A comparison of fungicides for the control of raspberry spur blight

Effective control of raspberry spur blight (Didymella applanata) and increased crop yields in the following season were obtained in a plantation of cv. Mailing Jewel with a programme of four or five sprays commencing when the new canes first appeared. Treatments were applied at 14-day intervals and continued until c. 2 wk before harvest. Thiram (0.16% a.i), benomyl (0.025% a.i.), dichlofluanid (0.10% a.i.) and captan (0.10% a.i.) gave good control of the disease but as benomyl and dichlofluanid were also effective in controlling powdery mildew (Sphaero-theca macularis) and Botrytis cinerea on the berries these fungicides appear to be the most suitable.     

An assessment of some new treatments for the control of rotting of stored apples

Benomyl (0.025% a.i.) and thiabendazole (0.05 % a.i.) applied in July, August and September to apple trees cvs. Sunset and Cox's Orange Pippin gave slightly better control of Gloeosporium spp. rots in stored fruit than captan (0.1% a.i.) applied at similar intervals. On Cox's Orange Pippin, treatment with captan at 0.1 % a.i. in July and at 0.2% a.i. in August was as effective as three sprays at 0.1 % a.i. in July, August and September in controlling both Gloeosporium spp. and Nectria galligena rots. Benomyl applied in the spring and early summer to control apple scab on orchard trees reduced the incidence of Gloeosporium spp. and Monilia fructigena in stored fruit. Pre-harvest sprays of benomyl and captan gave good control of rotting caused by N. galligena but thiabendazole was ineffective. Post-harvest dips of thiabendazole controlled rotting by Gloeosporium spp. butnot byN. galligena.     

Evaluation of fungicides for the control of Verticillium wilt (V. dahliae) of strawberry

The treatment of soil or plants before planting, in September 1969, significantly reduced Verticillium wilt on strawberry in the following season. One application of benomyl or thiabendazole (both 0–5% a.i.) at 6728 l/ha to soil 24 h before planting, dusting roots with formulated benomyl powder (50% a.i.) at planting, or a combination of both benomyl dust + drench treatments were effective. However, although the double treatment gave the most disease control in 1970, plants from the soil-drench treatments gave the highest yields. Residual effects of the 1969 applications were still evident in 1971 from increased vigour, lack of wilt and high yield, especially with the benomyl treatments.     

Strains of Colletotrichum coffeanum, the causal agent of coffee berry disease, tolerant to benzimidazole compounds in Kenya

The detection of Colletotrichum coffeanum tolerant to methyl ester of benzimidazole 2-carbamic acid (carbendazim) and a related benzimidazole compound, cypendazole, followed increases in levels of coffee berry disease observed on Coffea arabica in experimental plots sprayed for 2 yr with these compounds. Sporulation by the pathogen on naturally infected berries removed from carbendazim-, cypendazole- or benomyl-sprayed plots was not checked by a further application of 0–05 % (a.i.) of any of the compounds. Nearly all the isolates from these berries were capable of some growth on agar media containing 1000 ppm (a.i.) of either carbendazim or cypendazole. However, only a few could tolerate 1000 ppm of benomyl and the inability of this compound to reduce sporulation on berries infected with tolerant strains was presumably due to its rapid conversion to carbendazim within the host tissue. Less than 1 ppm of carbendazim, cypendazole or benomyl was needed to give 50% inhibition of conidia of the normal strain. Against the most tolerant strains, however, the LD 50 was > 100 ppm of carbendazim and about 30 ppm of benomyl. Whether isolated from unsprayed or benzimidazole-sprayed plots, all isolates of Colletotrichum acutatum, a saprophytic cohabitant of lesions initiated on berries by C. coffeanum, showed the highest degree of tolerance to benzimidazole compounds. No tolerance of either fungus to the ‘conventional’ fungicide captafol was detected.     

