فصلنامه گیاه پزشکی
سال سی و پنجم شماره 2 (تابستان 1391)

Effects of Mentha arvensis L. and Mentha pulegium L. essential oils were investigated against oviposition deterrence، egg hatching and adults'' mortality of Callosobruchus maculatus F. Essential oils were obtained by dry leaves that were subjected to hydrodistilation using a modified Clevenger-type apparatus. All experiments were conducted at 25±1ºC، 65±5 % R. H. in the dark condition with 5 replications for each essential oil. Results indicated that increasing the essential oil concentrations resulted in increase of insecticidal activity of essential oils on eggs، adults and oviposition deterrence. At the highest concentration tested (60 µl/l air)، of M. pulegium and M. arvensis essential oils، 89. 7 and 83. 8% of adults were killed، respectively. Oviposition deterrence of M. pulegium was more than M. arvensis; however، egg hatching effects of both essential oils were not significantly different. According to the data probit analysis، LC50 for adults and eggs of C. maculatus were found to be 1. 51 and 0. 98 µl/l air of M. pulegium oil and 1. 82 and 1. 1 µl/l air essential of M. arvensis. The results suggest that essential oils of these aromatic plants could be used as botanical fumigant to protect grains against C. maculatus.

The two spotted spider mite Tetranychus urticae Koch is one of the polyphagous pests of crops worldwide. Due to undesirable effects of synthetic pesticides such as expression of resistance in mites, this research was conducted to achieve alternative safe compounds to environment. Therefore, ovicidal activity of essential oils of Eucalyptus salmonophloia F. Muell and Eucalyptus kingsmillii Maiden (Mauden) blakely was studied on two-spotted spider mites at 27 ± 0.5°C, 50 ± 5% RH and photoperiod 16: 8 h (L: D). The essential oils were extracted by Clevenger type apparatus. Concentrations of 3.75, 8.28, 11.57, 15.60 and 19.32 µL/L air were put on filter papers with 2 cm diameter and kept in the cap of bottle. The eggs were fumigated for one and three days and then, they were transferred to new clean dishes. The hatched eggs were counted 24 h after fumigation. LC50 values of E. Salmonophloia and E. Kingsmillii were 14.39 and 14.14 µL/L air on one-day old eggs and 7.17 and 7.19 µL/L air on three-day old eggs, respectively. Based on LC50 values, ovicidal activity of these two essential oils was not significantly different; however, 72 h fumigation was significantly more effective than 24 h fumigation. The chemical composition of the essential oil was assessed by GC and GC-MS. 1,8-Cineol, P-cymene and α-Pinene were determined to be the major constituents of the oils.

Microcerotermes diversus Silvestri is the most economically destructive termite in structures in Ahvaz (Iran), and it consumes almost anything containing cellulose. This species lives in subterranean nests and gains access to buildings and vegetation by constructing underground galleries. Because of their insecticidal activity, boron compounds may be beneficial for treating soil to create insecticidal barrier effects against subterranean termites. The chemical barrier effect of boric acid against M.diversuswas evaluated in laboratory trials using glass tube and plastic container methods. Boric acid concentrations used ranged from 0.2 to 4.0% in soil. This study showed boric acid does not act as a repellent, but that soil treated with >1.5% of this compound was effective for inducing delay in penetration of termites through the treated soil. Boric acid at >1.5% also caused a gradual increase in mortality and reduced tunnel area and feeding activity into the treated soil during the 14-day trial. Results suggest that boric acid mixed in soil creates an effective, non-repellent lethal termite foraging area against M. diversus.

