Reduced Fungicide Applications Research Articles

Arthropods in the spotlight – identifying predators of vineyard pest insects with infrared photography

AbstractGrape berry moths, particularly Lobesia botrana Denis & Schiffermüller (Lepidoptera: Tortricidae), and vinegar flies, such as Drosophila melanogaster Meigen and Drosophila suzukii Matsumura (Diptera: Drosophilidae), are important vineyard pests, causing severe quality loss of grapes. Several arthropod taxa may be involved in the natural control of these pests. However, the role of arthropod predators in the natural control of vineyard pests remains unclear. We investigated 32 vineyards in the Palatinate region, southwest Germany, under organic and conventional management, which in both cases received either full or reduced fungicide applications (2 × 2 design). Predation of L. botrana eggs and pupae and D. melanogaster pupae on sentinel cards exposed in the vineyards was observed with infrared cameras. In total, nine predator taxa could be identified. The most dominant predator was the European earwig, Forficula auricularia L. (Dermaptera: Forficulidae), with 90% of all predation events. We conclude that F. auricularia is likely a key predator of vineyard pests, and that special attention should be paid to maintain it at high population densities.

Remote detection of fungal pathogens in viticulture using laser-induced fluorescence: an experimental study on infected potted vines

IntroductionPathogenic fungi, such as Plasmopara viticola and Erysiphe necator, severely threaten the annual yield of grapes in both quantity and quality. In contrast to other crop production systems, fungicides are intensively applied in viticulture as a countermeasure. The goal of precision viticulture is to optimize vineyard performance as well as the environmental impact by reducing fungicides and applying different techniques and combined strategies. Therefore, new emerging technologies are required, including non-invasive detection, as well as monitoring and tools for the early and in-field detection of fungal development. MethodsIn this study, we investigated leaves of potted vines (Vitis vinifera cv. ‘Riesling’) and traced the development of the inoculated leaves using our new remote detection system vinoLAS®, which is based on laser-induced fluorescence spectroscopy. We ran a measurement campaign over a period of 17 days.ResultsWe were able to detect a leaf infection with P. viticola, the causal agent of downy mildew, between 5 and 7 days after inoculation. Our results provide evidence for a successful application of laser-based standoff detection in vineyard management in the future. Thus, the vinoLAS system can serve as a model technology for the detection of pathogenic disease symptoms and thus monitoring complete vineyard sites. This allows for early countermeasures with suitable crop protection approaches and selected hot-spot treatments.DiscussionAs P. viticola is considered one of the most damaging fungi in European viticulture, disease mapping via this monitoring tool will help to reduce fungicide applications, and will, therefore, support the implementation of the European Green Deal claims.

Inorganic Fungicides (Phosphites) Instead of Organic Fungicides in Winter Wheat—Consequences for Nitrogen Fertilizer Productivity

Substitution of organic with inorganic fungicides (phosphites, Phi) does not change the efficiency of fertilizer nitrogen (Nf) in winter wheat. This hypothesis was tested in the 2016/2017 and 2017/2018 growing seasons. A two-factorial experiment with three phosphite variants (Cu–Phi, Mg–Phi, and Cu/Mg) and six plant protection methods (fungicides + Phi ⟶ reduced fungicide frequency + phosphite ⟶ phosphite). Grain yield decreased with increasing frequency of phosphites instead of fungicides. The decrease in yields was 3.6 t ha−1 in the favorable 2016/2017 and 1.1 t ha−1 in the dry 2017/2018. The primary reason for yield decrease in a given growing season was increased wheat infestation by pathogens. The direct cause was disturbances in the nitrogen status of wheat after flowering on treatments with a predominance of phosphites. The thousand grain weight (TGW) responded negatively to reduced fungicide application frequency. The critical stage in the assessment of pathogen pressure on wheat was the medium milk phase (BBCH 75). At this stage, indices of SPAD and leaf greenness together with indices of wheat infestation with pathogens allowed for a reliable prediction of both TGW and grain yield. It can be concluded that phosphites do not substitute organic fungicides in limiting pathogen pressure in winter wheat. Moreover, increased pressure of pathogens significantly reduces Nf productivity.