Evaluation of fungicides for control of South American leaf blight of Hevea brasiliensis

Of 43 fungicides tested in vitro, 19 showed strong, seven moderate and 17 weak inhibition of germination of conidia and ascospores of Microcyclus ulei. The formation of lesions on Hevea brasiliensis leaf discs was also suppressed by the first category of fungicides as well as by the five adjuvants tested. Ascospores were not released when perithecia were treated with urea, thiabendazole or alcoholic mercury chloride at 10.00, 0.10, 1.00 g/1 respectively; other fungicides had no such inhibitory effect. In field trials, thiophanate methyl (0.07% a.i.) and benomyl (0.025% a.i.) were most effective in controlling leaf infection, followed by chlorothalonil (0.15% a.i.) and mancozeb (0.32% a.i.). Benomyl suppressed conidial sporulation, whereas one application of thiophanate methyl (0.14% a.i.) to perithecia inhibited ascospore release; half of this concentration applied to conidial lesions or pycnidia caused the perithecia formed subsequently to abort. Thiophanate methyl thus shows promise for SALB control and elimination and benomyl may be valuable as a supplement in later rounds of spraying to control conidial sporulation. After 6 days of showery rain (2 mm for 17 min per day), water collected from sprayed leaves still gave complete inhibition of spore germination. However, inhibition was markedly reduced after 6 days of heavy rain (over 8 mm for 24 min per day).     

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.     

Control of tomato grey mould on unheated crops using non- systemic fungicide sprays

High volume sprays of dichlofluanid (0.1 % a.i.) reduced total fruit numbers but gave better control of Botrytis cinerea infections of tomato stems, leaves and fruit than sprays at 0.05 or 0.025% a.i. Surface residues from the sprays at 0–1, 0.05 or 0.025% a.i. were respectively 5.4, 1.6, 0.7 μg/g fresh weight of ripe fruit at harvest. Tank-mixed zineb (0.12% a.i.) and captan (0.2% a.i.) were less effective and increasing the spray intervals from 1 wk to 2 and 3 wk reduced the fungitoxicity of captan and zineb more than that of dichlofluanid. Harvest residues on ripe fruit were 7.1, 2.8 or 2.4 μg/g when dichlofluanid (0.1 % a.i.) sprays were applied at 1, 2 and 3 wk intervals respectively. Good control of B. cinerea was achieved if the whole plant was sprayed initially with dichlofluanid as soon as the second truss was flowering and subsequent sprays were restricted to the upper section of stem including the four or five youngest trusses of buds, flowers and fruit. When used as a post-infection spray there was a period of c. 8 wk before dichlofluanid markedly reduced the incidence of grey mould. Tank-mixed zineb (0.12% a.i.) controlled Botrytis fruit spotting but not leaf and stem infections. Botrytis stem lesions extended more rapidly on zineb-sprayed plants than on unsprayed plants or on plants treated with captan or dichlofluanid.     

Formulation of Bacillus amyloliquefaciens B190 for Control of Lily Grey Mould (Botrytis elliptica)

Calcium hydroxide (0.1%) significantly increased the growth of Bacillus amyloliquefaciens B190, inhibited completely the germination of Botrytis elliptica, and decreased the disease severity caused by B. elliptica on lily. Spraying B. amyloliquefaciens B190 mixed with either 0.025% calcium hydroxide, 0.05% sodium carbonate or 0.025% ammonium nitrate decreased the grey mould disease on lily leaves. B. amyloliquefaciens B190 mixed with 0.025% calcium hydroxide and 0.05% sodium carbonate, or mixed with 0.025% calcium hydroxide and 0.025% ammonium nitrate controlled lily grey mould completely. When the concentration of tested adjuvants was below 0.1% (v/v), adhesive adjuvant, i.e. carboxymethyl cellulose and spreader, i.e. Tween 80 were equally effective to assist B. amyloliquefaciens B190 to control lily grey mould. Calcium hydroxide (0.025%) and 0.05% sodium carbonate mixed with 0.1% Tween 80 significantly controlled lily grey mould. B. amyloliquefaciens B190 mixed with 0.025% calcium hydroxide and 0.05% sodium carbonate, and these two chemicals plus or without 0.1% Tween 80 and 0.05% mineral oil (i.e. emulsion and wettable powder, respectively) was consistently able to control grey mould on lily as well as 100 p.p.m. flusilazole in greenhouse and field trials, respectively.     

