Pathogenicity of <Emphasis Type="Italic">Beauveria bassiana</Emphasis> and <Emphasis Type="Italic">Metarhizium anisopliae</Emphasis> to the tobacco spider mite <Emphasis Type="Italic">Tetranychus evansi</Emphasis>

Seventeen isolates of Metarhizium anisopliae (Metschnikoff) Sorokin and two isolates of Beauveria bassiana (Balsamo) Vuillemin were evaluated for their pathogenicity against the tobacco spider mite, Tetranychus evansi Baker & Pritchard. In the laboratory all the fungal isolates were pathogenic to the adult female mites, causing mortality between 22.1 and 82.6%. Isolates causing more than 70% mortality were subjected to dose–response mortality bioassays. The lethal concentration causing 50% mortality (LC₅₀) values ranged between 0.7×10⁷ and 2.5×10⁷ conidia ml⁻¹. The lethal time to 50% mortality (LT₅₀) values of the most active isolates of B. bassiana and M. anisopliae strains varied between 4.6 and 5.8 days. Potted tomato plants were artificially infested with T. evansi and treated with B. bassiana isolate GPK and M. anisopliae isolate ICIPE78. Both fungal isolates reduced the population density of mites as compared to untreated controls. However, conidia formulated in oil outperformed the ones formulated in water. This study demonstrates the prospects of pathogenic fungi for the management of T. evansi.     

The influence of sublethal deposits of agricultural mineral oil on the functional and numerical responses of <Emphasis Type="Italic">Phytoseiulus persimilis</Emphasis> (Acari: Phytoseiidae) to its prey, <Emphasis Type="Italic">Tetranychus urticae</Emphasis> (Acari: Tetranychidae)

Occasional pesticide application in integrated pest management to at least part of a crop requires that any biological control agents must re-invade previously sprayed areas in order that resurgent pests can be constrained. The ability of the phytoseiid predatory mite Phytoseiulus persimilis to feed on adult two-spotted spider mite (TSSM) Tetranychus urticae on excised leaf discs in both control conditions and in a treatment with a sub lethal residue of agricultural mineral oil (AMO) was assessed. The predator exhibited a Type II functional response with the asymptote significantly higher in the AMO conditions due to the fact that the prey grew slower and reached a smaller size in this treatment. In terms of prey volume eaten, the satiation level of the predator was unchanged by the AMO deposits. The numbers of eggs produced by adult P. persimilis females at densities of 4, 8 and 16 TSSM adult females/disc in the control were significantly higher than those in the AMO treatment, but were similar for the higher density levels, 32 and 64 prey per disc. Thus the functional response in terms of volume of prey eaten explained the numerical response in terms of predator eggs produced. The presence of AMO deposits when the prey were at high density had no effect on predator efficiency (volume eaten) but resulted in a lower intake than that in control conditions when there was a greater distance between prey.     

Modelling the potential distribution of the invasive tomato red spider mite, <Emphasis Type="Italic">Tetranychus evansi</Emphasis> (Acari: Tetranychidae)

Predicting the potential geographical distribution of a species is particularly important for pests with strong invasive abilities. Tetranychus evansi Baker & Pritchard, possibly native to South America, is a spider mite pest of solanaceous crops. This mite is considered an invasive species in Africa and Europe. A CLIMEX model was developed to predict its global distribution. The model results fitted the known records of T. evansi except for some records in dry locations. Dryness as well as excess moisture stresses play important roles in limiting the spread of the mite in the tropics. In North America and Eurasia its potential distribution appears to be essentially limited by cold stress. Detailed potential distribution maps are provided for T. evansi in the Mediterranean Basin and in Japan. These two regions correspond to climatic borders for the species. Mite establishment in these areas can be explained by their relatively mild winters. The Mediterranean region is also the main area where tomato is grown in open fields in Europe and where the pest represents a threat. According to the model, the whole Mediterranean region has the potential to be extensively colonized by the mite. Wide expansion of the mite to new areas in Africa is also predicted. Agricultural issues highlighted by the modelled distribution of the pest are discussed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Host plant resistance among tomato accessions to the spider mite <Emphasis Type="Italic">Tetranychus evansi</Emphasis> in Kenya

