Incidence Of Mildew Research Articles

Influence of weather parameters on powdery mildew of mango inflorescence in humid tropics of South Gujarat

The influence of environmental parameters on the development of powdery mildew caused by Oidium mangiferae Berthet on mango inflorescence was studied for seven consecutive years (2012-18) in humid tropics climatic conditions of South Gujarat. The disease incidence and severity (DIS), area under disease progress curve-AUDPC (A-value) and apparent infection rate (r-value) were recorded at panicle and fruit setting stages of the tree at weekly intervals. The correlation studies showed that incidence and severity of powdery mildew significantly negative relationship with morning relative humidity (r = -0.631; p<0.05 and r = -0.721; p<0.01) and average relative humidity (r = -0.766 and r = -0.787; p<0.01). Temperature (maximum and average) and evaporation showed positive relationship with incidence and severity of powdery mildew. Further, stepwise linear regression model indicated that average relative humidity as single predictor independent variable had the strongest relationship disease incidence and severity, which explained 59 percent disease incidence and 62 percent for disease severity variability. This forewarning model can be useful for efficient management of powdery mildew disease of mango and as well as agro advisory services to farmers.

Reducing the Nursery Pesticide Footprint with Laser-guided, Variable-rate Spray Application Technology

Nursery producers are challenged with growing a wide range of species with little to no detectable damage from insects or diseases. Growing plants that meet consumer demand for aesthetics has traditionally meant routine pesticide application using the most time-efficient method possible, an air-blast sprayer, despite its known poor pesticide application efficiency. New variable-rate spray technology allows growers to make more targeted applications and reduce off-target pesticide loss. In this study, a prototype laser-guided variable-rate sprayer was compared with a traditional air-blast sprayer. Pesticide volume, spray application characteristics, and the control of powdery mildew were evaluated over the course of two growing seasons. Spray application characteristics were assessed using water-sensitive cards (WSCs) and DepositScan software. This prototype sprayer reduced pesticide volume by an average of 54% across both years despite being tested against a low rate (<250 L⋅ha−1). In 2016, the conventional sprayer had more than double the deposit density on target WSCs among distal trees than the variable-rate sprayer; however, within proximal trees, there was no difference between the two sprayer types. In 2017, when the trees were larger, within both the distal and proximal trees, the conventional sprayer had greater deposit density on target WSCs than the variable-rate sprayer. In 2016, coverage on target WSCs was nearly 7-fold greater with the conventional treatment than with the variable-rate treatment. In 2017, when trees were larger, there was greater coverage on target WSCs in proximal trees (3.8%) compared with those in distal trees (1.0%) regardless of the sprayer type. This variable-rate spray technology provided acceptable control of powdery mildew severity on individual branches and whole trees and maintained the incidence of powdery mildew to levels comparable to that occurring among trees sprayed with a traditional air-blast sprayer. Therefore, the variable-rate spray technology has the potential to effectively control disease, dramatically reduce the pesticide footprint, and preserve natural resources such as ground and surface water, soil, and beneficial insects found within and around nurseries.

Efficacy of different bio-organics for the management of important diseases of mango (Mangifera indica L.)

The powdery mildew, Oidium mangiferae Berthet, anthracnose, Colletotrichum gloeosporoides and sooty mould Capnodium spp. are the major diseases of mango in hot and humid coastal Konkan region of Maharashtra which causes severe losses in short span of period. The mango grower uses various pesticides for their management. However, the pesticides residue and their hazardous effect are well known. Therefore, most of the mango growers in the region are switching towards organic farming and trying variety of bio-organics especially against blossom diseases of mango and claiming their effectivity. Hence, the studies on efficacy of various bio-organics were conducted at Regional Fruit Research Station, Vengurla, Dist. Sindhudurg (M.S) during 2019–20 and 2020–21 cropping seasons. The profusely flowered plants were selected and sprayed with respective bioorganic at its full bloom stage. Only one spray was given at full bloom stage. The observations on natural incidence of powdery mildew, anthracnose and sooty mould on panicles were recorded. It was revealed from the pooled results of 2019–20 and 202021seasons that, the powdery mildew, anthracnose and sooty mould diseases were significantly controlled only by the treatments of chemical check Carbendazim 12% + Mancozeb 63% WP @ 0.2%. However, among the treatments of bio-organics Jeevamrut @10% and Vermiwash @ 10% were found promising against major diseases of mango blossom.

