نشریه آفات و بیماریهای گیاهی
سال هفتاد و هشتم شماره 2 (پیاپی 91، زمستان 1389)

Rice is one of the most important staple food crops for more than half of the world population. The striped stem borer Chilo suppresalis is one of the most devastating pests of rice, reducing yield world wide. The use of resistant cultivars remains one of the most reliable methods to manage the pests. In this study, mechanism of resistance in 10 lines of rice for 3 kinds of resistance (antixenoses, antibioses and tolerance) were studied. The egg set of striped stem borer on the leaf of lines, mean weight of larva and survival percentage of larva were measured for antixenosis and antibiosis resistance, respectively. Also, in this study the tolerance of 10 lines of rice was evaluated in the field against the striped stem borer. Percentage of white head was used for determination of tolerance to striped stem borer. The results showed that the maximum egg set, percentage of survival, dead heart and white head belong to line 3 (Sang-e-Tarom × Tarom-e- Daylamani) and the highest weight of larva was obtained on the line 5 (Iri-2 × Nok-siah). In this study the most susceptible and resistant genotypes were line 3 (Sang-e-Tarom×Tarom-e-Daylamani) and line 4 (fajr×Nok-siah), respectively. Also, results of greenhouse exaperiments proved the results of field exaperiments. The results of correlation study showed that the height of plant and amount of chlorophyll were effective on antixenosis. Also, stem diameter and number of tillers were effective on antibios mechanism. Finally, mechanism of tolerance was affected by stem diameter.

A study was conducted to compare the biological attributes of three different populations of Habrobracon hebetor Say collected from Chegeni, Gerit and Alashtar, in Lorestan province, Iran. The experiments were performed using fifth instar larvae of Ephestie kuehniella as host under laboratory conditions at temperature 28°C, a photoperiod of 16: 8 (L: D) h, and 60±5% RH. Total developmental time of Chegeni, Gerit, and Alashtar populations were 8.87, 9.17, and 8.38 days, and the values of life expectancy were 24.12, 29.85, and 35.12 days, respectively. Jackknife approach was used to estimate the values of the life table and population growth parameters of the same populations. The intrinsic rate of increase (rm) were 0.34, 0.35, and 0.38 females/female/day, the finite rates of increase (
) were 1.4, 1.42, and 1.47 females/female/day, the net reproductive rates (NRR) were 180.95, 231.88, and 342.28 females/female, the gross reproductive rates (GRR) were 334, 343, and 477 females/female and the mean generation time (T) were 15.3, 16.2, and 15.4 days, respectively in above mentioned populations. The obtained results revealed that the Alashtar population had the highest performance than the Chegeni and Gerit populations regarding the life table parameters.

Soil samples were collected from rhizosphere of tomato and olive plants in Golestan, Gilan, Zanjan and Qom provinces (Iran). Fluorescent pseudomonas bacterial strains were isolated on King’s B medium and their phenotypic features were characterized. For all tested strains production of fluorescent pigments on King’s B medium, arginine dihydrolase, growth at four and 41 ºC and oxidase were positive. Most of them reduced nitrate and produced gelatinase but tobacco hypersensitivity reaction (HR), levan formation and pectinolytic activity on potato slices were negative for all. Filtrate liquid was obtained from 48 h culture of the fluorescent pseudomonas on King’s B broth medium. Nematicidal activity of the bacterial filtrate against fresh hatched Meloidogyn javanica juveniles was investigated under laboratory condition. Results indicated that above 60% of the tested strains showed nematicidal activity (>50% nematode mortality) under this condition. Efficacy of the representative of the most effective strains along with the nematicide, Nemacur 10G against nematode egg production, the juveniles, mature females and gall formation, plant fresh root and aboveground weight of tomato were studied under green-house condition. Under this condition total nematode eggs, juveniles, mature females and gall formation on tomato roots were decreased significantly as compared to other treatments. The highest number of eggs,, juveniles,, mature females and gall formation on tomato roots were observed in control treatment, and the lowest were recorded in plants treated with Pseudomonas fluoresces strain 99. There was no significant differences between the treatments as far as fresh root and aboveground weight are concerned, however, they differed significantly as compared to control check treatments in which the highest fresh root and aboveground weight.

The beet armyworm, Spodoptera exigua (Hübner), is a highly polyphagus insect that feeds on many cultivated hosts and weeds. To understand how well this pest survives in cold temperature during winter, seasonal variation in the supercooling points (SCPs) were studied in field-collected and lab-reared samples. In this study, the beet armyworm overwintered as dark mature larvae in dried fallen leaves or on the soil surface. Their SCPs increased significantly (P<0.01) from -12°C in November to -6°C in March and these larvae could survive below their SCPs. However lab-reared ones could not survive below their SCPs. Supercooling points of different stages of lab-reared samples changed significantly (P<0.001) and it was lowest in eggs (-28°C). Trehalose, glucose, glycerol and sorbitol were identified as main cryoprotectants. Glycogen contents were significantly (P<0.01) decreased (more than 70%) in larvae collected in February and March rather than overwintering larvae collected in November and December. In different stages of lab-reared samples it changed significantly and was highest in pupae. So, it seems that overwintering larvae of beet armyworm are freeze tolerant and glycogen is a major reserve for overwintering during cold months.

