Effects of wetting on the persistence of quiescent conidia of Isaria fumosorosea

Quiescent conidia of Isaria fumosorosea were submitted to various wetting–drying cycles under different regimes of temperature and air humidity. Germination and viability of conidia collected on cultures freshly host-passed (P2) were not affected at 25 °C during five cycles at increasing wet phase duration (2–12 h per daily cycle) under any moisture conditions (13–86% RH). Infectivity levels remained stable, but mortality was slightly postponed. In vitro-cultured inocula (P5) were significantly affected after only one cycle at higher air humidity (75 and 86% RH) and temperature (35 and 40 °C). The persistence of I. fumosorosea conidia suspended in water soluble extracts of leaf surfaces (corn and cabbage) confirmed the better persistence of P2 conidia and the relatively higher detrimental effect of lower air humidity conditions when combined with moderate temperatures. Quiescent conidia deposited in situ on potted plants of cabbage showed a higher persistence on wet foliage and on foliage submitted to wetting–drying cycles, than on dry foliage. These results underline that constraints prevailing in targeted environments and ecological fitness of fungal isolates have to be taken into account for assessing microbial control strategies.     

Virulence of Hypocreales fungi to pecan aphids (Hemiptera: Aphididae) in the laboratory

There is need for efficacious biocontrol agents for aphids in commercial orchards. As a preliminary step to this end we determined the virulence of several Hypocreales fungi to pecan aphids. In the first experiment we tested the virulence of Isaria fumosorosea (ARSEF 3581) blastospores to three pecan aphids Monellia caryella, Melanocallis caryaefoliae, and Monelliopsis pecanis under laboratory conditions. Rates of 1 × 10⁷ or 1 × 10⁸ spores per ml were applied in 2 ml via a spray tower to 90 mm Petri dishes containing 10 aphids each. Mortality and mycosis were determined after 24, 48 and 72 h. Treatment effects were observed by 48 h post-application, and by 72 h the higher application rate caused >90% mortality and mycosis in M. caryella and M. caryaefoliae, whereas <70% was observed in M. pecanis.We conducted two subsequent experiments (Experiments 2 and 3), using the same methodology, to compare the virulence of several Hypocreales species and strains against the aphid of primary economic concern to most pecan growers, M. caryaefoliae. In Experiment 2, we compared blastospores and conidia of two I. fumosorosea strains (ARSEF 3581 and ATCC 20874 [= strain 97]). The blastospores of ARSEF 3581 and conidia of ATCC 20874 showed higher virulence than other treatments and thus were included in Experiment 3, which also compared the virulence of conidia of Beauveria bassiana (GHA strain) and Metarhizium anisopliae (F52 strain). Results in Experiment 3 indicated the highest virulence in I. fumosorosea 3581 blastospores and M. anisopliae (F52) followed by I. fumosorosea (20874) conidia. The detection of pathogenicity to pecan aphids establishes the potential for commercial usage and additional study. Results reported here will narrow treatments to test in future greenhouse and field trials.     

Effects of culture media on hydrophobicity and thermotolerance of Bb and Ma conidia, with description of a novel surfactant based hydrophobicity assay

Hypocrealean entomopathogenic fungal conidia are made up of multi-aged groups given their chronological conidiogenesis. Most thermotolerance assays have been conducted using mixed-age conidia. The present work exploited a polysiloxane polyether copolymer (siloxane) (Silwet L-77®) mediated conidial collection method, validated by a hydrophobicity assay. This was done to divide mixed-age conidia into two groups based on hydrophobicity and test their thermotolerance, relying on the relationship of conidial age with hydrophobicity. Beauveria bassiana GHA and ERL1170 and Metarhizium anisopliae ERL1171 and ERL1540 conidia, produced on millet agar, whey permeate agar, and ¼SDAY were subjected to hydrophobicity assays that included data on yield of conidia/unit of surface area. Conidia were also collected using 0.01% siloxane, and those remaining with 0.08% siloxane. Hydrophobicity was correlated with percent conidia collected in the two siloxane solutions and yield, suggesting a relationship between percent conidia collected and conidial age (maturation). The conidial suspensions were exposed to 45 °C for 45 min, and conidial germination was examined. Overall, conidia which were collected in 0.08% siloxane had lower germination after heat exposure than those collected in the 0.01% solution. Conidia of both fungi produced by incubation on millet or whey permeate for 14 d were more hydrophobic and exhibited greater thermotolerance than those produced on ¼SDAY. These results suggest that conidia can be divided into two groups with different thermotolerance by using a siloxane-mediated conidial collection method based on hydrophobicity. This depends on the types of substrates used that could influence conidial maturation.     

