Biochemical characteristics of Trichoderma atroviride associated with conidium fitness for biological control

Effects of abiotic factors during production (temperature, nutrients, water activity, pH) on conidium fitness (quantity and quality) of Trichoderma atroviride LU132 (a key biocontrol agent) were studied. Conidia from the culturing regimes which resulted in greatest and least bioactivity against Rhizoctonia solani in dual culture assays were selected to assess effects of storage conditions on conidial fitness over time. Further studies assessed interaction effects of temperatures (20°C or 30°C) and sugars (dextrose or sucrose) on conidium germination and bioactivity as fresh conidia, or after 6 months of storage. Biochemical analyses of sugars and fatty acids were carried out to determine relationships between quality variations and cellular characteristics for conidia produced in different culturing conditions. Low trehalose content in conidia (e.g. at 20°C) was associated with the least conidium fitness, although high trehalose content did not necessarily support conidium fitness. High proportions of total fatty acids in conidia were mostly associated with the least conidium fitness. When Trichoderma was grown at high carbon to nitrogen ratio (e.g. at C:N 160:1), the total conidium fatty acids content increased. This study also indicated that the monosaccharide dextrose is metabolically optimal for T. atroviride LU132 at 20°C while the disaccharide sucrose is optimal at 30°C. These studies indicate that physical growth conditions and nutritional requirements attribute in conidium fitness of T. atroviride LU132, and provide important knowledge supporting optimum production of biocontrol agents based on T. atroviride, and possibly other similar biocontrol agents.     

Factors affecting sporulation and germination of Pandora nouryi (Entomophthorales: Entomophthoraecae), a pathogen of Myzus persicae (Homoptera: Aphididae)

Pandora nouryi discharged large numbers of primary conidia between 8 and 25°C from cadavers on the surface of water-agar. At 8°C conidial discharge lasted for 120 h, but most conidia were produced within 48 h when temperature was >15°C. Saturated humidity alone was not enough to allow for sporulation to occur freely and where RH?<?95%, no conidia were discharged. Light did not affect the pattern of conidial production nor the total number of conidia. Germination percentages of conidia on the surface of water-agar were 40 and 66% at 8 and 30°C, respectively, and were significantly lower than that at 15–25°C where germination was >95%. Conidia on leaves germinated well when RH?>?74%, while no germination occurred when RH?<?100% on cover slips. All eight insecticides tested entirely inhibited conidial germination at recommended doses (R), in particular, both the organophosphorus pesticides Lorsben (chlorpyrifos) and the organochlorine pesticides Thiodan (endosulfan) completely inhibited conidial germination even at 0.2R dose.     

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.     

蝉拟青霉LB菌株的生物学特性

本文研究碳源、氮源、温度、湿度、pH值和光照等对蝉拟青霉LB菌株生长、产孢和孢子萌发的影响.结果表明,适合该菌株菌落生长和产孢的最佳碳源是可溶性淀粉和蔗糖,最佳氮源为蛋白胨;菌丝生长和孢子萌发的最适温度范围是25℃～27℃,产生分生孢子的最适温度是25℃;分生孢子萌发所需湿度范围是RH 90%～100%,当RH低于90%时很难萌发;在pH值4～10的范围内该菌能生长和产孢,菌丝生长最适pH为6,产生分生孢子和孢子萌发最适pH范围为6-7;光照处理对该菌产孢有一定的影响;分生孢子的致死条件为55℃ 10min.生物学特性显示,蝉拟青霉LB菌株是一株对营养要求不高、对环境适应能力较强的昆虫病原真菌.     

Development of pilot-scale fermentation and stabilisation processes for the production of microsclerotia of the entomopathogenic fungus Metarhizium brunneum strain F52

Using 100 L stirred-tank bioreactors, we evaluated the effect of fermentation parameters and drying protocols on the production and stabilisation of microsclerotia (MS) of the entomopathogenic fungus Metarhizium brunneum (formerly M. anisopliae F52). Results showed that stirred-tank bioreactors can be used to mass produce stable MS of Metarhizium and that culturing and drying protocols significantly affected MS yield and stability. Length of fermentation (4–7 days) for Metarhizium cultures had no significant impact on biomass accumulation, MS formation or the storage stability of the air-dried MS granules. Although cultures of Metarhizium grown on media with a carbon-to-nitrogen (C:N) ratio of 30:1 produced significantly more biomass when compared to cultures grown in media with a C:N ratio of 50:1, MS formation and desiccation tolerance following drying were similar. After storage for 1 year at 4°C, conidia production by air-dried MS granules from 50:1 media was significantly higher compared to MS granules from 30:1 media. The addition of diatomaceous earth (DE) to cultures of Metarhizium prior to drying at rates of 0–60 g L^?1 had no significant effect on MS desiccation tolerance but did impact conidia production. Air-dried MS granules without DE produced significantly more conidia g^?1 during the first 4 months of storage, but after 1 year, conidia production was similar regardless of DE content of the MS granule. Microsclerotial granules with higher moisture levels (2.6–5.0% w/w) produced significantly more conidia immediately after drying and MS granules with low moisture (0–2.5% w/w) produced more conidia after 12 months storage.     

