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 effect of the systemic fungicide benomyl on survival and reproduction of the bird cherry aphid (Rhopalosiphum padi)

Weight gain and intrinsic rate of population increase (r_m) of Rhopalosiphum padi were measured on wheat plants given soil drenches of benomyl at various concentrations. Reduced weight gain occurred with concentrations as low as 3.125 ppm. Mortality of aphids significantly exceeded control mortality at 25 ppm, and no aphids survived concentrations above 50 ppm. Development time was extended at 12.5 ppm and above. Reductions in fecundity and r_m became statistically significant by 25 ppm. Topical application of benomyl at 100 ppm or above increased aphid mortality, which reached 97% at 400 ppm. Weight gain of aphids was also reduced by topical application at 100 ppm. A factorial experiment showed absence of interaction between the effects on aphid weight of soil drench application to plants and topical application to aphids.     

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.     

Control of Verticillium wilt transmission in strawberry runners with systemic benzimidazole-type fungicides

Pre-planting root dips and soil drenches with benomyl, carbendazim (MBC), thiabendazole and thiophanate-methyl were used to reduce disease severity in mother plants. Transmission of the pathogen Verticillium dahliae through stolons and into young runners was prevented by two applications of benomyl or thiophanate-methyl at o-i% active ingredient applied at stolon appearance and 1 month later. Sufficient concentrations of fungistatic residues were detected in all plant tissues to suppress the internal spread of the pathogen.     

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.     

Experiments on soil drenching with fungicides against take-all in wheat

In short term pot experiments benomyl, iprodione and KWG 0599 applied as soil drenches in several types of soil significantly suppressed take-all symptoms from inoculum placed just below wheat seeds planted 1×5 cm deep, and in sand but not other soils when seeds were 5 cm deep. Benomyl was, however, effective against inoculum below seed planted 5 cm deep in a loam-sand mixture when the drench contained an alcohol ethoxylate surfactant. Computer simulations of fungicide distributions in the soils correlated well with disease control observations. In long term outdoor pot experiments two drenches with benomyl (without surfactant) controlled disease significantly for at least 3 months against inoculum placed 15 cm deep. The significance of these results for the practical control of take-all by fungicides is discussed.     

Systemic action of benomyl against late-wilt disease of maize.

Benomyl (methyl-I-(butyl carbamoyl)-2-benzimidazole carbamate) at 2.5 to 100 ppm completely inhibited the growth in vitro of Cephalosporium maydis Samra, Sabet & Hingorani, the causal fungus of late-wilt of maize. In pot experiments, late-wilt was controlled by applications equivalent to 10 ppm benomyl/unit wt dry soil at sowing but not by applications 30 days after sowing or by seed treatments (dusts and dips). A fungitoxic substance was detected in benomyl-treated soil, planted with maize, 120–150 days after treatment and for 150–180 days in unplanted soil. Sap expressed from maize grown in benomyl-treated soil was also fungitoxic, especially that from the roots and distal parts of the leaf blades. In the field, soil applications of benomyl to 10 kg/feddan (4200 m²) failed to control late-wilt. Tests indicated little fungitoxicity in the sap of maize plants 25 days after sowing.     

Benzoic acid induces tolerance to biotic stress caused by Phytophthora cinnamomi in Banksia attenuata

Banksia attenuata plants were treated with soil drenches or foliar sprays of benzoic acid (BZA) to determine induced resistance to Phytophthora cinnamomi. Stems of B. attenuata were inoculated with the pathogen 1 week after treatment with BZA. Resistance was estimated by measuring P. cinnamomi lesions on stems. Treatment with 0.10 mM, 0.25 mM or 0.50 mM BZA caused a reduction in lesion size with 0.50 mM BZA applied as a soil drench being the most effective treatment at suppressing the development of lesions. This is the first report of BZA induced host resistance in any plant species to any pathogen.     

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.     

