Reduce Fungicide Use Research Articles

Reduced fungicide use on a new Australian peanut cultivar, highly resistant to the late leaf spot and rust pathogens

Rust (caused by Puccinia arachidis) and late leaf spot (LLS, caused by Mycosphaerella berkeleyi) can cause significant yield losses in Australian peanut crops. Until recently, all commercial peanut varieties were highly susceptible to these pathogens, but the new Australian cultivar Sutherland has significantly higher levels of resistance than the older cultivars. Field trials were conducted at two sites in Queensland to (a) confirm the improved resistance of cv. Sutherland over another commercial cultivar, Menzies, (b) study the effects of timing of first spray, spray interval and cultivar on disease severity and yield, and (c) develop a suitable fungicide management program for cv. Sutherland. In the 2006 and 2007 trials, rust and LLS developed slower and had lower final disease ratings and AUDPC values on unsprayed plots of cv. Sutherland than on cv. Menzies. The timing of the first spray is critical in managing both rust and late leaf spot, with the results demonstrating that the first fungicide spray on cv. Sutherland should be applied as soon as rust and LLS are first seen on cv. Menzies. In most trials spray intervals of 14 days or 21 days were suitable to effectively control rust and LLS. In years with low disease pressure, few, if any, fungicide applications will be needed to manage the diseases, but in other years up to four sprays may be necessary.

Predicting the risk of soybean rust in Minnesota based on an integrated atmospheric model

To minimize crop loss by assisting in timely disease management and reducing fungicide use, an integrated atmospheric model was developed and tested for predicting the risk of occurrence of soybean rust in Minnesota. The model includes a long-range atmospheric spore transport and deposition module coupled to a leaf wetness module. The latter is required for spore germination and infection. Predictions are made on a daily basis for up to 7 days in advance using forecast data from the United States National Weather Service. Complementing the transport and leaf wetness modules, bulk (wet plus dry) atmospheric deposition samples from Minnesota were examined for soybean rust spores using a specific DNA test and sequence analysis. Overall, the risk prediction worked satisfactorily within the bounds of the uncertainty associated with the use of modeled 7-day weather forecasts, with more than 65% agreement between the model forecast and the DNA test results. The daily predictions are available as an advisory to the user community through the University of Minnesota Extension. However, users must take the actual decision to implement the disease management strategy.

Encouraging The Adoption of Decision Support Systems by Irrigators

The adoption of decision support systems (DSS) by irrigators and other farmers has been surprisingly slow. Various explanations have been given for the slow uptake including poor system design and inadequate marketing of the programs. Much of the work done to understand the adoption of technologies such as DSS amongst farmers is based on the diffusion model developed by Rogers. If the model holds, the optimal strategy for encouraging adoption is to develop a marketing strategy that will encourage innovators and early adopters to begin using the product, who will then influence others to imitate them. However, the diffusion model was originally developed to explain the adoption of the technologies such as hybrid corn, where adoption is relatively straightforward. Many modern technologies can be quite different, involving sizeable expenditures in equipment, infrastructure or human capital, and/or large additional commitments of time. In this study, the ability of the diffusion model to predict the adoption of a DSS known as Irrigator Pro is investigated. This DSS has the capacity to increase yields, reduce fungicide use and reduce the amount of water used for irrigation. A qualitative methodology involving in-depth interviews with irrigators in Georgia, USA is used to investigate farmers’ attitudes to Irrigator Pro. The results indicate that several variables suggested by the diffusion model do predict adoption, including age and attitude to risk. However, other variables not predicted by the diffusion model, including computer literacy and ownership of a mid-sized farm were found to be important predictors of adoption. This implies that more rapid and widespread adoption can be achieved by not just targeting those who are traditionally considered to be innovators or early adopters.

