Hydrosols evaluation in pest control: insecticidal and settling inhibition potential against Myzus persicae (Sulzer)

The hydrosols are by‐products derived during the extraction of essential oils. Although essential oils have been widely evaluated for their insecticidal activities, the possible use of hydrosols in pest control has been almost unknown. The effects of the hydrosols of Origanum majorana (marjoram), Mentha pulegium (pennyroyal), and Melissa officinalis (lemon balm) on the survival and settling behaviour of the aphid pest Myzus persicae were investigated. The hydrosols were isolated using Clevenger hydrodistillation (i) with conventional heating (HD) and (ii) assisted by microwaves (MWHD). GC‐MS analysis showed that the volatiles occurring in the hydrosols were similar between the two techniques. Hydrosols were assayed for possible settling inhibitory effects on M. persicae in Petri dishes (15 cm diameter). In each dish, a sprayed together with an unsprayed eggplant leaf piece was placed. An adult aphid <24 h old was released on the treated leaf and its path length was recorded during the initial 10 min. Then, its position (on the treated or untreated leaf) was recorded 10, 20, 30, 60 min and 24 h after spraying. M. officinalis HD hydrosol resulted in fourfold increase of the path length compared with the control (deionized water). The last observation (24 h) revealed that M. officinalis and M. pulegium HD hydrosols had the strongest inhibitory effect. Additionally, O. majorana hydrosols caused 10–15% aphid mortality after 24 h. In this study, the wider use of the MWHD technique is further supported as in addition to its well‐known advantages (i.e. shorter distillation time, less energy consumption), the effects of the hydrosols produced are comparable to those obtained by HD. Most importantly, the results clearly showed that the potential of hydrosols in pest control ought not to be ignored and should attract the interest of future studies.     

Adaptation of acaricide stress facilitates Tetranychus urticae expanding against Tetranychus cinnabarinus in China

The two‐spotted spider mite, Tetranychus urticae, and the carmine spider mite, Tetranychus cinnabarinus, are invasive and native species in China, respectively. Compared with T. cinnabarinus, T. urticae has expanded into most parts of China and has become the dominant species of spider mite since 1983, when it was first reported in China. However, the mechanism of the demographic conversion has not been illuminated. In this study, one T. urticae field population and one T. cinnabarinus field population were isolated from the same plant in the same field, and the toxicological characteristics were compared between these two species. Laboratory bioassays demonstrated that T. urticae was more tolerant to commonly used acaricides than T. cinnabarinus. The activities of detoxification enzymes were significantly greater in T. urticae, and the fold changes of enzymes activities in T. urticae were also greater following exposure to acaricides. Furthermore, more metabolism‐related genes were upregulated at a basal level, and more genes were induced in T. urticae following exposure to acaricides. The comparison of proteins and genes between both species led credence to the hypothesis that T. urticae was more resistant to acaricides, which was the reason explaining the expansion of invasive T. urticae against native T. cinnabarinus. Laboratory simulation experiments demonstrated that following the application of acaricides, the composition of a mixed T. urticae/T. cinnabarinus population would change from a T. cinnabarinus‐dominant to a T. urticae‐dominant population. This study not only reveals that T. urticae possesses stronger detoxification capacity than its sibling species T. cinnabarinus, which facilitated its persistent expansion in China, but also points to the need to accurately identify Tetranychus species and to develop species‐specific management strategies for these pests.     

