Volume 2 Numbers 1 & 2 2008
CONTENTS AND ABSTRACTS
Ivan H. Fischer, Jorge A.M. Rezende (Brazil) Diseases of Passion Flower (Passiflora spp.) (pp 1-19)
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Invited Review: There may be many factors contributing to reduction in longevity and productivity in passion fruit plants, especially diseases of viral, bacterial or fungal etiologies, among which passion fruit woodiness, bacterial spot, root and collar rot, fusarium wilt, anthracnose and scab are the most important. The incidence of woody fruits in young plants totally compromises the productivity and quality of fruits. Fusariosis, root and collar rot have swept out entire crops, leading to irreversible wilt and consequent death of plants. Bacteriosis, anthracnose and scab cause severe losses under favorable environmental conditions and the absence of preventive control. The permanent incidence of diseases in some areas may turn the crop unprofitable, causing its periodical migration to new areas. This review will cover the main passion fruit diseases, their symptoms, etiology, epidemiology and management.
Aly A. Aly, Mohmed A. Abdel-Sattar (Egypt), Kamel A. Abd-Elsalam (Egypt/Saudi Arabia), Moawad R. Omar (Egypt) Effect of Physical and Chemical Edaphic Factors on Susceptibility of Cotton Seedlings to Macrophomina phaseolina (pp 20-23)
Original Research Paper: Nineteen soil samples were obtained from different cotton-producing areas in Egypt. The geographic distribution of these samples was as follows: 1 (5.26%) from Minufiya; 4 (21.05%) from Kafr El-Sheikh; 2 (10.53%) from Minya; 3 (15.79%) from Gharbiya; 7 (36.84%) from Sharqiya; and 2 (10.53%) from Faiyum. Clay soil (84.21%) was the predominant type in the samples. Twenty-two physical and chemical parameters were measured in the 19 samples. Data for seedling disease variables (postmergence damping-off and dry weight) and edaphic factors were entered into a computerized stepwise multiple regression analysis. Using the predictors supplied by stepwise regression, two models were constructed. These models showed that edaphic factors accounted for 71.03 and 93.13% of the total variation in postemergence damping-off and dry weight, respectively, in models. From stepwise regression analysis, it was concluded that high soil saturation percent, high Ca++ content, low SO4= content, and high Mg++ content were associated with high postemergence damping-off. The present study also showed that high saturation percent, low potassium content, low calcium carbonate content, low Mg++ content, high coarse sand content, and high phosphorus content were associated with an increase in the dry weight of seedlings.
Waléria Guerreiro Lima, Roseane Cavalcanti Santos, Cláudio Augusto Gomes da Câmara, Marcos Paz Saraiva Câmara, Péricles de Albuquerque Melo Filho (Brazil) Citronella Oil Inhibits Cotton Ramulosis in Controlled Conditions (pp 24-27)
Original Research Paper: Ramulosis is a serious disease affecting cotton crops in Brazil. Control is often based on the use of chemical fungicides. Aiming to study an alternative form of control, we assessed the curative and preventive effects of citronella (Cymbopogon citratus) oil in cotton plants based on epidemiological components, in controlled conditions. Trials were conducted with the susceptible cv. ‘BRS 8H’ and Collethotrichum gossypii var. cephalosporioides (strain Cgc 287) at 1.0 x 106 conidia mL-1. Citronella oil was used at a concentration of 2000 SI. Assessment of the incidence and severity of ramulosis was based on Initial Disease Index (IDI), Final Disease Index (FDI), Disease Progress Rate (DPR) and Area Below Disease Progress Curve (ABDPC). In the curative treatment, citronella oil showed a limited effect at the concentration used but in the preventive aspect, the FDI in cotton plants was reduced providing more protection to them against the fungus severity.
