Journal of Plant Diseases and Protection

Feng, Jiale; Li, Ronggui; Wang, Chao; Yang, Hong; Deng, Wenjun; Du, Guicai; Guo, Qunqun

doi: 10.1007/s41348-022-00692-7pmid: N/A

AS the major causative agent of pine wilt disease, pine wood nematode, Bursaphelenchus xylophilus can result in rapid and massive deaths of pine forest, and even severe economy burdens globally. Botanical nematicides are the promising alternatives of the synthetic commercial nematicides which are causing more and more concerns such as drug resistance, threats to biodiversity and environmental pollution. In this review, we summarized the main nematicidal plant secondary metabolites against pine wood nematode including alkaloids, terpenoids, coumarins, flavonoids and glycosides. The chemical structures of the typical nematicidal phytochemicals with their activity index against pine wood nematode were illustrated, and the structure–activity relation and the action mode of the nematicidal phytochemicals were discussed, which will support future works on discovery of novel potent natural nematicides and the derivatives of natural products with higher nematicidal activity against pine wood nematode.

Pérez-Pizá, María Cecilia; Striker, Gustavo G.; Stenglein, Sebastián A.

doi: 10.1007/s41348-022-00703-7pmid: N/A

Information on fungal seed-borne diseases on main pasture grasses and legumes from the literature was reviewed. These diseases reduce biomass production, quality of forage, and persistence due to progressive plant mortality. The main fungal pathogens associated with forage seeds belong to the orders Hypocreales, Pleosporales, and Helotiales in the phylum Ascomycota. Hypocreales includes the genus Fusarium, which reduces seedling establishment, and contaminates plant tissues with mycotoxins. Pleosporales includes many genera associated with seeds of legumes (Leptosphaerulina and Ascochyta), grasses (Bipolaris, Pyrenophora, Curvularia, Drechslera, Alternaria, Exserohilum, and Phoma), and both (Stemphylium). Some fungal genera within this order induce the accumulation of coumestans (leafspot-producing fungi) or produce secondary metabolites that contaminate tissues (Alternaria). Within Helotiales, the main genera are Sclerotinia (affecting mainly legumes), Clarireedia and Gloeotinia (affecting grasses). Pyricularia (order Magnaporthales), Colletotrichum (order Glomerellales), and Cercospora (order Mycosphaerellales) also include seed-borne fungi that provoke diseases on forage species as well as Rhizoctonia (order Cantharellales) and Ustilago (order Ustilaginales) which belong to the phylum Basidiomycota. These pathogens affect pastures by (i) compromising seedling establishment at early stages and (ii) constraining growth by reducing yield and seed quality at later stages. Future research should address (i) generation of reliable data on forage yield loss due to seed-borne diseases, (ii) assessment of the interaction between seed-borne pathogens and other biotic and/or abiotic stresses, (iii) delve into the study of the role of wild and/or cultivated forage species as inoculum reservoirs of pathogens, and (vi) shed light on the contamination issue due to mycotoxins generation.

Sweellum, Tamer Ali; Naguib, Deyala M.

doi: 10.1007/s41348-022-00699-0pmid: N/A

Intercropping is a tried-and-true approach for restoring depleted agricultural soils, making better use of resources, controlling pests and disease, and ultimately boosting crop yield by reducing soil disease. This study tries to evaluate the role of tomato potato onion intercropping in induction tomato resistance against the soil-borne pathogen, Fusarium oxysporum. The study included four treatments Tomato seedlings monoculture in non-infected soil, Tomato seedlings monoculture in Fusarium infected soil, Tomato/potato onion intercropping in non-infected soil, Tomato/potato onion intercropping in Fusarium infected soil. Roots and shoots of tomato plants and soil were collected at 2 and 4 weeks after transplanting. Results showed that tomato/potato onion intercropping can enhance tomato resistance against Fusarium wilt. This is achieved through the improvement of soil enzymes and antifungal enzyme activity in the soil which release compounds from the Fusarium cell wall hydrolysis which act as elicitors to initiate defense response in the tomato plants. The defense response is represented in the elevation of the antioxidant capacity and enzymes which antagonize the oxidative stress. Additionally, as a result of the defense response, the secondary metabolism has improved, as evidenced by increased activity in the phenylalanine ammonia-lyase and consumption of the shikimic acid, which raises the amounts of phenols and flavonoids. Besides that, the intercropped tomato showed high activity in the antifungal enzymes and high content of cell wall-bound phenols which stop the fungal growth spread inside tomato plants.

