PLANT PEST RESEARCH
Year:2023 | Volume:13 | Issue:2|Papers Count:8

The rapeseed pollen beetle, Brassicogethes aeneus is one of the key and important pests of rapeseed in the northern provinces of Iran. In this research, the effectiveness of two botanical insecticides, Matrin and azadirachtin, as well as chemical insecticides, Alphacypermetrin and Imidacloprid, were investigated against this pest in laboratory and field conditions. Laboratory bioassay was performed by exposing the insects to different concentrations of the insecticides (five concentrations for each insecticide). In these assays, the highest susceptibility was recorded to Alphacypermetrin (LC50 = 0.1 mg ai/L) and after that, Matrin (1.2), Imidacloprid (60.0), and Azadirachtin (100.7 mg ai/L), respectively. A field experiment, in the form of a randomized complete block design, was implemented in three different methods: creating a barrier (lace fabric) before or after conducting the treatments and plots without any barriers. In the field conditions (common treatment; no barrier), the efficacy of botanicals was slower but after four days, their appropriate effectiveness was observed. However, after one week, the efficiency of all four treatments was more than 90 percent. At the endpoint of the experiment (four weeks), Imidacloprid was the most effective (73.4 %) and after that, there were Alphacypermetrin (59 %), Matrin (51.4 %), and Azadirachtin (47.9 %) treatments. The results of this research showed that Alphacypermetrin can be used as an alternative to Imidacloprid (the prevalent treatment) in pest outbreak conditions. In addition, the data showed the appropriate and competitive efficiency of Matrin, to control rapeseed pollen beetle.

The egg parasitoid wasp, Telenomus busseolae Gahan (Hym.: Platygastridae) is the most important natural enemy of sugarcane stem borers in sugarcane growing area of Khuzestan province. In order to know the parasitism rate of T. busseolae in plant crops compared with first ratoon crops an investigation was carried out in Amir-Kabir Agro-industry in southern Khuzestan. In this study six plant and six ratoon cane fields of commercial sugarcane cultivar, CP69-1062 was selected and sampling of sugarcane borers (Sesamia spp.) egg batches was made monthly from April to November. The results indicated that field age and sampling time has a significant effect on egg batch densities of sugarcane borers and parasitism of eggs by T. busseolae. The lowest egg batch density was observed in April and the highest was recorded in September both in plant crops and first ratoon crops. In plant crops the lowest egg parasitism rate (43.5 %) was observed in July, whereas the highest rate (84.4 %) was observed in April.  In the first ratoon crops the lowest rate of parasitism (38.8 %) was observed in June and then increased to 87.3 % in November. The percentage of adult emergence of T. busseolae was not significantly influenced by crop age and sampling time.There was no significant difference of progeny sex ratio in the two investigated crop ages, but sampling time significantly influenced on progeny sex ratio. The results of this study provide useful information on the population fluctuations of T. busseolae in plant and ratoon crops of sugarcane.

The black bean aphid, Aphis fabae Scopoli (Hemiptera: Aphididae) is an important pest of sugar beet fields in Khuzestan province. Knowledge about economic and precise sampling program can play critical role for developing integrated pest management (IPM) program of this pest. In this study, the spatial distribution of the pest was investigated in a research sugar, 1 ha, beet field of Shush district, and a fixed-precision sequential sampling program for estimating the aphid density was developed. Samplings were performed every 3 days and spatial distribution of this pest on sugar beet plants was evaluated using two models, Taylor's power law and Iwao's patchiness. The pest distribution on sugar beet plant was aggregated and Taylor's power law provided better fitness to the spatial distribution data of this aphid on sugar beet plants. Therefore, The Green's model was used for developing fixed-precision sequential sampling of the aphid. Based on the pest density, the optimum sample size ranged from 99-130 plants or 16-21 plants at desired precision level 0.1 or 0.25, respectively. Calculated stop lines implicated that the sampling has to be continued till the aphid cumulative number per sugar beet plant reach to 10 at precision level 0.25. The stop line was 25 aphids at precision 0.1.

Investigation of species biodiversity of parasitoid and predatory wasps in different habitats is one of the principles of pest management. In the present survey, species diversity of Spheciformes (Hymenoptera: Apoidea) was investigated in south areas counties of Kerman (Southeast of Iran). Sampling was done during March to September 2017 from 12 regions in 6 counties: Jiroft, Bam, AnbarAbad, Kahnuj, Qaleh-Ganj and Manujan with Malaise traps. All obtained specimens were identified to species level and also the number of each species per sample were counted. A total of 36 Species belonging to 17 genera are listed in this paper. Species biodiversity were analyzed by the SDR software. The results of indices of Shanon Winer species diversity and Pielou J Evenness showed that Bam county with 20 species has the highest diversity and evenness, followed by Jiroft and Kahnuj. Among all identified species, Gastrosericus funereus with 202 specimens (23.76%), Sphex flavipennis with 156 specimens (17.58%), and Bembix bidentata with 76 specimens (8.5%) have the most abundance, respectively. Besides eight species were determined as sporadic species in studied areas. The diversity and abundance of Spheciformes wasps is highest between early May and mid-July in the studied areas. This highlights the importance of considering Spheciformes wasps impact during pest management activities.

