Isolates of Phytophthora infestans (n = 178) were collected in 2002 to 2009 from the eastern United States, Midwestern United States, and eastern Canada. Multilocus genotypes were defined using allozyme genotyping, and DNA fingerprinting with the RG-57 probe. Several previously described and three new mulitilocus genotypes were detected. The US-8 genotype was found commonly on commercial potato crops but not on tomato. US-20 was found on tomato in North Carolina from 2002 through 2007 and in Florida in 2005. US-21 was found on tomato in North Carolina in 2005 and Florida in 2006 and 2007. US-22 was detected on tomato in 2007 in Tennessee and New York and became widespread in 2009. US-22 was found in 12 states on tomato and potato and was spread on tomato transplants. This genotype accounted for about 60% of all the isolates genotyped. The US-23 genotype was found in Maryland, Virginia, Pennsylvania, and Delaware on both tomato and potato in 2009. The US-24 genotype was found only in North Dakota in 2009. A1 and A2 mating types were found in close proximity on potato and tomato crops in Pennsylvania and Virginia; therefore, the possibility of sexual reproduction should be monitored. Whereas most individuals of US-8 and US-20 were resistant to mefenoxam, US-21 appeared to be intermediately sensitive, and isolates of US-22, US-23, and US-24 were largely sensitive to mefenoxam. On the basis of sequence analysis of the ras gene, these latter three genotypes appear to have been derived from a common ancestor. Further field and laboratory studies are underway using simple sequence repeat genotyping to monitor current changes in the population structure of P. infestans causing late blight in North America.

https://apsjournals.apsnet.org/doi/pdf/10.1094/PDIS-03-11-0156-RE

Recent Genotypes of Phytophthora infestans in the Eastern United States Reveal Clonal Populations and Reappearance of Mefenoxam Sensitivity.

Biopesticides are derivatives of plants, microorganisms and insects. Substances from plants and animals have been used to manage diseases in crops, animals and humans. Reliance on nature to heal nature is a practise for many people around the world. Use of natural products was overtaken by synthetic chemicals due to their efficacy, reliability and quick knock down effect. However, synthetic pesticides have become a health hazards for humans and environment due to their toxicity and pollution. Biopesticides are potential alternatives to synthetic pesticides. Sources of biopesticides are readily available, easily biodegradable, exhibit various modes of action, are less expensive and have low toxicity to humans and non-target organisms. Neem, pyrethrum, cotton and tobacco are known sources of botanical pesticides and have already been commercialized. Other sources of botanical pesticides include garlic, euphorbia, citrus, pepper among others. Species of Trichoderma, Bacillus, Pseudomonas, Beauveria have been commercialized as microbial pesticides. Biopesticides are however faced with challenges of formulation, registration, commercialization, acceptance and adoption. This paper describes several aspects of biopesticide development, including but not limited to, their sources, production, formulation, commercialization, efficacy and role in sustainable agriculture.

/pdf/biopesticides-and-their-role-in-sustainable-agricultural-40kg505hsn.pdf

Biopesticides and Their Role in Sustainable Agricultural Production

Numerous studies have demonstrated that water-based compost preparations, referred to as compost tea and compost-water extract, can suppress phytopathogens and plant diseases. Despite its potential, compost tea has generally been considered as inadequate for use as a biocontrol agent in conventional cropping systems but important to organic producers who have limited disease control options. The major impediments to the use of compost tea have been the lessthan-desirable and inconsistent levels of plant disease suppression as influenced by compost tea production and application factors including compost source and maturity, brewing time and aeration, dilution and application rate and application frequency. Although the mechanisms involved in disease suppression are not fully understood, sterilization of compost tea has generally resulted in a loss in disease suppressiveness. This indicates that the mechanisms of suppression are often, or predominantly, biological, although physico-chemical factors have also been implicated. Increasing the use of molecular approaches, such as metagenomics, metaproteomics, metatranscriptomics and metaproteogenomics should prove useful in better understanding the relationships between microbial abundance, diversity, functions and disease suppressive efficacy of compost tea. Such investigations are crucial in developing protocols for optimizing the compost tea production process so as to maximize disease suppressive effect without exposing the manufacturer or user to the risk of human pathogens. To this end, it is recommended that compost tea be used as part of an integrated disease management system.

