JOURNAL OF ENTOMOLOGICAL RESEARCH
Year:2013 | Volume:5 | Issue:2 (18)|Papers Count:8

Extreme use of pesticides on stored grains is hazardous for non-target organisms and result in resistance of the insects to the pesticides, pollution of the environment and etc. Nowadays, nonchemical methods, including biological agents are considered as safe methods to control the stored grain pests. Entomopathogenic nematodes are one of the most important biocontrol agents. A survey was designed to investigate the presence and efficiency of entomopathogenic nematodes in the soils of Kohgiluyeh and Boyer-Ahmad province, Iran. Sixty nine soil samples were collected from different regions of the province in 2010. Steinernema feltiae, S. carpocapsae and Panagrolaimus sp. were isolated. Because of danger in the use of chemical pesticides to protect the stored products, this study was performed to determine the efficiency of S. feltiae on adults of rice weevil, Sitophilus oryzae (L.), one of the most important pests of stored products. Under laboratory condition, adult insects were received different concentrations of infective juveniles (Ij) (0, 250, 500, 1000 and 2000 per ml) at different temperatures (25, 27.5, 30 and 32.5oC). Insects were placed on a double layered filter paper saturated with 1 ml of IJs suspension in 9 cm petri dishes. Mortality of the insects recorded every 24hrs, for three days. The best result (77.5% mortality) observed after 72 hours of exposure at concentration of 2000 IJs in 30oC.

Eotetranychus hirsti Pritchard & Baker is one of the most important pests in Pol-e-Dokhtar, Lorestan provice, Iran, the area where fig is extensively cultivated. In this research we aimed to study the control effects of the following treatments on the pest: one time application of water, two times application of water, one time application of detergent, two times application of detergent and application of envidore, oberon and Floramite. The experiment was conducted based on a randomized complete block design with four replications. Correct mortality was measured and calculated on after 3, 7, 14 and 29 day from the time of application. Results showed significance differences among treatments in all times of measure. One time application of detergent showed 78.21%, 56.63%, 50.31% and 40.03% mortalities on 3, 7, 14 and 29 day from the time of application, respectively. The mortality of mite treated two times with detergent on day 29 was 92.54% which show not significantly different from those treated with acaricides. Moreover, one time application of water showed 47.32%, 25.33%, 23.37% and 19.77% mortalities of mite on 3, 7, 14 and 29 day from the time of application, respectively. The mortality of mites treated two times with water on 29 day was 62.21%. The population of the pest in trees treated with acaricides was about zero at all times of measure. The results of this research revealed that some more environment friendly methods, i.e. application of water or detergent, could decrease the population of fig mite. Therefore, considering their less effects on natural enemies of the pest, these methods could be recommended for integrated pest management.

The spherical mealybug, Nipaecoccus viridis (Newstead) (Hemiptera, Pseudococcidae), is a serious pest of citrus and other cultural and non-cultural plants in tropical and sub-tropical regions of the world. The damage of the pest increased highly on citrus trees in Fars province in recent years. High reproductive potential and wide distribution the pest and problems of chemical control have led to a greater need for the use of natural enemies as IPM programs. In present investigation, some biological parameters of the encyrtid waspAnagyrus mirzai Agarwal & Alam, 1959, including developmental time, longevity, reproductive capacity and sex ratio were studied at laboratory conditions, 27±1.5oC, 60±5% RH and 16: 8h L: D, on 18 (3rd-instar nymphs) and 24 days old (young adult females) of N. viridis. The developmental time of female parasitoids within the host was 14.40±0.79 and 13.45±0.52 days in 18 and 24 days old nymphs, respectively. For males, the developmental time was 12.65±0.68 and 12.30±0.87 days, respectively. The mean longevity of female wasps was 14.25±0.78 and 14.70±0.69 days in 18 and 24 days old hosts; for males, this time was 6.40±0.83 and 7.10±0.74 days, respectively. The mean number of offspring per female was 32 and 47 in 18 and 24 d.o. mealybugs. The sex ratio (M/F) of the progeny was 1: 1.11 in 18 d.o. and 1: 1.33 in 24 d.o. mealybugs. The aggregate percentage of encapsulated eggs in the parasitized 18 d.o. mealybugs was 38.60% and 43.90% in 24 d.o. mealybugs. The percentage of efficient encapsulation was 14.40% and 20.10% in 18 and 21 d.o. mealybugs respectively.