Distribution of Harmonia axyridis as an invasive predator, newly appeared in Iran, was investigted in northern provinces of Iran. Some biological and morphological traits were studied, including color morphs, sex ratio, and adults body length. Samples were collected from four regions in north and east-north of Iran as well as two generations of Rasht population to assess the effect of geographical location and insect’s generation. Reproductive potential of females of two main color morphs (melanic and non-melanic) was also investigated in overwintering and summer generations. Sampling were succesful in Guilan, Mazandaran, Golestan, and North Khorasan. Proportion of melanic individuals in Heyran, Shaft, Bojnourd, Rasht (overwintering population), and Rasht (spring population) was 11.51, 12.64, 10.57, 12.17, and 11.63, respectively. Sex ratios ranged from 38 to 44% showing no difference among the obovevmentioned populations. Mean length of adult insect body in individuals from Bojnord (6.57±0.029 mm) was larger than others. There was no difference between females of the two main color morphs in terms of oviposition potential. However, overwintering females laid significantly more eggs than summer females, regardless of color morphs. This study confirmed progress of H. axyridis distribution towards new areas. Moreover, it was indicated that sampling location and generation have no effect on color morphs ratio in newly invaded areas, and oviposition rate cannot be a regulating factor for color morphs ratio in next generation.

The present study was designed to evaluate the lethal effects of aqueous extracts and nanoformulations of Rosmarinus officinalis L., Lavandula angustifolia Mill., Eucalyptus globulus Labill. and Artemisia dracunculus L. on Tetranychus urticae Koch (female and male adults) and Cuminum cyminum L. and Coriandrum sativum L. on Bemisia tabaci (Gennadius) (first and third instar) under laboratory conditions at 25 ± 2 ºC, 60% RH, and 16:8 h. photoperiod using contact toxicity method. Among aqueous and formulated extracts rosemary (LC50 = 3227 ppm) and tarragon (LC50 = 1454 ppm) had the highest toxicity against adult mites, respectively. Aqueous and formulated extracts of cumin also showed the highest toxicity with LC50 of 9639 and 6748 ppm on the first instar and 11670 and 9937 ppm on the third instar of B. tabaci, respectively. The first instar of B. tabaci showed more sensitivity to aqueous and formulated extracts than third ones. Based on the results of high-performance liquid chromatography (HPLC), Salcillic acid for rosemary (21.68%), lavender (33.90%) and coriander (9.9%), and quercetin for eucalyptus (76.62%), tarragon (23.49%) and cumin (15.68%) had the highest amount of chemical compounds. Our findings show the reliable toxicity of plant extracts and will facilitate the use of plant products in integrated pest management programs under greenhouse conditions.

Hemocytes are the most important hemolymph components in the circulatory system of insects, which in addition to feeding all cells and tissues of the body, play a key role in physiological defense. In this research, the identification of hemocytes in the gamma moth as a cosmopolitan and omnivorous pest was considered. To perform experiments, hemolymph was collected from pest larvae, and the cells were identified after settling on a slide and staining with Giemsa solution. Five types of hemocytes were observed in the hemolymph of insect larvae, including prohemocytes, granulocytes, plasmotocytes, oenocytoids, and spherulocytes. Prohemocytes are the smallest cells and round with a central nucleus were present in the fourth instar larvae of the moth. granulocytes are larger than prohemocytes, round with abundant granules in the cytoplasm, spindle-shaped plasmotocytes with one or two cytoplasmic cells, egg-shaped onocytoids with a lateral nucleus, and relatively large spherulocytes with spherule-shape cytoplasm. The frequency of granulocytes and plasma cells in fourth and fifth instar larvae was about 70% and more than other cells. While in younger larvae, the density of prohemocytes and plasmotocytes was relatively higher than other cells. Our findings can be used as the first stage of hematology studies of Plusia gamma.

The oriental spider mite, Eutetranychus orientalis Klein (Acari: Tetranychidae), is an important pest of Indian siris and some other trees in Ahvaz’s green landscape. By feeding on the Indian siris leaves, this pest causes leaf fall, reducing the aesthetic and green surface and its resistance to other potential pests and diseases. One of the important strategies to control the pest is application of acaricides. The choosing the efficient and safer acaricides plays critical role considering the daily contact of a large number of citizens with the urban green space. In this research, the short-term and long-term effectiveness of four pesticides abamectin, Palizin®, etoxazole, and Nimazal® which are all low-risk pesticides for humans and mammals, at concentrations 0.5, 2, 0.5, and 1 (L/1000 L), were evaluated to control the pest mite population in a field study, respectively. For this purpose, the population of nymphs and adults of this mite was recorded on the treated trees 1 day before, 2, 7, 14, and 21 days after treatment and statistically compared with the control treatment where the trees were treated only with water. This study showed that abamectin and etoxazole had very favorable short-term and long-term effects on E. orientalis population. Although Palizin® led to the control of the pest in the short term, it did not have a favorable long-term protective effect, and as a result, the treatment of trees has to be repeated in order to properly control the pest. Nimazal® also showed its effect with two to three weeks lag time and this effect was relatively lower than abamectin and etoxazole.