A. Manoj Kumar, Kalpana N. Reddy, Rohini Sreevathsa (India) Influence of Pesticides, Plant Oils and Antagonist on Entomopathogenic Fungus, Metarhizium anisopliae (Metsch.) Sorokin (pp 28-31)
Original Research Paper: Compatibility of the entomopathogenic fungus, Metarhizium anisopliae with representative pesticides, plant oils and a fungal antagonist were studied in vitro. The pesticides tested were: endosulfan, acephate, abamectin, ethion, chlorothalonil, iprodion + carbendazim, thiophanate methyl and dinocap, an antagonist, Trichoderma harzianum and the plant oils: coconut oil, groundnut oil, gingili oil, sunflower oil, neem oil, pongamia oil, and castor oil. Each product was tested in the laboratory at 27 ± 1°C and 65% RH, based on the recommended rates for application in the field. The products were added to PDA culture medium for growth of the entomofungal pathogen and the dual culture technique was followed in the case of T. harzianum. Reproductive and vegetative growth was evaluated for M. anisopliae. Results showed that the action of the pesticides on the vegetative growth and conidial spore formation of M. anisopliae varied as a function of the chemical nature of the products. Thiophanate methyl recorded maximum vegetative growth of 2.46 cm diameter, whereas the maximum conidial spore formation of 2.45 × 107 spores/ml was observed in chlorothalonil. Iprodion + carbendazim suppressed M. anisopliae completely. In the case of plant oils, sunflower oil yielded 5.77 × 107 spores/ml with a vegetative growth of 4.40 cm diameter indicating a synergistic effect when compared to all other treatments. However, 3.38 cm diameter and 3.4 × 107 spores/ml were recorded in the untreated control.
Raj Deepika, Amit Nath, Amarjit K. Nath (India) Toxicity of Trypsin Inhibitor from Phaseolus vulgaris L. Cultivar against Pieris brassicae (pp 32-37)
Original Research Paper: Trypsin inhibitor (TI), present in the seeds of a local yellow cultivar of French bean (Phaseolus vulgaris L.), which is native to the Himalayan region, was tested using the gut enzyme of Spodoptera littoralis. The midguts of cold-anesthetized larvae were dissected and homogenized in ice-cold 0.1 M sodium phosphate buffer (pH 7.5). The seed extract was tested for TI activity using gut extract. The Trypsin Units Inhibited (TUI) per gram of seed weight thus obtained were 892.67. TI was purified to near homogeneity by ammonium sulfate precipitation, ion exchange chromatography and gel permeation chromatography. The level of TI significantly increased in the leaves of P. vulgaris following mechanical wounding, indicating a strong systemic response of plants to injury. Purified TI was liquefied in distilled water, coated on cabbage leaf discs and fed to Pieris brassicae larvae along with distilled water-coated control leaf discs. It showed a marked effect on larval survival and development. Feeding inhibition and lesser fecal matter was observed in larvae reared on cabbage leaf discs coated with purified inhibitor as compared to control. The feeding bioassays showed that percent mortality of larvae fed on leaf discs coated with 150 µg and 300 µg of purified TI increased from 53.33% (after one day) to 78.67% (after four days) and 46.67% (after one day) to 90.00% (after five days), respectively. Further, excreta and size of the larvae were much smaller than controls. Therefore, the gene expressing this protease inhibitor could be used in vegetable crops to confer resistance against insect pests.
Márcia Soares Chaves, José Antônio Martinelli, Caroline de Lima Wesp, Felipe André Sganzerla Graichen (Brazil) The Cereal Rusts: An Overview (pp 38-55)
Invited Review: For centuries cereal rusts have been threatening mankind imposing severe yield losses on crops, economic and social impacts and sometimes even famine. By far, they are the most damaging diseases of cereals. The pathogens are obligate parasites that co-evolved with their hosts in a system greatly influenced by the environment. This review presents a historical retrospective of cereal rusts as well as aspects of their biology, such as taxonomy, life cycle, physiological specialization and the process of infection. In addition, more specific details are presented for each of the main rusts of wheat, barley, oats and rye. Methods of controlling them, particularly genetic, chemical and through cultural practices are also presented.
Thiago Lívio P. O. Souza, Ana L. Alzate-Marin, Fábio G. Faleiro, Everaldo G. de Barros (Brazil) Pathosystem Common Bean–Uromyces appendiculatus: Host Resistance, Pathogen Specialization, and Breeding for Rust Resistance (pp 56-69)
Invited Review: Common bean (Phaseolus vulgaris L.) is the world’s most important food legume for direct human consumption. This new world crop is adapted to many niches and it is grown in distinct regions and different seasons around the world. The common bean crop is grown by subsistence levels farmers with little technology as well as by farmers in developed nations that use high input technologies. Unfortunately, common bean yields are quite low compared to other grain legumes; e.g., soybeans and peas. One of the several factors contributing to this situation is the high number of pathogens that cause common bean diseases. Among these diseases is the common bean rust, incited by the basidomycete fungus Uromyces appendiculatus F. Strauss (syn. U. phaseoli G. Winter), which can cause great yield losses. We present here relevant information about the common bean rust including its etiology, epidemiology, the rust pathogen infection process, the symptomatology and genetic diversity of the pathogen. We also review progress on the control of the disease using cultural practices, biological and chemical methods. It is also reported and discussed the host resistance and pathogen specialization, genetics of host-pathogen interactions, the available molecular markers linked to rust resistance genes, and its utilization in marker assisted selection (MAS) for the development of rust resistance cultivars.