Influence of weather variables on the development of pearl millet downy mildew

The present study was undertaken during 2016 to 2018 to find out the effect of different weather variables on the initiation and development of downy mildew in pearl millet in Punjab. The maximum temperature ranged from 32.8ºC to 36.9ºC and minimum temperature ranged from 17.2ºC to 27.8ºC during the crop season. The correlation analysis showed significant negative correlation of maximum temperature (r = -0.665*), minimum temperature (r = -0.776**), wind speed (r = -0.898**), rainfall (r = -0.625**) and non-significant negative correlation of evening relative humidity (r = -0.523) with downy mildew incidence. The positive correlation with morning relative humidity (r = 0.871**) was significant and sunshine hours (r = 0.321) were non-significant with per cent disease incidence. A multiple regression model was developed using two years (2016 and 2017) data to predict the occurrence of downy mildew with R2 = 0.981, indicating that all weather parameters contributed 98.1 per cent towards disease development. The model was validated with 2018 data which shows that equation can be used in the disease forecasting for taking timely actions for control measures.

Disease Susceptibility of Interspecific Cold-Hardy Grape Cultivars in Northeastern U.S.A

Susceptibility to diseases of economically important grapes is critical to the evaluation of germplasm recommended for commercial production and for the development of sustainable production systems. In 2018–2019, the cold-hardy grape cultivars including ‘Brianna’, ‘Crimson Pearl’, ‘Itasca’, ‘Louise Swenson’, ‘Marechal Foch’, ‘Marquette’ ‘Petite Pearl’, ‘St. Pepin’, and ‘Verona’ were evaluated on non-treated vines for susceptibility to downy mildew, powdery mildew, black rot, anthracnose, Phomopsis leaf spot and fruit rot, and Botrytis bunch rot. No cultivars were consistently disease-free, and all exhibited some degree of black rot and powdery mildew infection. Relative susceptibility to disease was not consistent across both years, but ‘Brianna’ had greater incidence of black rot and ‘Louise Swenson’ showed lower incidence of powdery mildew in both years. The relatively new cultivars ‘Crimson Pearl’ and ‘Verona’ exhibited comparatively moderate disease susceptibility overall. Growers typically manage diseases with fungicides on commercial farms, so cultivar susceptibility is just one component of a sustainable pest management and production system.

Developing biopesticide-based programmes for managing powdery mildew in protected strawberries in the UK

Powdery mildew, caused by Podosphaera aphanis, is an important disease of strawberries and currently its control in the UK is very dependent on conventional fungicides. A series of experiments were carried out to integrate conventional fungicides with biopesticides and biostimulants for mildew control. In 2015–2016, the biopesticides Sonata (Bacillus pumilis) and AQ10 (Ampelomyces quisqualis) achieved at least as good as or better mildew control where they were applied alone rather than alternated with or tanked mixed with conventional fungicides. Three mildew management programmes were evaluated in 2017 on an ever-bearer cultivar. In the B. pumilis based programme, the need for treatment and the choice of products were partially determined by predicted mildew risks. The incidence of mildew on leaves was very low in untreated plots with virtually no mildew observed in the other treated plots. By contrast, mildew on the fruit rose rapidly from 2 % in late July to >90 % in late August in untreated plots. In treated plots, the percentage of fruit with mildew did not rise above 3 % with the three managed programmes based on B. pumilis. There were no significant differences in total yield and marketable yield between the managed programmes and the routine fungicide programme, but all were significantly greater than the untreated control. Most of the unmarketable fruit in the untreated control was due to infection with powdery mildew. The results suggested that strawberry powdery mildew can be effectively managed by the integrated use of biopesticides, biostimulants and conventional fungicides.