Influence of vermicompost and cucumber cultivar on population growth of Aphis gossypii Glover

The melon aphid, Aphis gossypii Glover (Hem., Aphididae), is one of the most important pests of cucumber throughout the world. This aphid has a short generation time and high fecundity that result in an enormous reproductive potential, especially in cucumber‐growing greenhouses. Vermicomposts, which are produced by exploiting interactions between earthworms and microorganisms, may enhance plant growth and plant resistance against some pests and disease. In this study, the effects of vermicompost and cucumber cultivar (Cucumis sativus L.) on infestation levels with A. gossypii were evaluated. We conducted a factorial experiment with two cucumber cultivars (Royal and Storm) and five concentrations of vermicompost in the soil, including 0% (control), 10%, 20%, 30% and 50%, employing a randomized complete block design with four replicates. The experiment was conducted in a growth chamber at 25 ± 2°C, 65 ± 10% RH and a photoperiod of 14 L: 10 D h. The number of aphids was counted 3, 5, 7, 9, 12, 15, 18 and 21 days after infestation of cucumber seedlings by aphids. We found that in all vermicompost‐amended treatments, aphid numbers were lower than when plants were grown in soil without any vermicompost. The highest and lowest aphid counts occurred in the control treatment on cucumbers of the Royal cultivar and in the 30% and 50% vermicompost treatments on the storm cultivar, respectively. Overall, our study showed that the application of vermicompost has a high potential for reducing A. gossypii populations in cucumber cultures.     

Yield,Composition and Antioxidant Capacity of the Essential Oil of Sweet Basil and Holy Basil as Influenced by Distillation Methods

The profile and bioactivity of essential oil (EO) depends on genetic, environmental, and other factors. We hypothesized that the basil EO may be influenced by the distillation methods. Hence, a study was conducted to evaluate the effect of steam distillation (SD) and hydrodistillation (HD) extraction method on the yield, composition, and bioactivity of EO of sweet basil (Ocimum basilicum) and holy basil (Ocimum tenuiflorum). In both basil species, the EO yield (content) was significantly higher from SD than from HD. There were significant differences in the compounds’ concentrations of EO obtained from SD and HD as well, however, the same compounds were identified in the EO from HD and SD. In the EO of O. basilicum, the concentration of 74% of the identified compounds were higher in SD than HD, whereas in the EO of O. tenuiflorum, the concentration of 84% of identified compounds were higher in SD than in HD. However, the concentrations of two of the major compounds of O. basilicum EO (estragole and methyl cinnamate) and a major compound of O. tenuiflorum EO (methyl eugenol) were significantly higher in HD than in SD. The type of distillation did not affect the antioxidant capacity of basil EO within the species. This study demonstrated that the type of distillation may significantly affect oil yield and composition but not the antioxidant capacity of the EO from sweet and holy basil.     

Acaricidal properties of essential oils from agro‐industrial waste products from citric fruit against Tetranychus urticae

Tetranychus urticae is a major agricultural pest with worldwide distribution that has caused considerable damage to vegetable crops in north‐eastern Brazil. The aim of the present study was to investigate the chemical and lethal/sublethal effects of essential oils from the peels of the lime (Citrus aurantiifolia), lemon (C. limon), mandarin orange (C. reticulata) and (C. reticulata × C. sinensis) as well as selected constituents (linalool, α‐terpineol, α‐pinene, β‐pinene, terpinolene and limonene) against T. urticae. The greatest yield was achieved with the mandarin and tangerine peel oils. The chemical analysis (gas chromatography‐mass spectrometry) of the essential oils from the Citrus fruit peels enabled the identification of 127 compounds, revealing a predominance of monoterpenes. Limonene was the major constituent, and α‐pinene, β‐pinene, linalool and α‐terpineol were found in substantial quantities. Regarding the susceptibility of T. urticae, the Citrus oils and selected constituents were more effective by fumigation than residual contact. The C. reticulata oil was the most toxic by fumigation, and the C. limon oil was the most toxic by residual contact. The constituent α‐terpineol exhibited the highest toxicity with both methods. At a sublethal concentration, the oils and selected constituents had significant effects on the fecundity, feeding preference and oviposition of the mite. Citrus oils and their constituents are potentially useful for the future integrated management of T. urticae due to their lethal and sublethal properties. However, further studies are needed to evaluate the action of these essential oils against non‐target organisms and determine the cost–benefit ratio for the formulation of an acaricide harvested from agro‐industrial waste from citric fruit processing activities for use in the integrated control of T. urticae.     