Fungicide programmes for the control of spur blight, powdery mildew and grey mould on raspberry

Five sprays of dichlofluanid (0–1% a. i.) reduced spur blight (Didymella applanata) on canes and powdery mildew (Sphaerotheca macularis) on fruit more than five sprays of captan (0–1% a. i.). Omission of the first three applications resulted in little increase in disease but when the fourth (full bloom) application also was omitted the incidence of disease was comparable with that on untreated plants. The final (fruitlet stage) application did not further reduce disease incidence. Five sprays of dichlofluanid reduced grey mould (Botrytis cinerea) on stored fruit more than five sprays of captan. There was an increase in grey mould with progressive reductions in the number of sprays. Incidence on canes was slight and was unaffected by treatments. A programme of five dichlofluanid sprays applied at 14-day intervals until c. 2 wk before harvest and supplemented by a single early full bloom spray of either dinocap (0–025% a. i.), binapacryl (0–05% a. i.), triforine (0–025% a. i.), benomyl (0–025% a. i.) or replaced by benomyl (0–025% a. i.) all halved both the number of fruits infected by powdery mildew and the number of spur blight lesions on canes, compared with unsprayed controls. Six applications of any of the following fungicides at 7-day intervals from 23 May until 29 June 1977 reduced powdery mildew incidence on fruit, the last fungicide being particularly effective: dinocap (0–0125%), dichlofluanid (0–075%), binapacryl (0–025%), triforine (0–0125%), bupirimate (0–0075%), ditalimfos (0–01875%) and fenarimol (0–0036%). Only triforine and bupirimate reduced the incidence of mildew on shoots. Dichlofluanid, binapacryl, triforine and fenarimol all reduced the amount of spur blight on canes. The largest fruit occurred on plants sprayed with bupirimate, ditalimfos and fenarimol, and late ripening was associated with triforine treatments.     

The effect of benomyl on the infection of tomatoes by Fusarium oxysporum f.sp. lycopersici and Botrytis cinerea

In glasshouse experiments at Auchincruive, drench applications of benomyl (100 or 142 mg per plant) to the soil surface around the stem bases of pot-grown tomato plants before inoculation with Fusarium oxysporum f.sp. lycopersici reduced the penetration of the fungus up the stems and/or decreased the development of vascular discoloration and associated severity of wilting. Similar drenches applied after establishment of the fungus in the stems either halted or considerably retarded the growth of the pathogen up the vessels. This again was reflected in reduced vascular discoloration and wilt symptoms. In experiments with benomyl over 2 years at a commercial holding in Argyll, the application of soil drenches (at the rates above) shortly after planting out and again 5 weeks later, coupled with a programme of stem and foliar sprays (at 0–05 % a.i.) during the summer, reduced the development of stem lesions caused chiefly by Botrytis cinerea and increased the general survival of plants more than did drench or spray treatments alone. There were indications that ‘ghost spotting’ of the fruit, particularly where spray applications were made, was also slightly reduced, but the magnitude of the effect was not consistent.     

Benomyl tolerance in isolates of Botrytis cinerea from tomato plants

Three hundred and forty-nine isolates of Botrytis cinerea were collected from tomato crops on forty-one nurseries and 173 (40/6 %) were found to be tolerant to benomyl. There was no obvious association between disease incidence and the occurrence of tolerance. In a fungicide comparison experiment on tomatoes in 1973, twenty of the sixty-four (31 %) isolates examined were benomyl tolerant, the majority of these were from benomyl sprayed plants. In 1974 in a similar experiment, 384 of the 394 (97-5 %) isolates examined were tolerant. Tolerance was monitored in two tomato experiments in relation to a spray programme in which benomyl and dichlofluanid were used in various combinations. There was no marked effect of the spray programmes on the incidence of tolerance on either site. In the experiments B. cinerea was controlled and significant increases in yield were obtained with benomyl in 1973 but not in 1974. This difference is attributed to the change in the pathogen population with a large increase in the incidence of tolerance on the experimental site in 1974.     