Effects of Moisture Content and Temperature on Storage of Metarhizium flavoviride Conidia

The effects of moisture content and temperature on the medium-term (3-4 months) storage of conidia of Metarhizium flavoviride were investigated. Conidia harvested after 24 days of culturing on rice showed greater tolerance to long storage than conidia from 12-day cultures. The moisture content of the conidia was of greatest importance; at harvest from the culture, conidial moisture contents could be 40%, while the optimal moisture content for storage was found to be 4-5%. Dried conidia stored in oil benefited from the addition of dried silica gel, as did conidia stored as powder. A range of mineral oils proved satisfactory for storage, and when dried silica gel was added to suspensions, germination levels were 79.8% after 105 days at 28-32 C. Dried conidia stored in oil maintained germination levels of up to 96 and 85% after 80 days at 10-14 C and 28-32 C respectively. Dried conidia stored as powder retained germination levels of 95% at 10-14 C, but only up to 27% at 28-32 C. In another experiment, dried conidia maintained greater than 90% germination over 128 days, with or without silica gel at 10 - 14 C or -15 - -18 C.     

Studies on Prolonged Storage of Beauveria bassiana Conidia: Effects of Temperature and Relative Humidity on Conidial Viability and Virulence against Chickpea Borer,Helicoverpa armigera

Unformulated conidia of Beauveria bassiana were stored at five different temperatures (0°, 10°, 20°, 30° and 40°C) at six different relative humidities (RH) (0, 33, 53, 75, 85 and 98%). Conidial viabilities and virulence against third instar larvae of Helicoverpa armigera were determined over a 24‐month period. Conidia survived longest at lower temperatures (0–20°C) and lower RH levels (0–53% RH). At higher temperatures (30–40°C) conidia did not survive. When the temperature was decreased from 30°C to 0°C, at nearly all RH levels the longevity of conidia increased. Conidia remained virulent for third instar larvae of H. armigera under favourable storage conditions for 24 months.     

Survivability and storage stability of Trichoderma atroviride TRS40 preserved by fluidised bed drying on various agriculture by-products

Agriculture by-products were applied to proliferate biomass of Trichoderma atroviride TRS40 in solid state fermentation (SSF) cultures. The culture media overgrown with mycelium together with conidia were preserved by fluidised bed drying at various temperatures (50°C, 60°C and 70°C) and the received biopreparations were stored for 12 months. In order to determine the suitability of TRS40 in the production of biopreparations, the influence of preservation process and storage time on their survivability was examined. The three-component mixture proved more effective in the SSF cultures, ensuring TRS40 count at 6.07?×?10^9?CFU/g?dm, which was ca. 6 times higher than in the mono-component medium. TRS40 survivability after preservation at various temperatures ranged from 40.4% to 100%, regardless of carrier type. In turn, after 12-month storage of the biopreparations produced on the three-component medium, regardless of drying temperature, the number of viable cells ranged from 2.43?×?10⁸ to 2.49?×?10^8?CFU/g?dm. Furthermore, selected parameters of growth kinetics in the Bioscreen C system were determined. The storage time of biopreparations had various effects on growth kinetic parameters. In addition, the preserved preparations based on the TRS40 retained their capability for biosynthesis of hydrolases, even after 12 months of storage.     