Female response to predation risk alters conspecific male behaviour during pre‐copulatory mate guarding

Mating behaviour often increases predation risk, but the vulnerability within mating pairs differs between the sexes. Such a sex difference is expected to lead to differences in responses to predation risk between the sexes. In the two‐spotted spider mite Tetranychus urticae, males engage in pre‐copulatory mate guarding because only the first mating results in fertilisation. We investigated (i) whether pre‐copulatory pairs are more conspicuous to the predatory mite Phytoseiulus persimilis than solitary females, (ii) whether the vulnerability to the predator differs between sexes within the pre‐copulatory pair, (iii) whether each sex of T. urticae responds to predation risk during pre‐copulatory mate guarding and (iv) whether T. urticae's response to predation risk affects predator behaviour. Because T. urticae females are immobile during pre‐copulatory mate guarding, we observed male behaviour to evaluate effects of predation risk. We found that the predators detect more pre‐copulatory pairs than solitary females and that more females than males of the pre‐copulatory pairs are preyed upon by the predators. The preference of spider mite males for pre‐copulatory pairs versus solitary females was affected by whether or not the female had been exposed to predators during development. Male T. urticae exposed to predation risk did not alter their behaviour. These results suggest that only the most vulnerable sex, that is the female, responds to predation risk, which modifies male behaviour. Regardless of T. urticae females’ experience, however, P. persimilis detected more T. urticae pre‐copulatory pairs than solitary females, suggesting that pre‐copulatory mate guarding itself is dangerous for T. urticae females when these predators are present. We discuss our results in the context of sex‐dependent differences in predation risk.     

Lethal activity of beauvericin,a Beauveria bassiana mycotoxin,against the two‐spotted spider mites,Tetranychus urticae Koch

The entomopathogenic fungi Beauveria bassiana (Balsamo) Vuillemin is known to produce a broad range of secondary metabolites. Beauvericin, a cyclic hexadepsipeptide, is the best known mycotoxin produced by B. bassiana; however, reports discussing the insecticidal activity of beauvericin per se are limited. In this study, we assessed the lethal activity of beauvericin against Tetranychus urticae Koch (Acarina: Tetranychidae). In addition, screening for suitable application of the mycotoxin against T. urticae on greenhouse strawberries is discussed. Beauvericin was able to control successfully T. urticae where concentrations of 10, 100 and 1,000 µg/g recorded mortalities of 84%, 100% and 100%, respectively, against motile stages. Furthermore, beauvericin inhibited egg hatching up to 83.3%, 69.3% and 53.3%, respectively, using the same concentrations under laboratory conditions. Under greenhouse conditions, the efficacy recorded was 52.6%, 85.7%, 72.4% and 72.4% at 1, 3, 7 and 10 days post‐inoculation, respectively. Beauvericin was efficacious under greenhouse conditions since the application increased strawberry yields while showing no phytotoxicity and ecotoxicological risk. Resistance to beauvericin was not detected initially at the unselected strain of T. urticae. Yet, the laboratory selection of populations of T. urticae exposed to beauvericin resulted in relatively resistant T. urticae strain that displayed no cross‐resistance to cyflumetofen and bifenazate. The acaricidal activity of beauvericin documented in this study would increase the efficacy of integrated pest management strategies.     

Dispersal of diapausing Tetranychus urticae and T. kanzawai

The spider mites Tetranychus urticae Koch and Tetranychus kanzawai Kishida (Acari: Tetranychidae) overwinter mostly as mated adult diapausing females. Their overwintering survival depends in part on their dispersal towards suitable habitats. We investigated the dispersal behaviour of diapausing females of T. urticae and T. kanzawai with respect to factors known to affect the dispersal of non‐diapausing mites: light, population density, gravity, and humidity. In general, diapausing females of T. urticae showed a stronger tendency to disperse than did those of T. kanzawai under all test conditions. High population density promoted the dispersal of diapausing T. urticae, but not of T. kanzawai. Dispersal of diapausing females of both species was not significantly affected by gravity, humidity, or whether feeding damage was caused by conspecifics or heterospecifics. On plants, more T. urticae than T. kanzawai moved downward. We propose that dispersal after the onset of diapause may be an important life‐history strategy in T. urticae, but not in T. kanzawai.     