Integrated Management of Gummy Stem Blight of Watermelon by Green Manure and Melcast-scheduled Fungicides

Watermelon gummy stem blight (GSB) management using a green manure cover crop, the weather-based disease forecasting program ‘Melcast,’ and bio- and reduced-risk fungicides was evaluated in Maryland. Soil incorporation of hairy vetch winter cover crop suppressed percent foliage affected by GSB in comparison to winter fallow in three of five trials conducted in 2004 and 2005. Programs of Reynoutria sachalinensis, Bacillus subtilis, or harpin protein applied in rotation with chlorothalonil provided control of GSB as effectively as did EBDC, boscalid, or cyprodinil plus fludioxonil. However, the bio-fungicide programs did not perform as well as chlorothalonil alternated with pyraclostrobin plus boscalid in 2005. Melcast-scheduled sprays of B. subtilis in rotation with chlorothalonil resulted in an average of 73% less synthetic fungicide applied to watermelon. However, GSB reduction in the B. subtilis program, although similar in 2005, was less that that obtained with chlorothalonil alone in 2004. These results suggest that the combined use of green manure with Melcast-scheduled fungicide applications could effectively manage GSB and reduce fungicide use. Biofungicides alternated with chlorothalonil also minimized use of synthetic fungicides and were effective under some conditions, but should be used with caution. Accepted for publication 22 September 2008. Published 20 November 2008.

Weather-based forecasting systems reduce fungicide use for early blight of celery

Two disease forecasting systems, the Tomcast and the Berger models, were tested for their utility in scheduling sprays of traditional protectant fungicides and newer ‘low-risk’ fungicides, including strobilurins, for management of early blight of celery caused by Cercospora apii. Excellent control of early blight was achieved in two seasons using the Tomcast and the Berger models with three to four sprays compared with 13 sprays applied on a weekly, calendar basis. Marketable yields were as high as 74,000 kg ha −1 with the Berger model compared with 28,000 kg ha −1 in the untreated controls. However, in a third season, the Berger model (nine sprays) was superior to Tomcast (two sprays) for predicting the need to spray for early blight, thus preventing yield losses. The newer strobilurin fungicides azoxystrobin and a combination product of pyraclostrobin and boscalid were superior to chlorothalonil when applied according to the two forecasting models or on a weekly, calendar basis. Using these newer fungicides and the Berger model, area under the early blight disease curve was reduced by up to 81%. Yields and quality of fresh-market celery were not compromised in two seasons when using the models. Savings of up to $500 ha −1 in cost of spray materials alone could be realized if growers would time fungicide applications according to weather data used in conjunction with these two disease forecasting models.

Modelling wheat growth and yield losses from late epidemics of foliar diseases using loss of green leaf area per layer and pre-anthesis reserves.

Crop protection strategies, based on preventing quantitative crop losses rather than pest outbreaks, are being developed as a promising way to reduce fungicide use. The Bastiaans' model was applied to winter wheat crops (Triticum aestivum) affected by leaf rust (Puccinia triticina) and Septoria tritici blotch (STB; Mycosphaerella graminicola) under a range of crop management conditions. This study examined (a) whether green leaf area per layer accurately accounts for growth loss; and (b) whether from growth loss it is possible to derive yield loss accurately and simply. Methods Over 5 years of field experiments, numerous green leaf area dynamics were analysed during the post-anthesis period on wheat crops using natural aerial epidemics of leaf rust and STB. Key Results When radiation use efficiency (RUE) was derived from bulk green leaf area index (GLAI), RUE(bulk) was hardly accurate and exhibited large variations among diseased wheat crops, thus extending outside the biological range. In contrast, when RUE was derived from GLAI loss per layer, RUE(layer) was a more accurate calculation and fell within the biological range. In one situation out of 13, no significant shift in the RUE(layer) of diseased crops vs. healthy crops was observed. A single linear relationship linked yield to post-anthesis accumulated growth for all treatments. Its slope, not different from 1, suggests that the allocation of post-anthesis photosynthates to grains was not affected by the late occurring diseases under study. The mobilization of pre-anthesis reserves completely accounted for the intercept value. Conclusions The results strongly suggest that a simple model based on green leaf area per layer and pre-anthesis reserves can predict both growth and yield of wheat suffering from late epidemics of foliar diseases over a range of crop practices. It could help in better understanding how crop structure and reserve management contribute to tolerance of wheat genotypes to leaf diseases.