Potential of compost tea for suppressing plant diseases.

Pest management is being confronted with immense economic and environmental issues worldwide because of massive utilization and over-reliance on pesticides. The non-target toxicity, residual consequence, and challenging biodegradability of these synthetic pesticides have become a serious concern, which urgently requires the alternative and prompt adoption of sustainable and cost-effective pest control measures. Increasing attention in environmental safety has triggered interest in pest control approaches through eco-friendly plant-based pesticides. Botanical pesticidal constituents are effective against myriads of destructive pests and diseases. More importantly, they are widely available, inexpensive, accessible, rapidly biodegradable, and have little toxicity to beneficiary agents. The phytochemical compositions in diverse plant species are responsible for their varying mechanisms of action against pests and diseases. However, difficulties in their formulation and insufficient appropriate chemical data have led to a low level of acceptance and adoption globally. Therefore, the review seeks to highlight the status, phytochemical compositions, insecticidal mechanisms, and challenges of plant-based pesticide usage in sustainable agricultural production.

/pdf/use-of-botanical-pesticides-in-agriculture-as-an-alternative-1nou9izk.pdf

Use of Botanical Pesticides in Agriculture as an Alternative to Synthetic Pesticides

Potato is one of the most important vegetable crops in Bangladesh which made it 7th producer in the world. This vegetable crop is affected by one of the most notorious soil borne pathogen, Ralstonia solanacearum and caused wilt symptoms in plant and brown rot in potato tuber throughout the world. The pathogen entered into the plants through different natural opening and wounds and is easily disseminated via infected biological material (seeds, vegetatively propagative materials, plants etc.), soil, contaminated irrigation water, surface water, farm equipment etc. and could survive for many years in association with alternate hosts. The bacteria is a quarantine organism being economically a serious problem for potatoes and other major crops in many tropical, subtropical and warmer areas of the world. It has an unusually wide host range including economically important crops (potato, tomato, tobacco, banana, ginger, geranium etc.) and weeds. The disease appeared as rapid and fatal wilting symptoms in the potato plants and vascular browning and/or rotting on tubers. The pathogen can be detected through the isolation of the bacteria on semi-selective TZC and/or selective SMSA (modified) media and through different biochemical tests and/or molecular test. It is a Gram-negative type bacterium, subdivided into five races based on host range and race 3 biovar III is reported in Bangladesh. Direct yield losses caused by R. solanacearum may vary 33 to 90% depending on the different factors such as cultivar, climate, soil type, cropping pattern, strain of the bacteria etc. Due to the latent infection of tuber by this organism, Bangladesh had been facing a temporary embargo on potato export which was imposed by Russia during 2014-15. But, latency and some other survival strategy of the pathogen created much more problems with disease detection, control and dispersal. The biological features of this pathogen makes it unusually successful against the traditional management practices. Therefore, the review focused on the biological abilities of R. solanacearum in relation to dispersal, survival and influences which might be important in designing effective management against the pathogen.

