Effect of Eucalyptus globulus and Ferula assafoetida essential oils and their nanoformulations on the life table parameters of Tetranychus urticae (Acari: Tetranychidae).

One of the most damaging pests of agricultural crops across the globe is the two-spotted spider mite, Tetranychus urticae Koch. A wide variety of arthropods and plant pathogens can be controlled by essential oils, which are secondary metabolites produced by plants. It is possible to enhance the stability as well as the anti-pest efficiency of plant essential oils by encapsulation. Water distillation was used to extract the essential oils from Eucalyptus globulus and Ferula assafoetida. The chitosan nanoparticles were used to load both essential oils into nanoformulations. Studies were conducted on T. urticae life table characteristics under experimental circumstances to determine the sublethal impacts of essential oils and their nanoformulations. Intrinsic growth rate (r) for population exposed to E. globulus, F. assafoetida essential oils, their nanoformulations and the control were 0.1, 0.069, 0.051, 0.018 and 0.21 per day, respectively. F. assafoetida and E. globulus nanoformulations resulted the lowest fecundity compared to the other treatments. According the result of the lethal and sublethal effects of purified essential oils and nanoformulations of F. assafoetida and E. globulus, they would be recommended for controlling the two-spotted spider mites, T. urticae.

Side effects of chlorantraniliprole, phosalone and spinosad on the egg parasitoid, Trichogramma brassicae.

The combined use of chemicals and biological control is not always a successful strategy owing to the potential side effects on biocontrol agents. Lethal and sublethal effects of three commonly used insecticides were assessed on adult and immature stages of the egg parasitoid Trichogramma brassicae Bezdenko (Hymenoptera: Trichogrammatidae). Recommended field concentrations of chlorantraniliprole, phosalone and spinosad caused mortality on preimaginal stages by 24, 87, and 98%, respectively. Lethal effects on parasitoid adults exposed to the insecticide dry residues were estimated as median lethal concentrations (LC50) that were 13.28, 0.25, and 0.03 µg a.i. ml-1 for chlorantraniliprole, phosalone, and spinosad, respectively. The effect of a low lethal concentration (LC30) of the compounds was evaluated on various adult biological traits, such as longevity, fecundity, emergence rate and other life table parameters. All compounds caused detrimental effects on all the estimated demographical indexes. Chlorantraniliprole affected the net reproductive rate, mean generation time and doubling time in comparison to the control; while, phosalone and spinosad adversely affected all assessed parameters. Phosalone and spinosad significantly reduced gross reproductive rate, net reproductive rate, intrinsic rate of increase, finite rate of increase, mean generation time and doubling time and reduced longevity, fecundity, emergence rate related to other biological parameters in comparison with control. The results suggest that all compounds are not fully compatible with the activity of T. brassicae, and that the inclusion of chlorantraniprole, spinosad and phosalone into Integrated Pest Management (IPM) involving this parasitoid has to be avoided. Nevertheless, further studies in open field conditions and on a multiple generation scale are necessary for providing a more definitive conclusion on the IPM suitability of the three tested insectcides.

Encapsulation of Satureja hortensis L. (Lamiaceae) in chitosan/TPP nanoparticles with enhanced acaricide activity against Tetranychus urticae Koch (Acari: Tetranychidae).

The objective of this study was the fabrication of encapsulated Satureja hortensis essential oil (S.EO) in chitosan/tripolyphosphate nanoparticles (CS/TPP-NPs) via ionic gelation technique and investigation of its acaricidal effect. A high encapsulation efficiency of 96.17% was obtained, which shows successful encapsulation of EOs in CS-TPP nanoparticles. Transmission electron microscopy (TEM) analysis proved the formation of spherical S. hortensis EO-loaded chitosan nanoparticles (S.EO@NPs). Fourier-transform infrared spectroscopy (FTIR) analysis demonstrated the presence of encapsulated S.EO in CS/TPP nanoparticles. The average size of nanoparticles was found to be 192.1 ±â€¯11 nm using dynamic light scattering (DLS) technique. Moreover, durability and fumigant acaricide activity of S.EO@NPs against Tetranychus urticae Koch were investigated. The obtained results demonstrated that there were considerable differences between pure S. hortensis EO and S.EO@NPs in their ovicidal, adulticidal, and persistence activities against T. urticae. The LC50 values of pure EO and as-prepared S.EO@NPs against adult mite were 4.95, 46.98 µL/L after 24 h exposure and 2.02, 31.30 µL/L after 72 h exposure, respectively. Fumigation exposure for 24 and 72 h showed that the sensitivity of adults T. urticae were more than the eggs of T. urticae. The LC50 values of fumigant toxicity of pure S.EO and S.EO@NPs against eggs of T. urticae were measured after 24 and 72 h. The experimental results for 24 h treatment showed 6.71 and 211.66 µL/L air LC50 values for pure S.EO and S.EO@NPs, respectively. In the case of 72 h exposure, The LC50 values of pure S.EO and S.EO@NPs were 4.15 and 107.38 µL/L air, respectively. A sustained release of S.EO from S.EO@NPs was observed during 25 days of the study, indicating the persistence acaricide activity for a long time. The as-prepared S.EO@NPs and pure S.EO illustrated 67% and 2% mortality at 18th day exposure, respectively. The notable increasing of the residual fumigant toxicity may be related to the slow and sustainable release of the active ingredient of EO. Based on this study, the S.EO@NPs showed significantly residual adulticidal activity against adults of T. urticae. S.EO@NPs would be recommended as an alternative for pure EOs and other common acaricides.