The spider mite Tetranychus evansi has a broad range of host plants. Control of T. evansi has been a big challenge to tomato farmers due to its fast rate of reproduction, development of resistance to chemical pesticides and its ability to use weeds as alternative hosts when the tomato plants are not available. The aim of the current study was to determine the host plant acceptance and the relative contributions of trichomes in the control of the red spider mite by comparing the survival, development and oviposition rates of the red spider mite on eight tomato accessions. Leaflets from eight tomato varieties were assayed with the spider mites to determine the egg laying capacity and developmental time of the spider mites on the tomato accessions as well as the trichome densities. Densities of trichome types I, IV, V and VI varied among the tomato accessions. Variation in types I, IV and VI accounted for most of the variation in mite responses. The varieties with high densities of types IV and VI had the highest fecundity and mite development did not go beyond the larval stage. The developmental time varied significantly among the tomato accessions. The results indicated that the higher the density of trichome type I the lower the adult survival. The findings indicated possible resistance of some of the tested tomato accessions against T. evansi which is partially associated with trichomes types and density.     

Predation by <Emphasis Type="Italic">Nesidiocoris tenuis</Emphasis> on <Emphasis Type="Italic">Bemisia tabaci</Emphasis> and injury to tomato

Tomato is the most important vegetable crop in Spain. The mirid bug Nesidiocoris tenuis (Reuter) commonly appears in large numbers in protected and open-air tomato crops where little or no broad-spectrum insecticides are used. Nesidiocoris tenuis is known to be a predator of whiteflies, thrips and several other pest species. However, it is also considered a pest because it can feed on tomato plants, causing necrotic rings on stems and flowers and punctures in fruits. Our objectives were to evaluate predation by N. tenuis on sweetpotato whitefly Bemisia tabaci Gennadius under greenhouse conditions and establish its relationship to N. tenuis feeding on tomato. Two different release rates of N. tenuis were compared with an untreated control (0, 1 and 4 N. tenuis plant⁻¹) in cages of 8 m². Significant reductions of greater than 90% of the whitefly population and correspondingly high numbers of N. tenuis were observed with both release rates. Regression analysis showed that necrotic rings on foliage caused by N. tenuis were best explained by the ratio of B. tabaci nymphs:N. tenuis as predicted by the equation y = 15.086x − 0.6359.

Life history of the predatory mite <Emphasis Type="Italic">Phytoseiulus fragariae</Emphasis> on <Emphasis Type="Italic">Tetranychus evansi</Emphasis> and <Emphasis Type="Italic">Tetranychus urticae</Emphasis> (Acari: Phytoseiidae,Tetranychidae) at five temperatures

Tetranychus evansi Baker and Pritchard and Tetranychus urticae Koch (Acari: Tetranychidae) are important pests of Solanaceae in many countries. Several studies have demonstrated that T. urticae is an acceptable prey to many predatory mites, although the suitability of this prey depends on the host plant. T. evansi, has been shown to be an unfavorable prey to most predatory mites that have been tested against it. The predator Phytoseiulus fragariae Denmark and Schicha (Acari: Phytoseiidae) has been found in association with the two species in Brazil. The objective of this work was to compare biological parameters of P. fragariae on T. evansi and on T. urticae as prey. The study was conducted under laboratory conditions at 10, 15, 20, 25 and 30°C. At all temperatures, survivorship was lower on T. evansi than on T. urticae. No predator reached adulthood at 10°C on the former species; even on the latter species, only about 36% of the predators reached adulthood at 10°C. For both prey, in general, duration of each life stage was shorter, total fecundity was lower and intrinsic rate of population increase (r _m ) was higher with increasing temperatures. The slower rate of development of P. fragariae on T. evansi resulted in a slightly higher thermal requirement (103.9 degree-days) on that prey than on T. urticae (97.1 degree-days). The values of net reproduction rate (R ₀), intrinsic rate of increase (r _m ) and finite rate of increase (λ) were significantly higher on T. urticae, indicating faster population increase of the predator on this prey species. The highest value of r _m of the predator was 0.154 and 0.337 female per female per day on T. evansi and on T. urticae, respectively. The results suggested that P. fragariae cannot be considered a good predator of T. evansi.     