Control of Grapholita molesta (Busck, 1916) (Lepidoptera: Tortricidae) with entomopathogenic nematodes (Rhabditida: Heterorhabditidae,Steinernematidae) in peach orchards

Oriental fruit moth Grapholita molesta (Busck, 1916) (Lepidoptera: Tortricidae) is considered a major pest in temperate fruit trees, such as peach and apple. Entomopathogenic nematodes (EPNs) are regarded as viable for pest management control due to their efficiency against tortricid in these trees. The objective of this study was to evaluate the effectiveness of native EPNs from Rio Grande do Sul state against pre-pupae of G. molesta under laboratory and field conditions. In the laboratory, pre-pupae of G. molesta were placed in corrugated cardboard sheets inside glass tubes and exposed to 17 different EPNs strains at concentrations of 6, 12, 24, 48 and 60 IJs/cm² and maintained at 25 °C, 70 ± 10% RH and photophase of 16 h. Insect mortality was recorded 72 h after inoculation of EPNs. Steinernema rarum RS69 and Heterorhabditis bacteriophora RS33 were the most virulent strains and selected for field application (LC₉₅ of 70.5 and 53.8 IJs/cm², respectively). Both strains were highly efficient under field conditions when applied in aqueous suspension directed to larvae on peach tree trunk, causing mortality of 94 and 97.0%, respectively.     

Phenotypic variation in hatchling Chinese ratsnakes (Zaocys dhumnades) from eggs incubated at constant temperatures

We incubated eggs of the Chinese ratsnake Zaocys dhumnades at four constant temperatures (24, 27, 30 and 30 °C) to examine the effects of incubation temperature on hatching success and hatchling phenotypes. Incubation length increased nonlinearly as temperature decreased, with the mean incubation length being 76.7 d at 24 °C, 57.4 d at 27 °C, 47.3 d at 30 °C, and 44.1 d at 33 °C. Hatching successes were lower at the two extreme temperatures (69% at 24 °C, and 44% at 33 °C) than at the other two moderate temperatures (96% at 27 °C, and 93% at 30 °C). Incubation temperature affected nearly all hatchling traits examined in this study. Incubation of Z. dhumnades eggs at 33 °C resulted in production of smaller hatchlings that characteristically had less-developed carcasses but contained more unutilized yolks. Hatchlings from eggs incubated at 27 and 30 °C did not differ in any examined traits. Taking the rate of embryonic development, hatching success and hatchling phenotypes into account, we conclude that the temperature range optimal for incubation of Z. dhumnades eggs is narrower than the range of 24−33 °C but should be wider than the range of 27−30 °C.     

Distributional range extension of the seagrass Halophila nipponica into coastal waters off the Korean peninsula

Eight temperate seagrass species (five in the genus Zostera, two in the genus Phyllospadix, and Ruppia maritima) have been previously reported in coastal waters off the Korean peninsula, which lies between 33°N and 43°N. Recently, a species of Halophila, a genus which occurs predominantly in tropical and subtropical areas, has been observed on the southern coast of Korea for the first time. The species was identified as Halophila nipponica. H. nipponica is distributed in warm temperate regions of Japan influenced by the warm Tsushima Current and was previously unknown outside the Japanese archipelago. Thus, we are able to report a range extension into Korea. The Korean Halophila meadow that we observed covered an area of about 2.1 ha, with average shoot density of about 1300 m⁻². We measured morphological features of vegetative and reproductive organs between June and September 2007. Morphological and reproductive features of the Halophila species in Korea were similar to those of the species in Japan. Increased water temperature in the coastal waters of Korea may at least partially account for the persistence of this new population.     