Evaluation of Germplasm of Pearl Millet (Penissetum glaucum L.) for Agronomic, Physiological and Biochemical Traits under Semi-arid Conditions of Hamelmalo

A field experiment was conducted at the experimental farm of Hamelmalo Agricultural College during summer 2017, to evaluate the agronomic, physiological, and biochemical performance of the collected Eritrean germplasm of pearl millet. A total of 16 accessions were tested, out of which 2 were improved varieties included as a check. The experiment was laid out in 4 x 4 Simple Lattice Design with Randomized Block using 4 replications with a gross plot size of 3.0 m x 1.2 m, row to row spacing of 75 cm and plant to plant spacing of 30 cm. The data collected were Agronomic parameters (growth, development, yield, and yield contributing characters); Physiological parameters (Relative water content and Water Use Efficiency); and Biochemical parameters (crude fat, crude fiber, protein content, TSS, and ash content). The data were analyzed using GENSTAT software and correlation analysis was worked to see the positive and negative contribution of agronomic, physiological, and biochemical attributes. The results of the study showed that Bariyay908 and Kona being statistically at par with Bariyay 910, Hagaz, Zibedi, Shleti, Delkata, Tokroray, and Kunama produced significantly higher grain yield. However, among these Baryay908 because of its superior agronomic characteristics, lower incidence of downy mildew, relatively higher water use efficiency and higher crude protein content were found to be comparatively superior to the check improved varieties Kona and Hagaz. Grain yield has shown a positive and significant correlation with harvest index, number of seeds per panicle, panicle length, leaf area and water use efficiency. These promising accessions need to be further tested for future breeding programs to develop varieties higher in productivity and resistant to downy mildew under semiarid conditions of Eritrea.

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.

Changing light promotes isoflavone biosynthesis in soybean pods and enhances their resistance to mildew infection.

Mildew severely reduces soybean yield and quality, and pods are the first line of defence against pathogens. Maize-soybean intercropping (MSI) reduces mildew incidence on soybean pods; however, the mechanism remains unclear. Changing light (CL) from maize shading is the most important environmental feature in MSI. We hypothesized that CL affects isoflavone accumulation in soybean pods, affecting their disease resistance. In the present study, shading treatments were applied to soybean plants during different developmental stages according to various CL environments under MSI. Chlorophyll fluorescence imaging (CFI) and classical evaluation methods confirmed that CL, especially vegetative stage shading (VS), enhanced pod resistance to mildew. Further metabolomic analyses and exogenous jasmonic acid (JA) and biosynthesis inhibitor experiments revealed the important relationship between JA and isoflavone biosynthesis, which had a synergistic effect on the enhanced resistance of CL-treated pods to mildew. VS promoted the biosynthesis and accumulation of constitutive isoflavones upstream of the isoflavone pathway, such as aglycones and glycosides, in soybean pods. When mildew infects pods, endogenous JA signalling stimulated the biosynthesis of downstream inducible malonyl isoflavone (MIF) and glyceollin to improve pod resistance.

Evaluation of Scab and Mildew Resistance in the Gene Bank Collection of Apples in Dresden-Pillnitz.

A set of 680 apple cultivars from the Fruit Gene bank in Dresden Pillnitz was evaluated for the incidence of powdery mildew and scab in two consecutive years. The incidence of both scab and powdery mildew increased significantly in the second year. Sixty and 43 cultivars with very low incidence in both years of scab and powdery mildew, respectively, were analysed with molecular markers linked to known resistance genes. Thirty-five cultivars were identified to express alleles or combinations of alleles linked to Rvi2, Rvi4, Rvi6, Rvi13, Rvi14, or Rvi17. Twenty of them, modern as well as a few traditional cultivars known before the introduction or Rvi6 from Malus floribunda 821, amplified the 159 bp fragment of marker CH_Vf1 that is linked to Rvi6. Alleles linked to Pl1, Pld, or Plm were expressed from five cultivars resistant to powdery mildew. Eleven cultivars were identified to have very low susceptibility to both powdery mildew and scab. The information on resistance/susceptibility of fruit genetic resources towards economically important diseases is important for breeding and for replanting traditional cultivars. Furthermore, our work provides a well-defined basis for the discovery of undescribed, new scab, and powdery mildew resistance.