Effects of azadirachtin on the two-spotted spider mite, <Emphasis Type="Italic">Tetranychus urticae</Emphasis> (Acari: Tetranychidae)

Effects of sublethal azadirachtin exposure to the biological performance of Tetranychus urticae Koch was studied under laboratory conditions. Bioassay was used to asses the effect of different concentrations of azadirachtin on longevity, fecundity, fertility, and offspring development. Azadirachtin (64 and 128 ppm) affected fecundity and mortality but had no effect on fertility and offspring development. A subsequent life-table study with 80 ppm of azadirachtin found that the compound caused a reduction of 50% in survival to adult stage. The peak of reproduction was reached at 5 days causing a decrease in the mean fecundity to almost eight times than of untreated females. The net reproductive rate (R ₀), the intrinsic rate of increase (r _m), and the finite rate of increase () of treated females were lower. Treatment showed a negative value of r _m, resulting in a declining population. These results suggest that azadirachtin could be incorporated in Integrated Pest Management (IPM) programmes of T. urticae.This revised version was published online in May 2005 with a corrected cover date.     

Management of <Emphasis Type="Italic">Tetranychus urticae</Emphasis> (Acari: Tetranychidae) in strawberry fields with <Emphasis Type="Italic">Neoseiulus californicus</Emphasis> (Acari: Phytoseiidae) and acaricides

The purpose of this study was to evaluate the performance of Neoseiulus californicus (McGregor) for the control of Tetranychus urticae Koch in commercial strawberry fields, under greenhouse conditions, in association or not with the use of acaricides. The N. californicus strain used in this study was tolerant or resistant to several pesticides. Three experiments were carried out in the State of São Paulo, Brazil. For the first experiment, the initial infestation of T. urticae was 87.1 active stages per leaflet. Two applications of propargite were made on the first and the 14th day of the experiment. Approximately 2 h after each propargite application, N. californicus was released at a rate of 3.0 and 1.9 adult mites per plant, respectively, for each application. The population of T. urticae decreased from 87.1 to 2.8 mites per leaflet in the first three weeks. After this period, the population of T. urticae was maintained at low levels (≤1.5 mites/leaflet) until the end of the experiment (10th week). Propargite and dimethoate sprayed on the strawberry field did not affect significantly the population of this predaceous mite. For the second experiment, the infestation of T. urticae was 29.1 mites per leaflet, when the acaricide chorfenapyr was applied on the strawberry field. The release of N. californicus (2 mites per plant) was made 2 weeks after spraying the acaricide. The population of T. urticae was maintained at low levels (≤2.8 mites/leaflet) for 8 weeks (evaluation period). The T. urticae infestations in plots with N. californicus were significantly lower than in non-release plots, for the experiments 1 and 2. In the third experiment, the initial infestation of T. urticae was 40.5 mites per leaflet (55.5 active stages/leaflet on release plants; 25.5 active stages/leaflet on non-release plants). Three releases of N. californicus (average rate of 3.0 adult mites/plant), without any acaricide application, were not sufficient to reduce significantly the T. urticae population in release plots (release plants + non-release plants) in 6 weeks from the first release, however, the spider mite population decreased from 55.5 to 7.8 active stages per leaflet on release plants, during this period. Interplant dispersal of N. californicus was low in this strawberry field with high infestation of T. urticae. The studies indicate the viability of the use of this strain of N. californicus for the control of T. urticae in strawberry fields under greenhouse conditions, especially in association with selective acaricides.     

