Plant Protection
Year:2015 | Volume:38 | Issue:3|Papers Count:11

Tuta absoluta (Meyrick) is one of the most destructive pests of tomato in many parts of the world including Iran. In this research, the effects of abamectin, indoxacarb, emamectin benzoate and acetamiprid were studied on the egg, first instar larvae, pupae and adults of T. absoluta under laboratory conditions. Bioassay tests were carried out on immature stages using dipping method and on adults by contact residue method using exposure cages. Treatments consisted of two concentrations of each insecticide and control with three replications in each treatment. Factorial analysis results showed that the percentage mortality of T. absoluta was significantly affected by developmental stage of the pest and treatment. Developmental stage and treatment interaction effects were also significant. Comparison of the susceptibility of different developmental stages of tomato leafminer moth to insecticides showed that larval and egg stages were the most and least susceptible stages to insecticides, respectively. Abamectin and indoxacarb had the most and least efficacy on this pest between tested insecticides, respectively. Analysis of developmental stage and treatment interaction effects revealed that four tested insecticides at the larval stage and acetamiprid at the adult stage caused the most mortality on the pest. These insecticides could be used in integrated pest management programs against this pest if they have a similar efficacy in the field and greenhouse conditions and in the absence of adverse effects on natural enemies.

Melon ladybird, Epilachna chrysomelina (F.) is one of major pests of cucurbitaceous plants. Larvae and adults feed on host plants and cause serious damage to them. Study of the digestive enzymes is necessary for engineering resistant host plants to pests. By determination of the biochemical characteristics of the digestive carbohydrases, the necessary information can be supplied for application of resistant plants containing inhibitors. In the present study, biochemical properties of galactosidases were studied in the alimentary canal of melon ladybird. The measuring of the enzymes activity in the digestive system of the 2nd, 3rd and 4th instars, female and male adults showed that the highest specific activity of digestive enzymes was in the digestive system of the 3rd instar and the enzyme activities in the male and female digestive systems did not show any significant difference. The optimal pH and temperature for galactosidases activity in the alimentary canal were found to be 5 and 40oC, respectively. The Km values of α and b galactosidases in the gut of E. chrysomelina were 0.013 and 0.02 mM, respectively. The results of zymogram pattern in the native gel revealed that a- and b-galactosidases had one isoform in the alimentary canal of E. chrysomelina.

This study was conducted for evaluation of the infestation levels in plants of six commercial cultivars of potato including: Impala, agria, savalan, florida, emeraude and markies to the tomato leafminer, Tuta absoluta (Meyrick) under field condition in Ardabil region during 2013 and 2014. The number of mines and live larvae per plant, the number of mines per leaf, dry weight of foliage and tubers, and the percent reduction in dry weight of foliage and tubers per plant in six potato cultivars were analyzed as a randomized complete block design. Our results indicated that amongst the six tested cultivars, emeraude and markies with the highest number of mines and larvae, and the greatest percent reduction in dry weight of foliage and tubers have the greatest relative suitability to the tomato leafminer. Whereas, florida with the lowest number of mines and larvae, and the lowest percent reduction in dry weight of foliage and tubers had the lowest relative suitability to the tomato leafminer. In savalan, with the medium number of mines and larvae, the percent reduction in dry weight of foliage and tubers was significantly lower than other cultivars (with florida). These results likely reflect the highest relative tolerance of savalan to tomato leafminer among the six tested cultivars of potato. Therefore, savalan (with the highest relative tolerance) and florida (with the least relative suitability) have potential for use in the sustainable management of T. absoluta in potato fields.

The tomato leafminer moth (Tutaabsoluta M.) has been identified as a major pest of Solanaseous especially tomato crops. According to risks of pesticide residue and environmental damage using biological control agents, especiallyBacillusthuringiensis is considered. In this study, the henna powder was used for enhancing effects. In this research work the interaction between bacterium and henna were assessed by using LC50 and LC25 values of both agents on different larval stages. After determining the LC50 and LC25 values of both agents, to evaluate the combined effects of bacterium and henna, an experiment was conducted in the form of completely randomized design with four treatments including LC50 (He), LC50 (Bt), LC25 (B) plus LC25 (H) and control. The result showed that in three larval stages additive effects was observed; percentage of mortality mixture of bacteria and henna treatments was increased in compare bacteria and henna alone. So that the average mortality in1st larval stage with Henna LC50, bacterial LC50 and LC25 mixture of bacteria and henna, after 24, 48 and 72 h were calculated (20, 26.67and 50), (23.33, 30 and 63.33) and (26.67, 33.33 and 66.67), in 2nd instar larvae (20, 26.67 and 56.67), (23.33, 30, 60) and (26.67, 33.33 and 63.33) and in 3rd instar larvae (20, 23.33and 56.67), (23.33, 30, 60) and (26.67, 33.33 and 63.33) percentage, respectively. Our current study indicated that the integrating B. thuringiensis with henna and other control tactics, especially with environmentally acceptable agents has opened further opportunities for their uses as integrated pest management.