Studies on the prolonged storage of Metarhizium anisopliae conidia: effect of growth substrate on conidial survival and virulence against mosquitoes

Metarhizium anisopliae was grown on six complex mycological media and on three types of rice at three moisture levels to determine the effect of growth substrate on conidial yield, viability, and virulence against mosquitoes immediately after spore maturation and after the storage of conidia at four different temperature-relative humidity (RH) combinations over a 1-year period. Conidial yields varied with the mycological media, but the viability and virulence of conidia against mosquitoes produced on all substrates were similar when spores were stored under the same conditions. The storage conditions were more critical to spore survival and virulence than the substrate upon which conidia were produced. The comparison of rice types for conidial production indicated that conidial yield, viability, and virulence to mosquitoes were more dependent upon the moisture level during growth and on the storage conditions that upon the rice used. The best storage conditions among those tested for the retention of both spore viability and virulence against mosquitoes were 19°C–97% RH and 4°C–0% RH.     

Persistence of <Emphasis Type="Italic">Isaria fumosorosea</Emphasis> (Hypocreales: Cordycipitaceae) SFP-198 Conidia in Corn Oil-Based Suspension

Long-term persistence of entomopathogenic fungi as biopesticides is a major requirement for successful industrialization. Corn oil carrier was superior in maintaining germination rates of Isaria fumosorosea SFP-198 conidia during exposure to 50°C for 2 h, when compared with other oils, such as soybean oil, cottonseed oil, paraffin oil, and methyl oleate. The corn oil-based conidial suspension (91.6% germination) was also better in this regard than conidial powder (28.4% germination) after 50°C for 8 h. Long-term storage stabilities of corn oil-based conidial suspension and conidial powder at 4 and 25°C for 24 months were investigated, based on the correlation of germination rate with insecticidal activity against greenhouse whiteflies, Trialeurodes vaporariorum. Viability of conidia in corn oil was more than 98.4% for up to 9 months of storage at 25°C, and followed by 23% at 21 months. However, conidial powder had only 34% viability after 3 months of storage at 25°C, after which its viability rapidly decreased. The two conidial preparations stored at 4°C had better viabilities than those at 25°C, showing the same pattern as above. These results indicate that corn oil-based conidial suspension can be used to improve conidial persistence in long-term storage and be further applied to the formulation of other thermo-susceptible biological control agents.     

The effects of photoperiod and light intensity on the sporulation of Brazilian and Norwegian isolates of Neozygites floridana

The objective of this study was to determine the effects of light intensity and duration (photoperiod) on the sporulation (discharge of primary conidia) and conidia germination (from non-infective primary conidia to infective capilliconidia) of Neozygites floridana isolates from Tetranychus urticae originating from Norway and Brazil. Two light intensities (40 and 208 μmol m⁻² s⁻¹), three photoperiods (24 h of continuous light (24 h D), 12 h of darkness followed by 12 h of light (12 h D: 12 h L) and 24 h of continuous darkness (24 h D)) and two temperatures (18 °C and 23 °C) were tested. The fungus produced similar amounts of primary conidia and capilliconidia at 12 h D:12 h and 24 h D, indicating that the fungus discharges almost all of its conidia during the first 12 h of darkness. Light had less of an effect on the production of primary conidia than on capilliconidia formation. At 24 h L, capilliconidia formation was significantly lower for all tested light intensities, temperatures and isolates compared to 12 h D:12 h L and 24 h D. At both light intensities, 24 h L resulted in a significantly lower capilliconidia formation for the Norwegian isolate compared to the Brazilian isolate. Our data suggest that, even though 24 h L reduced sporulation, some capilliconidia formation may occur at the low light intensities found on the underside of strawberry leaves during parts of the day as well as the top of a non-shaded strawberry leaf during the dim evening and morning hours in the tropics and during the dim, long summer days in temperate regions.     

