فصلنامه تحقیقات آفات گیاهی
سال چهارم شماره 2 (تابستان 1393)

The sugarcane stem borers, Sesamia cretica Led. and S. nonagrioides Lef. are the most important pests of sugarcane in Iran. The egg parasitoid wasp, Telenomus busseolae Gahan is the most important natural enemy of Sesamia spp. in Khuzestan province that play an important role in regulating populations of sugarcane stem borers. In order to evaluate the effect of host species on T. busseolae a laboratory investigation was carried out. Adult longevity, oviposition period, preoviposition period, fecundity and sex ratio of T. busseolae were studied on two hosts at three constant temperatures (20±1, 25±1 and 30±1 ºC). Results of analysis of variance showed that temperature had a significant effect on adult period, preoviposition period and fecundity of T. busseolae (P< 0.001) and had no effect on progeny sex ratio on both hosts. Oviposition period significantly affected by temperature on S. cretica (P< 0.001) and not affected on S. nonagrioides. Total fecundity of T. busseolae at all temperatures tested was higher on S. cretica than S. nonagrioides. Based on our results S. cretica eggs are the most favorable host for T. busseolae.

Concerns over health and environmental problems associated with using synthetic insecticides in storages, have led to an intensification of efforts to find safe, effective and viable alternatives. In this research, susceptibility of larvae of Ephestia kuehniella and Plodia interpunctella was investigated to neemarin. Probit analysis of concentration-mortality data was conducted to estimate the LC50. Our results showed that mortality of the both pests increased as concentration of the insecticide increased. Effectiveness of the insecticide against both pests was proportional to pesticide concentration and time of treatment. It was more effective in 14 than 7 days after treatments. The exposure time was comparatively increased neemarin efficacy against E. kuehniella more than P. interpunctella. In conclusion, susceptibility of both pests to neemarin was the same and relatively low. LC50s of E. kuehniella larvae after 7 and 14 days were 4252 and 2994 ppm, respectively and for P. interpunctella larvae were 4029 and 3581 ppm, respectively.

The family Chalcididae is considered as an important group in biological control of pests. Sampling was carried out in 2011-2012 using net and Malaise trap due to study of the family fauna in some part of East-Azarbaijan province. A total of 11 species belonging to 7 genera in the subfamily Haltichellinae were collected and identified. Of which, three species have not been recorded from Iran (**) and five species are new for fauna of East-Azarbaijan province (*). An identification key was provided for identified genera. List of identified species are as follow: Antrocephalus hypsopygiae Masi*, Hockeria magna Bouček**, H. singularis Bouček**, H. susterai Bouček*, H. unicolor Walker*, Kriechbaumerella gracilis (Nikol\'skaya), Lasiochalcidia cincticornis (Walker)*, Neochalcis fertoni (Kieffer), Neohybothorax hetera (Walker), Proconura brbara (Masi)** and P. nigripes (Fonscolombe)*.

Spatial distribution, precision levels, number of samples for Jasmine whitefly, Aleuroclava jasmini (Takahashi) (Hemi.: Aleyrodidae) was studied during 2010 and 2011 growing seasons in citrus orchards of Khuzestan Province, Iran. To do this, the samples were taken from 41 citrus orchards, in four geographical directions and four sides of a tree (five leaves on each sides of a tree) with stratified random sampling method. Number of eggs, 1st-4th instar nymphs and exuviae per 1 cm2 on lower surface of mature leaves were counted. Results showed that maximum of mean density of eggs and pupae in each citrus orchards was 34.9/cm2 and 49.13/cm2 on each leaf, respectively. There was no significant differences between the relative variation at each developmental stages at two spring and autumn generations, geographic directions of trees in citrus orchard and different geographical sides of each tree. The data of spatial distribution for the pest population among all citrus orchards with both Iwao’s Patchiness regression method and Taylor’s Power Law indicated that Taylor\'s Power Low showed a better fit than Iwao\'s model. The regression coefficient (b) for eggs, pupae and exuviae were 1.82, 1.67 and 1.79, respectively showing negative binomial distribution among populations. The common K for egg, pupae and exuviae, sum of alive stages and total population were determined 0.29, 0.57, 0.36, 0.7 and 0.79, respectively. The lowest level of permissible precision was determined 12.5% for this pest. Number of fixed samples in the precision level of 0.25 for egg, pupae, exuviae, sum of alive stages and total population were calculated 55, 28, 45, 23 and 20 leaves, respectively.