Chemical Variability,Antioxidant and Antifungal Activities of Essential Oils and Hydrosol Extract of Calendula arvensis L. from Western Algeria

The chemical composition of the essential oils and hydrosol extract from aerial parts of Calendula arvensis L. was investigated using GC‐FID and GC/MS. Intra‐species variations of the chemical compositions of essential oils from 18 Algerian sample locations were investigated using statistical analysis. Chemical analysis allowed the identification of 53 compounds amounting to 92.3 – 98.5% with yields varied of 0.09 – 0.36% and the main compounds were zingiberenol 1 (8.7 – 29.8%), eremoligenol (4.2 – 12.5%), β‐curcumene (2.1 – 12.5%), zingiberenol 2 (4.6 – 19.8%) and (E,Z)‐farnesol (3.5 – 23.4%). The study of the chemical variability of essential oils allowed the discrimination of two main clusters confirming that there is a relation between the essential oil compositions and the harvest locations. Different concentrations of essential oil and hydrosol extract were prepared and their antioxidant activity were assessed using three methods (2,2‐diphenyl‐1‐picrylhydrazyl, Ferric‐Reducing Antioxidant Power Assay and β‐carotene). The results showed that hydrosol extract presented an interesting antioxidant activity. The in vitro antifungal activity of hydrosol extract produced the best antifungal inhibition against Penicillium expansum and Aspergillus niger, while, essential oil was inhibitory at relatively higher concentrations. Results showed that the treatments of pear fruits with essential oil and hydrosol extract presented a very interesting protective activity on disease severity of pears caused by P. expansum.     

Characteristics of development and reproduction in Typhlodromus pyri on Tetranychus urticae and Cecidophyopsis ribis. II. Progeny of overwintered females

The results of this study on the bionomic parameters in progeny of overwintered females of Typhlodromus pyri Scheuten under constant laboratory conditions (18°C, R.H. 75%. 18L:6D) are described. The predatory mites were fed overwintering forms of two prey species, the two-spotted spider mite. Tetranychus urticae Koch and the black currant gall mite. Cecidophyopsis ribis (Westwood). The results corroborate that T. pyri is able to complete its life-cycle and reproduce when it feeds exclusively on the black currant gall mite. Juvenile development of females feeding on T. urticae and on C. ribis was 19.4 and 20.9 days respectively, while in males it was 18.4 and 17.5 days. Mortality of juveniles feeding on T. urticae was higher (33.0%) compared with that of juveniles fed on C. ribis (10.7%). The highest mortality was noted in protonymphs fed on T. urticae (21.9%). The difference between the mean total fecundity of females fed on T. urticae (16.4 eggs) and on C. ribis (17.8 eggs) was not statistically significant. Mean duration of preoviposition, oviposition and postoviposition periods were 19.1, 25.0 and 14.5 days in females fed on T. urticae and 19.7. 50.2 and 5.0 in those fed on C. ribis.     

Effects of prey mite species on life history of the phytoseiid predators Typhlodromalus manihoti and Typhlodromalus aripo