Reproductive performance of seven strains of the tomato red spider mite <Emphasis Type="Italic">Tetranychus evansi</Emphasis> (Acari: Tetranychidae) at five temperatures

The tomato red spider mite Tetranychus evansi Baker et Pritchard occurs on solanaceous plants, and causes serious damage to a variety of crops in Africa and Europe. In 2001 this species was also found in Japan, on nightshade (Solanum nigrum L.), and its invasion to solanaceous of agricultural importance is feasible. To evaluate its potential severity as a pest, the present study assessed the life-history parameters, such as the rate of development and the intrinsic rate of natural increase (r _m), on S. nigrum for T. evansi collected on seven sites worldwide. Increasing temperatures between 15 and 32.5°C significantly increased the developmental rate of the seven strains while immature developmental duration was about the same at 32.5–40°C. The rate of egg-to-adult development [(% hatch) × (% survival)] exceeded 88% at temperatures between 15 and 37.5°C. The lower thermal thresholds (LT) were 11.9–12.5°C for both egg-to-adult and egg-to-egg development. The optimum developmental temperatures ranged from 36.7 to 43.8°C and the upper developmental threshold (UT) ranged from 45.2 to 59.4°C. The r _m-values became higher with temperature increasing from 15 to 35°C. The r _m-values at 25°C ranged from 0.265 to 0.277 which are relatively high for species of the genus Tetranychus. These results indicate that T. evansi after invasion into Japan has the potential to become a serious pest on solanaceous crops, just the same as in Africa and Europe.     

Recent emergence and worldwide spread of the red tomato spider mite, <Emphasis Type="Italic">Tetranychus evansi</Emphasis>: genetic variation and multiple cryptic invasions

Plant biosecurity is increasingly challenged by emerging crop pests. The spider mite Tetranychus evansi has recently emerged as a new threat to solanaceous crops in Africa and the Mediterranean basin, with invasions characterized by a high reproductive output and an ability to withstand a wide range of temperatures. Mitochondrial (868 bp of COI) and nuclear (1,137 bp of ITS) loci were analyzed in T. evansi samples spanning the current geographical distribution to study the earliest stages of the invasive process. The two sets of markers separate the samples into two main clades that are only present together in South America and Southern Europe. The highest COI diversity was found in South America, consistent with the hypothesis of a South American origin of T. evansi. Among the invaded areas, the Mediterranean region displayed a high level of genetic diversity similar to that present in South America, that is likely the result of multiple colonization events. The invasions of Africa and Asia by T. evansi are characterized by a low genetic variation associated with distinct introductions. Genetic data demonstrate two different patterns of invasions: (1) populations in the Mediterranean basin that are a result of multiple cryptic introductions and (2) emerging invasions of Africa and Asia, each likely the result of propagules from one or limited sources. The recent invasions of T. evansi illustrate not only the importance of human activities in the spread of agricultural pests, but also the limits of international quarantine procedures, particularly for cryptic invasions.     

<Emphasis Type="Italic">Wolbachia</Emphasis>-induced cytoplasmic incompatibility in Japanese populations of <Emphasis Type="Italic">Tetranychus urticae</Emphasis> (Acari: Tetranychidae)

Intracellular bacteria of the genus Wolbachia (alpha Proteobacteria) induce cytoplasmic incompatibility (CI) in many arthropod species, including spider mites, but not all Wolbachia cause CI. In spider mites CI becomes apparent by a reduced egg hatchability and a lower daughter:son ratio: CI in haplodiploid organisms in general was expected to produce all-male offspring or a male-biased sex ratio without any death of eggs. In a previous study of Japanese populations of Tetranychus urticae, two out of three green-form populations tested were infected with non-CI Wolbachia strains, whereas none of six red-form populations harbored Wolbachia. As the survey of Wolbachia infection in T. urticae is still fragmentary in Japan, we checked Wolbachia infection in thirty green-form populations and 29 red-form populations collected from a wide range of Japanese islands. For Wolbachia-infected populations, we tested the effects of Wolbachia on the reproductive traits and determined the phylogenetic relationships of the different strains of Wolbachia. All but one green-form populations were infected with Wolbachia and all strains belonged to the subgroup Ori when the wsp gene was used to determine the phylogenetic relationships of different strains of Wolbachia. Six out of 29 red-form populations harbored Wolbachia and the infected strains belonged to the subgroups Ori and Bugs. Twenty-four of 29 infected green-form populations and five of six infected red-form populations induced CI among the hosts. Thus, CI-Wolbachia strains are widespread in Japan, and no geographical trend was observed in the CI-Wolbachia. Although three red-form populations harbored other intracellular bacteria Cardinium, they did not affect host reproduction.     