Efficacy of Oxamyl Against Heterodera schachtii on Cabbage

The efficacy of oxamyl in controlling Heterodera schachtii on cabbage was determined by applying various contbinations of soil drenches at 6.7 kg (a.i.)/ha and foliar sprays at 0.04 kg (a.i.)/100 liters of water to cabbage seedlings. Pretransplant drenches provided some control of H. schachtii over a 13-week period. A single foliar spray of oxamyl 1 week before transplanting apparently prevented penetration of H. schachtii larvae; post-transplant sprays were relatively ineffective. A pretransplant or transplant drench combined with a foliar application 2 weeks after transplanting provided the most effective control. The effectiveness of drenches plus post-transplant sprays is probably due to the spray augmenting the action of the drench in inhibiting the development of larvae after penelration.     

Effect of some fungicides on the yield of grass swards

When benomyl, drazoxolon, thiabendazole or zineb were applied as soil drenches to established grassland drazoxolon reduced the incidence of rhizoplane fungi. Benomyl and thiabendazole significantly increased yield at one harvest but only benomyl had a significant effect on total yield. When benomyl was applied at monthly intervals from March to July significant increases in total yield were obtained with the June applications which also significantly increased yield at the first harvest in the following year. Repeated applications from March to July also had a significant residual effect on total yield. Yield increases were not significantly affected by increasing the benomyl level from 2.5 to 5.0 g/m².     

Application of Metarhizium anisopliae (Metsch.) Sor. conidia to control Otiorhynchus sulcatus (F.) (Coleoptera: Curculionidae) larvae on glasshouse pot plants

The efficacy of the entomogenous fungus Metarhizium anisopliae was assessed against vine weevil (Otiorhynchus sulcatus) larvae in the glasshouse. Prophylactic application of M. anisopliae conidia to begonia resulted in total larval control, but curative applications were less effective with only 65% control when conidial application was delayed until 8 weeks after egg infestation. Prophylactic applications also provided effective larval control on begonia plants which received multiple egg applications over a six week period. Larval mortality was monitored on cyclamen plants which had received a prophylactic drench of M. anisopliae conidia. The population was reduced by 78% within 5 weeks of egg application and control rose to 90% after 17 weeks, although the increase was not significant. Prophylactic conidial drenches were compared with a similar number of compost incorporated conidia on cyclamen, but there was no significant difference between the two spore application strategies. Application of M. anisopliae conidia to impatiens modules before potting-on resulted in over 89% larval control compared to over 97% control when a similar number of conidia were applied to the plants after potting. Larval control was further reduced to 79% when the module drenches were reduced to one quarter of the highest dose (5 × 10⁷ compared to 2 × 10⁸ conidia per module). The persistence of three M. anisopliae strains was examined over a 20 week period on impatiens. There was no overall decline in efficacy over this period, although there was variability in the performance of the different strains and it was suggested that this was linked to temperature. The results of these experiments suggest that M. anisopliae has considerable potential as a microbial control agent for O. sulcatus on glasshouse ornamentals.     

Some effects of benomyl and carbendazim on Aphis fabae and Acyrthosiphon pisum on field bean (Vicia faba)

Field bean plants were treated with benomyl in a glasshouse, then nymphs of Aphis fabae and Acyrthosiphon pisum were caged on the second pinnate leaf. Soil drenches at concentrations of 150 and 75 μg benomyl/ml or above increased mortality of A. fabae and A. pisum respectively; 250 μg a.i./ml increased mortality and decreased progeny production of alate A. fabae. The effect on mortality persisted for at least 16 days after treatment. Foliar sprays increased mortality at concentrations of 75 μg a.i./ml and above (A. fabae). Field populations of A. pisum were reduced when bean plants were drenched or sprayed at a concentration of 250 μg a.i./ml and A. fabae populations were reduced by drenches but not by foliar sprays. A commercial formulation of carbendazim (Bavistin) increased aphid mortality whereas the formulation medium did not. Under the experimental conditions, benomyl affected the distribution of both species on young bean plants but did not induce a repellent effect; aphids preferred untreated leaves. Mortality and preference tests, and a field experiment, indicated that A. pisum was affected more than A. fabae.     