Heritability of Dollar Spot Resistance in Creeping Bentgrass

ABSTRACT The dollar spot disease incited by Sclerotinia homoeocarpa is an important disease of creeping bentgrass (Agrostis stolonifera). Genetic resistance is an important control strategy and could reduce fungicide use. Despite recent research, the genetic mechanism of dollar spot resistance in turfgrasses is still not fully understood. The objectives of this study were to (i) determine narrow-sense heritability and predicted gain from selection for dollar spot resistance in creeping bentgrass and (ii) evaluate inheritance characteristics of dollar spot disease resistance. Inheritance characteristics such as the detection of major genes, heterosis, maternal effects, and combining ability were determined by evaluating the disease severity of progeny from crosses between resistant and susceptible bent-grass clones. Parental clones and progenies from crosses were established in a field trial in a randomized complete block design and inoculated with one isolate of S. homoeocarpa applied at a rate of 0.25 g m(-2) of prepared inoculum. Differences in progeny means between crosses were observed over both years. Progeny from resistant x resistant crosses had significantly less disease severity than resistant x susceptible and susceptible x susceptible crosses. High narrow-sense heritability estimates (0.79 [2002], 0.79 [2003]) and large mean squares for general combining ability support the idea that additive gene action plays a significant role in disease resistance and support previous research that dollar spot resistance is most likely quantitatively inherited.

Optimisation of the chemical control of ascochyta blight in chickpea

Ascochyta blight, caused by Didymella rabiei, is the most devastating foliar disease of chickpea in southern Australia. As part of an effort towards developing disease management practices for susceptible cultivars, programs for timing fungicide applications were developed. The efficacy of chlorothalonil and mancozeb in suppressing ascochyta blight was evaluated in five field experiments conducted over 4 years. The results were variable; in some experiments disease was adequately suppressed (control efficacy >89%) whereas in other experiments, control efficacy was insufficient (<32%). Not all of this variability could be explained by differences in the fungicides used or their concentrations. Analysis of the time of spraying in relation to rain events identified possible causes for most of this variability. Ascochyta blight was suppressed when fungicides were applied in time to protect the plants from infections that occurred during rain events, but whenever the plants were not protected during rains, disease suppression was insufficient and control efficacy was low. The coincidence between control efficacy values and the amount of uncontrolled rain was highly significant (P<0.01; R 2 =0.937). Data recorded in the field experiments were then used as input into a series of simulations aimed at quantifying how several management approaches could reduce fungicide use. Results were analysed using multiple regression with dummy variables. Compared with continuous protection of the crop throughout the season, which required eight mancozeb or five chlorothalonil applications, using rain forecast to time sprays may enable a reduction in the number of sprays by up to 5.5 and 2.7 per season, respectively, hence, vastly reducing production costs. Initiating sprays after disease onset (based on monitoring) may enable a further reduction of 0.6 sprays per season, on average. Validation of the threshold amount in Australia for local cultivars and implementation of these strategies awaits examination in field experiments.

Seed-specific placement of in-furrow fungicides for control of seedling disease in cotton

Fungicides are often applied as in-furrow sprays during planting to control cotton seedling disease. To be effective, the fungicide product should cover each seed and the surrounding soil, thus forming a zone of protection for each emerging seedling. Traditional practice has been to apply the product as a solid band along the length of the furrow. However, limiting fungicide application to an area near the cottonseed, and minimizing the amount of chemical applied between seeds, could reduce fungicide inputs significantly while maintaining an acceptable level of disease control. To this end, a seed-specific applicator has been developed to apply discrete pulses of liquid chemical to individual seeds and the surrounding soil at planting. The concept of seed-specific fungicide application was evaluated during 2002 and 2003 using side-by-side, field comparisons of seed-specific and conventional applications of PCNB and etridiazole in plots inoculated with Pythium spp. and Rhizoctonia solani. Cotton was planted at 9.8 seeds m −1, and seed-specific treatments were applied as spray bands 5.1 cm in length such that fungicide savings of 50% were realized where seed-specific applications were implemented. Seedling disease pressure was present in both years of the study. Stands in the untreated plots averaged less than 25% of that in treated plots. Stand counts in all plots receiving an in-furrow fungicide treatment were significantly greater ( P=0.05) than in untreated plots. There were no significant differences in either year among the seed-specific and conventional treatments. In these tests, seed-specific fungicide applications provided seedling disease control comparable to conventional application while reducing fungicide use by 50%. Seed-specific application equipment has potential to help cotton growers reduce input costs and increase production efficiency.