Gary Peng, Thomas M. Wolf (Canada) Spray Retention and its Potential Impact on Bioherbicide Efficacy (pp 70-80)
Invited Mini-Review: Hydraulic spray systems are widely used for application of agrochemicals due to ease of operation and consistent performance, despite relative inefficiency in delivering pest-control products to intended targets. Frequently, spray parameters are optimized for maximum product deposition and retention, although success of this strategy is case dependant. There is limited information on application improvements for microbial pesticides (biopesticides). Biopesticides, especially those that employ a fungus as the active ingredient, are generally applied with a liquid carrier but their deposition or retention has rarely been characterized. Depending on the size of microbe and plant morphology or architecture, interactions among spray parameters can be complex in terms of the impact on retention, distribution and performance of the biopesticide agent. Extrapolation of information from chemical pesticide applications may not always be appropriate. This review, based primarily on authors’ experience in spray retention involving three bioherbicide-weed systems, is aimed to highlight the impact of spray parameters and additives (adjuvants) on deposition, retention, and efficacy of bioherbicide agents. Information from additional bioherbicide agents is also considered for different sizes of fungal inoculum or characteristics of target plants. Although the focus is on potential bioherbicides, the information may also be useful to application of other microbe-based biopesticide agents. Strategies for maximizing biocontrol efficacy through optimization of spray parameters as well as other application technologies are discussed.
Julien Saguez (France/Canada), Charles Vincent (Canada), Philippe Giordanengo (France) Chitinase Inhibitors and Chitin Mimetics for Crop Protection (pp 81-86)
Invited Mini-Review: Pathogen and pest management is a key element in agriculture. The Integrated Pest Management concept relies on the availability of an array of protective measures having different but complementary mechanisms. As a consequence, alternative strategies have to be developed. Because chitin occurs in the cell wall of fungi and in various structural components of arthropods, its metabolism has been considered as a suitable target to manage pathogens and pests. Disruption of chitinase metabolism is one of the strategies that have been considered. Studies led to the discovery of new molecules which interact with chitinases and induce antibiotic, antifungal or insecticidal effects. These compounds present different ranges of activity, depending on their biochemical classification, their structure and the nature of the targeted chitinase. Some are oligo- and polysaccharides (e.g. allosamidin, FPS-1) and others are peptides (e.g. argadin, argifin, cyclic dipeptides or psammaplin A). These natural molecules directly interact with the catalytic site of chitinases, mimicking chitin structure. In this review we will present a synthesis of the recent works that aimed to disrupt chitin metabolism by chitinase inhibition with the ultimate objective of developing new applications for crop protection.
Khalil Talebi, Aurang Kavousi, Qodrat Sabahi (Iran) Impacts of Pesticides on Arthropod Biological Control Agents (pp 87-97)
Invited Review: Information about the side-effects of pesticides on biological control agents is an essential requirement of integrated pest management (IPM). Different methods to test the effects of pesticides on natural enemies have been used and new methods are being developed. In the past, evaluations were mostly based on individual level (lethal or sublethal) endpoints. Differences in the used methods and the measured endpoints make it difficult to compare the results. There is increasing emphasis on using standard methods to combine the lethal and sublethal effects to a total effect. Especially, population-level effects or demographic toxicology has been concluded as a better measure because of its ecological relevance and is the current centre of attention. Very recently, molecular and biochemical methods, primarily, have been developed for detecting potential damage to populations at early stages. But these types of responses (i.e. biomarkers) to toxic stress are only demographically relevant if the response can be linked to effects at higher organism levels. We describe the methods used to study the effects of pesticides on beneficial arthropods and the current status of the evaluation of side-effects. We also provide new suggestions. In addition to methodological discussion, in the last part we presented a table containing summary database on the effect of key classes of commonly used pesticides on various natural enemies. This data may be helpful for researchers or IPM users.
Mark W. Brown (USA) Sustainable Biocontrol of Apple Insect Pests (pp 98-103)
Invited Mini-Review: Biocontrol of insect pests is a cornerstone to sustainable production of apples and other crops. The ecology of orchards lends itself to the application of many management options which will enhance the sustainability of biocontrol. Orchards remain in place for decades, allowing for an evolution of a stable, mature community of biological control species. Management tactics such as companion plants, interplanting, windbreaks and mulches have all been shown to lead to an increase in the abundance of insect natural enemies and higher rates of biocontrol. These tactics also have limitations in their implementation in commercial orchards. More research is needed to redesign the structure of apple orchards to incorporate sustainable biocontrol methods and optimize production. Biocontrol is an ecosystem service and as such needs to be studied holistically rather than with the more traditional reductionist science typically used in agricultural research.