Intraspecific tolerance of Metarhizium anisopliae conidia to the upper thermal limits of summer with a description of a quantitative assay system

Conidial tolerance to the upper thermal limits of summer is important for fungal biocontrol agents, whose conidia are formulated into mycoinsecticides for field application. To develop an efficient assay system, aerial conidia of eight Metarhizium anisopliae, four M. anisopliae var. anisopliae, and six M. anisopliae var. acridum isolates with different host and geographic origins were wet-stressed for ≤180 min at 48 °C or incubated for 14 d colony growths at 10-35 °C. The survival ratios (relative to unstressed conidia) of each isolate, examined at 15-min intervals, fit a logistic equation (r² ≥ 0.975), yielding median lethal times (LT₅₀s) of 14.3-150.3 min for the 18 isolates stressed at 48 °C. Seven grasshopper isolates from Africa had a mean LT₅₀ of 110 (73-150) min, but could not grow at 10 or 15 °C. The mean LT₅₀ of five non-grasshopper isolates capable of growing at 10-35 °C was 16 (10-26) min only. Three isolates with typically low (type I), medium (type II), and high (type III) levels of tolerance to 48 °C were further assayed for ≤4-d tolerance of their conidia to the wet stress at 38, 40, 42, or 45 °C. The resultant LT₅₀s decreased to 20, 53 and 167 min at 48 °C from 507, 1612, and 8256 min at 38 °C for types I, II and III, respectively. For the distinguished types, the logarithms of the LT₅₀s were significantly correlated to the temperatures of 38-48 °C with an inverse linearity (r² ≥ 0.88). The method developed to assay quantitatively fungal thermotolerance would be useful for screening of fungal candidates for improved pest control in summer.     

Diapause pupal color diphenism induced by temperature and humidity conditions in Byasa alcinous (Lepidoptera: Papilionidae)

We investigated whether diapause pupae of Byasa alcinous exhibit pupal color diphenism (or polyphenism) similar to the diapause pupal color polyphenism shown by Papilio xuthus. All diapause pupae of B. alcinous observed in the field during winter showed pupal coloration of a dark-brown type. When larvae were reared and allowed to reach pupation under short-day conditions at 18 °C under a 60 ± 5% relative humidity, diapause pupae exhibited pupal color types of brown (33%), light-brown (25%), yellowish-brown (21%), diapause light-yellow (14%) and diapause yellow (7%). When mature larvae reared at 18 °C were transferred and allowed to reach pupation at 10 °C and 25 °C under a 60 ± 5% relative humidity after a gut purge, the developmental ratio of brown and light-brown, yellowish-brown, and diapause light-yellow and diapause yellow types was 91.2, 8.8 and 0.0% at 10 °C, and 12.2, 48.8 and 39.0% at 25 °C, respectively. On the other hand, when mature larvae reared at 18 °C were transferred and allowed to reach pupation at 10 °C, 18 °C and 25 °C under an over 90% relative humidity after a gut purge, the developmental ratio of brown and light-brown, yellowish-brown, and diapause light-yellow and diapause yellow types was 79.8, 16.9 and 3.3% at 10 °C, 14.5, 26.9 and 58.6% at 18 °C, and 8.3, 21.2 and 70.5% at 25 °C, respectively. These results indicate that diapause pupae of brown types are induced by lower temperature and humidity conditions, whereas yellow types are induced by higher temperature and humidity conditions. The findings of this study show that diapause pupae of B. alcinous exhibit pupal color diphenism comprising brown and diapause yellow types, and suggest that temperature and humidity experienced after a gut purge are the main factors that affect the diapause pupal coloration of B. alcinous as environmental cues.     