Sublethal effects of spirodiclofen, abamectin and pyridaben on life-history traits and life-table parameters of two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae).

Two-spotted spider mite, Tetranychus urticae Koch, is one of the economically most important pests on a wide range of crops in greenhouses and orchards worldwide. Control of T. urticae has been largely based on the use of acaricides. Sublethal effects of spirodiclofen, pyridaben and abamectin were studied on life-table parameters of T. urticae females treated with the acaricides. LC25 values of spirodiclofen, abamectin and pyridaben (3.84, 0.04 and 136.96 µg a.i./ml, respectively) were used for sublethal studies. All acaricides showed significant effects on T. urticae biological parameters including developmental time, survival rate, and fecundity. The females treated with spirodiclofen, abamectin and pyridaben at LC25 exhibited significantly reduced net reproductive rate (R0), finite rate of increase (λ) and intrinsic rate of increase (r). The intrinsic rate of increase in spirodiclofen, abamectin and pyridaben treated groups and control were 0.0138, 0.0273, 0.039 and 0.2481 female offspring per female per day, respectively. The results indicated that sublethal concentrations of tested pesticides strongly affected the life characteristics of spider mite and consequently may influence mite population growth in future generations.

Differential Inhibition of Helicoverpa armigera (Lep.: Noctuidae) Gut Digestive Trypsin by Extracted and Purified Inhibitor of Datura metel (Solanales: Solanaceae).

The cotton bollworm, Helicoverpa armigera Hubner (Lep: Noctuidae), is an economically important pest of numerous major food crops worldwide. Protease inhibitors from plants, expressed constitutively in transgenic crops, have potential for pest management as an alternative to chemical pesticides. In this study, a protease inhibitor was isolated, purified, and characterized from Datura metel L. seeds. The purity of the isolated inhibitor was confirmed by reverse-phase high-performance liquid chromatography, and activity staining showed one major peak and one clear activity band for the protein. Electrophoretic studies following gel filtration and ion-exchange chromatography revealed two and one bands for purified proteins, respectively. Partial biochemical characterizations of the purified inhibitor were determined. Maximum inhibitory activity was observed at 40-45°C (optimal temperature) when tested against gut extracts of fourth to sixth instar H. armigera larvae. Thermo-stability of the trypsin inhibitor against sixth instar larval midgut trypsin was observed up to 50°C when incubated for 30 min and 2 h. Among metal ions tested, Fe2+, Cu2+, and Mn2+ were found to decrease the trypsin inhibitory activity, whereas Hg2+, Mg2+, K+, Zn2+, Na+, Ca2+, and Cd2+ were found to significantly increase the inhibitory effect. This trypsin inhibitor showed competitive inhibition where the apparent value of Michaelis-Menten Km increased, but the value of Vmax remained unchanged.

Acute, sublethal, and combination effects of azadirachtin and Bacillus thuringiensis on the cotton bollworm, Helicoverpa armigera.

The cotton bollworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) is a polyphagous and cosmopolitan insect pest that causes damage to various plants. In this study, the lethal and sublethal effects of azadirachtin and Bacillus thuringiensis Berliner sub sp . kurstaki (Bacillales: Bacillaceae) were evaluated on third instar H. armigera under laboratory conditions. The LC50 values of azadirachtin and Bt were 12.95 and 96.8 µg a.i./mL, respectively. A total mortality of 56.7% was caused on third instar larvae when LC20 values of the insecticides were applied in combination with each other. The LT50 values of azadirachtin and Bt were 4.8 and 3.6 days, respectively. The results of the sublethal study showed that the application of LC30 value of azadirachtin and Bt reduced the larval and pupal weight and increased larval and pupal duration of H. armigera. The longevity and fecundity of female adults were affected significantly by the insecticides. Female fecundity was reduced by the treatments, respectively. The lowest adult emergence ratio and pupation ratio were observed in the azadirachtin treatment. The results indicated that both insecticides have high potential for controlling of the pest.

