Field control of brown leaf rust (Puccinia recondita) of wheat with a triazole compound in north India

RH-124 (4-n-butyl-i,2,4-triazole) when applied as one or two foliar applications (at the rate of i-6 1 a.i./ha) or given by watering soil (at the rate of 0–8 1 a.i./ha) controlled brown leaf rust ( Puccinia recondita ) of wheat in microplot experiments. In north India where the rust appears 80–90 days before harvest, one foliar or soil application was sufficient to mitigate loss in yield. Seed treatment was not found useful when tested in one trial.     

Methyl jasmonate stimulates polyamines biosynthesisand resistance against leaf rust in wheat plants

Abstract

Leaf rust of wheat (Triticum aestivum L.), incited by Puccinia recondita ex Desm. f. sp. tritici Eriks, is one of the most important wheat diseases in Egypt. Methyl jasmonate (MJ) is a potential plant elicitor which induces a wide range of chemical and anatomical defense reactions in conifers and might be used to increase systemic resistance against biotic damage. In the greenhouse, different concentrations of MJ (10, 20 and 30 mM) were applied as seed soaking plus foliar spray or only as foliar spray to control leaf rust and induction of secondary compound production in leaves of wheat plants. Foliar spray was applied after 30 and 50 days of sowing. Results indicated that all concentrations and treatments reduced the severity of rust disease caused by P. recondita f. sp. tritici in wheat leaves during 45 days of inoculations. Disease incidence was decreased significantly in MJ-treated plants as seed soaking plus foliar spray with 20 and 30 mM when compared to 10 mM MJ or control plants. The study revealed that, with increasing concentrations of MJ, the secondary metabolites were greatly increased. Endogenous levels of both free and conjugated putrescine, spermidine and spermine increased in response to the elicitor. Activities of polyamine biosynthetic enzymes of ornithine decarboxylase (ODC) and polyamine oxidase (PAO) displayed up to threefold increases relative to untreated control. Moreover, significant increases in activities of plant defense-related protein, enzymes as peroxidase and chitinase as well as free and conjugated phenols contents were recorded in treated plants compared with untreated and infected plants. Furthermore, MJ treatment increased the chlorophyll-a, chlorophyll-b and carotenoids pigments contents, the higher increase was obtained with combined treatment between seeds soaking plus foliar spray at 20 and 30 mM of MJ. Under field conditions, three concentrations of MJ, i.e. 10, 20 and 30 mM as combined treatment between seeds soaking plus foliar spray or only as foliar spray were applied to study their effect against rust disease. Foliar spray was applied after 30 and 80 days of sowing. Results showed that the high reduction in disease severity was obtained with combined treatments between seeds soaking plus foliar spray with MJ at 20 and 30 mM compared with other treatments and control. At the same time, all treatments increased the growth and grain yield of wheat plants. It could be suggested that combination treatment between seeds soaking plus foliar spray with methyl jasmonate might be used commercially for controlling rust disease of wheat plants under field conditions.     

The effect of seed and stem base spray treatment with iprodione on white rot disease (Sclerotium cepivorum) in autumn-sown salad onions

Iprodione applied to seed at 250 g a.i./kg controlled white rot in autumn-sown salad onions until July the following year, and reduced losses during the winter caused by Botrytis spp. At 25–150 g a.i./kg seed, iprodione controlled autumn and spring infections but it was less effective later in the summer. Treatment of autumn-sown onions at 50 g a.i./kg seed followed in March by a single stem base spray at 0.031 g a.i./m row (total rate c. 2.4 kg a.i./ha) gave complete control; seed treatment at 25 g a.i./kg followed by a stem base spray at 0.125 g a.i./m row (c. 4.5 kg a.i./ha) was equally effective. Four stem base sprays of iprodione at 0.075 g a.i./m row/spray (9 kg a.i./ha) applied in spring to plants raised from untreated seed, controlled spring and summer infections but yields were low because of losses caused by infection in the previous autumn. A single stem base spray of iprodione at 0.125 g a.i./m row applied in spring to plants raised from thiophanate-methyl treated seed at 125 g a.i./kg gave complete control and high yields.     

