فصلنامه تحقیقات آفات گیاهی
سال نهم شماره 4 (زمستان 1398)

The corn stem borer Sesamia cretica Led. (Lepidoptera. Noctuidae) is one of the most important corn pests in Iran. Chemical control of this pest is rather difficult due to larval living inside the corn stem. As the role of nutrients is critical in plant resistance to pests, adequate crop fertilization can be a good preventive measure to control this pest. Phosphorus (P) is one of the essential elements required for plant’s performance, otherwise its limitation can impose severe consequences on cellular function and the growth rate. In the current study, the effect of different phosphorus fertilizer formulations was conducted on the corn stem borer infestation in a randomized block design of field conditions. Stem borer infestations were evaluated by the number of dead hearts and the percentage of infested stalks. The establishment of larvae under the greenhouse conditions were investigated. Results showed that the lowest and highest dead hearts were related to the application of P slow release fertilizer treatment with 1.15 % and the control treatment with 4.53 %. A significant decrease in infestation was observed when the slow-release phosphorus treatment by 10% stem compared to control and other treatments. Minimal and maximal percentages of larval establishment were observed in slow-release phosphorus treatment with 10% larvae and control with 57.5% larvae per plant respectively. Based on the results of this research, application of slow-release phosphorus fertilizer in corn stem borer management is recommended.

Chemical control is the most commonly practice in controlling pests. The application of chemical control is recommended in combination with other reduced risks control techniques such as biological control under Integrated Pest Management programs. Therefore, finding the appropriate chemical insecticide and the right time of spraying seems essential. In this study,three different growth stages of Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae) including larvae, pre-pupae, and pupae were exposed to the field recommended concentration of deltamethrin, Spirotetramat and flupyradifurone insecticides using insect dipping method. After which, the reproductive, biological characteristics and life table parameters of T. evanescens female adults were estimated. The eggs treated with deltamethrin in all three developmental stage of T. evanescens significantly reduced fecundity rate and oviposition period of the female adult parasitoids. Thegross reproductive rate (GRR), finite rate of increase (λ), intrinsic rates of increase (r), and net reproductive rate (R0) were not affected when larval and pre-pupal stages of T. evanescens were exposed to field recommended concentration of spirotetramat and flupyradifurone in comparison with control. However, the pupal stage showed to be the most susceptible stage and all of the life table parameters were affected upon exposure to three insecticides. Results of this research suggest a relative compatibility of spirotetramat and flupyradifurone with T. evanescens parasitoid. However, experiments under field conditions to evaluate the impact of tested insecticides on T. evanescens are required to confirm the results.

Acariphagous ladybird beetle, Stethorus gilvifrons Mulsant (Col., Coccinellidae) feeds on various growth stages of the tetranychus mites. Since Eutetranychus orientalis (Klein) mite is actively seen on castor bean crops during the months of autumn, winter and spring seasons, so it can be considered as a suitable host for maintaining ladybird beetles. Hence, the ladybird beetle population can be prevented from migration and maintained until the outbreak of sugarcane mite. In this study, possible use of castor bean, Ricinus communis Wild. (Euphorbiaceae) has been considered as a banker plant of acaraphagous ladybird beetle, S. gilvifrons. Initially, 30 castor bean plants were cultivated in the month of August 2016 around sugarcane fields in Khuzestan province and the population of mites and ladybird beetles were monthly sampled during one year (2016-2017) starting from August. The results showed ladybird beetles activity on castor bean plant throughout the year, however, during November till March only adults were observed that could start reproduction only from April to September. Also, the data analysis of the olfactometry system showed that the reaction of the ladybird beetle to volatile compounds of castor bean is significant. Therefore, the castor bean has the potential to form a niche for the acaraphagous ladybird beetle in maintaining its population throughout the year in order to control sugarcane mite population more efficiently and timely.

During 2018-2019, fauna of the oribatid mites (Acari: Oribatida) related to tea plant, Camellia sinensis (L.) in Guilan Province was collected and identified. Mites were extracted from soil samples by Berlese funnel and from leaves by direct examination under a stereomicroscope and cleared in Nesbitt’s solution. Cleared mites were mounted in Hoyer’s medium on microscopic slides. In this study totally, 34 species belonging to 27 genera and 20 families of oribatid mites were collected and identified. Among them, 30 species, 20 genera and 9 families reported related to tea plant, for the first time from Iran. List of the identified families, genera, and species in this study and their collection information are provided. Moreover, a checklist of the genera and species of oribatid mites related to tea plant in Iran and an identification key to them (in family, genus and species levels) are provided.