Foliar and root applications of the rare sugar tagatose control powdery mildew in soilless grown cucumbers

Powdery mildew is a constant threat to cucumber production in soilless systems requiring the intensive use of chemical fungicides to limit yield losses. However, the toxicity risks for the growers and the food safety issues linked to fungicide residues represent a major concern for crops with a frequent and extended harvest period, like cucumber, and create an urgent need of eco-friendly alternatives. The objective of this study was to assess the effectiveness of foliar and root applications of the rare sugar tagatose, against naturally occurring powdery mildew (Podosphaera xanthii and Golovinomyces cichoracearum) on cucumber plants grown in a soilless system under commercial-like greenhouse conditions. Foliar and root applications of tagatose reduced powdery mildew severity and incidence under conditions of low severity in untreated plants, but tagatose and the chemical standard strategy lost their effect in the control of powdery mildew when the disease severity was increasing steadily. The combination of sulphur with foliar applications of tagatose effectively reduced powdery mildew under high severity conditions. Overall, under high disease pressure, foliar and root applications of tagatose were more effective than the standard chemical treatment reducing powdery mildew disease incidence and severity. Foliar application of tagatose directly inhibited P. xanthii conidial germination. After root application, tagatose was translocated to the leaves guaranteeing a systemic protection with no accumulation in cucumber fruits. Root applications of tagatose represent a novel strategy for cucumber protection against powdery mildew and reduce fungicide applications.

Sensory and Physicochemical Quality, Residual Fungicide Levels and Microbial Load in 'Florida Radiance' Strawberries from Different Disease Control Treatments Exposed to Simulated Supply Chain Conditions.

Strawberries are greatly appreciated for their flavor and health-promoting properties. However, current agricultural and postharvest handling practices may result in decreased fruit quality. The objective of this work was to determine the effect of conventional or reduced fungicide applications on the quality of ‘Florida Radiance’ strawberries exposed to supply chain conditions. Strawberries held under steady temperature had better sensory and physicochemical quality than fruit exposed to supply chain conditions, regardless of the disease control treatment. Strawberries from the reduced fungicide treatment were firmer, lost less moisture, had higher sugar and higher or similar bioactive contents than fruit from the conventional treatment. Sensory scores were better for reduced fungicide fruit held under steady temperature conditions than other treatments at the consumer level. Microbial load increased during the supply chain but results strongly suggest that washing the fruit significantly reduces the microbial load and residual fungicide levels (fludioxonil, cyprodinil, pyraclostrobin, and captan) on the fruit. Overall, the use of reduced fungicide applications to control strawberry disease constitutes a promising alternative to conventional practices. It will help reduce costs by reducing labor and the amount of fungicides used while maintaining overall strawberry quality. Moreover, avoiding abusive and fluctuating temperature conditions during the supply chain will extend shelf-life and reduce strawberry waste.

Yeast diversity in the vineyard: how it is defined, measured and influenced by fungicides

This review focuses on the considerable amount of research directed at defining microbial diversity in the vineyard and the subsequent contribution to uninoculated fermentations, with an emphasis on the effect of fungicide applications. From this research it is clear that there are many factors affecting diversity in the vineyard including: sprays, climate, location and grape-derived parameters. With their increasing affordability, next generation sequencing methods to measure diversity in environmental samples are now being adopted for studies of the grapevine microbiome. We bring together the results of these studies, discuss how diversity is measured and consider the potential applications of current knowledge. An in-depth analysis of how fungicides affect yeast diversity in the vineyard and the mode of action of different fungicide groups are also discussed. Finally, we report on alternative treatments to maintain vineyard health and reduce fungicide applications in the future.