Mediterranean fruit fly (med fly), Ceratitis capitata (Diptera: Tephritidae), which was considered as an important quarantine pest in Iran was recorded on mandarin fruit in Shiraz in January 2007. To determine the best combination of trap and attractant for trapping of med fly, a field experiment was conducted in a randomized complete block design (RCBD) with 6 treatments in 3 replicates in a mixed fruit orchard (2-hactares) in 2009. Treatments were included: 1-Jackson trap baited with trimedlure, 2- Mcphail trap baited with trimedlure, 3- Tephri trap baited with Cera trap liquid, 4- Tephri trap baited with biolure, 5- Plastict bottle baited with Cera trap liquid and 6- Yellow sticky panel. Traps which were installed on trees in 26th July were checked weekly and the number of captured flies and non -target insects were recorded. Mean number of total captured flies per treatment per day (FTD) and non- target insects per treatment per day (NTID) were calculated. Data were transformed to homogenize their variance before analysis of variance (ANOVA) followed by Duncan’s Multiple Range Test (DMRT). Results revealed significant differences among the treatments at probability level of 0.01 (df =5, F=129.58; P>0.0001). FTD were 3.16, 3.08, o.24, 0.6, 0.07, and zero respectively but NITD were 0.05, 0.02, 7.42, 3.83, 11.06 and 1.86 respectively. Population peaks of med fly and non- target insect were observed between 11-25th October and 15th September respectively. The total capture rate of non target insects in treatments weres 2.3 times number of med fly. Minettia sp. (Diptera: Lauxaniidae) was the dominant species among the non target insects captured by some treatments. Percentages of total captured adult males in treatments 1-5 were 96, 95, 32, 22, and 25 respectively. In conclusion, treatments 1 and 2 are recommended as the best for mass trapping of the med fly in mixed fruit orchards in Shiraz city.

To study the role of Pythiym species associated with walnut root and crown rot, diseased sampled were collected from Fars province’s nurseries. Pieces of infected root and crown of walnut were washed with tap water blotted dry and plated on CMA supplemented with delvocid (10ppm pimarcin), ampicillin (250ppm), rifampicin (10ppm) and PCNB (150ppm). 23 isolates recoverd from various parts of the Fars province, 8 isolates were identified as P. vexans that were isolated from crown and root in Roodbal, Zarghan, Lapoee and Abbarik and Bohrghan. 5 isolates were identified as P. deliense which were isolated from walnut crown nurseries of Bisto due bahman, Roodbal, Sado ou dah and Abbarik. 10 isolates were identified as P. aphanidermatium that were isolated from walnut crown and root in Bohrghan, Zarghan, Lapoee, Sado ou dah and Bisto due bahman. Pathogenicity test of the isolates was carried out on detached branches. In all cases P. aphanidermatium was more pathogenic and aggressive than P. deliense and P. vexans. The reaction of crown and root of 2-month-old Reez Yasouj cultivars to virulent isolates of P. aphanidermatium, P. deliense and P. vexans were evaluated under greenhouse conditions. The inocula were produced for several weeks on vermiculite supplemented with hemp seed extract and applied around each two month-old walnut seedling. Comparative percent dead seedlings and crown and root colonization showed that Reez Yasouj cultivar was infected with these pathogens but in all cases P. aphanidermatium was more pathogenic and aggressive than P. deliense and P. vexans.

Functional response and mutual interference of two aphidophagous syrphid flies Episyrphus balteatus and Scaeva albomaculata fed on Myzus persicae were determined in laboratory conditions at 25 ± 2ºC, 55 ± 10 relative humidity and a photoperiod of 16L:8D h. Using logistic regression, a type II functional response was determined for both predators. The Rogers model was used for estimating searching efficiency (a) and handling time (Th). For the first, second and third instars of E. balteatus, the estimated values of searching efficiency were 0.0359, 0.0420, and 0.0677 and the values of handling time were 2.257, 0.506 and 0.316, respectively. For the second and third instars of S. albomaculata, the estimated values of searching efficiency were 0.0590, and 0.0655 and the values of handling time were 0.575 and 0.252, respectively. According to the obtained results, no significant relationship was observed between log searching efficiency (a) and log third instars density (P) of E. balteatus, but this relationship was significant in S. albomaculata and the value of interference coefficient for third instars of this predator fed on 100 density of M. persicae was -0.274.

The olive fruit fly, Bactrocera oleae Gmelin (Diptera: Tephritidae) is the most important and widespread pest in the olive growing countries in the world. This pest was reported from 13 provinces of Iran in 2004. The larvae feed upon the pulp, resulting in a significant quantitative and qualitative loss in the production of table olives and oil. For identification of suitable methods in attraction and trapping of the pest, this experiment was conducted in a randomized blocks design with 5 replication and 5 treatments, yellow sticky traps with pheromone, McPhail trap with hydrolyzed protein (3%) and malathion (0.2 %), pet traps (1.5 lit. mineral water bottles) with hydrolyzed protein (3%) and malathion (0.2 %), pet traps with Success bait (3%) and yellow sticky traps without any attractive materials. After analyzing data variances, a comparison was made on the averages using Duncan's methods in probability level of 5%. The study revealed a significant difference in attraction of adult B. oleae by pheromone traps (98.20 ± 16.48) than other treatments but there was not any significant difference within others (P<0.001, df=(4, 20), F=31.08). After the pheromone traps, there were the McPhail traps, pet traps with Success bait, pet trap with protein and yellow sticky traps respectively. Also pheromone traps had a significant difference in attraction of male (66.80 ±9.66) (P<0.001, df=(4, 20), F=43.61) and female adults (31.20 ±6.29) (P<0.001, df=(4, 20), F=19.23) than other treatments too. In this matter there was not any significant difference within others. It was noticed that pheromone traps had a significant difference in attracted the highest number of adult flies in every seasons during a year. In winter (late December) only pheromone traps were suitable to attract the adults.