Control of Globodera rostochiensis in Relation to Method of Applying Nematodes

Soaking potato tuber pieces for 15 min in 8,000 μg/ml of oxamyl just before planting reduced the number of Globodera rostochiensis cysts that developed on potato roots, but this treatment was phytotoxic. Five foliar applications of 1.12 kg a.i./ha of oxamyl or carbofuran at 10-day intervals beginning when 90% of the plants had emerged suppressed increase in G. rostochiensis densities. Similar foliar applications of phenamiphos were ineffective in controlling G. rostochiensis. Soil applications (in the row at planting) of aldicarb, carbofuran, phenamiphos, ethoprop, and oxamyl at 5.6 kg a.i./ha reduced the numbers of white females that developed on potato roots, but only those treatments involving aldicarb and oxamyl suppressed G. rostochiensis population increase. Combined soil and foliar treatments did not provide any advantage over soil treatment alone, as soil applications of 5.6 kg a.i./ha alone were equal to, or better than, combined soil (3.4 kg a.i./ha) and foliar (2.2 kg a.i./ha) applications in controlling G. rostochiensis.     

Investigations into the movement of glyphosate from treated to adjacent untreated plants

Transfer of glyphosate from treated to adjacent untreated plants was investigated under glasshouse conditions using wheat and Agropyron repens. When glyphosate was used at concentrations characteristic of conventional field application rates, and where shoot contact was prevented, no symptoms were observed on untreated plants. When there was shoot contact, and when glyphosate was used at 2 kg a. i./ha (10 g a. i./litre), phytotoxic effects were observed on untreated plants. At higher concentrations of glyphosate (90 or 180 g a. i./litre), typical of selective applications with ropewick or roller applicators, evidence of root transfer of herbicide was found. In pot experiments these phytotoxic effects were variable, due, perhaps, to variable amounts of root contact. Confining the roots, by growing the plants in tubes, increased the level of phytotoxicity.     

Use of Avermectins for the Control of Meloidogyne incognita on tomatoes

The efficacy of avermectins B₁ and B₂ for control of Meloidogyne incognita on tomato was studied in pots and field plots for two seasons. Avermectins were applied as granules and liquid in furrows or by low pressure drip irrigation systems, at rates ranging from 0.093 to 0.34 kg a.i./ha, as single or multiple applications. Levels of control comparable to those obtained by oxamyl and aldicarb at 3.36 kg a.i./ha were achieved by the avermectin with only 1/10 the volume of chemicals applied to the environment. Avermectin protection of the roots remained constant throughout the first 5 weeks giving slightly longer protection than oxamyl or aldicarb.     

The effect of seed, furrow and stem base spray treatment with iprodione on white rot disease (Sclerotium cepivorum) in spring-sown salad onions

Seed treatment with iprodione at 125 and 150 g a.i./kg was superior to calomel seed treatment at 500 g a.i./kg in reducing disease losses and increasing yields in field experiments with salad onions infected with white rot; iprodione at 50, 62·5 and 100 g a.i./kg and thiophanate-methyl at 150 g a.i./kg were as effective as calomel. Furrow treatment with iprodione or thiophanate-methyl at 0·05 and 0·15 g a.i./m row or calomel at 0·5 g a.i./m row gave similar control as equivalent rates of seed treatment. Neither seed nor furrow treatments gave adequate control with prolonged exposure of the crop to the disease. A single stem base spray of iprodione at 0·0625 g a.i./m row applied 5 wk after drilling, reduced losses from 46% with a standard calomel seed treatment to 20%; increasing the stem base spray concentration to 0·25 g a.i./m row did not improve the control but resulted in a doubling of yields. The most effective control was obtained with iprodione applied as a seed treatment at 62·5 g a.i./kg combined with a single stem base spray at 0·0625 g a.i./m row 5 wk after drilling and this reduced losses to 6% compared with losses of 46% with calomel treated seed and 88% with untreated seed; increasing the stem base spray concentration did not improve control but resulted in higher yields.     