Bacillus thuringiensis (Bt) is widely used in two forms, toxic crystal and a mix of spores and crystal for controlling of harmful insects. This research carried out in order to evaluate the effect of Bithurin on striped stem borer, Chilo suppresslis (SSB) under field conditions in Rasht during 2010. The experiment was conducted in a complete randomized design with two factors including: Dose and usage times with 3 replications. Results showed that 1.5 and 1 liter per hectare with two and three application times of Bithurin had the most effect on SSB and reduced the percentage of dead hearts to 0.42 and 0.47 %, respectively. Also, the highest efficacy in first generation of SSB was observed in the treatment of 1.5 liter per hectare with three times spraying (61.22%). In this study, spraying of one liter Bithurin with three times per hectare in the rice vegetative stage reduced the percentage of dead hearts to 0.52% in comparison with control. In reproductive stage of rice, percentage of the lowest infection white heads observed in 1.5 liter per hectare in plots with two and three times application, 0.78 and 0.83%, respectively. Also, the highest efficacy observed in plots with 1.5 liter per hectare with two and three times application in comparison with control (42.93 and 48.48%), respectively. Infection of white heads reduced by 3.84% in comparison with control in rice field. Therefore, if in a field infection is higher than the norm, 2-3 times of spraying can be recommended.

Since microbial factors have important role in control of pests, determination of interactions between immune system and entomopathogenic fungi can be useful in IPM programs. Cellular immunity of 4th instars of Spodoptera litura (Fabricus) was investigated against two isolates of Beauveria bassiana (Fashand and 566) and latex-bead. Number of prohemocytes, granulocytes, oenocytoids and phenoloxidase activity was measured too. A concentration of 106 spore/mL of spores and 106 particle/mL latex-bead were injected to larvae and their interactions with hemocytes were recoreded at 1, 3, 6, 12 and 24 h time-intervals. For control, distilled water was injected to larvae. The number of hemocytes were maximum after 3 and 6 h of injection. Nodulation was occurred 3 and 6 h after injection. Phenoloxidase activity was determined in the presence of L-DOPA as a substrate after injection of fungal spores and latex beads. Phenoloxidase activity was highest in 3 and 6 h post injection. Result showed that hemocytes and phenoloxidase in S. litura had an important role in immune reaction. So, with increasing of hemocyte number, hemocytes aggregated around spores and lead to spore death.

One of important aspects in evaluating the efficiency of a natural enemy is the attack rate across a range of host densities, i.e., its functional response. In this research, age-specific functional response of wolbachia-infected strain of parasitoid, Trichogramma brassicae to different egg densities (5, 10, 20, 30, 40, 60 and 80) of Ephestia kuehniella at 23 ± 1° C, 60 ± 5% RH and 16:8 h (L:D) photoperiod was evaluated. The type III functional response was obtained for one and two day old wasps, and a type II for 3 to 9 day old ones. Searching efficiency (a), handling time (Th) and maximum parasitism rate (T/Th) of parasitoid wasps were significantly affected by their ages. With increasing in parasitoid age a non-significant declining trend was shown in searching efficiency (a) but handling time (Th) increased significantly as adult parasitoid aged and the lowest value was observed at 1st day of parasitoid’s life (0.573 h). Also, by increasing in parasitoid age maximum parasitism rate (T/Th) clearly declined and it ranged from 41.75 to 5.51 hosts at 1st up to 9th days of wasp life. The results illustrated that age-specific functional response of T. brassicae wasps were different and the highest efficiency gained in the first two days of their life.