Field Validation of PBcast in Timing Fungicide Sprays to Control Phytophthora Blight of Chili Pepper

Field validation of PBcast, an infection risk model for Phytophthora blight of pepper, was conducted through a designed field experiment in 2012 and 2013. Conduciveness of weather conditions at 26 locations in Korea in 2014-2017 was also evaluated using PBcast. The PBcast estimated daily infection risk (IR) of Phytophthora capsici based on weather and soil texture data. In the designed filed experiment, four treatments including routine sprays at 7-day intervals (RTN7), forecast-based sprays when IR reached 200 (IR200) and 224 (IR224), and no spray (CTRL) were compared in terms of disease incidence and number of sprays recommended for disease control. In 2012, IR had reached over 200 twice, but never reached 224. In 2013, IR had reached over 200 three times and once higher than 224. The RTN7 plots were sprayed 17 and 18 times in 2012 and 2013, respectively. Weather conditions throughout the country were generally conducive for Phytophthora blight and 3-4 times of fungicide sprays would have been reduced if the PBcast forecast information was adopted in the decision-making for fungicide sprays. In conclusion, the PBcast forecast would be useful to reduce fungicide applications without losing the disease control efficacy to protect pepper crop from Phytophthora blight.

Fungicide reduction favors the control of phytophagous mites under both organic and conventional viticulture

Pesticides can have detrimental effects on non-target biodiversity, especially in intensively managed agroecosystems such as vineyards. However, new fungus-resistant grape varieties can greatly reduce the need and use of fungicides. Fungicides can have direct and indirect effects on economically important predatory mites (mainly Phytoseiidae) and on phytophagous mites (Tetranychidae, Eriophyidae) on which they prey. We investigated the impact of fungicide treatments on beneficial and phytophagous mite densities in 32 vineyards of organic and conventional wineries planted with susceptible and fungus-resistant grape varieties in the Palatinate region, Germany. Organic vineyards were sprayed with different formulations of sulfur, copper and potassium bicarbonate, while conventional vineyards received mostly synthetic fungicides. Fungicide applications were reduced by 47-80 % in fungus-resistant varieties, with stronger reductions under organic than under conventional management. Regardless of organic or conventional management, predatory mites (Phytoseiidae and Tydeidae) were significantly enhanced in vineyards planted with fungus-resistant varieties. Contrastingly, phytophagous mites (Eriophyidae) were enhanced in vineyards with fungus-susceptible varieties and in those under organic management. Densities of further predatory mite families increased under organic farming (Anystidae) or showed an interactive response to farming system and grape variety (Trombidiidae). Reduced fungicide applications through cultivation of fungus-resistant varieties enhance predatory mite densities and thus contribute to higher natural pest control potential. Thus, the cultivation of fungus-resistant grape varieties is an effective approach towards more environmentally friendly viticulture.

Management strategies for Alternaria leaf blight on American ginseng

Cultivated American ginseng (Panax quinquifolius) is a perennial herb valued as a traditional Chinese medicine. The crop is commercially produced under polypropylene shade cloth, creating a climate favorable for leaf blight caused by Alternaria panax; frequent fungicide applications are required annually to protect yields of the root and seed. Our objective was to improve Alternaria leaf blight tactic by identifying effective products and application intervals using a calendar or the TOM-CAST disease forecaster. Product efficacy trials were conducted at two sites over two years and included 14 products and an untreated control. The fungicides pyraclostrobin and azoxystrobin + difenoconazole were consistently effective in limiting leaf blight compared to the untreated control. Fluxapyroxad + pyraclostrobin was also effective both years across both sites with one exception. Mancozeb, fluazinam, chlorothalonil, difenoconazole, and penthiopyrad were effective when disease pressure was not severe. Applications of pyraclostrobin or mancozeb resulted in a higher seedhead yield than the untreated control. The TOM-CAST disease forecaster, with spray thresholds of 10 or 15 disease severity values (DSVs) was tested at four field sites for each of two years and compared to fungicides applied every 7 or 10 days or not applied (untreated control). All treatments at three of the four sites limited disease severity compared to the untreated control in both years. According to the area under the disease progress curve (AUDPC) data, fungicide treatment programs in 2013 were similar and better than the untreated control. The AUDPC data from 2014 indicated that the 7-day application treatments had fewer diseased plants than the untreated control at all sites; the TOM-CAST 10 and 15 DSV treatments limited disease compared to the untreated control at three of the four sites. The TOM-CAST 10 DSV treatment yielded similarly to the 10-day treatment at one site for both fresh and dried root; the TOM-CAST 10 and 15 DSV treatment yields were similar. At a second site, fresh and dried root yields were similar for the 7-day and TOM-CAST 10 DSV treatments; 10-day and TOM-CAST 15 DSV treatments were similar. TOM-CAST 10 DSV may provide a balance between reducing fungicide applications while protecting valuable ginseng root yields.