Çakar, Deniz; Akıllı Şimşek, Seçil; Maden, Salih

doi: 10.1007/s41348-023-00710-2pmid: N/A

Efficacies of phosphorous acid (PA) and potassium silicate (KSi) foliage applications against collar rots caused by Phytophthora × cambivora and P. cinnamomi was investigated on three-year-old chestnut saplings in Bolu province under field conditions. Protective effects of PA and KSi were determined in two treatment modes. For the first mode, the chemicals were sprayed onto the saplings first, and the pathogens were inoculated after one or two weeks from the treatments. For the second mode, the pathogens were inoculated first, and then the chemicals were applied after a week. Evaluation of the treatments was made by measuring the lesion lengths after 28 and 35 days from the inoculations. PA treatments (4 ml/l of 40% Agrifos) made before the inoculations showed more than 90% effectiveness against both P. × cambivora and P. cinnamomi infections, the effectiveness on the latter being higher. A high rate of protection was also achieved by the applications of PA two weeks before the inoculations, even after 5 weeks from the challenges by the pathogens. Applications of PA after the infections did not provide a high rate of protection. KSi foliage treatments (10 mM of KSi salt) made on both ways did not show any protection against collar rots caused by Phytophthora spp.

Göze Özdemir, Fatma Gül; Uzun Yiğit, Asiye; Demirözer, Ozan

doi: 10.1007/s41348-022-00698-1pmid: N/A

In the present study, the effects of different concentrations of culture filtrate (1×, 5×, 10×, 20× and 50×) of two isolates of Beauveria bassiana (BIM-001 and BY2) on Meloidogyne incognita were investigated under controlled conditions on tomato. The control effect (%) of culture filtrate concentrations compared to that of the positive controls, Nostalgist (0.25 ml/l) (B. bassiana strain Bb-1) and Velum (0.16 ml/l) (Fluopyram). It was determined that the control effect of all concentrations of both isolates was significantly higher than the negative control (sterile distilled water). At undiluted concentration of the filtrate (1×), the control effect of BIM-001 and BY2 isolates was found to be over 70% on galls, egg masses, and soil J2 density. In addition, the most dilute concentration (50×) of BIM-001 decreased root galls, egg masses, and soil J2 density of M. incognita by approximately 35%, while BY2 suppressed about 14.5%. In the study, the chemical nematicide Velum provided the highest control (98%) on the number of galls and egg masses formed by M. incognita on tomato roots and soil J2 density. At the same time, 1× and 5× concentrations of BIM-001 ranked second after Velum. BIM-001 was found to have higher nematicidal effect than BY2. The nematicidal effect of Nostalgist was lower than that of the 1× and 5× concentrations of BIM-001 and BY2 isolates. These results indicate that the entomopathogenic fungus B. bassiana is a good alternative for the biocontrol of M. incognita.

Abdel-Kader, Mokhtar Mohamed; El-Mougy, Nehal Samy; Khalil, Mohamed Saied Ali; El-Gamal, Nadia Gamel; Attia, Magdy

doi: 10.1007/s41348-023-00705-zpmid: N/A

Foliar diseases, like powdery mildew, septoria leaf blotch (SLB) and stem rust, affect wheat plants causing severe yield losses. Biofertilizers Pseudomonas fluorescens Migula (NRC2041) and Bacillus subtilis Ehrenberg (NRC313) or the arbuscular mycorrhizal fungi Glomus mosseae Tul. & C. Tul. (NRC212A) and G. fasciculatum Tul. & C. Tul. (NRC212B) were used for soil treatment followed by foliar spray with Trichoderma harzianum or P. fluorescens to manage severity of wheat foliar diseases under field conditions for two successive growing seasons. Under field conditions, at all soil drench and foliar application treatments, Sids 14 was the most sensitive cultivar for high disease severity followed by Misr 2 and Giza 168. Also, the obtained results showed that the most effective treatments were soil drench with mycorrhizae followed by foliar spray with either T. harzianum or P. fluorescens. Meanwhile, the fungicide Amistar showed a superior reduction in disease severity compared to other applied treatments. In addition, the increased yield was correlated to the decreased severity of the recorded diseases. The present study suggests using bioagents for reducing the severity of wheat leaf diseases and increasing the grain yield under field conditions.

Verdugo-Contreras, Xavier Eduardo; Martínez-Álvarez, Juan Carlos; Díaz-Camacho, Sylvia Paz; Félix-Gastélum, Rubén; Leyva-Madrigal, Karla Yeriana; Ibarra-Sarmiento, Carlos Ramiro; Romero-Urías, Cecilia; Mora-Romero, Guadalupe Arlene