Olive soft scales Euphyllura straminea Loginova and olive psyllid Euphyllura straminea Loginova are important pests of olive trees in Tarom region of Zanjan province. The use of dormant oil in winter to control of these pests is recommended based on research done in the past years. Due to reports of inefficiency of dormant oil for the control of olive soft scales and olive psyllid, this project was conducted to evaluate the results of previous findings as well as to evaluate the possibility of simultaneous control olive soft scales and olive psyllid. Experiment was carried out based on RCBD with split plot arrangement in four replications. Main factor was time of application in three levels:  1- winter 2- winter + spring and 3- spring and sub-factor was type of spraying solution in four levels:  1- dormant oil, 2- mixture of oil (1.5%) + chlorpyrifos (0.2%), 3- chlorpyrifos (0.2%), and 4- control treatment. Sampling was performed once before and 3 times including 2, 3 and 4 weeks after treatments and subsequently number of alive and dead specimens were counted. Based on results, the mixture of oil + chlorpyrifos caused 94.25 and 100% mortality and chlorpyrifos caused 85.75 and 100% mortality on olive soft scales and olive psyllid respectively in winter (preferably the second half of March in Tarom climatic conditions).

The predatory stink bug, Andrallus spinidens Fabricius, is a common natural enemy in Northern paddy fields of Iran. In the current study, life table parameters and consumption rate of A. spinidens fed on Plodia interpunctella Hübner larvae were determined under laboratory conditions. The evaluations were based on age-stage, two sex life table using TWOSEX and CONSUME-MSChart theories. According to obtained results, the total immature developmental times were 23.39±0.23 and 23.66±0.29 days for male and female, respectively. The adult pre-oviposition period (APOP) and total pre-oviposition period (TPOP) were evaluated to be 7.46±0.21 and 31.07±0.41 day, respectively. The intrinsic rate of increase (r), finite rate of increase (λ), net reproductive rate (R0), and mean generation time (T) were 0.136±0.004 day-1, 1.146±0.005 day-1, 188.52±26.61 offspring/individual and 38.54±0.49 day, respectively. The mean predation rate of total nymphal stage of the predator was 21.70±0.80 P. interpunctella larvae. Furthermore, the predation rate for female nymphs was significantly higher than male nymphal stage. Female and male adults of A. spinidens consumed 101.93±5.32 and 96.43±4.8 P. interpunctella larvae, respectively. In addition, the net predation rate (C0) of the total life span for A. spinidens was 104.32±6.22 P. interpunctella larvae per predator. The transformation rate (Qp) showed that A. spinidens consumed 0.55 P. interpunctella larvae to produce one viable egg. According to life table and predation parameters, it seems that the larvae of P. interpunctella might be a suitable intermediate prey for rearing this predator.

Wheat thrips, Haplothrips tritici (Kurdjumov) (Thysanoptera: Phlaeothripidae) is one of the most important sucking pests in wheat fields. In this study, in order to select different sampling patterns as well as the most suitable method for estimating wheat thrips population, regularly sampling was done during wheat growing period in the wheat fields in Eyvan city (Ilam province, west of Iran) during years 2017-2018.After the start of wheat growth, wheat thrips was sampled once in a week by using four sampling methods i.e. X- shaped movement, zig-zag, U and S shape.In each sampling, 100 wheat plants were selected randomly in each field and wheat thrips was counted and recorded.Relative variation (RV) and relative net precision (RNP) were compared to determine the best sampling methods.Comparison of the four sampling methods showed that the X- shaped movement was more precise than the other three patterns.Also, the analysis of variance and comparing the average of the density of wheat thrips between different shaped and growth stages of wheat were used to determine the best sampling space.The results showed that there was a significant difference between the sampling patterns and growth stages and based on these results, the highest density of wheat thrips was observed in X- shaped pattern in the flowering stage. Therefore, according to the results, the flowering stage was determined as the most suitable space for wheat thrips.