Integration of partial resistance,plant density and use of fungicide for management of white mould in common bean

In-row plant densities have not been studied for common beans with type II growth habit and contrasting reactions to white mould. Advanced breeding lines with partial resistance or susceptibility to white mould were combined with 4, 7, 10 or 13 plants m⁻¹ and with or without fungicide at a constant between-row spacing of 0.5 m in five sprinkler-irrigated field trials conducted during the autumn–winter season in Brazil. White mould pressures in the trials covered the whole range from zero to moderate/high (46–60% of white mould severity index). In all trials, means of white mould incidence, severity and yield did not vary significantly between 7 and 13 plants m⁻¹ for the partially resistant line, regardless of the fungicide levels. For the susceptible line, 13 plants m⁻¹ increased white mould incidence and severity under moderate disease, regardless of the fungicide levels, and decreased yield compared with 10 plants m⁻¹ when fungicide was applied twice under moderate/high disease pressure. For the susceptible line, 7 or 10 plants m⁻¹ maximized yield in all trials, with or without fungicide applications. The results suggest that the current recommendation of 11–13 plants m⁻¹ could be used for type II beans with partial resistance to white mould in either a conventional or organic system. For susceptible genotypes, 7–10 plants m⁻¹ seems to be the most appropriate in-row plant density. This study may improve the recommendation of in-row plant density for type II beans cultivated under white mould pressure.     

Pseudocercospora griseola,the causal agent of common bean angular leaf spot: Strain characterization and sensitivity to fungicides

Angular leaf spot (ALS), an important disease of common bean (Phaseolus vulgaris), is caused by the fungus Pseudocercospora griseola. This pathogen has a wide genetic variability and, therefore, poses a challenge to integrated disease management. The use of resistant cultivars is difficult; hence, the application of fungicides has been a common practice in common bean cultivation. P. griseola strains were morphophysiologically characterized and their sensitivity to common fungicides used to control ALS was studied. The strains were evaluated for sporulation capacity and a representative sample of 34 strains was bioassayed to determine their sensitivity to commercial concentrations of five fungicides, namely pyraclostrobin, mancozeb, pyraclostrobin + metconazole, chlorothalonil and tebuconazole. Another sample of 29 strains was studied for conidial germination and dimensions. Sporulation capacity ranged from 0.88 to 27.67 × 10⁴ conidia/ml and germination percentage ranged from 39% to 72%. The large differences among strains suggest a wide genetic variability among the strains. A wide variability in aggressiveness of P. griseola was observed, which has consequences for breeding programmes aimed at resistance. The behaviour of pathogen strains differed in every fungicide evaluated, even in a population that has not been under selection pressure in the field. These results confirm the need for further studies and may guide future research with this pathogen.     

The use of host resistance in disease management of rust in common bean

Bean rust, caused by Uramyces appendiculatus, is one of the major diseases in dry and snap bean production world-wide. Numerous advancements in disease management have been made to reduce rust losses. Host resistance is an important component of rust management. However, durability of disease resistance has often been short due to the use of single genes for resistance interacting with extremely high virulence diversity of the bean rust fungus. The challenge to increase durability of resistance has led to strategies such as gene pyramiding of race-specific resistance, selection and use of partial resistance, and investigation and discovery of leaf morphological features that may slow the rust epidemic. Germplasm with multiple sources of rust resistance has been developed in specific bean seed classes and released for public and commercial use in intensive production systems such as those in the United States. However, progress to develop rust resistant germplasm for the subsistence agriculture of Latin America and Africa where intercropping and mixed cultivars dominate the production system has been slow. Incorporation of high yielding, disease-resistant components as partial replacement in farmer's mixtures has the potential to reduce severity in the crop and increase yield in the presence of rust. This strategy would not erode the genetic diversity that is historically known to enhance resistance durability and for many years has given stability in production in the subsistent agriculture systems.     