The interaction of protectants with EPTC on field bean, and tri-allate on wheat

Protectants (antidotes) were tested for their potential to protect field beans (Vicia faba L.) from EPTC damage, or wheat (Triticum aestivum L.) from triallate damage. For both crops there was considerable variation in the degree of protection shown from similar treatments in different experiments. For field bean, a seed treatment of 1,8-naphthalic anhydride (NA) at 5 mg/g seed gave some protection from EPTC applied pre-planting at 4–8 kg a.i./ha but not in all experiments. NA also caused marked chlorosis of the foliage. N, N-diallyl-2, 2-dichloroacetamide (R25788) at 20 mg/g seed severely damaged field bean in the absence of herbicide but 5 mg/g gave comparable protection from EPTC to that given by NA and did not cause chlorosis. Mixing R25788 with EPTC in the spray tank gave reduced protection. In a single experiment R4115 (chemistry undisclosed) gave some protection against EPTC damage. For wheat, a seed treatment of 5–20 mg/g NA sometimes countered damage from tri-allate applied pre-planting at 1 kg a.i./ha but not generally from higher doses. R25788 sometimes protected from weight loss due to tri-allate at 1 kg a.i./ha but not from damage symptoms, whereas R4115 at 20 mg/g seed alleviated these symptoms but did not prevent weight loss. R25788 at 4 kg a.i./ha mixed in the spray tank with the herbicide partially reduced weight loss and damage symptoms from a dose of 2 kg a.i./ha. Some treatments of R29148 gave complete protection from tri-allate at 1 kg a.i./ha. The results are discussed in the context of the full data from the two series of experiments.     

Chemical control of the cabbage stem flea beetle, Psy Modes chrysocephala, on winter oil-seed rape

In East Anglia, from 1974 to 1976, field experiments were carried out on the chemical control of the cabbage stem flea beetle (PsyModes chrysocephala). Carbofuran, 5% granules, proved an outstanding autumn preventive and mid-winter eradicant treatment under both wet and dry conditions, with 1–5-2-24 kg a.i./ha giving virtually 100% control of larvae. Fonofos and phorate granules at 2–24 kg a.i./ha were also effective. AC 92 100 and thiofanox granules were less extensively tested but both gave good control of P. chrysocephala. Several materials showed little or no activity against the pest. The effective preventive granule treatments were all superior to a standard spray of gamma-HCH.     

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.     

Effects of permethrin sprays on the mite fauna of apple orchards

In two apple orchard trials, single high volume sprays of 25–50 mg permethrin/ litre greatly reduced numbers of the phytosend predatory mite Typhlodromus pyri whether the spray was timed pre-bloom at growth stages from ‘bud-burst’ to ‘late green cluster’ or post-bloom in June. At ‘bud-burst’T. pyri were partially protected in hibernating sites on the bark, but the lethal effect of the spray was only delayed; no appreciable selectivity could be obtained by this early timing. Bioassays showed that the persistent toxicity of permethrin residues on bark or on leaves declined to a low level within 20 days, and was related to the decline in residue levels determined by G.C. analyses. Residues were detectable for 3 months or longer. Resurgence of spider mites, Panonychus ulmi, occurred within 2 months after all spray timings, and effective predation by T. pyri was only fully re-establised after several months. In one trial, apple rust mite, Aculus schlechtendali also increased when T. pyri was reduced by spraying. Tydeid mites were killed by permethrin.     