The effects of prey mite suitability on several demographic characteristics of phytoseiid predators and the relationship of these effects to the potential of phytoseiid predators to control herbivorous mite populations are well documented. Evidence has also accumulated in the last 20 years demonstrating that phytoseiid predators utilize herbivorous prey mite-induced plant volatiles as olfactory cues in locating their herbivorous mite prey, but less well established is the predictability of reproductive success from the ability of the predators to utilize olfactory cues to locate their prey, and how these processes are related to the success of the predators as biological control agents of the herbivorous mite. In this study, we determined in laboratory no choice experiments, the development, survivorship and fecundity of the two neotropical phytoseiid predators Typhlodromalus manihoti Moraes and T. aripo DeLeon when feeding on three herbivorous mites, including the key prey species Mononychellus tanajoa (Bondar), and the two alternative prey species Oligonychus gossypii (Zacher) and Tetranychus urticae (Koch). Intrinsic rate of increase (r_m) of T. aripo was 2.1 fold higher on M. tanajoa as prey compared with T. urticae as prey, while it was almost nil on O. gossypii. For T. manihoti, r_m was 2.3 fold higher on M. tanajoa as prey compared with O. gossypii as prey, while reproduction was nil on T. urticae. An independent experiment on odor-related prey preference of the two predator species showed that T. manihoti and T. aripo preferred odors from M. tanajoa-infested leaves to odors from O. gossypii-infested leaves. Moreover, both predator species preferred odors from M. tanajoa-infested leaves over those from T. urticae-infested leaves. As reported here, life history of the two predatory mites matches odor-related prey preference if the key prey species is compared to the two inferior prey species. The implications of our findings for the persistence of T. manihoti and T. aripo and biological control of M. tanajoa in the cassava agroecosystem in Africa are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Intercropping with aromatic plants hindered the occurrence of Aphis citricola in an apple orchard system by shifting predator–prey abundances

Enhancing biological control of pests through habitat management in agricultural systems has gained increasing attention. Three different aromatic plants, ageratum (Agerarum houstonianum Mill.), French marigold (Tagetes patula L.) and basil (Ocimum basilicum L.), were chosen as intercrops for apple orchards to evaluate the effects of intercropping on Aphis citricola Van der Goot and its local natural enemies in China. We found that compared with natural vegetation, A. citricola abundance was significantly decreased by 29.26%, 35.80% and 38.28% in plots intercropped with ageratum, French marigold and basil, respectively. The number of natural enemies of A. citricola in plots intercropped with T. patula and O. basilicum were significantly higher than in plots of natural vegetation. Equally important, intercropping affected the composition of natural enemies and the population dynamics of A. citricola and its natural enemies. Annual cumulative numbers of natural enemies were significantly negatively correlated with A. citricola annual cumulative individual numbers except for O. tantillus. Our results demonstrate that intercropping with aromatic plants could be an effective method for biological control of A. citricola in apple orchards.     

The effects of spiromesifen on life history traits and population growth of two-spotted spider mite (Acari: Tetranychidae)

Laboratory bioassays were conducted to evaluate the effects of spiromesifen on gross fecundity, gross fertility, net fertility and population growth of two-spotted spider mite (Tetranychus urticae Koch) after treatments with four acaricide concentrations: 180 mg/l, i.e. maximum recommended concentration for use in glasshouses against spider mites, 18, 1.8, and 0.18 mg/l, i.e. concentration discriminative for eggs and immatures in preliminary studies which produced 100% mortality of these stages. Quiescent female deutonymphs were treated in the first assay, and young pre-ovipositing females in the second and third, in which exposure lasted 6 h and 20 h, respectively. In the first assay, the 180, 18, and 1.8 mg/l concentrations significantly reduced gross fecundity (61–85%), gross fertility (64–87%) and net fertility (85–94%) of the surviving females. In the second one, only the highest concentration achieved a significant statistical reduction in gross fecundity (52%), gross fertility (67%) and net fertility (84%). In the third assay, fecundity and fertility reduction under the two highest concentrations was 98–99% and 93–98%, whereas it was 50–74% under the 1.8 mg/l concentration, and statistically different from control values. In all three trials, treatments with 180, 18, and 1.8 mg/l concentrations significantly reduced the instantaneous rate of increase. In the third assay, treatments with the two highest concentrations caused population decline. Sublethal activity of the 0.18 mg/l concentration was not found in any assay to be statistically significant. Sublethal effects of spiromesifen and its impact on T. urticae management are discussed.     