Integrated management of late leaf spot and rust diseases of groundnut (Arachis hypogaea L.) with Prosopis juliflora leaf extract and chlorothalonil

Abstract

Late leaf spot (LLS, Phaeoisariopsis personata) and rust (Puccinia arachidis) are the two major biotic constraints of groundnut (Arachis hypogaea L.) of global importance. To identify economic and eco-friendly disease management options, we evaluated extracts of 38 plant spp. of 23 families, for their antifungal activity. Aqueous leaf extracts (20%, w/v) of Prosopis juliflora and Lycopersicon esculentum completely inhibited the in vitro germination of P. personata and P. arachidis, and extracts of Achras sapota, Cyamposis tetragonolobus, Piper betle and Tagetus patula were inhibitory by >95%. In the greenhouse, the severity of LLS and rust corresponded with the time interval between the foliar application of leaf extract and fungal inoculum. Extract of P. juliflora (2%, w/v) in simultaneous application reduced the lesion frequency of LLS and rust by ～75%, and 35.7% and 50.7% in a prophylactic spray of 96 h before the pathogen inoculation. The extract had no effect on the phenolic content of groundnut leaves both during LLS and rust infections. In the field, P. juliflora extract applied four times at 15-day intervals, was effective against LLS and rust up to 95 days after sowing (d.a.s.). Foliar application of P. juliflora extract at 45, 75 and 90 d.a.s. and chlorothalonil at 60 d.a.s. effectively reduced foliar diseases severity and increased the pod yields by 81–98%. This study identified P. juliflora extract as a significant component for the integrated management of groundnut foliar diseases.     

Evaluation of hydrophobic and hydrophilic kaolin particle films for peach crop, arthropod and disease management

Hydrophobic and/or hydrophilic kaolin particle film treatments to peach (Prunus persica (L) Batsch) trees were evaluated for crop and pest management capabilities in six studies from 1997 to 2000. Unsprayed control and standard treatments, the latter consisting of a commercial pesticide program, were included for comparison. Treatments in initial studies were applied via handgun, which resulted in a uniform and heavy deposit of kaolin after the first application. In contrast, treatments in subsequent studies used airblast equipment, which provided a uniform but less dense coverage, even after multiple applications. Results showed that both formulations of kaolin provided control of oriental fruit moth (Grapholita molesta (Busck)), plum curculio (Conotrachelus nenuphar (Herbst)) and Japanese beetle (Popillia japonica Newman) that was comparable with or better than the standard pesticide program. Effective management of late season catfacing insects (tarnished plant bugs Lygus lineolaris (Palisot de Beauvois) and stinkbugs Acrosternum hilare (Say), Euschistus servus (Say), and E tristigmus (Say)) and leafrollers (undetermined species) was also observed, although kaolin applications significantly increased phytophagous mite (Panonychus ulmi (Koch)) levels. In contrast to arthropod management, kaolin failed to control either peach scab (Cladosporium carpophilum (Von Thumen)) or rusty spot (Podosphaera leucotricha (Ell and Ev) ES Salmon) in any of the 4 years of the study. However, hydrophobic kaolin provided effective brown rot (Monilinia fructicola (G Winter) Honey) control when applied via handgun, and partial control when applied via airblast; hydrophilic kaolin failed to provide any control. These results suggest that hydrophobicity and deposit density may be important factors for effective disease management. The application of kaolin significantly delayed fruit maturation, increased fruit size and increased soluble solids relative to the standard. This effect, attributed to a reduction in plant stress, also resulted in increased fruit number and yield on young trees, indicating that an accentuated beneficial response from kaolin applications may be possible.     