Delaying the first grapevine fungicide application reduces exposure on operators by half

Downy mildew is a severe disease of grapevines treated by repeated fungicide applications during the growing season. The impact of these treatments on human health is currently under scrutiny. Fungicide application long before disease onset is not thought to be greatly beneficial for grape production, but the first fungicide treatment is applied at least six weeks before disease onset in more than 50% of the vineyards in the Bordeaux region, a major French vine-growing area. We estimate that applying one fungicide every two weeks at disease onset would reduce fungicide applications against downy mildew by 56% (95%IC = [51.0%, 61.3%]), on average, relative to current levels. This decrease is slightly greater than the level of exposure reduction resulting from the random suppression of one out of every two fungicide treatments (i.e. 50%). The reduction is lower when treatments are sprayed weekly but still reaches at least 12.4% (95%IC = [4.3%, 20.8%]) in this case. We show that this and other strategies reducing the number of treatments would decrease operator exposure to pesticides as effectively as the use of various types of personal protective equipments in the Bordeaux region. The implementation of this strategy would significantly decrease fungicide use, health risks, and adverse environmental impacts of vineyards.

Using model-based fungicide programing to effectively control Botrytis and Anthracnose fruit rots in Mid-Atlantic strawberry fields and co-manage strawberry sap beetle (Stelidota geminate)

Effective fruit rot management is essential for profitable strawberry production in the Mid-Atlantic. With recent fungicide resistance development in two high-impact fruit rot pathogens, Botrytis cinerea [the cause of Botrytis fruit rot (BFR)] and Colletotrichum acutatum [the cause of Anthracnose fruit rot (AFR)], there is increasing interest in using disease forecasting to reduce fungicide applications and thus preserve existing chemistries. We conducted field trials in the Mid-Atlantic over two years to evaluate use of a model-based fungicide program [the Strawberry Advisory System (StAS)] for: (1) efficacy in reducing fungicide applications, (2) ability to achieve fruit rot control similar to the existing calendar-based program, and (3) effects on non-target diseases and pests. Across the two years, fungicide applications were reduced by an average of 50% for BFR control and 58% for AFR control. The model and calendar-based programs resulted in similar yields in both years, based on both percent of marketable fruit and marketable fruit yields (P > 0.05). Confirming fungicide treatment efficacy, yields were significantly lower in the non-treated control (NTC) in 2016 (incidence: P = 0.024; fruit biomass: P = 0.012). Yields were uniform in 2017, with 94–96% of fruit marketable, and there was no treatment effect. AFR incidence in the calendar and model-based programs were similar in both years (P > 0.05). AFR incidence in the NTC was significantly greater than both fungicide treatments in 2016 (P = 0.004) but not in 2017 (P = 0.63), likely due to low AFR levels (<2% of fruit with AFR across treatments). BFR incidence in the model-based program was likewise similar in model and calendar programs in both year (P > 0.05). Neither program differed from the NTC in 2016 (P = 0.84), likely due to low BFR levels (>4% of fruit with BFR); in 2017 BFR incidence in the NTC was significantly greater than calendar program (P = 0.032). This study also revealed a 55% reduction strawberry sap beetle (Stelidota geminate) incidence in the model-based fungicide program compared to the NTC (P = 0.027) in 2016 due to reduction in fruit rots. Model-based spray programming therefore has the potential to mitigate fungicide resistance development in the Mid-Atlantic strawberry production while providing effective fruit rot control. Potential to co-manage strawberry sap beetle should be further examined and would greatly enhance industry profitability.