Fusarium oxysporum f. sp. fatshederae, a new forma specialis causing wilt of x Fatskedera lizei

A Fusarium oxysporum sensu Snyder & Hansen was pathogenic in the vascular tissue and caused a severe wilt and dieback of ×Fatshedera lizei, Fatsia japonica and Hedera helix. The fungus appeared nonpathogenic on plants of 29 species in numerous genera. Benomyl soil drenches were effective in preventing infection. A new forma specialis, Fusarium oxysporum f. sp. fatshederae, f. sp. nov. is proposed for this pathogen.     

Field control of sore shin (Rhizoctonia solani) of tobacco with benomyl and benodanil*

Benomyl and benodanil, applied to tobacco seedlings before transplanting, reduced sore shin infection. Benodanil was the more effective, sometimes restricting damage to 5% of the surface area of the buried portion of stems, compared with 50–60% in untreated plants. The fungicides were applied either as a seedbed drench or a root-stem dip. The dip method used less fungicide and was generally more effective than the drench at equal concentration but was less practical. Benodanil was over three times as active as benomyl against Rhizoctonia solani in liquid culture.     

The effect of Benlate and cytokinins on the content of tobacco mosaic virus in tomato leaf disks and cucumber mosaic virus in cucumber cotyledon disks and seedlings

Tomato leaf disks were inoculated with tobacco mosaic virus (TMV) and floated for 7 days on solutions of kinetin and benzyladenine in the range 20-0-002 mg/1. Virus content was reduced at the higher and increased at the lower concentrations. Benlate and benomyl showed a peak of cytokinin activity in the Amaranthus betacyanin bioassay equivalent to c. 0–002 fig/l kinetin. At concentrations above 25 and 100 mg a.i./l for Benlate and benomyl respectively, both compounds increased the TMV content of tomato leaf disks. Cucumber mosaic virus (CMV) content in cucumber cotyledon disks was increased by Benlate and benomyl treatment (50–100 mg/1). Applied as a soil drench (50–500 mg a.i./l) when the plants were inoculated, Benlate increased the CMV content of infected seedlings. The number of starch-iodide lesions (a measure of susceptibility) was unaltered in cotyledons treated with Benlate 7 days before or immediately after inoculation. Infectivity of crude infective cucumber sap was unaffected by benomyl incorporation, whereas Benlate reduced infectivity at higher concentrations (1000–5000 mg/1). Under the experimental conditions described, Benlate, benomyl, benzyladenine and kinetin had no effect on the chlorophyll content of tomato leaf disks, and intact seedlings.     

Benzothiadiazole Induces Resistance to Plasmopara helianthi in Sunflower Plants

A novel synthetic chemical CGA 245704 [benzo (1,2,3) thiadiazole-7-carbothioic acid S methyl ester (acibenzolar-S-methyl) (BTH)] applied as a soil drench and foliar spray was shown to provide good protection against Plasmopara helianthi in sunflower plants. Soil drenches at the rates of 150 and 200 mg/kg soil, were applied 3 days before the inoculation and induced high levels of protection (80–82%) against downy mildew. At the highest concentrations (up to 300 mg/kg soil) about 90% protection was observed but at these rates phytotoxic symptoms were noted. This compound also provided good protection against P. helianthi when applied 1 day before the inoculation as well as when applied 1 day post-inoculation. The chemical had no antifungal activity in vitro against P. helianthi . In addition the combination of CGA 245704 and metalaxyl, as a seed dressing at low rates, provided a high level of control against the disease; however, the activity of this combination was not significantly different from metalaxyl alone. CGA 245704 applied as a soil drench and foliar spray also protected sunflower plants from P. helianthi foliar infection.     