Influence of temperature and humidity on the survival of Monilinia fructicola conidia on stone fruits and inert surfaces

The survival of the fungus Monilinia fructicola on fruit and inert surfaces at different temperatures (range: 0–30°C) and relative humidity (RH) (range: 60–100%) was investigated. M. fructicola conidia survived better on fruit than on inert surfaces. The viability reduction rate at 20°C and 60% RH was 1.2 and 5.8 days^?1 on fruit and inert surfaces, respectively. Overall, on fruit surfaces, conidia viability was reduced at high temperatures and was longer at higher RH than at lower RH; in contrast, on inert surfaces, conidia viability was longer at only low temperatures. On fruit surfaces, at 0°C and 100% RH, conidia survived up to 35 days, and at 30°C and 60% RH, conidia survived up to 7 days. However, on inert surfaces at 20°C and 30°C, conidia lost their viability after 48 and 24 h, respectively. These results suggest that M. fructicola can remain viable in cold rooms for over 30 days on fruit surfaces or over 25 days on inert surfaces. Furthermore, under the orchard conditions during the growing season, conidia may remain viable for only 2–3 days on immature fruit surfaces before conidia will be unable to penetrate the host.     

Optimising inoculum yield and shelf life of Plectosphaerella cucumerina,a potential bioherbicide for Cirsium arvense

Plectosphaerella cucumerina was identified as a potential bioherbicide for controlling Cirsium arvense in Canada and New Zealand. The current study evaluated production conditions using two isolates (one from each country) to determine whether the yield and shelf life of inoculum are suitable for mass production. Mycelial growth and sporulation in culture both increased from 15°C to 25°C and declined at higher temperatures with no mycelial growth at 37°C. The Canadian isolate produced fewer conidia than a New Zealand isolate. Potato dextrose-based liquid media with moderate to high concentrations of carbohydrates (25%, 50%, and 100%) maximised conidia production and these base media produced conidia with the highest germination rate (>80%) both at harvest and after 4 weeks stored at 4°C in 2.5% glycerol, 40% milk glycerol or after air drying. However, after 10-week storage, the conidia failed to germinate. Sporulation occurred during growth on all solid substrates tested (rice, rolled barley, and triticale), but conidial germination was highest on rice and barley, both before and after air drying. By contrast to conidia, 90% of mycelia-infested barley grains were viable after 3 years of storage at room temperature, although viability was lost by this time on the other substrates. This study has shown that the nutritional base is an important determinant of sporulation and shelf life for P. cucumerina. Although the yield of conidia in liquid medium was adequate to justify further development of P. cucumerina as a bioherbicide, improvement in its shelf life, or alternate formulation types that extend the shelf life, must be made for commercial efficiency.     

The impact of temperature on the production and fitness of microsclerotia of the fungal bioherbicide Mycoleptodiscus terrestris

The impact of growth temperature was evaluated for the fungal plant pathogen Mycoleptodiscus terrestris over a range of temperatures (20–36°C). The effect of temperature on biomass accumulation, colony forming units (cfu), and microsclerotia production was determined. Culture temperatures of 24–30°C produced significantly higher biomass accumulations and 20–24°C resulted in a significantly higher cfu. The growth of M. terrestris was greatly reduced at temperatures above 30°C and was absent at 36°C. The highest microsclerotia concentrations were produced over a wide range of temperatures (20–30°C). These data suggest that a growth temperature of 24°C would optimize the parameters evaluated in this study. In addition to growth parameters, we also evaluated the desiccation tolerance and storage stability of air-dried microsclerotial preparations from these cultures during storage at 4°C. During 5 months storage, there was no significant difference in viability for air-dried microsclerotial preparations from cultures grown at 20–30°C (>72% hyphal germination) or in conidia production (sporogenic germination) for air-dried preparations from cultures grown at 20–32°C. When the effect of temperature on germination by air-dried microsclerotial preparations was evaluated, data showed that temperatures of 22–30°C were optimal for hyphal and sporogenic germination. Air-dried microsclerotial preparations did not germinate hyphally at 36°C or sporogenically at 20, 32, 34, or 36°C. These data show that temperature does impact the growth and germination of M. terrestris and suggest that water temperature may be a critical environmental consideration for the application of air-dried M. terrestris preparations for use in controlling hydrilla.     

Effects of Culture Age, Washing and Storage Conditions on Desiccation Tolerance of Colletotrichum truncatum Conidia

Colletotrichum truncatum conidia produced from a one week-old culture in a liquid semi-defined medium with a C:N ratio of 5:1 were more tolerant of desiccation than those harvested from two or three week-old cultures. Conidia washed with 20% (w/v) sucrose germinated better than unwashed conidia or those washed in 10% (w/v) sucrose, 10 and 20% (w/v) glucose or fructose, 0.1% (w/v) soluble starch, 0.9% (w/v) NaCl or deionized water. Washing with sucrose (20% w/v) also resulted in significantly longer germ tubes than those produced by unwashed conidia or conidia washed with deionized water or NaCl (0.9% w/v). Conidia washed twice in sucrose showed greater desiccation tolerance during storage at 15% relative humidity (RH) and 15°C than at 30% RH and 15 or 25°C or at 15% RH and 25, 5 or -10°C.     