Predation of ladybird beetles by the orb-web spider <Emphasis Type="Italic">Araneus diadematus</Emphasis>

Ladybirds face a diversity of potential predators from which their main protection is powerful alkaloid-based chemical defence. In the laboratory, adults of the European orb-web spider Araneus diadematus Clerck readily consumed the native European ladybird Coccinella septempunctata L. and non-melanics and melanics of the exotic Harmonia axyridis (Pallas). The spider was little deterred by their defensive chemistry and apparently suffered no ill effects after eating ladybirds. This is particularly notable for H. axyridis, which possesses a novel alkaloid not known from European ladybirds and to which European predators are not expected to be adapted. Examination of inhabited A. diadematus webs and experimental determination of for how long captured ladybirds remained in webs indicated that ≤2% of spiders consume a ladybird each day. Ladybirds and A. diadematus are probably complementary rather than antagonistic in controlling crop pests, with ladybirds being at greatest risk from A. diadematus predation in autumn, during migration to overwintering sites.     

Search for effective natural enemies of <Emphasis Type="Italic">Tetranychus evansi</Emphasis> (Acari: Tetranychidae) in northwest Argentina

The mite Tetranychus evansi Baker & Pritchard (Tetranychidae) probably originated in South America. Because of its importance as a tomato pest in Africa, an extensive project has been conducted to detect potentially effective natural enemies in South America for the classical biological control of the pest in Africa. A search for the natural enemies of T. evansi was conducted in the Province of Tucumán, northwestern Argentina, in December 2004, and this report describes the results. One hundred predatory mites of the family Phytoseiidae referring to 11 species were collected on 11 examined species of solanaceous plants. The most abundant phytoseiid species collected were Neoseiulus californicus (McGregor) and Euseius concordis (Chant). Adults and immatures of those species, as well as of Neoseiulus idaeus Denmark & Muma, Phytoseiulus fragariae Denmark & Schicha and Proprioseiopsis cannaensis (Muma) were found in association with T. evansi, suggesting that they were developing on the pest. However, because of the possible biological differences between populations of a given species, biological studies evaluating T. evansi as a prey for those predators seem desirable.     

Life-history traits of the acarophagous lady beetle,<Emphasis Type="Italic">Stethorus japonicus</Emphasis> at three constant temperatures

Stethorus japonicusKamiya (Coleoptera: Coccinellidae) is an indigenous ladybird beetle in Japan, which feeds on many spider mite species. We evaluated the development, survivorship and life-history parameters of this lady beetle on a diet of eggs of the two-spotted spider mite, Tetranychus urticae Koch (red form) (Acari: Tetranychidae). In addition, the effect of short photoperiod on its reproduction was assessed. Survival rates from egg to adult were more than 71% at temperatures between 17.5 and 30 °C. The highest immature mortality was 100% at 35 °C followed by 76% at 15 °C and 52% at 32.5 °C. The lower threshold temperature for development from egg to egg-laying adult was 13.0 °C and the thermal constant was calculated as 238.7° days. Based on these data, the maximum number of generations that could complete development in a year under field conditions in Ibaraki, central Japan, would be between five and seven. The intrinsic rates of natural increase (r_m) were 0.093 at 20 °C, 0.156 at 25 °C and 0.241 at 30 °C. Reproductive diapause was induced at photoperiods with light phases shorter than 13 h at 18 °C.     