Ralstonia solanacearum: A Threat to Potato Production in Bangladesh

An experiment was conducted in the field laboratory, Department of Plant pathology, Bangladesh Agricultural University, Mymensingh to evaluate the efficacy of compost tea and poultry litter extract in controlling late blight of potato and tomato under natural infection condition. Significant effects of different organic amendments were observed on the incidence and severity of late blight in potato and toma to as compared to control. The results showed that the minimum late blight incidence, per cent late blight infected leaves per plant and per cent leaf area diseased per plant were recorded in T 3 (compost tea applied as foliar spray) followed by T2 (foliar spray of Ridomil) while these parameters of late blight assessment were recorded maximum in control treatment (T1). Application of IPM lab Biopesticide and BAU-Biofungicide performed better as compared to remaining treatments used in the study. All other c omponents such as soil application of poultry litter, mustard oil cake, soil drenching of compost tea and poultry litter extract resulted significantly lower late blight incidence and severities as compared to untreated control (T 1). Foliar application of compost tea showed best performance in increasing the plant height and yield as compared to all other treatments although soil application of mustard oil cake and compost produced tallest plant and highest number of plants, respectively in potato while the maximum plant height, number branches per plant, and fruit yield in tomato were recorded in case of compost tea applied as soil drench as compared to control. The other treatments showed significant effect in increasing all the growth and yield parameters of both potato and tomato as compared to control. Benefit cost analyses revealed that foliar spray of compost tea showed highest BCR (65.20) followed by T8 (Soil application of IPM Lab Biopesticide) with BCR 54.38 in case of potato while the highest BCR (28.32) was calculated in plots received compost tea as soil drenching followed by T9 (BAU-Biofungicide as foliar spray) in case of tomato. The other treatments showed comparatively higher BCR as compared to untreated control in both vegetables. The results indicated that an investment of Tk. 1.00 may lead to a profit up to Tk. 65.20 by foliar application of compost tea in potato and may lead to a profit of Tk. 28.32 with soil drenching of compost tea in tomato which are maximum profit in the present study.

Organic Management: An Alternative to Control Late Blight of Potato and Tomato Caused by Phytophthora infestans

Genetic diversity of the bacterial wilt pathogen Ralstonia solanacearum using a RAPD marker

Citrus greening disease (HLB) on Citrus reticulata (Mandarin) caused by Candidatus Liberibacter asiaticus in Bangladesh

Growing two or more cultivars of the same crop species in mixture reduces intra-specific competition for growth resources by inducing variation in spatial and temporal patterns of crop growth, increases competitive ability of crops against weeds and thus enhances crop yield. This study was conducted to evaluate the potentiality of wheat cultivar mixtures to reduce weed growth and increase the wheat yield under different irrigation regimes, and determine the best row mixture ratio of two wheat cultivars for better weed suppression and higher productivity of wheat. Factors included seven cultivar mixture ratios viz. sole BARI Gom 25, sole BARI Gom 30, 1:2, 2:1, 2:3, 3:2 and 1:1 of BARI Gom 25 to BARI Gom 30, and three water management practices viz. no irrigation, one irrigation at crown root initiation (CRI) stage, and two irrigation at CRI and flowering stages arranged in a split-plot design with three replications. Results clearly indicated that cultivar mixture can improve the competitive ability of wheat plants against weeds and can increase wheat productivity. Both cultivars showed better growth, higher weed suppression and increased yield when grown in mixture irrespective of ratios compared to their monoculture. Based on the combined grain yield, different mixture ratios performed in the order 1:1, 2:3, 1:2 and 2:1 BARI Gom 25 to BARI Gom 30 under two irrigation regimes. BARI Gom 25 and BARI Gom 30 inter-planted in 1:1 row ratio under two irrigation appeared as the best practice resulting 9% and 5.83% yield advantages over sole culture of BARI Gom 25 and BARI Gom 30, respectively; while mixture ratio of 3:2 resulted in 6.43% and 3.36% weed dry matter reduction over sole culture of BARI Gom 25 and BARI Gom 30, respectively. In conclusion, cultivar mixture strategy can be adopted as an effective tool for better weed management and increased yield of wheat.

https://www.jrweedsci.com/article_86927_2a0326b8e9b5fcb910215f56cea97977.pdf

Rashidul Islam

Papers

Organic Management: An Alternative to Control Late Blight of Potato and Tomato Caused by Phytophthora infestans

Genetic diversity of the bacterial wilt pathogen Ralstonia solanacearum using a RAPD marker

Citrus greening disease (HLB) on Citrus reticulata (Mandarin) caused by Candidatus Liberibacter asiaticus in Bangladesh

Weed competitiveness and productivity of interplanted wheat cultivars under varying water management