Khalil I. Al-Mughrabi (Canada) Biological Control of Phytophthora infestans of Potatoes using Trichoderma atroviride (pp 104-108)
Original Research Paper: The efficacy of Trichoderma atroviride against late blight (Phytophthora infestans) was studied in trials conducted in growth chamber and in vitro. The growth chamber trials were randomized as complete blocks with four treatments replicated five times. The treatments included: 1) untreated control inoculated with P. infestans; 2) tubers inoculated with P. infestans and treated with T. atroviride; 3) tubers inoculated with P. infestans and treated with Bravo 500F; and 4) tubers inoculated with P. infestans and treated with both T. atroviride and Bravo 500F. Among the different treatments, Bravo 500F was significantly superior to T. atroviride alone or in combination with Bravo 500F. Late blight disease severity was reduced by 27 and 36%, respectively, as a result of treatments with T. atroviride alone or in combination with Bravo 500F. The efficacy of T. atroviride applied at various concentrations was tested in vitro for their efficacy in reducing disease severity in leaf disc assays. T. atroviride applied at high concentration provided complete control of late blight incidence on leaf discs. The results of the present studies suggest that higher disease control efficiency can be achieved if T. atroviride is used in an integrated late blight management approach.
Vasileios Fotopoulos (UK/Cyprus) Assessment of Potential for Biological Control of Botrytis cinerea by an Indigenous Trichoderma harzianum Isolate with a Novel Detached Leaf-droplet Inoculation Bioassay and Correlated Increase in Phytoalexin Production (pp 109-113)
Original Research Paper: A simple detached leaf-droplet inoculation bioassay was devised in order to investigate the potential for biological control of Botrytis cinerea by indigenous Trichoderma harzianum isolates. Following preliminary in vitro screening of the antagonistic capacity of four local isolates of Trichoderma harzianum (T1-T4) against B. cinerea, T3 spore suspensions were then tested for their ability to control infection development of B. cinerea on T3 pre-inoculated lettuce and broad bean leaves, using different nutrient concentrations in B. cinerea infection inocula. Again, T3 proved to significantly control infection development in all but one of the treatments, as long as T3 spores were introduced in a nutrient solution. This bioassay provides a rapid and simple method of assessing biocontrol efficacy under in vivo conditions. T3 was also tested for its ability to induce plant defense mechanisms in the form of phytoalexin production after inoculation of broad bean cotyledons with T3 spore suspension. Thin layer chromatography indicated that T3 lead to the induction of relatively high phytoalexin yields, suggesting that this could be another potential ‘indirect’ mechanism of protection from pathogens by T. harzianum strain T3.
Gulshan Mahajan (India), Bagirth Singh Chauhan Chauhan (The Philippines) Performance of Penoxsulam for Weed Control in Transplanted Rice (pp 114-116)
Short Communication: The efficacy of penoxsulam on weed control was evaluated in field experiments during the 2006 and 2007 kharif seasons at the research farm of Punjab Agricultural University, Ludhiana, India. There were seven treatments consisting of two doses of penoxsulam (22 and 25 g/ha) applied at 3 and 12 days after transplanting (DAT), butachlor (1500 g/ha) applied at 3 DAT, hand weeding (twice at 20 and 40 DAT) and weedy check (untreated control). The main dominant weeds in the field were Echinochloa crus-galli and Cyperus iria. Maximum weed control efficiency (90%) was attained with penoxsulam (25 g/ha) applied at 12 DAT followed by the hand weeding treatment (76%). The plots treated with penoxsulam (25 g/ha) applied at 12 DAT resulted in highest grain yield (7.95 t/ha) and this treatment increased yield to about 104% and 13% more than weedy check and butachlor (1500 g/ha) treatments, respectively. Penoxsulam applied at 12 DAT was superior in terms of increasing grain yield and reducing weed dry matter when compared to its application at 3 DAT. The hand weeding treatment was found to be as effective in reducing weed dry matter as butachlor at 1500 g/ha and both treatments resulted in a similar yield. This study identifies an alternate herbicide to butachlor in transplanted rice, and this may reduce the development of resistance in weeds against widely used butachlor.