Effect of Four Fungicides on Barley Net Blotch Caused by Drechslera teres

The effect of four fungicides (benomyl, carbendazim, triadimefon and sulp hur), used in intensive barley cropping on the epidemiology of Drechslera teres f. maculata and f. teres, was investigated under a controlled environment. Two fungicides (benomyl and carbendazim) increased disease development, especially at the recommended field rate, sulphur had the same effect at lower concentrations and triadimefon promoted net blotch caused by D. teres f. teres. At the recommended field rate, carbendazim enhanced sporulation in the two pathogen forms, whereas benomyl and sulphur enhanced 14 sporulation only on the maculata form. The results showed that, under controlled conditions, most of the fungicides promotednet blotch development and that sporulation increased either as a result of the pathogen form or of the concentration of the active ingredient.     

Studies on the fungicidal control of stem lesions caused by Botrytis cinerea on glasshouse tomatoes

In glasshouse pot experiments, uptake of benomyl, thiophanate-methyl and carbendazim from equivalent soil applications (in the range 0–003– 0–035 %^a-i- ^atarateof ²&4 ml/plant) gave equal levels of control of Botrytis lesions developing from inoculations of freshly exposed leaf scars on tomato stems. Spray applications of benomyl to exposed leaf scars controlled infection at concentrations down to 0025 % a.i. The effect of lower concentrations of the stem spray could be markedly enhanced either by the addition of a mineral oil (2 % Actipron) or by a prior soil application of benomyl at a low rate which on its own had little effect on lesion development. Protectant spray applications of glycophene and vinclozolin gave levels of control quite comparable to that of benomyl at equivalent concentrations. Evidence was obtained that the lesions formed at the artificially-inoculated leaf scars at the top of the stems of young pot-grown tomato plants were larger than those lower down. In spite of this, the level of disease control with soil applications of fungicides containing or generating carbendazim (MBC) was greater at the top than at the bottom, probably because of the normal migration of the fungicides and their accumulation at the extremities of the plant. In an observation trial in a commercial crop of tomatoes, benomyl applied either as five soil drenches at approximately monthly intervals, or as two drenches followed by five sprays at three-weekly intervals, or as five sprays alone gave marked reductions in plant loss and number of Botrytis stem lesions in both cvs Eurocross BB and Cudlow Cross. Those stem lesions which did develop, however, were generally as large as those on untreated control plants. Five sprays of dichlofiuanid gave similar levels of disease control. All the treatments gave apparently higher yields (statistically untested) in Eurocross BB, but less consistent responses were recorded in Cudlow Cross.     

The incidence of benomyl tolerance in Verticillium fungicola, Mycogone perniciosa and Hypomyces rosellus in mushroom crops

Of the 229 isolates of Verticillium fungicola examined 63 % were found to show some benomyl tolerance and 53% were very tolerant having EDg, values in excess of 50 ppm. There was a tendency for the tolerant isolates to have a slower growth rate than the sensitive ones on unamended potato dextrose agar (PDA) and forty-five isolates (19 %) showed growth stimulation at 5 ppm benomyl. No major differences were found in ten isolates of V. fungicola tested on benomyl, thiabendazole and thiophanate methyl agars or of twelve isolates compared on benomyl and carbendazim hydrochloride agars. Tolerant isolates of V. fungicola and higher levels of crop loss were linked in the east and north of the country but not in the south-east. Tolerance was not found in sixty-six isolates of Mycogone perniciosa or twenty-four of Hypomyces rosellus. Benomyl was used on 89 % of the farms in the survey either applied to the casing (34%) or as a spray (55 %) or both (10%).     