Molecular, ecological and evolutionary approaches to understanding Alternaria diseases of citrus

SUMMARY Alternaria fungi cause four different diseases of citrus: Alternaria brown spot of tangerines, Alternaria leaf spot of rough lemon, Alternaria black rot of several citrus fruits and Mancha foliar of Mexican lime. The first three diseases are caused by the small-spored species, Alternaria alternata and the causal agents can only be differentiated using pathogenicity tests, toxin assays or genetic markers. Mancha foliar is caused by the morphologically distinct, large-spored species A. limicola. Substantial progress has been made in understanding the biology, ecology, population biology, systematics, molecular biology and biochemistry of the interactions between these pathogens and citrus. Epidemiological studies have focused on brown spot of tangerines and their hybrids and have contributed to the development of a model of disease development which has improved control and reduced fungicide use. Studies of the population genetics, host specificity and ecology of A. alternata from different ecological niches on citrus have revealed host specific forms of the pathogen which cause disease on different citrus species, the existence of three phylogenetic lineages of the fungus which cause brown spot world-wide, and closely related non-pathogenic isolates which colonize healthy citrus tissue. The role of host-specific toxins in Alternaria diseases of citrus has been extensively studied for over 20 years, and these pathosystems have become model systems for host-pathogen interactions. Recent molecular research has started to unravel the genetic basis of toxin production and the host susceptibility to toxin, and the role of extracellular, degradative enzymes in disease.

Factors Associated with Foliar Disease of Staked Fresh Market Tomatoes Grown Under Differing Bed Strategies

The use of mulch or compost to reduce foliar disease in fresh market tomato could reduce fungicide use. Between 1997 and 1999, foliar disease was monitored in tomatoes grown in beds with bare soil, black polyethylene, composted dairy manure, or hairy vetch. Early blight was reduced in plots with vetch compared with bare soil or compost in all years and compared with polyethylene cover in 1 year. Early blight was reduced in plots with polyethylene versus compost and bare soil in 1 and 2 years, respectively. Septoria leaf spot was reduced in plots with vetch versus other bed strategies in 1998 and bare soil or compost in 1999. This disease was reduced in plots with polyethylene versus bare soil or compost in 1998 and 1999. Soil coverage of tomato leaflets and soil particle dispersal were reduced in plots with polyethylene or vetch versus bare soil or compost in both years that these variables were assessed. Sensor wetness duration was reduced in plots with polyethylene or vetch versus bare soil or compost in one of two years. These findings suggest that foliar disease reduction in mulch was associated with reduced splash dispersal and, in one year, reduced leaf wetness.

Comparison of the NegFry decision suport system with routine fungicide application for the control of potato late blight in Ireland

Field experiments between 1996 and 2000 compared the efficacy of fungicide programmes applied in accordance with the NegFry and Met Eireann (ME) decision support systems (DSS) for the control of late blight with 7- and 10-day routine fungicide programmes. The ME DSS reduced fungicide use by 68% and 54% respectively while NegFry reduced fungicide use by 49% and 27% compared with the 7- and 10-day programmes. The NegFry DSS was similar to the 10-day routine programme in terms of late blight control, quality and marketable yield. A similar result was found when the NegFry DSS was compared with a 7-day routine mancozeb programme (included for two seasons only). Within the NegFry DSS the use of fluazinam resulted in improved yield, foliage blight and tuber blight control compared with mancozeb, but this benefit was significant for tuber blight only. The ME DSS resulted in inferior disease control, yield and quality.

Optimization of Chemical Suppression of Alternaria dauci, the Causal Agent of Alternaria Leaf Blight in Carrots.

Alternaria leaf blight, caused by Alternaria dauci, is a major constraint to carrot production in Israel. Israeli carrot growers apply prophylactic sprays at 3- to 10-day intervals throughout the season until harvest, up to 30 sprays in a growing season. In this study, we attempted to optimize the chemical suppression of the disease, in order to reduce fungicide use. The efficacy of nine fungicides was determined in two field experiments. All fungicides reduced disease severity, but there were significant differences in efficacy among them. The most effective were difenoconazole and chlorothalonil; less effective were copper hydroxide, tebuconazole, trifloxystrobin, and mancozeb; the least effective in our experiments were flutrifol, propineb, and iprodione. The effect of the time of spray initiation on fungicide efficacy was determined in three field experiments. Qualitative (analysis of variance) and quantitative (regression) analyses of the data revealed that initiating sprays after disease onset reduced control efficacy. Thus, an action threshold model could not be developed for A. dauci in carrots. The time before harvest at which sprays could be terminated was tested in two field experiments and it was found that terminating sprays 14 days before harvest did not significantly affect the overall control efficacy. The main conclusions derived from these experiments were tested and corroborated in two additional field experiments.