Hemocytes are the important immune index against entomopathogens and parasitoides. Exact identification of hemocytes and reaction to foreign agent in which induce to hemolymph, cause better study on different aspects of cellular defence. In this research, hemocytes of all stages Hyles euphorbiae were examined by light microscopy. Five identified types of hemocyte in this insect were; Prohemocyte, Plasmotocyte, Granulocyte, Oenocytoide and Spherulocyte. All hemocytes types were detected in each stage but frequency of them in each stage was different. THC showed that Total hemocyte count increase with increase in larval instars gradually. Then THC decrease in pupa and adult. Differential count hemocyte indicated that plasmotocytes and granulocytes are the most abundant in 4th and 5th instars. Mitotic divisions were observed among some hemocytes in primary instars. Identification of hemocytes in H. euphorbiae was carried out for the first time and could provide background for immune study of this insect against parasitoides.

The strawberry spider mite, Tetranychus turkestani (Ugarov & Nikolski) is one of the most important pests of agricultural crops in Iran. Orius albidipennis (Reuter) is also an active predator of spider mites in agricultural ecosystems in Iran. One of the characters which is used for the evaluation of predators is their response to the different densities of prey (functional response). Functional response of different developmental stages of this bug by feeding on adult female T. turkestani was investigated at 25±1oC, 60±5% RH and a photoperiod of 16:8 (L:D) h under laboratory condition. The experiments were carried out in a petri (10 cm diameter) on a bean leaf with the densities of 5, 10, 20, 30, 50 and 70 adult female mites. Mean maximum feeding rate of first, second, third, fourth and fifth nymphal stages as well as female and male adults of this bug were 9.6, 23, 34.8, 39.2, 48.1, 56.4 and49.1female adult T. turkestani, respectively. Functional response of all developmental stages (except for fourth nymphal stage) was of the Holling’s type II. Fourth nymphal stage showed Holling’s type III. Based on the Rojer’s equation, estimated attack rates of O. albidipennis were0.0654, 0.0678, 0.075, 0.0098, 0.1834, 0.1691 and0.165 and estimated handling times were 2.3048, 0.8259, 0.4684, 0.6585, 0.3666, 0.2484 and 0.3336 h for the first, second, third, fourth, fifth, female and male adult, respectively.

Khapra beetle Trogodermagranarium (Evert.) (Coleoptera: Dermestidae), has been considered as one of the most invasive pest for stored products in the world. The insect has become tolerant to conventional pesticides including fumigant such as phosphine and methyl bromide. Application of plant essential oils can be a suitable alternative for fumigation. In this study, fumigant and persistence toxicity of the essential oils from leaves of Mentha pulegium L., Eucalyptus microtheca F. Muell and walnut hulls Juglans regia L. evaluated against T. granarium under laboratory conditions of 30±2oC, 65±5% R.H and darkness. Adult stage have high sensitivity to essential oils. In a period of 48 h exposure, LC50 value against adult stage of T. granarium were 6028.66, 6383.48 and 5498.20 ppm for eucalyptus, walnut and pennyroyal essential oils, respectively. LC50 values indicated that essential oil of pennyroyal (confidence limit: 4646.17-6482.07) had the most insecticidal activity against T. granarium. There was significant differences among LC50 values at p<0.5. The persistence assay against adult stage of insect showed the LT50 value was 8.69, 9.71 and 8.54 d for eucalyptus, pennyroyal and walnut, respectively. Therefore, the persistence of pennyroyal (8.44-11.10) essential oil was the most among the tested plants.

Today, biological control of plant pathogens such as nematodes has been widely studied. One of the promising biological control agents isPochonia chlamydosporiawith high potential to reduce root-knot nematode (RKN) and cyst nematode populations. In this study, the effects of four isolates of P. chlamydosporia var. chlamydosporia on root-knot nematode Meloidogyne javanica were examined under in vitro and greenhouse conditions. In the vitro experiment, the effects of fungus culture filtrates were evaluated on mortality of juveniles and egg hatching of M. javanicain in three time intervals (24, 48 and 72 hours after application) and three concentrations (100%, 10-1 and 10-2) as well as parasitism of nematode eggs. In the greenhouse experiment, the effect of different isolates of P. chlamydosporia var. chlamydosporia on tomato growth factor and nematode population were tested. Data were subjected to analysis of variance and the means were compared according to the LSD test. In the Lab trial, culture filtrates, in comparison to control, showed larvicidal effects and prohibited larval emergence from the eggs and all isolates colonized the nematode eggs. On the basis of statistical analysis in all the three laboratory experiments, IRAN 1131C and IRAN 504C isolates were more effective in comparison to the other 2 isolates. In the greenhouse trial, isolates suppressed nematode growth on the host plant and nematode percentage growth, in comparison to the control, decreased. The greenhouse data showed that the least tomato nematode infection was due to the isolates IRAN 504C and Hamedan.