doi: 10.1007/s41348-022-00671-y

Ogunsola, Justina Folasayo; Ogunsola, Kayode Ezekiel

doi: 10.1007/s41348-022-00690-9pmid: N/A

Citrullus lanatus (Thumb Mansf.) (Egusi melon) is an important vegetable in West Africa grown for its edible seeds and oil. Its productivity is limited by leaf blight disease (LBD) which is dangerous to humans and the environment to control with synthetic fungicides. This study investigated the antifungal activity of some botanicals on Colletotrichum truncatum and Colletotrichum gloeosporioides causing LBD of Egusi melon. Four concentrations (5.0, 7.5, 10.0 and 12.5%) of aqueous extracts of Phyllanthus amarus leaves (PaL), Passiflora foetida leaves (PfL), Costus afer leaves (CaL), -stems (CaS) and -rhizomes (CaR) were evaluated against the pathogens in vitro, using agar poisoning. These extracts, except CaS (at 5, 10 and 50% w/v/50 seeds), were also evaluated for seed treatment under screen-house conditions. Data were collected on colony diameter reduction, sporulation, disease incidence, severity, seed germination, vine length, number of leaves and number of vines. Fungitoxicity of the botanicals varied with plant parts and extract concentrations. Phyllanthus amarus (7.5–10%), PfL (12.5%) and CaR (5–10%) significantly (p˂0.05) reduced C. truncatum mycelia growth (by 8.5–44.5%) and sporulation (by 22.3–90.9%), whereas 5–10% of PaL, PfL, CaR and CaL reduced growth (14.3–33.3%) and sporulation (9.6–96.4%) of C. gloeosporioides. Fungitoxicity was lowest in CaS. The botanicals, when used in seed treatment, significantly reduced disease incidence and severity, increased vine length and number of leaves without any effect on seed germination, while PfL, PaL and CaR (at 5, 10 and 50% w/v/50 seeds) were as effective as the synthetic fungicide (Mancozeb). High contents (mg/100 g) of alkaloids, flavonoids, saponins, tannins, glycosides, steroids and phenols detected from the botanicals might have enhanced their antifungal property. The high fungicidal potentials of P. amarus, P. foetida and C. afer (leaf and rhizome) on leaf blight of Egusi melon can be harnessed as safe biopesticides towards a better crop protection.

Liebe, Sebastian; Imbusch, Frederike; Erven, Tobias; Varrelmann, Mark

doi: 10.1007/s41348-023-00708-wpmid: N/A

Cercospora leaf spot is an important foliar disease in sugar beet caused by Cercospora beticola. Tolerant cultivars are available, but application of fungicides is still mandatory for disease control. The timing of the fungicide application is crucial as it determines the outcome of disease epidemiology. A disease incidence (DI) of 5% is widely used as a threshold for fungicide application. Recently a method was developed that allows the quantification of aerial spore dispersal of C. beticola for measuring spore flight intensity. It was aimed in this study to prove if fungicide application based on spore flight might improve disease control compared to DI. In a field trial with artificial inoculation, a single fungicide application at the onset of spore flight slowed down disease development as indicated by reduced disease severity and aerial spore dispersal. However, it did not provide sufficient control in terms of sugar yield. Only a second fungicide application based on spore flight detection achieved an efficacy similar to two fungicide applications based on DI. In contrast, a single fungicide application based either on spore flight or DI was sufficient in two on-farm trials under natural infection with moderate disease pressure. This highlights the necessity of an early timed first fungicide application followed by a second application under high disease pressure induced by artificial inoculation. Although fungicide application based on spore flight achieved sufficient control success in on-farm trials, it seems not to improve disease control compared to the usage of DI as threshold.

Brand, Thomas; Beltz, Heinrich; Adhikari, Urmila; Daughtrey, Margery; Luster, Douglas G.; Kong, Ping; Hong, Chuanxue

doi: 10.1007/s41348-022-00691-8pmid: N/A

Fungicide protection is the current approach for management of boxwood blight caused by Calonectria pseudonaviculata (Cps) and C. henricotiae (Che). However, published studies evaluating fungicides under field conditions have been focused on Cps. The objective of this study was to evaluate fungicides in Northern Germany where both Cps and Che were present. Three trials were conducted between 2006 and 2016. In 2006, plants were artificially inoculated with a conidial suspension, while infested soil and plant debris were added to a different field as inoculum for the 2012 trial and this field was used again without further addition of inoculum in 2015. Fungicides were applied one to five times and assessments were done three to six times, depending upon the trial. The highest level of disease severity occurred in 2015 (0.91), while the lowest occurred in 2012 (0.01). Among the fungicides evaluated in 2006, preventive sprays of Cercobin FL, Switch, Harvesan, Pugil 75 WG, Dithane NeoTec and Euparen M WG were most effective, with blight control above 65%. In 2012, all treatments including Askon, Cabrio Top, Malvin WG, Dithane NeoTec and Osiris showed > 75% blight control. In 2015, Bayer Rosen-Pilzfrei Baymat and Switch were the most effective (> 82%). Extended in-season blight control was also observed with some fungicides. Additionally, a few fungicides that were evaluated in more than 1 year showed reduced effectiveness over time. This study filled several major knowledge gaps especially regarding fungicide efficacy against Che under field conditions and thus provides crucial information for developing chemical control strategies.