Limits to the Negative Logarithmic Relationship Between Moisture Content and Longevity in Conidia ofMetarhizium flavoviride

Conidia ofMetarhizium flavoviridewere hermetically stored at50 °C and 14 moisture contents between 2.5 and 31.8% (freshweight basis) for up to 146 d, and tested for germination onSabouraud Dextrose Agar at 25 °C for 24 h. Survival of conidiaconformed to cumulative negative normal distributions and all14 survival curves could be constrained to a common origin.There was a negative logarithmic relation between longevityand conidia moisture content, but limits to the relation weredetected: the lower-moisture-content limit was 4.6% [in equilibriumwith 10.7% relative humidity (RH) at 20 °C], below whichvalue further reduction in moisture content did not increaseconidia longevity; and an upper-moisture-content limit betweenabout 21.2 and 31.8% moisture content (between 77 and 90.0%equilibrium RH at 20 °C) above which conidia longevity nolonger decreased. The observations could also be described bya negative semi-logarithmic relation between conidia longevityand equilibrium relative humidity. In this model, each reductionin equilibrium relative humidity by 11.2% within the range 10.7to 80% RH doubled conidia longevity. The similarities in theserelations, and the limits to these relations, between the conidiaof this entomopathogenic fungus and the orthodox seeds of higherplants are discussed.Copyright 1998 Annals of Botany Company Conidia longevity, equilibrium relative humidity,Metarhizium flavoviride, moisture content, hermetic storage, viability equation     

Optimising sporulation and virulence in Drechslera avenacea

Studies were conducted on agar media to optimise sporulation of Drechslera avenacea, a fungal pathogen being evaluated as a biological control agent for Avena species (wild oats). Conidium production was affected by nutrition, pH, temperature and light conditions. Of the agar media tested, Czapek Dox agar (CZA) and half-strength oatmeal agar (½OMA) were the only media where sporulation occurred at all temperatures tested under a 12-h light:12-h dark photoperiod (L/D). The optimum temperature for conidium production was 20°C on ½OMA, whereas there was no optimum temperature on CZA. Under a 12-h near-ultraviolet (NUV):12-h dark photoperiod (NUV/D), similar numbers of conidia were produced on CZA at 6.66, 14.56, and 22.78 W m^?2, whereas on ½OMA conidium production was the highest at 14.56 W m^?2. When NUV/D and L/D conditions were compared, similar numbers of conidia where produced on CZA, whereas ½OMA conidium production was superior under the NUV/D photoperiod. Considerable variation in sporulation and degree of virulence of D. avenacea was detected among isolates from different geographic areas. The most virulent conidia were obtained on ½OMA at 20°C incubated under continuous illumination NUV light. Therefore, the most suitable conditions for conidium production of D. avenacea were growth for 1 week on ½OMA at 20°C under continuous NUV at an intensity of 14.56 W m^?2. Under these conditions, 1.1×10⁵ conidia mL^?1 were produced which is the highest sporulation yet reported for any Drechslera spp., which are traditionally poor sporulators.     

The survival ofZoophthora radicans (Zygomycetes: entomophthorales) isolates as hyphal bodies in mummified larvae ofPlutella xylostella (Lep.: Yponomeutidae)

The survival of three isolates ofZoophthora radicans (NW 250, NW 253 & NW 182) as hyphal bodies in dried larvae ofPlutella xylostella stored at 4, 10 and 20°C and 20% R.H was determined. After storage at 20°C, the production of conidia by all isolates was unaffected after 2 weeks but diminished increasingly after 4 and 8 weeks and was entirely lost after 16 weeks. By comparison conidium production at 10°C was unaffected after 16 weeks (isolates NW 250 and NW 182) and, 24 weeks (NW 253) of storage though it declined rapidly in all isolates thereafter. At 4°C many conidia were produced by all isolates even after 34 weeks of storage. These results are consistent with work on other entomophthoralean fungi in dried cadavers suggesting that this may be a common survival strategy in these fungi. NW 250, 253 and 182 were isolated fromP. xylostella in Malaysia and Taiwan, where conditions allow the host to remain active throughout the year. None produced resting sporesin vivo orin vitro but as hosts are always available the ability to survive short dry periods is probably more important than long-term survival for which resting spores are most adapted.      

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.     