In this study, the effect of ground based skidding using rubber-tired skidder in changing the soil fauna associations of surface of skid trails with the age of 5, 10, 15 and 20 years were investigated in Hyrcanian Forests, north of Iran. Comparison of structural features and biological indices of soil macro-invertebrate communities living on trails showed extreme decreasing of density, number of taxa, and abundance of macrofauna in 5-year trail. Total biomass of macrofauna had not significant difference; but 5-year trail showed lowest mean value. Shannon’s biodiversity and Margalef’s richness indices also had minimum mean value in 5-year and maximum in 20-year trail and control forest respectively. Moreover, comparison among traffic segments showed a minimum mean value of these variables related to high traffic and maximum to low traffic segments. The results of current publication demonstrated severe impacts of skidder on soil invertebrate communities on trails surface even until 20 years. But induced impacts at macrofauna communities was actively improving and recovering during times.

Cryptolaemus montrouzieri Mulsant is the most important predator of the mealybugs in citrus orchards of northern Iran. In this study, the lethal and sublethal effects of different doses of chlorpyrifos+oil, abamectin, and chlorpyrifos+abamectin+oil on the adult ladybeetles were investigated under laboratory conditions. Each pesticide was applied at 25, 50 and 100% recommended field application rates (i.e. chlorpyrifos at 500, 1000 and 2000 ppm and abamectin at 50, 100 and 200 ppm concentrations) with 1% oil on 7-day old female ladybirds through three exposure methods, including topical direct contact, residual contact and feeding on sprayed preys. 24, 48, and 72 hours after treatment the parameters such as survival rate, mean of daily oviposition, and hatching percent of the eggs were measured. The results showed that chlorpyrifos+abamectin+ oil affected the survival rates through all three exposure methods, whereas chlorpyrifos effect on the survival rate was only observed in topical contact, and abamectin had no adverse effect on the adult survival. Among all treatments, chlorpyrifos 2000+abamectin 200 ppm had the highest adverse effect on female ladybird survival (with 16 percent mortality). In contrast to survival rate, mean daily oviposition, and egg hatching percent were significantly reduced in all three treatments and exposure methods, and this reduction continued until 72 hours after exposure. The lowest mean of daily oviposition (8.2 eggs per female) was observed 24 hours after feeding on preys treated with chlorpyrifos 2000 ppm+abamectin 200 ppm+oil, and the lowest egg hatching rate (57.9 percent) was recorded 24 hours after topical contact with the same treatment. In conclusion, using field rates of chlorpyrifos and chlorpyrifos+abamectin with oil adversely affect survival and fecundity of the ladybird. So, it is necessary to use of pesticide in suitable time and spraying to increase compatibility between pesticide application and ladybird activity, in citrus orchards.