Contrasting effects of Wolbachia on cytoplasmic incompatibility and fecundity in the haplodiploid mite Tetranychus urticae

Recent studies on Wolbachia‐induced incompatibility in haplodiploid insects and mites have revealed a diversity of cytoplasmic incompatibility (CI) patterns among host species. Here, we report intraspecific diversity in CI expression among four strains of the arrhenotokous mite Tetranychus urticae and in T. turkestani. Variability of CI expression within T. urticae ranged from no CI to complete CI, and included either female embryonic mortality or male conversion types of CI. A fecundity cost attributed to the infection with the high‐CI Wolbachia strain was the highest ever recorded for Wolbachia (?80 to ?100% decrease). Sequence polymorphism at a 550‐bp‐portion of Wolbachia wsp gene revealed two clusters distant by 21%, one of which included three Wolbachia strains infecting mite populations sampled from the same host‐plant species, but showing distinct CI patterns. These data are discussed in the light of theoretical predictions on the evolutionary pathways followed in this symbiotic interaction.     

Antipredator responses in Tetranychus urticae differ with predator specialization

The behavioural response of Tetranychus urticae to chemical cues from specialist predatory mites, Phytoseiulus persimilis, or generalist predatory bugs, Orius majusculus, on either bean or strawberry was studied in experimental arenas. Predators were placed on the leaf disc for 24 h and removed before T. urticae females were introduced. After 24 h, prey fecundity (number of eggs laid) and dispersal (number of prey drowned in the water barrier) were assessed. Chemical cues from the specialist predator resulted in reduced prey fecundity, significantly different from the generalist predator and control treatments. No interaction effect was found between plant species and prey fecundity, while significantly more eggs were laid on bean than on strawberry. Predator cues irrespective of predator specialization resulted in more prey dispersal than in the control. Findings emphasize the importance of specialization in the predator species complex for the degree and type of antipredator responses and resulting biological control.     

Preliminary evaluation of <Emphasis Type="Italic">Cladosporium cladosporioides</Emphasis> (Fresen.) de Vries in laboratory conditions,as a potential candidate for biocontrol of <Emphasis Type="Italic">Tetranychus urticae</Emphasis> Koch

A survey for natural entomopathogenic fungi of two spotted spider mite (Tetranychus urticae) adults was made in Erzurum, Turkey, during the period 2006. Tetranychus urticae (65.8%) infected with a strain of the fungus Cladosporium cladosporioides were found. Thirteen isolates of C. cladosporioides were assessed against T. urticae, in a single dose (8 × 10⁶ conidia ml ⁻¹), laboratory bioassay on bean leaflets. The total mortality percentage caused by C. cladosporioides isolates varied from 50.95 to 74.76% and LT₅₀ values ranged from 2.34 to 3.90 days. The results revealed that isolates of C. cladosporioides were effective against two spotted spider mite. This is the first record of natural infection of T. urticae by C. cladosporioides.     

Repellent and acaricidal activities of basil (Ocimum basilicum) essential oils and rock dust against Ixodes scapularis and Dermacentor variabilis ticks