Heterosis for Resistance against Sorghum Downy Mildew [Peronosclerospora sorghi (Weston and Uppal) C.G. Shaw] Infection in Maize (Zea mays L.)

Background: Sorghum downy mildew (SDM) of maize caused by the fungus Peronosclerospora sorghi (Weston and Uppal) C.G. Shaw is one of the most important diseases of maize and it remains vital constraint in maize production. Since maize is the highly cross pollinated crop, exploitation of heterosis is one of the breeding methods to increase the production. Negative values in the expression of heterosis indicate a contribution towards resistance which is highly needed in order to have reduced incid ence of sorghum downy mildew in maize hybrids.Methods: The materials selected as parents for the present study consisted of nine maize inbred lines which comprised of three resistant (UMI102, UMI936(w) and UMI285), three moderately resistant (UMI176, UMI13 and UMI57) and three susceptible (UMI79, UMI432 and UMI467) inbreds to SDM incidence. Nine inbred lines were crossed in all possible combinations including reciprocals in diallel fashion and the resultant seventy two hybrids along with their parents and the check (COH(M)5) were raised and evaluated for resistance against SDM under glass house condition. The extent of heterosis was estimated over mid parent, better parent and popular check hybrid.Result: Analysis of variance for sorghum downy mildew incidence revealed highly significant differences among parents and hybrids indicating greater diversity among the genotypes for sorghum downy mildew incidence under study. Out of seventy two hybrids, only three hybrids namely UMI 13 x UMI 936 (W), UMI 467 x UMI 936 (W) and UMI 432 x UMI 936 (W) exhibited three types heterosis significantly in negative direction.

English

The powdery mildew caused by air borne pathogen (Podosphaera fusca) is an important disease of cucurbits including melon (Cucumis melo L.) plants. Three antagonistic bacterial strains (M4, M10 and M11); isolated from the melon plants were tested for antagonistic activity against P. fusca and soil-borne pathogens of melon plants (Monosporascus cannonballus, Fusarium oxysporum f. spp. melonis, F. solani and Phomopsis spp.). All the three strains were identified as Bacillus velezensis based on sequence analysis of gyrase subunit A (gyrA) gene sequence. The bacterial strains showed significant antagonistic activity against soil and air borne pathogenic fungi. Among all strains, M10 showed a broad spectrum of mycelial growth inhibition against phytopathogenic fungi. The tested culture broth did not affect the pollen fertilization, flowering, fruit rot occurrence and fruit set development during blooming and cultivation season of the melon plants. The M10 culture broth stored for 3 and 6 months displayed biocontrol efficiency of 73.2 and 72.3%, respectively. Application of mixed solution of M10 culture broth + paraffin oil strongly suppressed the incidence and spread of powdery mildew. These results suggested that the combination of paraffin oil and B. velezensis M10 culture broth is an ecofriendly approach and possess strong biocontrol potential against melon powdery mildew and can also be used as antifungal agents for several plant pathogens. © 2021 Friends Science Publishers

Up‐regulation of pathogenesis‐related genes in strawberry leaves treated with powdery mildew‐suppressing ultraviolet irradiation