Some effects of differently-acting nematicides on the cereal cyst-nematode (Heterodera avenae) and on the appearance of ''scorch'' in spring wheat on light loamy sand

In fungitoxicity tests against Phytophthora cinnamomi on Chamaecyparis lawsoniana cv. Ellwoodii, a drench of furalaxyl (1000 mg a.i./l) applied to the compost in which 1-yr-old plants were growing, 1 wk before they were inoculated with 650 000 zoospores, controlled disease for at least 12 months. With an inoculum dose of 650 zoospores/plant, furalaxyl at 500 mg a.i./l controlled disease even when inoculation was 12 wk after fungicide treatment. Aluminium tris (ethyl phosphonate) (2000 mg a.i./l) applied as a drench 1 wk before inoculation with 650 000 zoospores/plant did not prevent root infection but delayed foliar symptoms for 9 months: the same treatment, using etridiazole (500 mg a.i./l) only slightly reduced disease incidence. When applied as a single drench 2 days before inoculation, prothiocarb (2000 mg a.i./l) and cuprammonium compounds (200 mg a.i./l) were much less effective than furalaxyl (1200 mg a.i./l), sodium ethyl phosphonate (1500 mg a.i./l), aluminium tris (ethyl phosphonate) (1500 mg a.i./l) or etridiazole (500 mg a.i./l). However, a drench of furalaxyl at 1000 mg a.i./l, aluminium tris (ethyl phosphonate) at 2000 mg a.i./l or etridiazole at 500 mg'a.i./l did not eradicate P. cinnamomi from compost containing infected root debris. Pre-planting drenching of the compost was ineffective. All fungicide treatments were non-phototoxic to 1-yr-old C. lawsoniana cv. Ellwoodii. These results are of special relevance to the control of P. cinnamomi on container-grown woody ornamentals.     

The influence of climatic conditions around the time of spraying isoproturon on the subsequent injury to barley

Winter barley cv. Igri was grown in pots, either outside under cover, in a glasshouse or under controlled conditions and treated post-emergence with isoproturon. There was a linear relationship between the subsequent weight of plants treated with 2.5 kg a.i./ha and either evaporation from a water surface between 2–7 days post spraying or cumulative temperature between sowing and spraying. The relationship between subsequent weight of plants treated to the foliage only with 5 kg a.i./ha and cumulative temperature between sowing and spraying varied between years 1984–86. The post spraying environment had the major influence on subsequent activity of isoproturon at 2.5 kg a.i./ha applied overall to barley under controlled conditions. There was a greater reduction in CO₂ exchange in plants grown after treatment under high compared to low relative humidity. When isoproturon at 5 kg a.i./ha was applied to barley plants with wet foliage, plants were slower to recover their initial rate of photosynthesis when kept wet for 24 h as compared with 11 h or when allowed to dry after treatment. Photosynthesis was decreased to a lesser extent under the same post spray conditions by 2.5 than by 5 kg a.i./ha and reduction was greater and recovery of photosynthesis slower in plants grown inside compared to outside.     

Induction of Growth Increase and Systemic Resistance to Exserohilum turcicum in Maize by Foliar Spray of Phosphates

A single foliar spray of 0.1 M solution of phosphate salts on the upper side of maize (cv. ‘jubilee') leaves 1, 2 and 3 at the 5–6 fully–expanded leaf-stage, 2-4 h before inoculation induced systemic resistance to northern leaf blight caused by Exserohilum turcicum. Nine days after challenge, protection was demonstrated by 91% reduction in the size and 69% in the number of E. turcicum lesions developing on leaves 4, 5, 6 and 7. Appropriate mixing of phosphate solution with KOH revealed that the level of protection was not necessarily dependent on the pH of the solution. The size and number of lesions decreased to 62% and 56%, respectively, 12 days after challenge. There was no damage or chlorotic stipling on the induced leaves (1, 2, and 3) as a result of the phosphate spray. There were no significant differences in the reduction in the number or size of the lesions obtained when the foliar spray was applied 2-4 h or 1, 3, 6, 8, or 10 days before inoculation. One foliar spray ofK₂HPO₄ on leaves 1, 2 and 3 in these intervals before inoculation, remarkably stimulated growth of inoculated plants, which was expressed by several parameters. The possible dual use of phosphate salts as foliar fertilizers and as resistance-inducing agents is discussed     

