and a visual colonisation scoring system. Visible green mould contamination, similar to that observed in practice, developed within 21 days. The visual colonisation scoring was reliably related to the re-isolation success. In this evaluation, Trichoderma spp showed considerable differences in their relative abilities to colonise spawned and un-spawned compost, with Th2 isolates being consistently superior to the other isolates of Th1, Tk and Tv in colonising spawned compost. This technique was employed to evaluate the effects of fungicides on the colonisation of mushroom compost by three Trichoderma spp: Th2, Th1 and Tk, using 1-litre and 5-litre mini-bag systems. Aqueous suspensions of benomyl, carbendazim, thiabendazole, prochloraz and prochloraz+carbendazim incorporated into the compost at 50 mg litre(-1), or applied to spawn at 50 mg kg(-1), reduced the colonisation by Trichoderma spp. Prochloraz and prochloraz+carbendazim were superior to benomyl, carbendazim or thiabendazole in reducing compost colonisation by Th2, Th1 and Tk, with Th2 being the most persistent type, capable of colonising treated compost in the presence of all five fungicides. The prochloraz+carbendazim mixture, not normally used in mushroom production, was equal to or better than prochloraz alone. The incidence of green mould colonisation by Th2 was as extensive in the 5-litre compost bags as in the 1-litre bags, but colonisation by Th1 and Tk was more apparent in the 5-litre bags. The in vivo mini-bag evaluations using wheat grain Trichoderma inoculum and needle stab re-isolation procedures proved an efficient method for studying colonisation and screening for effectiveness of fungicides applied to mushroom compost or spawn.     

Control of Glomerella cingulata f.sp. camelliae with fungicides

A critical test of fungicidal activity against the wound pathogen Glomerella cingulata f.sp. camelliae on camellias involved the application of a conidial suspension to scratches on detached leaves, treated with fungicide 24 h previously. In this test, prochloraz at 250–500 μg/ml a.i. in both EC and manganese WP formulations was highly effective, inhibiting leaf rotting by 90–100% compared with 55% or less in some tests with benomyl, chlorothalonil and captafol at 500–1000 μg/ml and captan at 1200 μg/ml. Prochloraz gave similar protection to leaves when applied to whole plants. Protection was less, especially on older leaves, when wounding and inoculating were delayed by 7 or more days after treatment. Prochloraz did not prevent all infection through comparatively large wounds, e.g. leaf scars, made on stems 24 h after treatment.
Poor control of the disease in a nursery was not due to resistance of the pathogen to benomyl; in vitro tests failed to detect full resistance at this time. Under nursery conditions a statutory policy of destroying infected plants and spraying the remainder with prochloraz or prochloraz manganese (both at 500 μg/ml), alternating with benomyl (500 μg/ml) on a weekly basis apparently prevented spread of the disease to healthy plants.     

Integrated control of apple postharvest pathogens and survival of biocontrol yeasts in semi-commercial conditions

The biocontrol yeast isolates Rhodotorula glutinis LS11, Cryptococcus laurentii LS28 and Aureobasidium pullulans LS30 were tested against Botrytis cinerea and Penicillium expansum on apples artificially inoculated and stored at 3 and 20 °C. Isolates LS28 and LS30 were most effective, consistently resulting in high reductions of fungal decay, while isolate LS11 was effective only on apples stored at 3 °C. The yeasts showed good in vitro resistance to dicarboximides and copper fungicides, while they were inhibited by triazoles. Isolate LS11, in contrast to LS28 and LS30, was also inhibited by benzimidazoles. The yeasts were tested on naturally-infected apples in semi-commercial conditions for 2 years. They were applied twice: soon after harvesting and 20 days later, at the beginning of the cold storage. The antagonists significantly reduced fungal decay when combined with a low dosage of benomyl showing an activity comparable to that exerted by the fungicide alone at full dosage. Periodical monitoring of the epiphytic biocontrol yeast populations in both the field and cold room showed a good rate of survival of the antagonists on the skin of treated apples. Specific fingerprints relying on amplified restriction length polymorphism (AFLP) were used to integrate the morphology-based monitoring of the yeasts.     