Abdel-Rheem El-Samawaty, Abdel-Mongy Asran-Amal, Moawad Omar (Egypt), Kamel A. Abd-Elsalam (Egypt/Saudi Arabia) Anastomosis Groups, Pathogenicity, and Cellulase Production of Rhizoctonia solani from Cotton (pp 117-124)
Original Research Paper: Fifty-two isolates of Rhizoctonia solani were isolated from cotton seedlings infected with postemergence damping-off disease, and obtained from cotton-producing areas in Upper Egypt governorates. Morphological characterization indicated that 13.46% of the isolates belonged to AG 2-2, 25% belonged to subgroup AG 4-HgI and 61.54% were AG 4-HgII. Fifty percent of R. solani isolates were effective in producing cellulase when they were grown on artificial medium. Pathogenicity assay of the 52 isolates of R. solani was conducted on four cotton cultivars under greenhouse conditions. Analysis of variance showed that isolates and interaction between isolates × cultivars were highly significant source of variation in all the tested parameters. Statistically significant, isolates and the interaction between cotton cultivars and isolates suggest that physiologic specialization exists within R. solani isolates pathogenic on cotton. Also, pathogenicity of the tested isolates is a mixture of virulence and aggressiveness, and the isolates significantly differ in both types of pathogenicity. Correlation between seedling disease variables (pathogenicity parameters) and efficiency in cellulase production was affected by cotton cultivar and the anastomosis group (AG) of the fungus. Conversely, correlation among pathogenicity parameters was not affected by cultivar. Cluster analysis of isolates of R. solani was constructed based on their virulence on four cotton cultivars. Grouping the isolates was not related to their geographic origin or AG type.
Lalithanjalie D. Amarasinghe (Sri Lanka) Entomopathogenic Nematodes from the Coastal Belt of Sri Lanka and their Efficacy in Controlling Termites (pp 125-129)
Original Research Paper: The present study was carried out to assess the availability of entomopathogenic nematodes in the north-western coastal belt around Puttalum lagoon, three selected agricultural lands in Gampaha district of Sri Lanka and from the coastal belt along the city of Colombo. Nematodes could only be recovered from the coastal belt along the city of Colombo belonging to Heterorhabditis and Steinernema spp. One common isolate was identified as Heterorhabditis indicus (Poinar). Attempts were also made to examine the relationship between the presence of entomopathogenic nematodes and the texture of the soil. Statistical analysis showed that percentage clay and soil moisture are inversely relate to the recovery of entomopathogenic nematodes. The potential use of H. indicus to control two species of subterranean termites, Odontotermes horni and Odontotermis redemanni (Isoptera: termitidae) was tested in the laboratory. LD50 for O. horni was 2.8 × 102 or 2.2 × 102 after four or five days of exposure (LD50 for O. redemanni was 2.3 × 102 or 1.8 × 102) to infective nematodes, respectively.
Meena Thakur, Rajender S. Rana (India) Studies on the Role of Insect Pollination on Cucumber Yield (pp 130-133)
Original Research Paper: Foraging activities of insect visitors were studied during summer 2007 on inbred lines of cucumber hybrid KH-1. The insect visitors in decreasing order of abundance were Formica sp. > Apis mellifera > Bombus haemorrhoidalis >Halictus sp. > other insects > Apis cerana > syrphids. The activity of insects peaked between 09:00 and 10:00 followed by 12:00-13:00 and 15:00-16:00. The foraging behaviour of A. mellifera, B. haemorrhoidalis and Halictus sp. was studied. The foraging speed and foraging rate were maximum in B. haemorrhoidalis followed by A. mellifera and Halictus sp. The bees spent significantly more time per flower during morning hours (15.92 sec/flower) and foraged significantly fewer flowers (5.48 flowers/min) compared to evening hours. There were significantly more nectar foragers (5.71/m²/10 min) than pollen foragers (4.84/m²/10 min). Most pollen foragers were observed during morning hours (6.27/m²/10 min) whereas nectar foragers were most active during noon hours (6.31/m²/10 min). There was no significant difference in the number of bees shifting from one line to another or vice versa. The effect of honey bee pollination, open pollination and hand pollination on quantity and quality of cucumber was also studied. Significant increase in fruit set was observed; highest being in hand pollination (75.68%) followed by honey bee (74.96%) and open (62.09%) pollination. Percentage of misshapen fruits was maximum in open pollination (20.05) followed by hand (14.1%) and honey bee (8.05%) pollination. Honey bee pollination resulted in significantly highest percentage of healthy fruits (92.22%) as compared to hand (85.85%) and open pollination (79.64%). Similarly weight of fruits (1184.5 g), number of seeds per fruit (472.8), fruit size (28.8 cm) and weight of 1000-seeds (29.14 g) was highest in honey bee pollination as compared to other modes of pollination.