Some factors affecting the control of Rhizoctonia solani by systemic and non-systemic fungicides

In laboratory tests, Rhizoctonia solani grew best on agar at 30 ^oC and pH 5-5. Mycelial growth was strongly inhibited by benomyl, chloroneb and quintozene, less so by thiophanate-methyl. The optimum temperature for inhibition was 25 ^oC for quintozene; the other three fungicides gave greatest inhibition at the lowest temperature tested (20 ^oC). Benomyl and thiophanate-methyl were most inhibitory at pH 7–8, chloroneb and quintozene at pH 5–6. In pot trials using mung bean, long melon, egg-plant, common pea and sugar beet, R. solani caused maximum disease at 20 ^oC and in wet and alkaline soils. As seed treatments, benomyl and thiophanate-methyl gave optimum control at 20 ^oC and pH 7-6; chloroneb and quintozene were most effective at 30 ^oC and pH 5-4. All four fungicides gave maximum control on plants growing in wet sandy loam. Comparisons of host effects showed that, on all the four hosts tested, thiophanate-methyl wettable powder at 0.25% (0.175% a.i.) gave 90% control, chloroneb w.p. at 0.3% (0.195% a-i-) gave 80% control on mung bean and sugar beet, benomyl w.p. at 0.3% (0.15% a.i.) was satisfactory on mung bean, egg-plant and sugar beet but not on long melon, quintozene w.p. at 0.3 % (0.225 % a-i-) gave effective control on sugar beet only. The senior author is grateful to the Council of Scientific and Industrial Research, New Delhi, India, for the award of a Research Fellowship for undertaking these studies. Thanks are due to Dr S. D. Gupta and Mr S. L. Verma for determining the soil characteristics.     

Characterizing the production of a wild-type and benomyl-resistant Fusarium lateritium for biocontrol of Eutypa lata on grapevine

Benomyl-resistant (BR) and wild-type (WT) strains of Fusarium lateritium were examined for their tolerance to benomyl on potato dextrose agar (PDA) containing benomyl and control of the Eutypa lata in grapevine bioassays. The WT strain grew on PDA containing 1 μg/ml benomyl at 13, 26 and 29°C. The BR strain grew on PDA containing 10 μg/ml benomyl at 4°C, on PDA containing 100 μg/ml benomyl at 29°C, and on PDA containing 1000 μg/ml benomyl at 13 and 26°C. The BR strain was also able to colonize grapevine segments and control E. lata in the presence of 1000 μg/ml benomyl. Both strains were amenable to production via liquid fermentation and both achieved 100% control of E. lata in grapevine bioassays. Neither the duration of fermentation nor incubation temperature during grapevine bioassays influenced the efficacy of either strain against E. lata. The results suggest that application of BR F. lateritium alone or in combination with benomyl may provide good control of E. lata. Journal of Industrial Microbiology & Biotechnology (2001) 26, 151–155. Received 22 December 1999/ Accepted in revised form 20 October 2000     

Comparison of fungicides for the control of Rhizoctonia solani causing datnping-off of mung bean (Phaseohis aureus)

Of 41 fungicides tested in the laboratory, copper carbonate, copper sulphate, mercuric chloride, Agrosan GN, quintozene, kasugamycin, carboxin, pyracar-bolid, carbendazim, chloroneb, benomyl, Ohric, RH 893 (2-n-octyl-4-isothiazole-3-one) and Terrazole were most inhibitory to the mycelial growth of Rhizoctonia solani on Czapek's agar plates and had EC₅₀ values of less than 1 μg a.i./ml, while copper oxychloride, Udonkor, zineb, ziram, F 319 (3-hydroxy-5-methyl isoxazole) and anilazine were much less toxic, ziram being least inhibitory with an EC₅₀ of 214 μg a.i./ml. Of 17 fungicides tested in the greenhouse as seed treatments, thiabendazole, carbendazim, benomyl, thiophanate-methyl, dichlozoline and Ohric gave 80–90% control of damping-off of mung bean seedlings. A single soil drench with thiophanate-methyl and two drenches with benomyl gave about 90% disease control, More seedlings with R. solani infection survived when thiophanate-methyl was used as a post-inoculation soil drench than when benomyl or chloroneb were used.     