Management of Blackspot on Three Rose Cultivars Using Antitranspirants in Combination with Chlorothalonil

Abstract The efficacy of reducing fungicide use, by combining chlorothalonil with film-forming antitranspirant products and lengthening intervals between applications, was evaluated for control of blackspot of rose. Antitranspirants included three highly refined pine oil (pinolene) products (Nu Film 17, Vapor Gard, and Wilt Pruf) and two latex products (Stressguard and Transfilm), each of which were applied in combination with chlorothalonil fungicide. Antitranspirant solutions were applied at 2- or 3-week intervals, depending on recommended use of the antitranspirant. Blackspot severity, based on proportion of symptomatic foliage, did not differ among treatments in either year of the study. In both study years, defoliation was lower on plants treated weekly with the fungicide alone, with Stressguard (applied at 0.25% in combination with chlorothalonil every 2 weeks), or with Vapor Gard (applied at 2% in solution with chlorothalonil every 3 weeks) compared to nontreated plants. Overall, the above fungicide and antitranspirant solutions reduced season-long fungicide use by 40-69%, without a decrease in disease control, compared to the weekly chlorothalonil treatment. Plant vigor and/or growth, however, was lower with the antitranspirant treatments compared to chlorothalonil alone.

Evaluation of BSPcast Disease Warning System in Reduced Fungicide Use Programs for Management of Brown Spot of Pear.

A forecasting model (BSPcast) developed for prediction of brown spot (Stemphylium vesicarium) of pear was evaluated as an advisory system for reduced fungicide use in disease management programs. Eleven trials were performed during 1995, 1996, and 1997 in five orchards in two different climatic areas in Catalunya (Spain) and Emilia-Romagna (Italy). Values of 3-day cumulative daily infection risk (CR) provided by the model were used to determine risk periods during the growing season of pear and were taken as thresholds to schedule fungicide sprays. The fungicide application programs tested using the model consisted of guided schedules with CR action thresholds of 0.4, 0.5, or 0.6, and fixed sprays following a standard commercial schedule. In nine out of 10 trials, no significant differences were observed in disease incidence on fruit at harvest between the fixed-spray commercial schedule and guided sprays using thresholds of 0.4 or 0.5. The average savings in number of fungicide sprays applied using BSPcast compared with the fixed-spray schedule were 20 to 70% when using fungicides with a 15-day protection period (kresoxim-methyl or procymidone) and ranged from 20 to 50% when using a fungicide with a 7-day protection period (thiram).

Economic Impact of Pecan Integrated Pest Management Implementation in Texas

The Texas pecan integrated pest management (IPM) program, begun in the early 1970s, was evaluated using research and demonstration IPM trial data and producer survey responses. The initial survey conducted in 1981 was chosen as the base line against which later surveys were compared to measure the economic impact of an IPM program. Producers in Texas reduced fungicide use 30%, insecticide use 35%, and the overall number of spray applications per season 9% from 1980 to the present. Producers practicing an IPM program realized contemporaneous benefits of $3.93 million annually from 1994 to 1996 compared with conventional program producers, and the overall economic benefits to pecan producers were estimated to be $6.06 million per year during 1990-1996 from the pecan IPM program in Texas. Needed nutritional amendments of zinc were identified as the current principal spray component applied to improved pecans that prevents further substantial reductions in management costs.