Lethal and sublethal effects of azadirachtin and cypermethrin on Habrobracon hebetor (Hymenoptera: Braconidae).

Habrobracon hebetor Say is an ectoparasitoid of larval stage of various lepidopteran pests. Lethal and sublethal effects of azadirachtin and cypermethrin were evaluated on adult and preimaginal stages of H. hebetor under laboratory conditions. Contact exposure bioassays with adults indicated that the lethal concentration (LC50) of two commercial azadirachtin-containing formulations, NeemGuard and BioNeem, were 43.5 and 10.2 microg a.i./ml, respectively. The LC50 of cypermethrin was 5.4 microg a.i./ml. When larval stage of H. hebetor was exposed to these insecticides with a field recommended concentration of NeemGuard, BioNeem, or cypermethrin by a dip protocol, the emergence rate was reduced by 39.0, 36.6, and 97.6%, respectively. To assay the sublethal effects of these insecticides, adult wasps were exposed to an LC30 concentration of the insecticides, and then demographic parameters of the surviving wasps were determined. Fecundity, fertility, and parameters including the intrinsic rate of increase (r(m)) were affected negatively. The r(m) values following exposure to NeemGuard, BioNeem, cypermethrin, or mock treatment were 0.143, 0.149, 0.160, and 0.179, respectively, female offspring per female per day, respectively. The current study showed that cypermethrin had more acute toxicity on larval and adult stages of H. hebetor compared with azadirachin. The commercial formulations of azadirachtin and cypermethrin negatively affected most of the life table parameters of the parasitoid. Semifield and field studies are needed for obtaining more applicable results on combining H. hebetor and the tested insecticides for an integrated pest management-based strategy for crop protection.

Lethal and sublethal effects of essential oils from Eucalyptus camaldulensis and Heracleum persicum against the adults of Callosobruchus maculatus.

The cowpea weevil, Callosobruchus maculatus F. (Coleoptera: Bruchidae), is an important pest of stored cowpea, Vigna ungiculata (L.) Walpers (Fabales: Fabaceae), with ample distribution in tropical and subtropical regions. Many plant essential oils have a broad-spectrum activity against pest insects, and these oils traditionally have been used in the protection of stored products. In this study, the lethal and sublethal effects of essential oils from Eucalyptus camaldulensis Dehnh. (Myrtales: Myrtaceae) and Heracleum persicum Desf. (Apiales: Apiaceae) were evaluated on the adults of C. maculatus at 26 ± 1° C, 70 ± 5% RH, and a photoperiod of 16:8 L:D. The LC50 values of E. camaldulensis and H. persicum were 56.7 and 219.4 µL/L air after 12 hr and 26.1 and 136.4 µL/L air after 24 hr of exposure, respectively. The LT50 values of E. camaldulensis and H.persicum were 6.3 and 10.9 hr, respectively. The results showed that low lethal concentration (LC20) of essential oils negatively affected the longevity, fecundity, and fertility of female adults. The sex ratio of C. maculatus offspring was not significantly affected by essential oils. Therefore, these essential oils can be suggested for controlling C. maculatus in storage systems. The introduction of essential oils into storage systems could potentially decrease seed losses.

Acute and population level toxicity of imidacloprid and fenpyroximate on an important egg parasitoid, Trichogramma cacoeciae (Hymenoptera: Trichogrammatidae).

One focus of integrated pest management (IPM) is the use of biological and chemical control in an optimal way. The availability of selective pesticides is important as is information about both lethal and sublethal effects of pesticides on biocontrol agents. Acute and sublethal effects of imidacloprid and fenpyroximate exposure were studied on adult stage of egg parasitoid Trichogramma cacoeciae Marchal and the emergence rate and life table parameters were determined. The adult wasps were exposed to field recommended concentration (FRC) of the pesticides on glass plates. Field rates of imidacloprid and fenpyroximate caused 100 and 32% adult mortality, respectively. Based on concentration-response experiments, the LC(50) values of imidacloprid and fenpyroximate were 6.25 and 1,949 ppm, respectively. The effect of imidacloprid and fenpyroximate on larvae, prepupae and pupae of the parasitoid was tested by exposing parasitized eggs of Sitotroga cerealella Olivier or Cydia pomonella L. to the FRC. Imidacloprid and fenpyroximate reduced adult emergence by 10.7 and 29%, respectively, when S. cerealella eggs were used as the host and 10.9 and 24.9%, respectively, when C. pomonella eggs were used as the host. Population parameters of emerged adults from treated pre-imaginal stages by FRC of the pesticides were also studied. The parameters were longevity and progeny production of emergent adults and also intrinsic rate of increase (r ( m )), generation time (T) and doubling time (DT). Longevity and progeny production of the emergent adults was not affected by pesticide exposure in comparison to the control. In addition, none of population parameters such as r ( m ), T and DT were affected by pesticide exposure. The intrinsic rate of increase for the control, fenpyroximate and imidacloprid exposed populations were 0.388, 0.374, and 0.372 female offspring per female per day, respectively. Overall, results of this study suggest a relative compatibility between fenpyroximate and T. cacoeciae, but imidacloprid showed deleterious effects on adults of the parasitoid.