Control of Ditylenchus dipsaci in Infected Garlic Seed Cloves by Nonfumigant Nematicides

Different rates of granular formulations ofaldicarb, carbofuran, ethoprop, fensulfothion, and phenamiphos were applied directly onto garlic seed cloves in the seed furrow in sandy clay loam, clay loam, and loam soils at planting to assess efficacy for control of Ditylenchus dipsaci in infected seed cloves. All treatments were compared to hotwater-formalin clove dip disinfection treatment and to nontreated infected controls. Aldicarb and phenamiphos at 2.52 and 5.04 kg a.i./ ha, but not at lower rates, effectively suppressed infection by D. dipsaci and increased yields. Although both nematicides slightly slowed the rate of plant emergence, normal stands were established. Trace levels of infection occurred in all treatments, including the hotwater-formalin dip. Carbofuran at 5.04 kg a.i./ha controlled the nematode but was phytotoxic. Ethoprop was phytotoxic. Fensulfothion did not control D. dipsaci even at the highest application rate, 8.90 kg a.i./ha. Single and multiple applications of oxamyl at 1.12-8.96 kg a.i./ha, applied as a surface spray or in furrow irrigation water, slowed the early progression of disease symptoms but failed to provide season-long nematode control.     

Control of potato cyst-nematode, Heterodera rostochiensis, in three soils by small amounts of aldicarb, Du Pont 1410 or Nemacur applied to the soil at planting time

Aldicarb or Du Pont 1410 (S-methyl 1-(dimethylcarbamoyl)-N-[(methylcarbamoyl) oxy] thioformimidate) at 2.6–11.2 kg a.i./ha applied to the soil at planting time controlled potato cyst-nematode, Heterodera rostochiensis, in sandy loam, peaty loam and silt loam and greatly increased tuber yields of susceptible potatoes. Nemacur (O-ethyl-O-(3-methyl-4-methylthiophenyl) isopropylamido-phosphate) controlled potato cyst-nematode in sandy loam at 2.9–10.3 kg a.i./ha and in silt loam at 11.2 kg a.i./ha but did not control the nematode well in peaty loam even at 22.4 kg a.i./ha. In peaty loam aldicarb and Nemacur were more effectively incorporated by rotavation than by a modified power harrow.     

Effects of dalapon and TCA on the growth and yield of oilseed rape (Brassica napus)

The tolerance of oilseed rape (Brassica napus cv. Jet Neuf) to the herbicides dalapon and TCA was studied in two series of 10 experiments over four years. TCA (7.6–30.4 kg a.i./ha) was applied pre-emergence and dalapon (2.9–11.6 kg a.i./ha) was sprayed post-emergence between September and November at two growth stages (2–5, 4–7 leaves). Dalapon at all doses caused the leaves to appear yellow-green in colour and at the higher rates (5.8–11.6 kg a.i./ha), especially when applied at the later of the two growth stages, scorched the leaf margins and stunted the plants. TCA also caused the leaves to appear yellow-green and was noted to affect the retention of water by the leaf surfaces. In general the visible effects of treatment with dalapon were more severe than those of TCA. The effects of these two herbicides on rape seed yields were variable, with some trials showing statistically significant reductions and others none. However by combining the results of trials with similar treatments some underlying trends were identified. In the overall analyses dalapon at 11.6 kg a.i./ha, applied at both growth stages and at 5.8 kg a.i./ha, applied at the later one, reduced yields significantly. TCA at 15.2, 22.8 and 30.4 kg a.i./ha also caused significant yield reductions in the combined analyses. Further statistical analysis questioned the safety of the lower rates of both herbicides, which were similar to those recommended by the manufacturers. The severity of the foliar damage caused by dalapon was well correlated with the risk of significant yield reductions but not with the actual percentage loss of yield. No such correlations were possible with TCA as the visual symptoms were similar on all sites and were unaffected by dose. Recent changes in agricultural practices and in crop cultivar do not appear to have altered the sensitivity of rape to dalapon and TCA appreciably.     