Effect of temperature on sporulation of Neozygites floridana isolates from different climates and their virulence against the tomato red spider mite, Tetranychus evansi

The fungal pathogen Neozygites floridana Weiser and Muma has been evaluated as a classical biological candidate for introduction into Africa against the invasive tomato red spider mite Tetranychus evansi Baker and Pritchard. In this study, the effect of temperature on sporulation, germination and virulence of three isolates of N. floridana collected from T. evansi in three climatically distinct regions of Brazil and Argentina was determined. Six constant temperatures of 13 °C, 17 °C, 21 °C, 25 °C, 29 °C and 33 °C were tested for their effect on the ability of the three fungal isolates to sporulate, germinate and kill the mites. Six alternating-temperature regimes of 17-13 °C, 21-13 °C, 29-13 °C, 33-13 °C, 33-23 °C, 33-28 °C under a 12 h photophase were also tested to estimate virulence of the three isolates against T. evansi. The Vipos isolate discharged more conidia than isolates from Recife or Piracicaba at all temperatures and sporulation was strongly temperature dependent. Optimal sporulation rates were observed at 25 °C while optimal germination rates were observed at 25 °C and 29 °C. At 29 °C, the shortest mean survival time of T. evansi (3.16 days, 95% CI of 3.05-3.27) was observed for the isolate from Vipos, while the longest LT₅₀ (3.47 days, 95% CI 3.34-3.59) was observed for the isolate from Piracicaba. Mortality of mites increased as the differences between alternating day and night temperatures increased from 8 °C (21-13 °C), to 10 °C (33-23 °C), to 16 °C (29-13 °C), with smallest and highest temperature differences of 4 °C (17-13 °C) and 20 °C (33-13 °C), both producing low mortalities. The overall results suggest that the Vipos isolate is better adapted to a wider range of temperatures than the other isolates tested.     

Persistence of conidia of Entomophthora muscae in relation to age, temperature, and humidity

In this paper, the effect of age, humidity, and temperature on the conidial survival of Entomophthora muscae was evaluated. E. muscae was obtained from Musca domestica in a dairy in Itatiba (São Paulo, Brazil) and maintained in the laboratory by continuous passage through flies. Furthermore, the ability of conidia to infect flies at three temperatures (17, 21, and 27 °C), four ages of conidia (12, 72, 96, and 154 hours) and two humidities (100 and 60% RH) was evaluated. The temperature of 21 °C was the most favorable for the infection of house flies. Humidity was a cause of variation at 27 °C when the conidia were up to 12 hours old, but had no effect at lower temperatures. Conidia held at 100% RH and aged 72 hours caused no infection at 17 °C, but were infective at 21 °C. In the present study, conidia retained viability much longer than previously observed. Finally, the effect of humidity, temperature, and conidial age is discussed.     

Characterization of an extracellular lipase from the biocontrol fungus, Nomuraea rileyi MJ, and its toxicity toward Spodoptera litura

An extracellular lipase from Nomuraea rileyi MJ was purified 23.9-fold with 1.69% yield by ammonium sulfate precipitation followed by Sephacryl S-100 HR column chromatography. By mass spectrometry and SDS-polyacrylamide gel electrophoresis, the molecular weight of the homogenous lipase was 81 kDa. The N-terminal sequence was determined as LeuSerValGluGlnThrLysLeuSerLysLeuAlaTyrAsnAsp and it showed no homology to sequences of known lipases. The optimum pH and temperature for activity were 8.0 and 35 °C, respectively. The enzyme was stable in the pH range 7.0-9.0 and at 15-35 °C for 1 h. Higher activity was observed in the presence of surfactants, Na⁺, NH₄⁺ ions, NaN₃ and ethylenediaminetetraacetic acid (EDTA), while Co²⁺ and Cu²⁺ ions, cysteine and dithiothreitol (DTT) strongly inhibited activity. The purified lipase hydrolyzed both synthetic and natural triglycerides with maximum activity for trilaurin and coconut oil, respectively. It also hydrolyzed esters of p-nitrophenol (pNP) with highest activity for p-nitrophenyl caprate (pNPCA). The purified lipase was found to promote N. rileyi spore germination in vitro in that germination reached 98% in conidial suspensions containing purified lipase at 2.75 U. Moreover, it enhanced toxicity of N. rileyi toward Spodoptera litura larvae with mortality via topical application reaching 63.3% at 4-10 days post-treatment which calculated to be 2.7 times higher than the mortality obtained using conidial suspensions alone.     