Sensitivity of Lasiodiplodia theobromae from Brazilian papaya orchards to MBC and DMI fungicides

Stem rot caused by Lasiodiplodia theobromae is an important postharvest disease of papaya in Brazil, responsible for reducing the quality and quantity of fruits. Fungicide use is one of the main disease management measures. However, there are no estimates available of pathogen sensitivity to commonly employed fungicides. Therefore, the EC₅₀ from 120 isolates of L. theobromae from northeastern Brazil, representative of six populations of the pathogen, was estimated in vitro for fungicides of the methyl benzimidazole carbamates—MBC (benomyl and thiabendazole) and demethylation-inhibiting—DMI (imazalil, prochloraz, tebuconazole) groups. Mycelial growth on fungicide-free media and virulence on papaya fruits of the MBC-sensitive and non-sensitive isolates were compared. For MBCs, 8.4% of isolates were non-sensitive to fungicides. For the remaining 91.6%, the mean EC₅₀ ranged from 0.002 to 0.13 μg ml⁻¹ and 0.36 to 1.27 μg ml⁻¹ for benomyl and thiabendazole, respectively. For DMIs, the mean EC₅₀ range for imazalil was 0.001 to 2.27 μg ml⁻¹, 0.04 to 1.75 μg ml⁻¹ for prochloraz, and 0.14 to 4.05 μg ml⁻¹ for tebuconazole. The EC₅₀ values of non-sensitive isolates were significantly (P≤0.05) higher those for the sensitive isolates for each of the DMI fungicides. Differences (P≤0.05) were found in the levels of sensitivity to DMI fungicides among the isolate populations associated with orchards. The populations from two orchards were less sensitive to DMIs. No solid evidence was found for fitness costs relating to MBC non-sensitive isolates because mycelial growth in fungicide-free media and virulence on papaya fruits were similar to those of sensitive isolates.     

Effect of some ergosterol biosynthesis inhibiting fungicides on sterols and cytochrome P-450 from the Japanese quail Coturnix coturnix

Nine fungicides that inhibit ergosterol biosynthesis (diclobutrazol, fenarimol, fenpropimorph, imazalil, nuarimol, prochloraz, propiconazole, triadimefon, triadimenol) and one plant growth regulator (ancymidol) were administered to Japanese quails (Coturnix coturnix). Most of these compounds had a moderate or no effect, but prochloraz, imazalil and, to a lesser extent, propiconazole were shown to produce a dramatic increase in liver weight and cytochrome P-450 level. These three compounds were also found to be potent in-vitro inhibitors of 7-ethoxycoumarin O-de-ethylase and aniline hydroxylase, thus resulting in a biphasic effect on drug-metabolising enzymes. With these three compounds, and some others, an accumulation of lanosterol in liver was also observed, suggesting an inhibition of sterol synthesis.     

Sensitivity of Drechslera teres and Septoria nodorum to sterol-biosynthesis inhibitors

The sensitivity of 282 isolates ofSeptoria nodorum was tested on prochloraz, propiconazole and guazatine, and of 129 isolates ofDrechslera teres on prochloraz, propiconazole, imazalil and triadimefon. There was a great variation in sensitivity between isolates particularly at relatively low concentrations of the fungicides. However, none of the isolates was considered resistant towards the sterol biosynthesis inhibitors tested. Some isolates ofS. nodorum grew on concentrations of guazatine that may present difficulties in controlling them under practical conditions.Samenvatting Isolaten vanSeptoria nodorum (n=282) werden getoetst op gevoeligheid voor prochloraz, propiconazool en guazatine en vanDrechslera teres (n=129) voor prochloraz, propiconazool, imazalil en triadimefon. Er waren grote verschillen in de gevoeligheid van de isolaten, in het bijzonder bij lage concentraties van de fungiciden. Geen van de isolaten kan echter als resistent tegen sterolbiosynthese-remmers worden opgevat. Het feit, dat sommige van de isolaten vanS. nodorum zich ontwikkelden op media die hoge concentraties guazatine bevatten, kan echter duiden op moeilijkheden bij de bestrijding onder praktische omstandigheden.     

赣南脐橙绿霉病菌对常用杀菌剂抗性监测

 本文研究了来自赣南7个县的柑橘绿霉病菌(Penicillium digitatum)种群对该地区常用杀菌剂抑霉唑、咪鲜胺、甲基硫菌灵和百可得的抗性频率、抗性水平和对抑霉唑的抗性分子机制。结果表明:病菌对抑霉唑和咪鲜胺存在基本一致的抗性;2011和2012年病菌种群对抑霉唑和咪鲜胺的抗性频率分别为82%和90%,平均抗性倍数为51.5倍,抗性分子机制均属于IMZ-R3,即CYP51B基因启动子区发生199 bp插入的突变;病菌种群对甲基硫菌灵的抗性频率分别为82%和91%;病菌种群对百可得均表现敏感。本研究为采后柑橘病害防治药剂选择提供了科学的依据。     

Fungi in stored barley treated with systemic fungicides

Six fungicides (benomyl, carbendazim, fuberidazole, thiabendazole, thiophanate and thiophanate-methyl) were applied as dusts to barley in concentrations of 100, 1000 and 10 000 μg g^?1 and the barley then stored at 20°C and 90% relative humidity for 60, 105 and 150 days, respectively. Fungal development during storage was assessed by counting the visible patches of developing mould and by dilution plating. None of the fungicides completely prevented fungi developing but for the period up to 60 days, all provided a degree of control that was generally greatest for the highest concentration of fungicide. Benomyl was the most effective of the fungicides but no clear pattern was established for the others. Of the fungi that developed, species of Aspergillus and Penicillium accounted for 94% of the total count.     