The effect of varying rates of glyphosate and an organosilicone surfactant on the control of gorse

The herbicidal effect of glyphosate applied to gorse (Ulex europaeus L.) was improved by the addition of increasing amounts (0.5–20 g/litre) of Silwet L-77, an organosilicone surfactant. Increasing the rate of herbicide also enhanced control. There was a highly significant interaction between surfactant rate and herbicide dosage; as the amount of Silwet L-77 was increased the rate of glyphosate could be reduced without loss of herbicide efficacy. However, without any added organosilicone surfactant, glyphosate did not provide more than 73% control of gorse at any rate up to 6.5 kg a.i./ha. With the addition of Silwet L-77, complete mortality of all plants could be achieved with 2.2 kg glyphosate/ ha.     

Effect of Time of Spraying of Fungicide and Foliar Nutrient on Soybean Powdery Mildew

With the objective of determining the effects of initial infection level (% leaf area infected, % l.a.i.) at the time of fungicide and foliar nutrient application for the control of powdery mildew, a study was carried out under greenhouse conditions at Embrapa Soja, Londrina, P.R. The fungicide tebuconazole (100 g a.i./ha/application) and sulphur fungicide (2.0 kg a.i./ha/application), sprayed at 20, 30, 40 and 50% l.a.i. (growth stages V3 and V5, between R5.1 and R5.3), and three applications (at V3, V4 and R5.1, beginning at 20% l.a.i.) of tebuconazole were compared with sulphur foliar nutrient (sulphur at the dose of 125 g a.i./ha/application). The highly susceptible BR‐16 cultivar was used in a completely randomized design with 11 treatments, five replications (pots) and five plants per pot. The parameters evaluated were: % l.a.i., % yellowing leaf when the control reached growth stage R7.2 (between 50 and 75% yellow/mature leaves), % defoliation (% defol.) when the control plants reached R8.2 (pre‐harvest maturity), number of pods and seeds and seed weight (s.w.) per plant. The area under the disease progress curve (AUDPC) was determined based on disease progress. The % l.a.i. and AUDPC of the control (98% and 65.41) differed from other treatments (3.5–64.2% l.a.i. and 13.57–40.59 AUDPC). The % l.a.i. for the sulphur fungicide treatment (41.9–64.2%) and sulphur foliar nutrient (49.8%) were greater than for tebuconazole (3.5–28%). The % defol. of the control (90%) differed from tebuconazole applied at 30% initial infection (48%), with three applications (45%), and from sulphur foliar nutrient (47%). The s.w./plant of the control (2.23 g) was lower than that of tebuconazole treated at 40% IL (3.03 g) and at 20% IL (3.35 g) and for sulphur foliar nutrient (3.7 g). The initial disease severity (20–50% l.a.i.) did not affect the level of powdery mildew control and the sulphur foliar fertilizer resulted in greater number and higher s.w./plant.     

Effectiveness of late copper and streptomycin sprays for the control of halo-blight of beans (Pseudomonas phaseolicola)

Two sprays of copper oxychloride or streptomycin sulphate (0–1 % a.i., 675 1/ha) applied to dwarf beans at first flowering and at pod set reduced pod infection by c. 70%. When applied as single sprays at pod set, copper was more effective than streptomycin and reduced pod infection by 50%. Although a copper spray at pod set increased the proportion of pods suitable for processing, more effective control was obtained with a regular spray programme, commencing at the seedling stage.