Evaluation of strobilurins,acibenzolar and other chemicals,alone and in spray programs for the control of yellow Sigatoka leaf spot (Mycosphaerella musicola) of bananas in far northern Queensland,Australia

Abstract

Several chemicals including the strobilurins (trifloxystrobin, azoxystrobin, pyraclostrobin and DPX KZ 165), a plant activator (acibenzolar), the triazoles (propiconazole, tebuconazole, epoxiconazole, fenbuconazole and JAU 6475) and tridemorph, spiroxamine, pyrimethanil, fenarimol and various formulations of mancozeb were evaluated in three field experiments in northern Queensland, Australia for control of yellow Sigatoka of banana (caused by Mycosphaerella musicola). In all experiments, the strobilurins used alone or in spray programs with mancozeb and acibenzolar were as effective or better than the industry standards mancozeb and propiconazole. Acibenzolar used in spray programs with mancozeb significantly improved the control of Sigatoka compared to mancozeb alone. The triazoles, epoxiconazole, fenbuconazole and JAU 6476 used alone and tebuconazole in a spray program with mancozeb were as effective as the industry standard propiconazole. Tridemorph, pyrimethanil and spiroxamine were as effective as the industry standard mancozeb, and fenarimol failed to effectively control the disease. In 2004, trifloxystrobin, pyraclostrobin and epoxiconazole were registered for control of yellow Sigatoka of banana.     

小麦条锈病跨区域全周期绿色防控技术体系的构建与应用

小麦条锈病是我国小麦生产上一种跨区域流行的重大病害。1949年以来, 我国小麦条锈病研究, 治理能力明显提升, 发病面积、流行程度、流行频率明显降低, 但由于条锈菌Puccinia striiformis f.sp. tritici新毒性小种不断产生和气候异常变化等因素的影响, 近年来其流行规律和成灾机制出现了新的变化, 发生危害加重, 严重威胁小麦生产和国家粮食安全。基于“十二五”以来我国在小麦条锈病菌毒性新小种产生、有性生殖、侵染循环和大区流行规律等方面的最新研究成果, 作者在学习和实践以往病害治理经验的基础上, 坚持长短结合、标本兼治、分区治理、综合防治的指导思想, 制定了“以绿色防控为基础, 以全周期管理为重点, 以跨区域联防联控为保障”的防控策略, 提出了精准监测预报、毒性小种变异监测、早期菌源控制、抗病品种合理布局和应急防控等关键技术, 集成构建了全国小麦条锈病跨区域全周期绿色防控技术体系, 制定了越夏易变区、冬季繁殖区(越冬区)和春季流行区分区防控技术体系。经在小麦条锈病主要流行区大面积试验示范, 取得了防控效果85%以上, 化学农药用量减少10%以上, 小麦单产提高5%以上的成效。2022年-2023年在全国小麦主产区大范围组织推广应用, 有效控制了小麦条锈病严重流行势头, 全国病害发生面积出现了新低, 有效减轻了灾害损失, 保障了国家粮食安全。     

Evaluation of cucumber (<Emphasis Type="Italic">Cucumis sativus</Emphasis>) cultivars grown in Eastern Europe and progress in breeding for resistance to angular leaf spot (<Emphasis Type="Italic">Pseudomonas syringae</Emphasis> pv. <Emphasis Type="Italic">lachrymans</Emphasis>)

Increased occurrence of cucumber angular leaf spot, Pseudomonas syringae pv. lachrymans, has caused significant losses in cucumber, Cucumis sativus, yield in Poland in recent years. These losses necessitated evaluation of the level of resistance in cucumber cultivars of mainly Polish breeding, cultivated in Eastern Europe, and initiation of a breeding programme for resistance to this disease. Screening for resistance was performed on 84 cucumber accessions under growth chamber conditions using a highly aggressive strain of P. syringae pv. lachrymans. Most of the screened accessions were either susceptible or displayed intermediate resistance. The screening resulted in the identification of five F₁ hybrid cultivars moderately resistant to angular leaf spot. The identified F₁ hybrids were self-pollinated up to the F₄ generation. Individuals resistant to angular leaf spot were identified. These individuals can be used as a source of resistance to angular leaf spot in future breeding efforts.