AbstractStrawberry powdery mildew caused by Podosphaera aphanis, one of the most important diseases affecting strawberry production in Japan, can be effectively controlled by supplemental ultraviolet (UV) irradiation. Here, we investigated disease severity on plants irradiated with UV light at 270–380 nm with/without inoculation and demonstrated significant decreases in disease severity on the UV‐treated plants throughout almost all of the experiment periods. Daily UV irradiation for 3 hr (0.17–0.96 kJ ⋅m−2 ⋅day−1) significantly reduced the incidence of powdery mildew on UV‐treated strawberry at day 58 after initiation of UV irradiation in a natural infection and at day 168 in artificial inoculation tests compared with non‐UV‐treated controls. Furthermore, we found that two pathogenesis‐related protein (PR) genes were up‐regulated 7 days after initiation of UV irradiation on plants before or after transplantation into raised beds. Transcript levels of five defence‐response genes were estimated using quantitative reverse transcription PCR to determine whether UV irradiation induced a defence response; PR‐3 and PR‐5 transcripts were significantly higher in the UV‐treated strawberry leaves after UV irradiation than in the non‐irradiated controls. In addition, transcript levels of both genes were significantly up‐regulated in plants irradiated with a higher radiant dose (0.90–0.96 kJ ⋅m−2 ⋅day−1) within 7 days after initiation of UV treatment, compared with plants exposed to a lower dose (0.17 kJ ⋅m−2 ⋅day−1) and with controls. Thus, PR‐3 and PR‐5 are induced in strawberry leaves as part of a defence response that is induced by UV irradiation.

ACTIVIDAD ANTIFÚNGICA DE EXTRACTOS VEGETALES CONTRA Erysiphe necator EN EL CULTIVO DE VID EN CONDICIONES DE CAMPO EN LA REGIÓN ICA-PERÚ

<p><strong>Background</strong>. Grape cultivation in Peru is one of the most important fruit activities, and ensuring its safety is essential to keep a successful production. <strong>Objectives</strong>. The study was focused on implementing a clean technology using plant extracts from <em>Larrea tridentata</em> and <em>Reynoutria sachalinensis</em> to control <em>Erysiphe necator</em> “oidium” in the Italian vine variety under field conditions. <strong>Methodology.</strong> Two treatments were carried out in parallel. The first treatment consisted in the use of two plant extracts and the second treatment in the exclusive use of chemical products. Applications in both treatments were applied once a week, from the phenological stage of flowering to the maturing and beginning of ripening of the berries. Recorded variables were incidence and severity of powdery mildew on leaves and clusters, total soluble solids, pH, acidity, and yield. <strong>Results.</strong> The treatment with the use of vegetable extracts showed an average control of the phytopathogen of 74% in the leaves and 88% in clusters. <strong>Implications</strong>. The cultivation of grapes in Ica is traditional and represents the area with the highest production in Peru, however, the production systems are monoculture with high dependence on chemical phytosanitary inputs that have economic, environmental and social effects for the sustainability of this agroecosystem. <strong>Conclusion.</strong> This study demonstrated that these two extracts have potential for use in the integrated managemed of <em>Erysiphe necator</em>, being environmentaly safer. To ensure its effectiveness, proper management of the plant canopy and a correct application in the field should be considered.</p>

Complex System Analysis of Blumeria graminis f.sp. tritici Isolates Collected in Central Hebei Province, China

Wheat powdery mildew (WPM), caused by Blumeria graminis f.sp. tritici, is a significant disease of wheat throughout the world and has resulted in substantial yield and economic losses in wheat production. It is particularly important to understand the population distribution and genetic resistance of B. graminis f.sp. tritici. In 2019, the cumulative incidence of wheat powdery mildew in China was nearly 8.7 million hm2, which seriously affected the safe production of wheat in China. However, the proportion of disease-resistant wheat varieties in actual production was relatively low, and effective disease-resistant genes were lacking. As one of the main wheat-producing provinces in China, it is of great significance for normal wheat production to understand powdery mildew resistance in Hebei province. In this study, using wheat seedling culture in vitro, the physiological races of wheat powdery mildew in central Hebei province were identified, and the population toxicity frequency was analyzed. The results were as follows: (1) 36 strains were purified and 20 physiological races were identified. Among them, the dominant race is 015, and the distribution frequency is 16.7%. Race 077 is the second dominant race. (2) The frequency of virulence genes VEra, V8, V1, V3c, and V3f in population toxicity frequency analysis was more than 70%, while the frequency of virulence genes V2, MID, V20, V21, V4b, and V4 was less than 16.7%, and 46% of virulence genes of powdery mildew were higher than 40%. It shows that the virulence gene frequency of powdery mildew in Hebei province is high, and the varieties containing Pm2 + MID, Pm20, Pm21, Pm1b, Pm1, and other disease resistance genes have a certain value inbreeding.