Sub-lethal effects of fenbutatin oxide on prey location by the predatory mite <Emphasis Type="Italic">Iphiseiodes zuluagai</Emphasis> (Acari: Phytoseiidae)

We used a Y-tube olfactometer to assess the sub-lethal effects of the acaricide fenbutatin oxide on the olfactory response of the predatory mite Iphiseiodes zuluagai towards odours from: (1) air or undamaged coffee plants; (2) undamaged or red spider mite Oligonychus ilicis-infested coffee plants; (3) undamaged or false spider mite Brevipalpus phoenicis-infested coffee plants. Predatory mite adult females were exposed to residues of fenbutatin oxide or distilled water on leaf discs during a period of 72 h prior experiments. When exposed to distilled water (control treatments), predatory mites significantly preferred undamaged plants over air, O. ilicis-infested plants over undamaged plants, and they did not prefer B. phoenicis-infested plants over undamaged plants. However, predatory mites that had been exposed to residues of fenbutatin oxide were neither attracted towards undamaged plants nor to O. ilicis-infested plants. Thus, fenbutatin oxide affected negatively the olfactory response of I. zuluagai. We conclude that sub-lethal-effect studies should be considered in pesticide selectivity programs since the ability of predatory mites to locate their prey may be negatively affected by non-lethal concentrations of pesticides.     

Comparison of thread-cutting behavior in three specialist predatory mites to cope with complex webs of <Emphasis Type="Italic">Tetranychus</Emphasis> spider mites

Anti-predator defenses provided by complex webs of Tetranychus mites can severely impede the performance of generalist predatory mites, whereas this may not be true for specialist predatory mites. Although some specialist predatory mites have developed morphological protection to reduce the adverse effects of complex webs, little is known about their behavioral abilities to cope with the webs. In this study, we compared thread-cutting behavior of three specialist predatory mites, Phytoseiulus persimilis, Neoseiulus womersleyi and N. californicus, exhibited inside the complex web of T. urticae. No major difference was observed among them in the basic pattern of this behavior, using chelicerae and palps, and in the number of silken threads severed while moving inside the web. These results and observations suggest that each predator species cut many sticky silken threads to move inside the complex web without suffering from serious obstruction. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Development and reproductive capacity of the predatory mite <Emphasis Type="Italic">Parasitus consanguineus</Emphasis> (Acari: Parasitidae) reared on the larval stages of <Emphasis Type="Italic">Megaselia halterata</Emphasis> and <Emphasis Type="Italic">Lycoriella ingenua</Emphasis>

Development and reproduction of the predatory mite Parasitus consanguineus Oudemans et Voigts (Acari: Parasitidae) reared on a diet of first and second instars of Megaselia halterata (Diptera: Phoridae) or Lycoriella ingenua (Diptera: Sciaridae) were studied. Mites were allowed to feed on these diets until death. The developmental time of immature stages of P. consanguineus was significantly longer when reared on L. ingenua than on M. halterata larvae (8.3 vs. 7.9 days, respectively). Survival to adulthood of P. consanguineus reared on L. ingenua or M. halterata larvae was 63 and 49%, and mite fecundity was 17.8 and 12.3 eggs/female, respectively. Adult females reared on L. ingenua lived on average 6.9 days, whereas those reared on M. halterata lived for 5.7 days. Mite survival, female longevity and fecundity were significantly different among the two diet types.     

Functional response of the predator <Emphasis Type="Italic">Scolothrips takahashii</Emphasis> to hawthorn spider mite, <Emphasis Type="Italic">Tetranychus viennensis</Emphasis>: effect of age and temperature