Debilitation in conidia of the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae and implication with respect to viability determinations and mycopesticide quality assessments

Germination of Beauveria bassiana (Bb) and Metarhizium anisopliae (Ma) conidia determined from a fast-rehydration (FR) protocol were compared to those obtained when dry conidia were subjected to slow rehydration (SR) by holding under high humidity conditions prior to aqueous suspension. Differences in viability estimates obtained using the FR vs. SR protocols increased markedly after conidia were exposed to various stress factors in storage (high a_w, temperature, and O₂ concentrations), with the SR protocol producing higher estimates of viability in all cases. After Bb conidia were stored under moist conditions for 21 days at 25 °C, the SR estimate of viability was >21% greater than the FR estimate. In jars flushed with different O₂ concentrations and stored at 50 °C for 34 days, proportional differences between protocols varied, depending on water activity, from 18-44% in jars flushed with 0% O₂ (100% N₂) to as high as 63-93% when treated with 21-22% O₂. For conidia stored over a broad range of moderate to high temperatures in the absence of O₂, SR-FR differences were ?9% at 25-40 °C but 30% at 50 °C. Germination of stressed Bb and Ma conidia increased substantially when incubation time on the germination substrate was increased from 24 to 72 h, whereas germination of non-stressed conidia showed little change. Conidia debilitated by stress were characterized by hypersensitivity to lethal imbibitional damage (damage that is mitigated by slow rehydration) and slow germination. Viability protocols that may provide more reliable assessments of overall mycopesticide quality are discussed.     

Experimental ecology and hibernation of Onchidium struma (Gastropoda: Pulmonata: Systellommatophora)

This study investigated both laboratory-reared and pond-cultured subjects to explore the habit and hibernation patterns of the sea slug Onchidium struma (Mollusca, Gastropoda, Systellommatophora, Onchidioidea, Onchidiidae) from Shanghai and Zhejiang in China. Movement and feeding habits and the process of hibernation were observed in culturing tanks from June 2004 to March 2008. Our results showed that the conditions of movement are as follows: a minimum air temperature of 12 °C; a maximum light intensity of 25 lux and a minimum relative air humidity of 72%. Major movement is usually at dusk and during the night, and the average temperatures for fasting and beginning hibernation are 13.8 °C and 11.4 °C respectively. The analysis showed that the temperature is an essential factor affecting movement and feeding of O. struma and that RH and light intensity also play an important role, but are not necessarily required at the same time. In this study, the survival rate of O. struma through hibernation in high-biodiversity culturing tanks is 77.57% ± 2.86%.     

Survival of Neozygites cf. floridana (Zygomycetes: Entomophthorales) in mummified cassava green mites and the viability of its primary conidia

The survival of Neozygites cf. floridana (Weiser and Muma) as dry hyphal bodies in mummified cassava green mites, Mononychellus tanajoa (Bondar), at 5.0% RH in the dark was affected by storage temperature. Survival of the fungus in mummies kept at 24±1.0°C could be demonstrated for 6–7 months. When stored at 4°C, the fungus sporulated from 90% of the mummies liberating an average of 186.9 primary conidia per mummy even after a storage period of 16 months, when the experiment was terminated. The temperature, humidity and light condition significantly affected the viability of primary conidia. The percent viability across all factors dropped from 98.4% after 0 h (beginning of the experiment) to 23.4% after a 1 h exposure to the conditions tested. Lower temperatures maintained higher viabilities with 86.3% of the conidia surviving after 18 h at 18°C, whereas almost all conidia died after 12 h at 33°C. Conidia survived less than 1 h when exposed to SDs (saturation deficit) of 2.0 mm Hg or higher at any tested temperature.     