Temperature and moisture requirements for conidial germination of an isolate of Beauveria bassiana,pathogenic to Rhodnius prolixus

The effects of temperature, relative humidity and water activity on germination of conidia of an isolate of Beauveria bassiana (Bals.) Vuill. pathogenic to the triatomine vector of Chagas' disease, Rhodnius prolixus Stål., were investigated in vitro. Germination occurred at temperatures between 15 °C and 35 °C under saturated atmosphere and the optima ranged from 25 °C to 3O °C. At the extreme temperatures tested (15 °C and 35 °C) the germination process was delayed, but germination rates reached more than 95%. Germination of B. bassiana conidia was strongly affected by moisture conditions. The availability of water, in both atmospheric and liquid conditions, caused changes in germination times as well as in germination rates. For example, at 25 °C + O.5 °C, germination took place within 20 h at 95.5% RH, whereas it needed 72 h of incubation at 90% RH. Germination times increased as the water activity declined from 0.96 a_w to 0.92 a_w. Below 0.92 a_w, o germination was observed after a 72 h incubation time.     

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.     

Algorithm-based design of novel synthetic media for Metarhizium anisopliae simulating its nutritional conditions in the environment

Aims:  The objective of this study was to develop a novel synthetic growth medium for increased conidium production of the entompathogenic fungus Metarhizium anisopliae. The medium should simulate natural nutritional conditions.
Methods and Results:  Macro- and micronutrients were selected in concentrations found in insects or from sources which are believed to be advantageous for virulence. Medium development was guided by a problem-oriented genetic algorithm (GA) implemented with 'mutation' and 'recombination' operators specific for this optimization problem. Following five optimization steps and a total of 181 medium variations, 19 synthetic media led to increased conidium production as compared with the standard Sabouraud dextrose agar medium: increases in conidia yields of up to 120% and a 17-fold higher conidium production per square centimetre of mycelium were achieved. Rapid germination of conidia, conidial C : N ratio, as well as spore-bound Pr1 protease production were monitored as proposed quality control markers for a virulent inoculum.
Conclusions:  It was demonstrated that our problem-oriented GA is a powerful tool for the design of chemically defined cultivation media with special/enhanced properties for anamorphic fungi.
Significance and Impact of the Study:  This is the first study, which demonstrates the advantage of the use of a GA for the rapid design of solid synthetic media for maximum production of virulent conidia.     

Life tables of the predatory mite Neoseiulus cucumeris (Acari: Phytoseiidae) on two pest mites as prey,Aculops lycopersici and Tetranychus urticae

Abstract

Studies on the life history and life table parameters of Neoseiulus cucumeris Oudemans (Acari: Phytoseiidae) were carried out under laboratory conditions of 25?±?1?°C and 65?±?5% RH; 30?±?1?°C and 60?±?5% RH; 35?±?1?°C and 55?±?5% RH. As prey, immature stages of tetranychid spider mite T. urticae Koch (Acari: Tetranychidae) and the moving stages of the Tomato Russet Mite A. lycopersici (Massee) (Acari: Eriophyideae) were selected. The predatory phytoseiid mite, Neoseiulus cucumeris (Oudemans) was able to develop successfully from egg to adult stage through the entire life history on both preys. The higher of different temperatures and relative humidities shortened the development and increased reproduction and prey consumption and vice versa. The maximum reproduction (3.91, and 3.09 eggs/♀/day) was recorded at 35?°C and 65% RH, while the minimum (2.12, and 1.90 eggs/♀/day) was at 25?±?1?°C and 55?±?5% RH. when N. cucumeris fed on A. lycopersici and T. urticae, respectively. The reproductive rate on eriophyid was significantly higher than previously recorded on tetranychid. Life table parameters indicated that feeding of phytoseiid mite N. cucumeris on tomato russet mite A. lycopersici led to the highest reproduction rate (rm?=?0.268, 0.232 and 0.211 females/female/day), while feeding on T.urticae gave the lowest reproduction rate (rm?=?0.159, 0.143 and 0.131) at 35?°C and 55% RH, 30?°C and 60% RH and 25?°C and 65% RH, respectively. The population of N. cucumeris multiplied (36.81, 28.71 and 20.47) and (24.60, 19.58 and 14.62 times) in a generation time of (20.10, 23.20 and 25.14) and (22.35, 25.36 and 27.79 days) when a predator fed on A. lycopersici and T. urticae at the same temperature above mentioned, respectively. These results suggest that the two mites, particularly A. lycopersici, proved to be suitable prey for N.cucumeris, as a facultative predator.