Repellent and acaricidal activity of essential oils extracted from three varieties of basil (Ocimum basilicum L.) were evaluated on blacklegged ticks (Ixodes scapularis Say) and American dog ticks (Dermacentor variabilis Say) in laboratory conditions. Essential oils were extracted and characterized through gas chromatography-mass spectrometry, and tested at different concentrations for long-term repellent activity using horizontal bioassays. In addition, basil essential oils were combined with an inert material (i.e., granite rock dust) with known insecticidal and miticidal properties to assess acaricidal activities against adult ticks. Among the tested basil varieties, var. Jolina essential oil at 15% vol/vol concentration repelled 96% of tested ticks up to 2 h post-treatment. The EC₅₀ for I. scapularis nymphs was 4.65% vol/vol (95% confidence interval: 4.73–4.57). In acaricidal tests, the combination of essential oil from var. Aroma 2 at 10% wt/wt with rock dust resulted in 100% tick mortality after only 24 h post-exposure, with a LD₅₀ of 3.48% wt/wt (95% CI 4.05–2.91) for freshly prepared treatment tested on I. scapularis adults. The most common compounds detected in basil essential oils by GC–MS were linalool (52.2% in var. Nu Far, 48.2% in Aroma 2, 43.9% in Jolina), sabinene (6.71% in Nu Far, 8.99% in Aroma 2, 8.11% in Jolina), eugenol (11.2% in Jolina, 8.71% in Aroma 2), and estragole (18.2% in Nu Far). The use of essential oils alone and in combination with rock dust provides an innovative and environmentally friendly approach for managing ticks and inhibiting vector-borne disease transmission.

     

Prey-related odor preference of the predatory mites Typhlodromalus manihoti and Typhlodromalus aripo (Acari: Phytoseiidae)

Typhlodromalus manihoti and Typhlodromalus aripo are exotic predators of the cassava green mite Mononychellus tanajoa in Africa. In an earlier paper, we showed that the two predators were attracted to odors from M. tanajoa-infested cassava leaves. In addition to the key prey species, M. tanajoa, two alternative prey mite species, Oligonychus ossypii and Tetranychus urticae also occur in the cassava agroecosystem. Here, we used a Y-tube olfactometer to determine the attraction of the predators to odors from O. gossypii- or T. urticae-infested cassava leaves and their prey-related odor preference. T. aripo but not T. manihoti was slightly attracted to odors from O. gossypii-infested leaves. Both predator species showed a stronger response to odors from cassava leaves infested by M. tanajoa over odors from cassava leaves infested by O. gossypii. Neither predator species was attracted to odors from T. urticae-infested leaves and the predators preferred the odors from M. tanajoa-infested leaves over those from T. urticae-infested leaves. When O. gossypii was present together with M. tanajoa on the same leaves or on different sets of leaves offered together as an odor source the two predators were attracted. In contrast, after mixing non-attractive odors from T. urticae-infested leaves with attractive odors from M. tanajoa-infested leaves, neither T. aripo nor T. manihoti was attracted. Ecological advantages and disadvantages of the predators’ behavior and possible implications for biological control of M. tanajoa are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Toxicity of some insecticides to <Emphasis Type="Italic">Tetranychus urticae</Emphasis>, <Emphasis Type="Italic">Neoseiulus californicus</Emphasis> and <Emphasis Type="Italic">Tydeus californicus</Emphasis>

Three mite species are frequently found on vegetable crops in Italy: the pest Tetranychus urticae Koch (Acari: Tetranychidae), the predator Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) and the unspecialised feeder Tydeus californicus (Banks) (Acari: Tydeidae). In laboratory trials, the direct and residual effects of six insecticides recommended for the control of aphids, whiteflies and thrips in vegetable crops, (Biopiren® plus (pyrethrins), Confidor® (imidacloprid), Oikos® (azadirachtin), Plenum® (pymetrozine), Naturalis® (Beauveria bassiana) and Rotena® (rotenone)), were evaluated for the three mite species. All the products affected the mites and their effect was often favourable towards T. urticae and unfavourable towards N. californicus and T. californicus. Rotenone was more toxic to eggs than females of T. urticae. It was highly toxic to N. californicus and caused the death of all treated females of T. californicus. Pyrethrins and imidacloprid increased T. urticae fecundity, but decreased fecundity of N. californicus. Imidacloprid decreased T. californicus fecundity more than pyrethrins. Beauveria bassiana was not toxic to T. urticae and T. californicus, but induced high mortality in the progeny of treated females of N. californicus. Azadirachtin and pymetrozine were the least toxic to T. urticae and N. californicus, but decreased production of larvae in T. californicus. Implications for integrated pest management on vegetables are discussed.