Molecular cytogenetic characterization of wheat\u2013Elymus repens chromosomal translocation lines with resistance to Fusarium head blight and stripe rust

BackgroundFusarium head blight (FHB) caused by the fungus Fusarium graminearum Schwabe and stripe rust caused by Puccinia striiformis f. sp. tritici are devastating diseases that affect wheat production worldwide. The use of disease-resistant genes and cultivars is the most effective means of reducing fungicide applications to combat these diseases. Elymus repens (2n = 6x = 42, StStStStHH) is a potentially useful germplasm of FHB and stripe rust resistance for wheat improvement.ResultsHere, we report the development and characterization of two wheat–E. repens lines derived from the progeny of common wheat–E. repens hybrids. Cytological studies indicated that the mean chromosome configuration of K15–1192-2 and K15–1194-2 at meiosis were 2n = 42 = 0.86 I + 17.46 II (ring) + 3.11 II (rod) and 2n = 42 = 2.45 I + 14.17 II (ring) + 5.50 II (rod) + 0.07 III, respectively. Genomic and fluorescence in situ hybridization karyotyping and simple sequence repeats markers revealed that K15–1192-2 was a wheat–E. repens 3D/?St double terminal chromosomal translocation line. Line K15–1194-2 was identified as harboring a pair of 7DS/?StL Robertsonian translocations and one 3D/?St double terminal translocational chromosome. Further analyses using specific expressed sequence tag-SSR markers confirmed that the wheat–E. repens translocations involved the 3St chromatin in both lines. Furthermore, compared with the wheat parent Chuannong16, K15–1192-2 and K15–1194-2 expressed high levels of resistance to FHB and stripe rust pathogens prevalent in China.ConclusionsThus, this study has determined that the chromosome 3St of E. repens harbors gene(s) highly resistant to FHB and stripe rust, and chromatin of 3St introgressed into wheat chromosomes completely presented the resistance, indicating the feasibility of using these translocation lines as novel material for breeding resistant wheat cultivars and alien gene mining.

Avaliação de sistemas de previsão para a septoriose do tomateiro tutorado em Caçador, SC, Brasil

A septoriose, causada pelo fungo Septoria lycopersici, é uma das mais importantes doenças do tomateiro tutorado em Caçador, SC, Brasil. A doença é geralmente controlada pela aplicação preventiva de fungicidas. Experimentos de campo foram realizados com o objetivo de avaliar sistemas de previsão dessa doença: um com base no sistema TomCast (10, 15 e 20 valores de severidade – VSD), outro pelo período de molhamento foliar (limiar ≥ 12 horas), ambos comparados com a aplicação semanal de fungicidas. O TomCast utiliza a duração do molhamento foliar e a temperatura média deste período para calcular o valor de severidade diário da doença (VSD). Não houve diferença significativa entre o tratamento semanal e os previsores em relação a produtividade, severidade final, área abaixo da curva do progresso da doença e taxa de infecção aparente (r). Entretanto, com o tratamento 20-VSD houve redução de 12,5 a 70% das pulverizações em relação ao tratamento semanal. Termos para indexação: Solanum lycopersicum; sistema de alerta; TomCast; Septoria lycopersici; método de controle

Reduced fungicide applications improve insect pest control in grapevine

Agricultural intensification is a major driver of biodiversity decline in many species including arthropods. This may also affect important ecosystem services such as natural pest regulation. Traditional grapevine varieties rely on a high number of fungicide applications, which can be greatly reduced in novel fungus resistant cultivars. Additionally, in contrast to the traditional trellis system, the semi-minimal pruned hedge offers a structurally more diverse habitat for arthropods. We investigated natural control of the grapevine pest Lobesia botrana ([Denis & Schiffermuller], 1775) (Lepidoptera: Tortricidae) with artificial inoculation of grape bunches, egg baits, camera surveillance and beatsheet sampling of predators. Reduced fungicide applications enhanced densities of L. botrana predators along with increased egg predation and reduced damage of inoculated grape bunches. Minimal pruning did not have a clear effect. Improved pest control potential adds to other advantages of reduced fungicide applications. Planting fungus-resistant varieties should be augmented, potentially also in other crop systems that rely heavily on fungicides.

Sensory Quality, Physicochemical Attributes, Polyphenol Profiles, and Residual Fungicides in Strawberries from Different Disease-Control Treatments.