Sunflower downy mildew, caused by Plasmopara halstedii, is one of the most important diseases of this crop in West-Azarbaijan, Urmia. It causes economic yield losses during favorable environmental conditions. The pathogen is a polycyclic one, and it is likely that physiological changes occur in its population and subsequent appearance of new physiological races. Hence, identification of the existing races among the population in infected areas would play a significant role in breeding and the use of resistant cultivars to control the disease. Infected sunflower plants showing systemic symptoms were collected from different areas of Urmia in 2009. The isolates were inoculated and mass-produced on susceptible cultivar record, using Whole Seedling Immersion (WSI) inoculation method, and finally 15 isolates were obtained. The isolates were inoculated on nine differential lines (RHA-265, HA-304, PM-13, PM-17, 803-1, HA-R4, QHP-1, HA-335, RHA-274) by the same method. Three days old seedlings, after inoculation, were sown in pasteurized mixture of sand and perlite (3:2 v/v), and incubated in greenhouse for two weeks. To induce the sporulation, favorable conditions (16˚C, 90-100% R.H and darkness) were provided for 48 h. The results showed that differential lines had a similar reaction pattern to the isolates. Thus, one race was identified as dominant in the area. Following international system of nomenclature, the race was called number 100. This is the first report of identification of physiological races of sunflower downy mildew based on the international system for nomenclature in Iran.

The use of resistant plant cultivars and parasitoids could be an effective strategy in IPM of Liriomyza sativa Blanchard. Cucumber is a preferable host for this insect. In this research, antixenosis resistance of 17 cultivars of cucumber was evaluated to L. sativae under greenhouse condition. Results indicated that there were significant differences between cultivars with regard to the number of feeding sting and larval tunnels (p<0.01). Cucumber cultivars were ranked by cluster method based on all measured characters and were classified to four groups: susceptible, semi-susceptible, semi-resistant and resistance. Density of leaf hairs and trichomes of cucumber cultivars were evaluated and the result showed that the density of glandular hairs on leaves of field cultivars was higher in comparison to greenhouse cultivars. These results suggested that the local and field cultivars are generally more resistant to leaf miner than the greenhouse cultivars. In this study, a wide range of genetic variation in traits related to leaf miner resistance was found in cucumber germplasm. Also in tritrophic level system, the effects of first level (cucumber cultivars) on third level (parasitoid wasps) were studied and the results showed no significant differences between cultivars in attracting parasitoid wasps.

The larvae of the Tephritidae, known as fruit flies, feed on the fruits and cause decaying and reducing their market-friendliness. In this study, the adults were collected once a week using common entomological net as well as Malaise traps during 2009-2010 in Horand region, East Azerbaijan. Thirteen species belonging to seven genera of subfamily Tephritinae were identified. All these species are new records for Horand region and two species, marked with an asterisk, are reported as new to the Iranian fauna. The species are listed as follows: Campiglossa misella (Loew, 1869)، C. tessellate (Loew, 1844), Ensina sonchi (Linnaeus, 1767), Noeeta pupillata (Fallen, 1814), Tephritis dioscura (Loew, 1856), T. postica (Loew, 1844), T. praecox (Loew, 1844), Tephritomyia lauta (Loew, 1869), Terellia fuscicornis* (Loew, 1844), T. gynaecochroma (Hering, 1937), Urophora hermonis* (Freidberg, 1974), U. mauritanica (Macquart, 1843) and U. terebrans (Loew, 1850). A code is provided for identification of the new collected species.

Cotton whitefly, Bemisia tabaci is considered as one of the most important pests of fall cucumber in Khouzestan province. Studies were conducted to examine the seasonal dynamics and spatial distribution of B.tabaci on fall cucumber during 2006 and 2007 in Mollasani area. In both years, adult whiteflies first appeared on the plants in early September. In 2006 and 2007, mean maximum of adults occurred on 15th of September (58 adults / leaf) and 7th of September (25 adults/ leaf), respectively. In the above mentioned years, the mean maximum of eggs was found on 15th of September (134 eggs/ 2cm2 leaf) and 7th of September (92 eggs/ 2cm2 leaf). Likewise the mean maximum numbers of nymphs in 2 cm2 were 81 and 39 nymphs on 15th of September and 7th of September, respectively. In the aforementioned years, the mean maximum pupae were counted on 20th of September (2.3 pupae/2cm2 leaf) and 14th of September (1.4 pupae/ 2cm2 leaf), respectively. The population of all developmental stages reached zero in the beginning of November. The results of this study have applications for integrated management of cotton whitefly.