A leaf disc bioassay was employed to examine the effects of temperature and predator age on functional response of an acarophagous thrips, Scolothrips takahashii Priesner, to hawthorn spider mite, Tetranychus viennensis Zacher, in the laboratory. The results indicated that the predatory thrips exhibited type-II functional responses against the mites under various temperatures, and that females are more voracious than males. Analysis showed that temperature had significant effects on the predatory capacity of adult thrips over the range of 20–35 °C. Attack rate in females linearly increased with temperature while in males it was independent of temperature. Handling times in both males and females decreased linearly with increasing temperature. Extended response models describing the functional response with temperature incorporated as a parameter were developed, yielding an estimated maximum numbers of prey attacked at four temperatures were 38.38, 55.06, 71.74 and 88.42 eggs per day for females, and 15.11, 26.11, 37.11 and 48.01 eggs per day for males, respectively. The age of predator affected both the type of the functional response shown and the magnitude of predation by S.␣takahashii on the spider mite. Females of various ages exhibited Type-II functional responses with similar attack rates, but handling time prolonged linearly as age increased: the handling times in 15- and 18-d-old females were significantly longer than in 6-d-old thrips. However, Type-I functional responses were determined for males aged 12 d or more; the maximum number of prey eaten in 24 h decreased as age increased. The implications of the results for the management of hawthorn spider mite are discussed.     

<Emphasis Type="Italic">Trichoderma harzianum</Emphasis>: a biocontrol agent against <Emphasis Type="Italic">Bipolaris oryzae</Emphasis>

Rice brown spot, caused by Bipolaris oryzae, can be a serious disease causing a considerable yield loss. Trichoderma harzianum is an effective biocontrol agent for a number of plant fungal diseases. Thus, this research was carried out to investigate the mechanisms of action by which T. harzianum antagonizes Bipolaris oryzae in vitro, and the efficacy of spray application of a spore suspension of T. harzianum for control of rice brown spot disease under field conditions. In vitro, the antagonistic behavior of T. harzianum resulted in the overgrowth of B. oryzae by T. harzianum, while the␣antifungal metabolites of T.␣harzianum completely prevented the linear growth of B. oryzae. Light and scanning electron microscope (SEM) observations showed no evidence that mycoparasitism contributed to the aggressive nature of the tested isolate of T. harzianum against B. oryzae. Under field conditions, spraying of a spore suspension of T. harzianum at 10⁸ spore ml⁻¹ significantly reduced the disease severity (DS) and disease incidence (DI) on the plant leaves, and also significantly increased the grain yield, total grain carbohydrate, and protein, and led to a significant increase in the total photosynthetic pigments (chlorophyll a and b and carotenoids) in rice leaves.     

Biological control of twospotted spider mite, <Emphasis Type="Italic">Tetranychus urticae</Emphasis>, with predatory mite, <Emphasis Type="Italic">Neoseiulus californicus</Emphasis>, in strawberries

Greenhouse and field experiments were conducted from 2005 to 2007 to determine the effectiveness of different release times with the predatory mite, Neoseiulus californicus (McGregor), for control of the twospotted spider mite (TSSM), Tetranychus urticae Koch, in strawberries (Fragaria x ananassa Duchesne). The effect of N. californicus releases over time and on development of TSSM populations during a growing season were evaluated. Our hypothesis was that repeated applications of N. californicus, which is currently recommended by biological control companies, might be unnecessary to attain season-long control of TSSM. In greenhouse trials, three treatments consisting of releases of N. californicus at five-day intervals: day 0, day 5, and day 10, and an untreated control were evaluated. The treatment releases significantly reduced TSSM below the control within five days of each release. Neoseiulus californicus significantly reduced TSSM in treatments with high densities (leaflets with ≥ 40 TSSM) below that of treatments with lower densities (leaflets with ≤ 10 TSSM) demonstrating that if released at a predator: prey ratio of 1:10, timing of release does not alter the effectiveness of N. californicus in controlling TSSM. However, we found that if the ratio of predator: prey remains adequate, N. californicus is a more efficient predator at high TSSM densities. Field studies included three treatments consisting of releases of N. californicus at one-month intervals. All treatments significantly reduced TSSM compared with the control plots (no releases). Releases applied early in the season sustained TSSM significantly below those in the control plots for the whole season. Our results indicate that one release of N. californicus is able to sustained control of TSSM in strawberry throughout a growing season if released when TSSM populations are low early in the season in the southeastern United States.