Tolerance of Sargassum thunbergii germlings to thermal, osmotic and desiccation stress

The construction of artificial seaweed beds in the intertidal zone is a challenge due to extreme levels of physical stress. In order to provide a basis for the construction using the dispersal of microscopic juveniles, a three-way factorial experimental design was used to evaluate the tolerance of Sargassum thunbergii germlings shortly released from fertile thalli to temperature, salinity and desiccation in this study. Results revealed that temperature, salinity and desiccation significantly affected the growth and survival of germlings. Germlings showed rapid growth with relative growth rate (RGR, % day⁻¹) over 16% when cultured at 25 °C and full immersion in normal seawater. Although growths of germlings subjected to moderate conditions were significantly inhibited, RGRs over 13% were obtained. The RGRs of germlings below 10% were observed only at 35 °C and 9 h desiccation treatments. In comparison to growth, survival was less affected by physical stress. Germlings showed low mortalities below 10% under appropriate conditions (25 °C and 30 °C combined with full immersion), and below 60% under moderate conditions, by the end of experiment. However, the mortality rates increased to over 90% under extreme conditions (9 h desiccation and 35 °C combined with full immersion in salinity of 12). These results showed that S. thunbergii germlings had high tolerance to physical stresses. In addition to the main effects, both two-way and three-way interactions between temperature, salinity and desiccation were significant. Based on the magnitude of effect, desiccation was the predominant factor affecting both growth and survival. According to the results, construction of artificial tanks in natural habitat to minimize desiccation may be an effective strategy for S. thunbergii restoration using germlings.     

Effect of relative humidity,temperature and fungicide on germination of conidia of Cercospora canescens caused the Cercospora leaf spot disease in mungbean

The aim of the present investigation was to determine the impact of relative humidity (RH) and temperature on conidial germination, nuclear position and effect of important fungicides on growth and conidial germination of Cercospora canescens. Germination of conidia was observed at RH range 92–100% at 5–35°C. Significant interaction between temperature and RH indicated that higher humidity and high temperature promoted quick germination both in the presence and absence of free moisture. Although in absence of free moisture at 92–95% RH higher temperatures 25–35°C promoted quick evaporation of moisture and no conidial germination. Number of germtube was increased significantly at the optimum temperature 25–30°C and higher humidity (98–100%). But higher temperature 25–35°C with lower RH did not support the conidial germination. This finding is very important for disease forecasting using meteorological data. The spray of Carbendazim as contact fungicide may not be useful since it is not effective against the conidia of C. canescens. Triadimefon did not inhibit the conidia germination but completely inhibited mycelium development at 50 μg/ml. Propriconazole inhibited both conidia germination and mycelial development. Therefore, Propiconazole may be taken as protective as well as curative spray. In non-systemic fungicide, Copper oxychloride gave anticipated result by inhibiting both conidial germination and mycelium development. Therefore, copper oxychloride can be used as protectant fungicides for Cercospora leaf spot caused by C. canescens.     

Effect of water temperature on dietary protein requirement,growth and body composition of Asian catfish, Clarias batrachus fry

This study aimed to evaluate the protein requirement of Clarias batrachus fry, were estimated at two different water temperatures, 28 and 32 °C. The influence of dietary protein level and water temperature on body composition, weight gain, food and nutrient utilization were estimated. The Asian catfish, C. batrachus fry were fed four diets containing 28% (diet 1), 32% (diet 2), 36% (diet 3) and 40% (diet 4) protein levels and reared at two water temperatures 28 and 32 °C for 60 days. Fry fed with diet 3 containing 36% protein showed the highest mean final body weight at 32 °C. Final body weight was significantly (P<0.05) affected by dietary treatments and temperatures. Clarias batrachus fry raised at 28 °C had higher feed efficiency (93.20%) than the fry reared at 32 °C (87.58%) with 28% dietary protein level. Further, feed efficiency decreased with increase in dietary protein level. Higher daily protein retention (0.089%) observed at lower (0.0217 g) daily protein intake at 28 °C than 0.0283 g at 32 °C. While, optimal (0.0282 g) daily protein intake showed higher daily weight gain at 32 °C. Productive protein value (% PPV) was maximum (1.76%) at 32 °C than at 28 °C (0.76%). Final body lipid recorded higher value than initial body lipid at both the temperatures. Hepatosomatic index (HSI) observed to have been influenced (P<0.05) by diets and temperatures, while viscerosomatic index (VSI) affected (P<0.05) by only diets and not (P>0.05) by temperatures. The study concluded that the diet 3 containing 36% protein was optimal for growth of C. batrachus fry at both the temperatures.