Sublethal effects of abamectin on the biological performance of the predatory mite, Phytoseius plumifer (Acari: Phytoseiidae).

Traditionally estimating pesticide effects by measuring only lethal effect may underestimate the total negative effect on beneficial arthropods and sublethal effects should be assessed to estimate the total effect of their applications. In this study, sublethal effect of the acaricide abamectin (Vermectin(®) 1.8% EC, Giah, Iran) on the predatory mite Phytoseius plumifer (Canestrini & Fanzago) (Acari: Phytoseiidae) fed on Tetranychus urticae Koch was assessed in laboratory conditions. The adult predators were exposed to the residues of the acaricide on fig leaves and the LC(50) value was determined based on a concentration-response analysis. The results showed that sublethal concentrations (LC(10), LC(20) and LC(30)) of abamectin severely affected the fecundity and longevity of the treated females of P. plumifer. Furthermore, reproductive and life table parameters of the subsequent generation were affected. The results indicated that adverse effects of abamectin on population growth of P. plumifer were significant, so the results from this study can be used to develop approximate guidelines for the use of abamectin in order to minimize their impact on P. plumifer and related natural enemies.

Lethal and sublethal effects of fenitrothion and deltamethrin residues on the egg parasitoid Trissolcus grandis (Hymenoptera: Scelionidae).

Effects of fenitrothion and deltamethrin, the most commonly used insecticides in Iran for controlling Eurygaster integriceps Puton (Heteroptera: Scutelleridae), in wheat and barley were assessed on adults and preimaginal stages of egg parasitoid Trissolcus grandis Thompson (Hymenoptera: Scelionidae). Adult parasitoids exposed to field recommended concentrations of the insecticides suffered 100% mortality within 24 h. LC50 values of fenitrothion and deltamethrin for T. grandis were 8.1 and 3.9 microg (AI) /ml, respectively. Both insecticides and the preimaginal stage of exposure had a significant influence on the level of adult emergence from host eggs treated with field recommended rates. Fenitrothion and deltamethrin reduced the emergence rates by 18 and 34.4%, respectively, compared with the control. However, neither insecticide significantly affected the longevity or reproductive capacity of emerged females, or the sex ratio of their progeny. This study revealed that application of these insecticides should be avoided in early season to conserve natural or released populations of T. grandis. Both insecticides seemed to be detrimental to the parasitoid and need to be applied cautiously through season.

Effects of azadirachtin/Neemazal on different stages and adult life table parameters of Trichogramma cacoeciae (Hymenoptera: Trichogrammatidae).

The effects of azadirachtin/Neemazal on adults, emergence, and life table parameters of Trichogramma cacoeciae Marchal were studied. The adults were exposed to fresh residues of the insecticide applied on glass plates. Based on the dose-response study, the LC50 value was 1330 ppm or 13.3 microg (AI)/ml. The effect of Neemazal on three developmental stages of the parasitoid was tested by dipping parasitized Sitotroga cerealella (Olivier) and Cydia pomonella (L.) eggs at the field-recommended concentration 3, 6, and 9 d after parasitization corresponding to larval, prepupal, and pupal stages. The emergence of adult parasitoids was adversely affected in both hosts, but the adverse effect was more in S. cerealella eggs compared with C. pomonella. The adult emergence was reduced by 73.3 and 33.76% in Sitotroga and Cydia eggs compared with controls, respectively. Longevity and progeny production of the emergent adults did not differ significantly from control. Neemazal affected stable population parameters (r(m), T, and DT) significantly. The intrinsic rate of increase for the control and Neemazal-exposed populations was 0.340 and 0.335 female offspring per female per day, respectively. Because some of postemergence life table parameters of adults were significantly reduced by the insecticide treatment, emergence rate of the parasitoid from treated eggs is not an adequate measure of ecological selectivity, and field studies are needed to determine the actual impact of neem on T. cacoeciae.