药剂对稻曲病菌的毒力测定及复配研究

为筛选防治稻曲病的有效单剂和复配组合,采用菌丝生长速率法,测定烯唑醇、腈菌唑、丙环唑、咪鲜胺、苯菌灵、多菌灵、戊唑醇、井冈霉素、松脂酸铜9种杀菌剂及互相复配后对稻曲病菌的毒力,并比较了不同复配组合的协同作用.结果表明:稻曲病菌对烯唑醇最敏感,EC5o为0.145 μg/mL;井冈霉素对稻曲病菌的毒力作用最弱,EC50为13.6 μg/mL.从252种不同比例复配的药剂中,筛选出12种增效配方,其中烯唑醇和咪鲜胺复配(1∶10),协同系数高达3.70,增效作用最大;烯唑醇和咪鲜胺(1∶10)对稻曲病菌的毒力作用最强,EC5o为0.06μg/mL,其次是烯唑醇和咪鲜胺(1∶20)与烯唑醇和腈菌唑(10∶1),EC50分别为0.10μ/mL和0.11μg/mL.田间试验结果也表明:烯唑醇与咪鲜胺(1∶10)复配,对稻曲病的平均防效为79.2％,高于其他常用药剂.     

铁皮石斛黑斑病菌室内药效试验

通过供试的18种药剂对铁皮石斛黑斑病菌体外抑制作用测试结果表明,除克菌特外,所有药剂对其孢子萌发都有显著的抑制作用,其中代森锰锌、易保、代森锌和炭疽福美可完全抑制孢子萌发,霉克特、扑海英、使百克、新太生、甲基托布津和世高对孢子萌发有较强烈的抑制作用。与对照比较,克菌特促进孢子萌发率高于对照23.34%,克菌特和庄园乐都能促进芽管生长。18种药剂对石斛黑斑病菌菌丝体的抑制作用测定结果显示,所有药剂对菌丝生长都有显著的抑制作用,其中使百克和世高对菌丝体抑制效果最好,抑菌率都达91.28%,其次是施佳乐、福星和扑海英。     

Effects of Sterol Biosynthesis Inhibitor Fungicides on Growth and Sterol Composition of Ustilago maydis,Botrytis cinerea and Pyrenophora teres

The effects of the sterol biosynthesis inhibitor (SBI) fungicides fenarimol, fenpropimorph, imazalil, prochloraz, propiconazole and triadimenol on growth and sterol composition of Ustilago maydis, Botrytis cinerea and Pyrenophora teres, grown from spores or sporidia in liquid culture, were determined. Growth of U. maydis was only slightly inhibited by SBI fungicides at concentrations which caused considerable changes in both sterol content and composition. Conversely, in B. cinerea and P. teres, growth was strongly inhibited under conditions where ergosterol was still the predominant sterol, suggesting that, in these two fungi, growth may be more sensitive to SBI fungicides than overall sterol production. Demethylase inhibitor fungicides behaved as a homogeneous group in their effects on growth and on sterol profiles of the three fungi studied.     

Control of blue mold (Penicillium expansum) by fludioxonil in apples (cv Empire) under controlled atmosphere and cold storage conditions

A reduced risk fungicide, fludioxonil, was tested for its efficacy against blue mold caused by thiabendazole-resistant and -sensitive Penicillium expansum (Link) Thom in apples under three storage conditions. In a co-treatment, fludioxonil and inoculum were applied together to test the protective activity of the fungicide on wounds that had been aged for 1 or 2 days. The fungicide was also tested for its curative activity in post-inoculation treatment on apples that had been inoculated for 1 or 2 days. Fludioxonil was very effective as co-treatment and as post-inoculation treatment. At a concentration of 300 mg litre(-1), fludioxonil gave complete control of post-harvest blue mold caused by the thiabendazole-resistant and -sensitive P expansum for 105 days in controlled atmosphere (CA) storage at 2 (+/-1) degrees C, for 42 days in common cold storage at 4 (+/-1) degrees C and also in a shelf-life study for 6 days at 20 (+/-1) degrees C. Comparison on the effect of fludioxonil in CA storage and common cold storage showed that higher concentrations of fungicide were needed in cold storage than in CA storage. Fludioxonil at a concentration of 450 mg litre(-1), gave 98 and 92% control of blue mold of apples in the simulated shelf-life studies after CA and common cold storages, respectively. Fludioxonil has a potential to be incorporated in the fungicide resistance management strategies for control of blue mold in apples stored for 105 days.