PLANT PEST RESEARCH
Year:2017 | Volume:7 | Issue:3 |Papers Count:7

Grape leafhopper, Arboridia kermanshah Dlabola (Hemiptera: Cicadellidae), is the most important pest of vineyards in Iran, that by laying eggs in the leaf tissue, feeding on leaves and transmission of viral pathogens, weaken the trees and reduce the quality and quantity of grape production. To reduce the use of chemical insecticides, application of mineral compounds was tested in a vineyard in Khalilabad region (Khorasan Razavi Province), in 2015. Treatments included kaolin (5% concentration), sulfur WP (3000 ppm), sulfur dust, a mixture of kaolin and sulfur WP, phosalone insecticide (1500 ppm), and control (water spray), respectively. Spraying times including late April, early May and mid-July, Samplings were carried out one day before and 3, 7, 14 and 21 days after spraying. At each sampling time, the total number of leafhopper adults and nymphs on 5 leaves per tree were counted. Based on the field studies, mineral compounds application reduced the leafhopper population at all spraying intervals. The mean percentage of leafhopper population reduction was observed in treatments including kaolin, kaolin and sulfur mixture, phosalone insecticide, sulfur WP, sulfur dust and control in 3 days after spraying, 89, 86, 57, 25, 25 and 3 percent, respectively, and also in 21 days after spraying, 48, 47, 17, 7, 12 and 2 percent, respectively. Therefore, kaolin (Sepidan® WP), with 5% concentration, or kaolin and sulfur mixture spray over the whole canopy of trees could be used successfully to reduce leafhoppers population on grape.

Russian Wheat Aphid, Diuraphis noxia is an important pest on barely, which is also the vectors of viral diseases. In order to identify resistant genotypes, resistance of 30 wild barley genotypes, including international Hordeum spontaneum germplasms, was evaluated in the greenhouse experiments. In this experiment, plants infested with aphids at two-leaf stage and 21 days after infestation, were assessed qualitatively for leaf rolling and leaf chlorosis, based on a scale from 1 to 9 In the experiment, the content of chlorophyll a, b and total chlorophyll were evaluated. Results showed genetic variation among genotypes for leaf chlorosis and leaf rolling. Moreover, a significant positive correlation was found between leaf chlorosis and chlorophyll a and b, in general, according to all traits, genotypes of IG401552, IG140073, IG120794, IG40154, IG142356, IG119447, IG40155, IG38669, IG140189, IG1 and IG2 were placed in resistant group.

One of the most important pests of agricultural crops is sweet potato whitefly, Bemisia tabaci.Although some essential oils and plant extracts have shown suitable insecticidal properties against this pest, because of considering the high volatility and instability of essential oils, application of these substances for pests control is not practically and commercially possible. In this study, essential oils of Rosmarinus officinalis, Mentha piperita and Eucalyptus globules and extract of Thymus vulgaris, formulated based on micro and nano-emulsion and their insecticidal efficiency and stability was tetted against B. tabaci in laboratory condition. Bioassay was carried out by leaf dip method on second instar nymphs and LC50, LC90, and LT50 values were determined. Also, alive second instar nymphs to alive adults conversion ratio and fecundity in treated insect were determined as sublethal effects and compared with PalizinÒ vegetable soap, distilled water and control (without treatment). The results showed that nano-emulsion treatment containing all tested essential oils was the most efficacious with LC50=0.7454 mg/l, LC90=3.1208 mg/l, and LT50=15.92 h. Also, alive second instar nymphs conversion ratio to alive adults in this treatment was 80% and the mean number of eggs was 191.33 that was most efficacious. Afterwards, microemulsion treatment containing essential oils and extract had a acceptable effect. These two treatments were known as promising compounds in integrated management of this pest and further testing is required for commercialization of these compounds.