電気分解強酸性水噴霧による作物病害防除に関する基礎研究 （２） キュウリべと病の発病抑制と生理障害の発生

Effect was investigated of spraying electrolyzed strong acid water (ESAW) obtained by electrolysis of a NaCl dilute (ca. 50mg L-1) water solution on the incidence of downy mildew (Pseudoperonospora cubensis Rostowzew) in cucumber (Cucumis sativus L, cv. Naoyoshi) grown in a plastic house. pH, free effective chlorine concentration and oxidation-reduction potential of the ESAW were 2.8, 32 ppm and 1 120 mV, respectively. Different amounts of either the ESAW (0.25, 0.5 or 1 L plant-1) or well water (0.5 L plant-1) were sprayed onto the leaves once every third or, fourth day. The incidence of downy mildew was controlled almost perfectly for the experimental period of 17 d by spraying the ESAW, regardless of the amount sprayed, while the symptom of downy mildew was observed on day 10 with well water and on day 13 with non-treated control. On day 17, the incidence was significantly reduced by spraying the ESAW (0 or 2%) as compared to both well water (48%) and non-treated control (32%) . However, spraying the ESAW caused a leaf burn-like physiological disorder in some leaves after day 7, regardless of the amount sprayed. The results indicate that ESAW can be a viable alternative to some fungicides to control several crop diseases, or it can at least be effective in reducing fungicide use ; however, there remains the problem of eliminating the leaf burn-like physiological disorder.

Disease-management components of advanced integrated pest management in apple orchards

Reducing fungicide use in commercial apple orchards is particularly problematic, although success would positively effect other aspects of orchard ecology, primarily arthropod management, and may alleviate ecological and food-safety concerns. Methods for reducing fungicides were tested in the context of advanced integrated pest management (IPM), in which arthropod pests are managed with minimal use of pesticides following the petal-fall stage of apple growth. The potential ascospore dose (PAD) method for predicting inoculum density of Venturia inaequalis, which causes apple scab, was used in conjunction with ascospore-maturity evaluation and ergosterol-biosynthesis-inhibiting fungicides to manage scab in advanced IPM blocks. In 78% of the cases studied, PAD indicated growers should delay the first fungicide application, but growers actually followed this recommendation in only half of these cases. Where growers followed the recommendation, they applied significantly less fungicide, saving an average of over one application during the primary apple scab season, a 26% reduction. A combination of summer pruning and limited captan use was recommended for management of flyspeck (caused by Schizothyrium pomi) and sooty blotch (caused by three associated fungi). Growers generally followed the advanced IPM recommendations, and during the summer applied 34% less fungicide in the advanced IPM blocks. The program showed that growers could achieve significant fungicide reductions in apples using these methods, although it also indicated that they were sometimes reticent to implement them.

Integration of Genotype and Age-Related Resistances to Reduce Fungicide Use in Management of Alternaria Diseases of Cotton and Potato

Concepts for the integration of genotype resistance, age-related resistance, and fungicide for the suppression of Alternaria diseases were developed and evaluated by a computer simulation model and in the field. The model reflects the effects of environment, genotype resistance, and fungicide efficacy on Alternaria solani in potatoes. We found that changes in host resistance, with age and among genotypes, could be compensated for by adjusting the intensity of fungicide applications, i.e., by increasing the frequency of sprays toward the end of the season and spraying moderately resistant cultivars at longer intervals than susceptible cultivars. The time during the growing season when application of a systemic spray within a routine application of protectant sprays would most effectively suppress Alternaria spp. was examined in simulation experiments and in the field. The efficacy of a single systemic spray was highest when applied toward the end of the season when host susceptibility increased. The concepts for integration were evaluated in six field trials, three involving A. macrospora in cotton and three involving A. solani in potatoes. In most cases, the disease suppression achieved by the integration treatment did not differ significantly from that achieved by application of either protectant fungicides (maneb, mancozeb, or chlorothalonil) on a 7-day schedule or systemic fungicides (tebuconazole or difenoconazole) on a 14-day schedule, although up to five fewer sprays were applied in the integration treatment.

Economics of reducing fungicide use by weather‐based disease forecasts for control ofVenturia inaequalisin apples

Abstract In seven field trials conducted over four seasons, black spot incidence was consistently greater in treatments where fungicide use was reduced by timing sprays with weather information compared to standard calendar‐based treatments. Fungicide use was measured as the total number of label‐rate applications of fungicides with activity against black spot and the individual components of mixed applications of fungicides were counted separately. Over all trials, the mean disease incidence at harvest increased logarithmically as the number of fungicide applications decreased. A regression equation describing disease increase in terms of number of fungicides and number of infection periods was used in an economic analysis of apple production. When the savings from reduced fungicide use were weighed against the increased harvesting and grading costs and revenue losses from increased disease, there appeared to be scope to reduce fungicide use by up to 25% before increased disease adversely affected profit...