Characterization of powdery mildew (Leveillula taurica) in globe artichoke (Cynara scolymus)

Globe artichoke (Cynara scolymus L.) is an economically important plant that is mostly grown in Mediterranean Basin in the world. In 2016 and 2017, chlorotic spots on adaxial surface but white fungal patches abaxial surface of leaves of globe artichoke were observed in the Western Mediterranean Region of Turkey. To determine causal agent of these symptoms, leaf samples were taken sporadically in 2016, 2017 and 2020. Based on morphological and ITS sequence data, the causal agent was determined to be powdery mildew fungus Leveillula taurica (Lév.) G. Arnaud. Pathogenicity test was conducted using seedlings of globe artichoke in a greenhouse. Additionally, infections caused by the fungus were examined in a two-year field study. Several surveys were carried out according to simple random sampling method and a total of 79 farmer fields (570 da) were screened in the region. Disease incidence and prevalence of the powdery mildew in 2016 were 14.2 and 36.1%, while they were 30.1 and 53.4% in 2017, respectively. Mean disease incidence and prevalence in the both years were 22.1 and 45.5%, respectively. The disease was previously reported on globe artichoke in Italy, U.S.A., Spain and Egypt. To our knowledge, this is the first record of L. taurica causing powdery mildew on globe artichoke in Turkey and globe artichoke is a new host for L. taurica in Turkey.

Potensi Fungisida Perlakuan Benih terhadap Perenosclerospora sp. penyebab Penyakit Bulai Jagung

Jamur patogen Perenosclerospora sp. merupakan penyakit penting pada tanaman jagung. Dampak yang ditimbulkan dapat menimbulkan kerugian hingga 100%. Penelitian ini bertujuan untuk mengetahui pengaruh bahan aktif fungisida sebagai perlakuan benih dalam mengendalikan penyakit bulai (Perenosclerospora sp.) pada tanaman jagung. Penelitian dilaksanakan dengan diawali menanam tanaman jagung yang diinokulasi bulai sebagai tanaman spreader (sumber inokulum alami) dan pembatas antar perlakuan. Selanjutnya saat tanaman border sudah terinfeksi bulai baru ditanam benih perlakuan yang sudah dicampur dengan bahan aktif fungisida. Penelitian disusun dalam rancangan acak lengkap dengan delapan perlakuan dengan tiga ulangan. Perlakuan terdiri atas kontrol tanpa fungisida (P0), dimetomorf (P1), dimetomorf + piraklostrobin (P2), fenamidon (P3), fenamidon dan propamokarb hodroklorida (P4), metalaksil (P5), mefenoksam (P6), dan fluopikolid+propineb (P7). Hasil penelitian menunjukkan perlakuan kontrol lebih bagus dalam meningkatkan daya kecambah dibandingkan dengan menggunakan fungisida. Benih jagung yang diberikan perlakukan bahan aktif dimetomorf + piraklostrobin memiliki potensi yang paling tinggi dalam menekan keterjadian penyakit bulai pada jagung manis dan mampu meningkatkan pertumbuhan tinggi tanaman jagung yang dibandingkan perlakuan lainnya.

The effect of biological agent and botanical fungicides on maize downy mildew

Abstract. Prasetyo J, Ginting C, Akin HM, Suharjo R, Niswati A, Afandi A, Adiwijaya R, Sudiono, Nurdin M. 2021. The effect of biological agent and botanical fungicides on maize downy mildew. Biodiversitas 22: 1652-1657. This study was conducted to evaluate the effect of the combination of Trichoderma asperellum and mycorrhizae with botanical fungicides made from betel leaf extract or turmeric extract against maize downy mildew. The study used a randomized complete block (RCB) design with three replications. The treatments applied were: single applications of T. asperellum (Ta); arbuscular mycorrhizal fungi (AMF); turmeric extract (T); betel extract (B); the combination of T. asperellum and AMF (TaM); turmeric extract and T. asperellum (TTa); turmeric extract and AMF (TM); turmeric extract + T. asperellum + AMF (TTaM); betel extract + T. asperellum (BTa); betel extract + AMF (BM); betel + T. asperellum + AMF (BTaM); and Control (C). The observed variables were disease incidence, incubation period, and shoot dry weight. The data were analyzed using ANOVA. Differences between treatments were tested by the LSD test at 5% significance level. The results showed that the combination of botanical fungicides with biological agents could reduce the incidence of downy mildew, extend the incubation period, and increase the dry weight of corn shoots. The best combination treatment was achieved from the combination of T. asperellum with betel extract. There was a synergistic effect between botanical fungicides and biological agents in reducing the disease incidence.