The spirea aphid, Aphis spiraecola Patch (Hemiptera: Aphididae), is a serious pest of citrus in northern Iran. It causes direct damage by sap feeding and extracting honeydew and also indirect damage by transmission of several virus diseases. The aim of this study was determining the relationship between genetic structure of different populations of A.spiraecola with its geographical distribution on citrus trees in northern Iran. The genetic structure of A. spiraecola collected on citrus trees in eight localities, was described by seven polymorphic microsatellite loci. Among 271 individuals, 195 multilocus genotypes were identified and the clonal diversity in populations were 0.5 to 0.93. They confirmed that A. spiraecola reproduces by cyclical parthenogenesis on citrus trees in North of Iran. The mean of Polymorphic Information Content was (PIC=0.62). There were significant deviations from Hardy-Weinberg equilibrium in all populations. The analysis of molecular variance revealed high intrapopulation and weak interpopulation genetic differentiation among geographic populations. Also, the UPGMA dendrogram of 8 populations based on Nei's genetic distance indicated no considerable genetic differentiation among them, which is in accordance with structural analysis. The findings of this research provide useful information about the genotypic distribution of A. spiraecola in Northern Iran which can be integrated with life cycle information of the pest and used in pest management programs.

A taxonomic review was done on species of the rare subgenusPauesiella Sedlag & Stary, of the genus Pauesia Quilis in the Palaearctic region. They are exclusively parasitoids of Cinara Curtis (Hemiptera, Aphididae, Lachninae) on the coniferous trees, both in natural habitats and urban areas. The studied specimens were collected either by rearing the host aphids or using the Malaise traps. The biogeographical area is expanded from the Europe to Russia, including some parts of the central and western Asia. Identification of the species and taxonomic studies were done based on the reliable diagnostic characters including antennal segments, forewing venation, propodeum, first metasomal tergit and ovipositor sheath. As a result, four closely related species including Pauesia hazratbalensis Bhagat, 1981, Pauesia kunashirensis Davidian, 2007, Pauesia sachalinensis Davidian, 2007 and Pauesia spatulata Sedlag & Stary, 1980 were identified and their validity was confirmed on the basis of reliable diagnostic characters. An identification key, as well as brief description of each species are also provided, and supplemented with illustrations from the external morphological details. Paueisa hazratbalensis is recorded for the first time from Uzbekistan. This species was found in the northern border of Iran from central to eastern part of Alborz mountains, and in central highlands (Kerman), as well. Pauesia spatulata is also recorded from Russia (Ural region) for the first time. Considering the economic and ornamental importance of their coniferous host plant, it seems the distribution of this species is yet expanding.

Wheat thrips, Haplothrips tritici (Kurdjumov) (Thysanoptera: Phlaeothripidae) is one of the most important pests in wheat fields in Ilam Province. In order to study the population fluctuations and spatial distribution of wheat thrips in wheat fields of Eyvan city, sampling was weekly carried out during different growing stages of wheat from April to the end of June 2016. Spatial distribution of immature as well as adults of wheat thrips was estimated using Taylor’s power law and Iwao’s patchiness regression methods. The population peaks in both of the irrigated and rainfed wheat fields occurred in middle of May. Based on R2 and F values of regression analysis, in irrigated wheat fields, Iwao's patchiness provided a more adequate description of spatial distribution than Taylor’s power law for wheat thrips. The spatial distribution for adults was randomized but for larval stages and the total stages (larvae and adults) was aggregated. Whereas, in rainfed fields, Taylor’s power law provided a more adequate description of spatial distribution than Iwao's patchiness. The spatial distribution for both larval and adult stages was clumped and for the total was randomized.

Loreyi armyworm, Leucania loreyi (Duponchel) (Lep.: Noctuidae) is a cosmopolitan species and one of the most common armyworms reported on rice and some of other important gramineous plants. In Iran, it has been recorded as a pest of maize and sugarcane in southwest of the country. In a survey on rice pests in Guilan province (North of Iran) during 2015-2017, many larvae and adults of L. loreyi were collected from paddy fields. This is the first report of damage caused byL. loreyi on rice in Guilan province. In this study, Leucania zeae (Duponchel) and Mythimna congrua (Hubner) are also recorded for the first time from paddy fields in Guilan province.