Canola (Brassica napus L.) is one of oilseed plants that has caught the attention of Iranian farmers. Cabbage aphid Brevicoryne brassicae (L.) is one of the important pests of canola in Urmia region. Regarding to the importance of this pest, an investigation was carried out under both conditions of field and green house in order to evaluate the resistance of 21 canola genotypes against cabbage aphid during 2005-2008. Under field conditions, two separate experiments, each of three replications were performed based on complete randomized blocks designs under both natural infestation and no-infestation conditions to assess tolerance. Natural infestations occurred in all three experimental years. The evaluation of tolerance under field conditions was performed based on the indices as yield loss, 1000 kernal, the number of seed per capsule, and the number of capsules per main and accessory stems. Data analysis indicated highly significant differences (p£%1) among different genotypes from the stand point of the studied indices. The genotypes Opera, Sahara and Okapi had the least index of yield loss, and the genotypes Geronimo, Talent and Celisius had the most highest index of yield loss. Based on cluster analysis, the genotypes Opera and Sahara were placed in tolerant group and the genotypes Talent, ARG-91004, Geronimo, Celisius and ARC-5 were classified as members of susceptible group. The evaluation of 21 genotype tolerance based on randomized plots design with three replications was carried out in two separate infected to aphid and control treatments under greenhouse conditions during two experimental years. Results indicated differences (p£%1) among various genotypes from the view point of their disformation and stem growth decrease indices. Considering these two indices, two genotypes Okapi, and Opera were placed in tolerant group, and the genotypes Talent, Geronimo, Ebonite, ARG-91004, and ARC-5 were known as members of the susceptible group. The comparison of the results obtained through field and green house experiments illustrated that Geronimo was highly susceptible to cabbage aphid, and the genotypes Opera had an acceptable resistance applicable in the integrated management programs against cabbage aphid.

The pomegranate fruit moth, Ectomyelois ceratoniae Zeller, and quince moth, Euzophera bigella Zeller, are the major frugivorous pest. They cause qualitative and quantitative losses of pomegranate fruit. Sexual pheromone traps may provide a real estimation of adult emergence and flight activity periods, emigration and immigration of such pests. To fulfill such a purpose, an experiment was performed to observe the population fluctuation of E. ceratoniae and E. bigella using synthetic pheromone traps in pomegranate orchards of Tang-e-Siab Koohdasht (Lorestan, Iran), in 2011. Adults of E. ceratoniae and E. bigella appeared in late April and May, respectively, and their flights continued until mid November. These pests populations showed four and three flight peaks during the growth season, respectively. The quince moth's population was higher than on pomegranate fruit moth's population, while the peak of the moth flight was between late July to early August. So in the pomegranate orchards of Lorestan region, in addition to pomegranate fruit moth, quince moth is one of the important fruit pests. The quince moth appears a month later in comparison to pomegranate fruit moth and both are active until the end of the season.

The gypsy moth, Lymantria dispar L. (Lep., Lymantriidae) is one of the most destructive pests of forest shrubs and trees throughout the Arasbaran region (East Azarbaidjan, Iran). The pest causes serious periodical damage on its host plant species, especially oak trees. In this study, the effects of two formulations of Bacillus thuringiensis containing Btk (commercial product Dipel) and BtH (made in Iran) were evaluated on gypsy moth larvae. Results showed that there was a significant difference between Dipel and BtH. Dipel (1.2 g/L) and BtH (6 g/L) treatments caused maximum mortality 29.23% and 23.05%, respectively and 1.2 g/L dosage of BtH with average 13.61% caused the less mortality on the pest larvae. Mean comparison of L. dispar larvae mortality in different times after treatments (for both formulations) indicated that there was no significant difference between 1 and 3 days, but difference between those two mentioned days with 7 and 14 days was significant, so that the treatment effect increased with time. By comparing the number of parasitoid wasp and nematode emerged from treated survived larvae, the treatments effects on natural enemies was quite evident. Natural enemies emerged from larvae treated by 1.2 g/L, 3 g/L and 6 g/L dosage of BtH and Dipel were reduced 12.3, 34.7, 59.8 and 81.6 percent, respectively in comparison to control. In other words, by increasing the effectiveness of Bt treatments, the possibility of natural enemies emergence was reduced. In this regard, high concentrations of BtH and Dipel have the most impact in reduction of natural enemies emerging. Assessment of larval feeding on the treated leaves revealed that because of the rapid effects of Bt to 2nd instar larvae, there was no possibility to continue their feeding. But in the 4th instar larvae, because of slow effects of Bt, their feeding on leaves in some treatments continued for up to 100 percent. Thus, application of Dipel and high dosage BtH against 2nd instar larvae of the pest will be more effective than other treatments in Arasbaran forests.