Using alternative agricultural practices in combination with proper postharvest handling has become a major goal to improve fresh produce quality. Here, two different strawberry ( Fragaria × ananassa) genotypes were used as a model to study the impact of repeated, reduced-fungicide or no-fungicide applications on the sensory quality, physicochemical attributes, polyphenol profiles, and residual fungicide in strawberries. Strawberries grown under reduced-fungicide applications had similar or better physicochemical quality than conventionally and organically grown fruit and lower levels of fungicide residues than conventional fruit. Overall, flavor- and health-related attributes of strawberries from reduced-fungicide applications were intermediate between conventional and organic fruit. Thus, growing strawberries with reduced-fungicide applications can be an alternative to conventional or organic agricultural practices.

A new interspecific pear cultivar Yutaka: highly resistant to the two major diseases scab and black spot on Asian pears

Scab, caused by Venturia nashicola, is the most important disease of Asian pears. In Japan, the most popular and widely grown pear cultivar (cv.) Kousui is resistant to black spot, caused by the Japanese pear pathotype of Alternaria alternata, but highly susceptible to scab. Recently, a new interspecific pear cv. Yutaka carrying high fruit quality was registered officially after a cross between the Chinese pear cv. Hongli and the Japanese pear cv. Housui. Accordingly, tests were conducted to assess resistance of cv. Yutaka to scab, black spot and anthracnose. When conidial suspensions of V. nashicola were spray inoculated onto potted trees, leaves of cv. Yutaka showed no disease symptoms although severe scab development was recorded on the susceptible reference cv. Kousui. Furthermore, neither black spot symptoms nor necrosis formation were observed when leaves of cv. Yutaka were inoculated with conidial suspensions of the A. alternata Japanese pear pathotype or treated with a culture filtrate containing the host-specific AK-toxin of this pathogen, respectively. These results strongly indicate that cv. Yutaka is highly resistant to scab and black spot. Inoculation tests also suggested the potential high levels of resistance of cv. Yutaka to anthracnose caused by Colletotrichum gloeosporioides sensu lato. The introduction of this new pear cultivar will reduce fungicide applications in pear orchards and thus lower the risk of fungicide resistance development in these pathogens.

Temporal dynamics and management of downy mildew on the table grape ‘BRS Vitória’ in northern Paraná

Downy mildew caused by Plasmopara viticola is a major disease of grapes in Paraná State, Brazil and other wine-producing regions. The seedless table grape ‘BRS Vitória’ stands out for its tolerance to this disease and is a viable alternative to reduce fungicide applications. The objectives of this study were to analyze the influence of weather-related factors, such as temperature and rainfall on disease progress and to evaluate the efficacy of fungicide spray programs for controlling downy mildew of grapes during the summer-fall and winter-spring crop seasons in northern Paraná, Brazil. Field trials were conducted in Marialva, Paraná, during the winter-spring crop seasons (August to December) in 2013 and 2014 and the summer-fall crop seasons (January to May) in 2014 and 2015. The experimental design used was completely randomized with repeated measurements over the phenological periods, with five treatments and 10 replicates. The following treatments were compared: (1) conventional, in which fungicides were applied according to conventional standards; (2) preventive fungicide sprays every seven days; (3) preventive fungicide sprays every 14 days; (4) fungicide sprays after observing the first downy mildew symptoms; and (5) no fungicide sprays. In the conventional fungicide program, sprays were performed two or three times per week. Treatments 2 and 3 received sprayings between the start of branch budding and fruit ripening. In treatment 4, sprays started from the first occurrence of oil spot symptoms, and then, the applications were spaced every seven days until fruit ripening. The severity of disease was evaluated weekly. The disease was severe only in the 2014 and 2015 summer-fall crop seasons, reaching a maximum severity of 17.3% and 21.3% of the leaf area, respectively. The highest disease severity in the summer-fall crop seasons was associated with higher frequencies of rainy days and higher temperatures. Disease severity in conventional treatments did not differ from severity in treatments with sprayings made every seven and 14 days during the summer-fall crops in both years. Severity index on bunches were not observed for the evaluated trials. The seedless grape ‘BRS Vitória’ is less dependent on the use of fungicides to control downy mildew in northern Paraná.

Meta-Analysis of a Web-Based Disease Forecast System for Control of Anthracnose and Botrytis Fruit Rots of Strawberry in Southeastern United States.