Drench treatments for management of larval Japanese beetle (Coleoptera: Scarabaeidae) in field-grown balled and burlapped nursery plants

Insecticide drenches were applied to postharvest field-grown nursery plants harvested as 60-cm-diameter balled and burlapped (B&B) root balls for controlling third instars of Japanese beetle, Popillia japonica Newman (Coleoptera: Scarabaeidae). Bifenthrin, chlorpyrifos, lambda-cyhalothrin, and thiamethoxam were drench-applied in fall and spring tests at volumes of runoff (1X; approximately equal 2.57 liters per drench per root ball) or twice runoff (2X). Tests also examined consecutive drenches (two, four, or six) and B&B rotation between drenches. Fall-applied drenches did not meet the Domestic Japanese Beetle Harmonization Plan (DJHP) standards of < or =1 grub and ranged from 0 to 90% control. However, most fall-applied drenches significantly reduced grub numbers relative to the untreated root balls. Spring-applied drenches were more effective than fall drenches: chlorpyrifos treatments gave 94-100% control, whereas other spring-applied treatments were less consistent, including thiamethoxam (83-100% control) and bifenthrin (61-100% control). Lambda-cyhalothrin was not effective. A higher drench volume (2X) did not significantly improve treatment efficacy; however, grub numbers decreased as the number of drenches increased for fall-applied chlorpyrifos and thiamethoxam and spring-applied bifenthrin. Rotation of root balls significantly reduced grub numbers compared with nonrotated treatments for fall-applied chlorpyrifos (six drenches) and bifenthrin (two or six drenches), but these treatments did not meet DJHP standards. The study indicates chlorpyrifos, bifenthrin, and thiamethoxam drenches can control Japanese beetle in the spring and may provide a new postharvest option to certify B&B plants for Japanese beetle.     

Pathogenicity of benomyl-tolerant variants of Verticillium dahliae to strawberry, cv. Cambridge Vigour

Plants of cv. Cambridge Vigour were inoculated either with a benomyl-sensitive isolate of Verticillium dahliae or with one of two variants selected from it in vitro; these variants, Ri/8 and Ri/ii, were tolerant of benomyl at concentrations of 5 and 10 ppm respectively in the culture medium. The parent isolate and Ri/8 caused only mild wilt symptoms, but Ri/n was strongly pathogenic. A single treatment with benomyl (0–04 g/plant, in 100 ml water), applied as a soil drench o, 14, 29 or 57 days after inoculation, tended to reduce the mild symptoms caused by the parent isolate; the treatments had no apparent effect on Ri/8, but they slightly increased the severity of the wilt caused by Ri/n, especially after the earlier applications.     

Effect of aqueous extract of Sargassum johnstonii Setchell & Gardner on growth, yield and quality of Lycopersicon esculentum Mill.

Experiments were conducted on tomato to study the potential of brown alga Sargassum johnstonii as a biofertilizer. Seaweed extract was applied as a foliar spray, soil drench, and soil drench + foliar spray to assess its effect on plant growth, yield, and concentration of lycopene and vitamin C. The main objective of the study was to enhance the biochemical constituents with neutraceutical and antioxidant values in tomato fruit. Different concentrations (0.1%, 0.4%, 0.8%, 2%, 6%, 8%, and 10%; v/v) of seaweed extract were used and growth was observed over a period of 7 months. A total of 14 sprays/drenches were applied at 15-day intervals during the entire vegetative and reproductive phase. A statistically significant increase in vegetative growth (plant height, shoot length, root length, and number of branches), reproductive parameters (flower number, fruit number, and fresh weight), and biochemical constituents (photosynthetic pigments, proteins, total soluble sugars, reducing sugars, starch, phenols, lycopene, and vitamin C) was recorded following all three methods of treatment at higher concentrations of seaweed extract. The study also reports auxin- and cytokinin-like activity, and the presence of macro- (Ca, Mg, Na, and K) and micronutrients (Fe, Cu, Zn, and Mn), in seaweed extract of S. johnstonii, which makes it a potential biofertilizer.