Effects of Nitrogen and Intercropping on the Occurrence of Wheat Powdery Mildew and Stripe Rust and the Relationship With Crop Yield.

Wheat powdery mildew (Blumeria graminis f. sp. tritici) and stripe rust (Puccinia striiformis Westend f. sp. tritici) restrict wheat production in southwest China. Nitrogen fertilizers may influence outbreaks of these wheat diseases where wheat/faba beans are intercropped. To clarify how intercropping and varying nitrogen levels influence wheat powdery mildew and stripe rust and their relationship with crop yield, two consecutive field experiments were conducted from 2015 to 2017. Three cropping regimens (monocropped wheat, monocropped faba beans, and intercropped wheat/faba beans) and four nitrogen levels [N0 (0 kg⋅ha–1), N1 (90 kg⋅ha–1), N2 (180 kg⋅ha–1), and N3 (270 kg⋅ha–1)] were evaluated. In two consecutive planting seasons, the incidence and disease index of powdery mildew and stripe rust increased, while the disease index was more affected by nitrogen levels than their incidence. Both diseases were most prevalent at the N3 level. Compared with monocropping, intercropping (N0–N3 levels) reduced the incidence of powdery mildew by 2.8–37.0% and disease index by 15.5–47.4%, increased the relative control effect by 10.7–56.2 and 16.3–47.2%, reduced the incidence of stripe rust by 2.9–42.7% and disease index by 8.3–42.2%, and increased the relative control effect by 5.9–43.7 and 8.8–42.1%. The relative control efficacy of intercropping was most affected by N2 level. Intercropping yield increased with increasing nitrogen by 25.0–46.8%, and overall land equivalent ratio (LER) was 1.30–1.39. The correlation coefficient between disease index and wheat yield for both diseases was −0.7429 to −0.9942, a significant negative correlation, most significant at N1. Nitrogen regulation in intercropped wheat/faba beans can control powdery mildew and stripe rust, and optimize wheat yield. Intercropping at 180 kg ha–1 N2 resulted in the highest yield.

Molecular identification of Peronospora viciae causing downy mildew on field pea pods and its management

In the growing season 2016–2017, downy mildew disease was initially occurred on pea pods followed by plantlets leaves that observed in different locations where pea plants were grown at Kafr-El-Dawar district, Beheria governorate, Egypt. This irregular observation leads to thought that the cause of disease is new to this particular region. Molecular identification of the isolated fungus proved that the causal agent is Peronospora viciae. The sequences of the fungal isolate sent to GenBank and registered under accession number MN620384. Under field trials, it was observed that throughout the two cultivated seasons the fungicides application had greater effect on downy mildew incidence comparing with applied chemical inducers. Along the two cultivation seasons, pea plants sprayed with salicylic acid, potassium sorbate and ascorbic acid highly suppressed the disease incidence between 12.4 and 17.1%. Moderate effect was recorded as 19.2–22.7% disease reduction with potassium bicarbonate, lemongrass oil, lemongrass oil and humic acid application. The lowest effect was recorded as 32.5% at sodium benzoate treatment; meanwhile, 54.3% disease incidence was recorded at untreated control. Under field conditions, significant reduction in pea downy mildew disease was achieved by the use of fungicide alternative as foliar application. Therefore, these approaches could be utilized successfully for controlling this foliar disease especially they distinguished with safely use and avoidance of environmental pollution.