Strawberry production in Florida and South Carolina is affected by two major diseases, anthracnose fruit rot (AFR) and Botrytis fruit rot (BFR), caused by Colletotrichum acutatum and Botrytis cinerea, respectively. The effective management of both diseases traditionally relied on weekly fungicide applications. However, to improve timing and reduce the number of fungicide sprays, many growers follow the Strawberry Advisory System (StAS), a decision support system for forecasting fungicide applications based on environmental conditions and previously developed models. The objective of this study was to perform a meta-analysis to determine the effectiveness of the StAS for AFR and BFR management compared with a calendar-based spray program. Thirty-nine trials were conducted from 2009 to 2014 in Florida and South Carolina commercial strawberry fields. Meta-analysis was conducted to quantify the treatment effects on four effect sizes, all based on the difference in response variables for StAS and the calendar-based treatments in each trial. The mean difference in BFR incidence, AFR incidence, yield, and number of marketable fruit between the two treatments was not significantly different from 0 (P < 0.05). However, the number of fungicide applications per season was reduced by a median of seven when using the StAS, a 50% reduction in sprays compared with the calendar-based approach. Effect sizes were not influenced by location or the favorability of the environment for disease development. These findings indicate that use of StAS in commercial fields is effective in controlling fruit rot diseases with no reduction in yield while substantially reducing fungicide applications.

Minimal Pruning and Reduced Plant Protection Promote Predatory Mites in Grapevine.

Improving natural pest control by promoting high densities of predatory mites (Acari: Phytoseiidae) is an effective way to prevent damage by pest mites (e.g., Eriophyidae, Tetranychidae) and other arthropod taxa that can cause serious damage to vineyards. Here, we investigate the influence of innovative management on predatory mite densities. We compare (i) full versus reduced fungicide applications and (ii) minimal pruning versus a traditional trellis pruning system in four fungus-resistant grapevine varieties. As predatory mites also feed on fungus mycelium, we assessed fungal infection of grapevine leaves in the experimental vineyard. Predatory mites were significantly more abundant in both minimal pruning and under reduced plant protection. Increases in predatory mites appeared to be independent of fungal infection, suggesting mostly direct effects of reduced fungicides and minimal pruning. In contrast to predatory mites, pest mites did not increase under innovative management. Thus, conditions for natural pest control are improved in fungus-resistant grapevines and under minimal pruning, which adds to other advantages such as environmental safety and reduced production cost.

Late Blight and Early Blight Resistance from Solanum hougasii Introgressed Into Solanum tuberosum

Late blight and early blight, caused by Phytophthora infestans and Alternaria solani, respectively, are the two most widely occurring foliar diseases of potato in the U.S.A. Resistance to both diseases is necessary if growers are to reduce fungicide applications. Field resistance to late blight has previously been reported in an accession of Solanum hougasii (2n = 72). The putative aneuploid clone E53.61, derived from (S. hougasii x S. tuberosum) x S. tuberosum was obtained from C.R. Brown and crossed with three S. tuberosum clones. Thirty-five hybrid clones were evaluated for foliar late blight resistance at the Russell E. Larson Agricultural Research Center near State College, PA along with the susceptible check ‘Atlantic’ and for foliar early blight resistance in Presque Isle, ME along with the susceptible check ‘Harley Blackwell’ for 3 years (2012 to 2014). The experimental design was a randomized complete block design with two to three replications each year. The US-23 genotype of P. infestans occurred naturally and/or was used in inoculations in PA and plants were infected naturally with A. solani in ME. Relative area under the disease progress curve (RAUDPC) values were calculated based on visual assessment of foliar disease four to five times late in the season each year and subjected to statistical and stability analyses. There were significant differences among clones and the clone x environment interaction was significant for both diseases. Of the 35 hybrid clones evaluated for late blight, 16 were more resistant, 7 were more susceptible, and 12 were as susceptible as ‘Atlantic’. Of those same hybrid clones evaluated for early blight, 23 were more resistant than ‘Harley Blackwell’; the rest were as susceptible. Late blight resistance or susceptibility was independent of the stability of resistance, however, early blight resistance was associated with greater stability. Fourteen clones were more resistant than the check varieties for both late blight and early blight, suggesting that resistance genes for both late blight and early blight have been combined in this genetic material; three of these clones also had high specific gravity and acceptable chip color out of 10 °C storage.