Fungitoxic and phytotoxic effects of fungicides controlling powdery mildew on apple

Benomyl, pyrazophos (HOE 2873), triarimol, triforine and the non-systemic fungicide diethyl phthalimidophosphonothionate (Dowco 199) were sprayed at c. 200 gal/acre (2250 1/ha) at 14-day intervals from pink bud (late April/early May) on seven apple cultivars including Cox's Orange Pippin, Golden Delicious and Jonathan. Compared with binapacryl or dino-cap (and with elemental sulphur on the sulphur-tolerant cv. Golden Delicious), these compounds were more phytotoxic without substantially or consistently improving the control of Podosphaera leucotricha; fruit russet was increased and the crop and fruit size of some cultivars were reduced in some trials. In 1969 the inclusion of bis(dimethylthiocarbamoylthio)-methylarsine (44 ppm) as Urbacid^(R) in the sprays reduced russeting by benomyl and Dowco 199 so that these fungicides became as safe as captan on several cultivars; Dowco 199 was also safened by captan (500 ppm). Urbacid^(R) (88 ppm a.i.) safened benomyl and triarimol on fewer cultivars in 1970 when russet was less severe. The addition of Urbacid^(R) did not prevent yield losses caused by sprays in either year. The crop is most sensitive to spray damage from pink bud until late June. This is a crucial period for the control of mildew, and unless new fungicides are less phytotoxic, palliatives may become necessary adjuvants.     

Use of acephate, benomyl and alginate encapsulation for eliminating culture mites and fungal contamination from in vitro cultures of hardy hibiscus (Hibiscus moscheutos L.)

Summary Shoot cultures of three Hibiscus moscheutos (L.) cultivars were infested with micro-arthropods (mites). Nodal segments (1 cm long) were excised from these cultures and encapsulated in a sodium alginate gelled Driver and Kuniyuki Walnut DKW medium containing 10, 50, or 100 mg l⁻¹ acephate (insecticide) or 10 mg l⁻¹ acephate plus 0, 50, or 100 mg l⁻¹ benomyl (fungicide), then placed in refrigerated (5°C) darkness for 4 wk. Acephate was tested alone if visible fungus was not touching the shoot masses and benomyl was tested if fungus was in contact with the proliferating shoots. Cold-stored encapsulated nodes were then placed on DKW medium with 0.1 μM thidiazuron for 6 wk for subsequent shoot development. The presence of acephate in the encapsulation medium completely eradicated or killed the mites, with 38–69% of cultures fungus-free; 12% of the fungal-contaminated nodes encapsulated with 100 mg l⁻¹ benomyl were fungus-free.     

The effect of carbendazim-generating fungicides with and without a mineral oil additive on tomato stem lesions caused by carbendazim-sensitive and tolerant strains of Botrytis cinerea

Isolates of Botrytis cinerea were obtained from tomatoes in several localities in the West Scotland. Some isolates grew on agar containing 100 mg/1 benomyl (carbendazim-tolerant), while others did not (carbendazim-sensitive). Pot-grown tomato plants treated with benomyl and other carbendazim-generating fungicides, applied either as sprays or soil drenches, were inoculated on the leaf scars with some of these isolates. On treated plants the carbendazim-tolerant isolates formed lesions which were about as large as those on untreated plants. Sensitive isolates formed much smaller lesions on treated plants. There was evidence that the increase in lesion size during the period 7–14 days after inoculation with a carbendazim-sensitive isolate was less on plants sprayed with benomyl or carbendazim with added mineral oil (2% Actipron) than on plants to which the fungicides alone had been applied. No such effect was recorded with thio-phanate-methyl. There was also an indication that the addition of Actipron to a benomyl spray improved the effect of the fungicide against two tolerant isolates, though there was no effect on the relative increase in lesion size during the second week after inoculation. In two tests the addition of 2% and 4% Actipron to benomyl soil drenches did not improve the level of leaf scar lesion control.