Journal Of Crop Protection
Volume:12 Issue: 1, Mar 2023

Hibiscus chlorotic ringspot virus (HCRSV), genus Betacarmovirus, family Tombusviridae, is a common pathogen of hibiscus plants in tropical and subtropical regions. During 2020-2021, leaf samples of Chinese hibiscus Hibiscus rosa-sinensis L. with mottling and chlorotic ring spot symptoms were collected from Ahvaz and Molasani Khuzestan province, southwestern Iran. Total RNA extracted from symptomatic samples was subjected to RT-PCR analysis to amplify the sequence of the coat protein gene (CP) (p38) of HCRSV. Complete (1038 bp) and partial (932 bp) p38 sequences were determined and deposited in the GenBank database. The consensus sequences obtained from CP were compared with those of known isolates using the nBLAST program and phylogenetic analysis. The phylogenetic tree constructed based on the p38 sequences showed different ancestors for Iranian isolates of HCRSV. Additionally, the isolates studied were grouped into clades regardless of their geographic distribution, suggesting that there is no differentiation of population based on location and that populations are interconnected. Recombination analysis based on p38 sequences predicted at least two acceptable recombinant isolates, Ahvaz (Iran) and Israel. In silico prediction of CP structures of isolates involved in recombination events showed low sequence to structure identity between HCRSV isolates. In addition to reporting two new HCRSV isolates from Iran, our work demonstrated that HCRSV exhibits a high genetic variation through recombination and that the classification criterion could be changed from low nucleotide sequence identity to a higher value, along with the structural analysis of betacarmovirus proteins.

Grapevine viruses cause significant losses in the yield of grape. This study describes applying silver nanoparticles (AgNPs) to produce virus-free grapevine plants and compares it with chemo and thermotherapy. Preliminary molecular analysis proved the presence of Grapevine fanleaf virus (GFLV) and grapevine leafroll-associated virus-1 (GLRaV-1) in the ʻAsgariʼ, ʻPeykaniʼ, and ʻShahaniʼ cultivar samples, then single node explants were cultivated in the MS medium. Thermotherapy at 35 ± 1 ºC and cycles of 35/38 ± 1 ºC, chemotherapy with ribavirin 0, 20, 25, and 30 μg.ml-1 and using AgNPs at 0, 10, 15, and 20 ppm in medium and 40, 50, and 60 ppm sprayed during acclimatization stage were applied to obtain virus-free explants. The results indicated that using 20 ppm AgNPs in medium and AgNPs combined treatment (15 ppm AgNPs in medium and sprayed with 50 ppm AgNPs in the acclimatization stage) were the most effective treatments for the elimination of viruses. The best treatment led to 100% eradication of GLRaV-1 and 67% of GFLV in ʻAsgariʼ, 100% eradication of GLRaV-1 and GFLV in ʻPeykaniʼ and 100% eradication of GLRaV-1 and 67% of GFLV in ʻShahaniʼ. Furthermore, applying of AgNPs improved plant growth parameters, including plant height, which in infected plantlets was (18.06, 12.36, and 14.92 cm in ʻAsgariʼ, ʻPeykaniʼ, and ʻShahaniʼ, respectively) less than virus-free plantlets. Leaf number was 45, 34, and 27 in virus-free plantlets of ʻAsgariʼ, ʻPeykaniʼ, and ʻShahaniʼ, respectively, but in infected plantlets, it was 24.40, 19.80, and 12. Leaf area increased from 5.34, 5.50, and 5.94 cm2 in infected plantlets to 9.56, 11.43, and 12.33 cm2 in virus-free plantlets of ʻAsgariʼ, ʻPeykaniʼ, and ʻShahaniʼ, respectively. Complementary results proved that chlorophyll content in virus-free is significantly higher than in virus-infected plantlets, which explains and confirms the change in growth parameters after virus removal.

The effects of long-term rearing of Trichogramma brassicae (Bezdenko) on host preference and switching behavior was examined when parasitizing two common factitious hosts, including Mediterranean flour moth (MFM), Ephestia kuehniella Zeller and Angoumois grain moth (AGM), Sitotroga cerealella (Olivier) over 45 generations. Both host species eggs were offered to the parasitoid over 24 h. Significantly more MFM eggs were parasitized in all generations, but a distinct negative switching behavior was found in all experiments. The parasitoid negatively switched from MFM when they became abundant compared to AGM and vice versa. The preference coefficient (c) estimated using Murdoch's index ranged from 2.056 (in G5) to 1.734 (in G45) for MFM and 0.486 (in G5) to 0.577 (in G45) for AGM. The linear regression indicated that despite preferring MFM, the intensity of the preference decreased over 45 generations. Negative switching behavior in T. brassicae may be advantageous for this species in controlling pests in given situations.

Yellow rust of wheat caused by Puccinia striiformis f. sp. tritici is one of the most important wheat diseases that threaten its production. Host resistance is the most economical and healthiest method of yellow rust management. In this study, slow rusting resistance parameters including infection coefficient, disease severity as well as reaction type were recorded for 48 rain-fed wheat genotypes along with sensitive control in 6 rain-fed environments. The field experiment was done for two consecutive years in three distinct geographical regions including Ardebil, Zarghan, and Mashhad. The additional screening test was established in greenhouse conditions. Results showed genetic variability among studied germplasms in resistance against yellow rust. In this research, G1, G04, G05, G06, G20, G21, G32, G33, G39, and G45 out of the studied genotypes had resistant and stable reactions across years and locations. Ward clustering algorithm produced three heterotic groups which can be utilized in yellow rust breeding programs through parental selection for the construction of a yellow rust mapping population. Differential genotypes testing resulted in “6E142A +, Yr27”, “38E158A +, YR27” and “134E150A +, YR27” isolates which belonged to Ardebil, Mashhad as well as Zarghan regions respectively. The resistance reaction in the seedling stage varied from that found in the field state which indicated the existence of adult plant resistance genes in their genome.

The two-spotted spider mite (TSSM) Tetranychus urticae Koch is one of the most destructive mites in many plants due to its characteristics, such as high reproductive potential, short life cycle, and feeding method. Excessive use of chemical compounds without considering environmental factors has led to high residual toxins in food products and resistance to pesticides. Temperature is an essential non-living factor that affects various biological aspects of pests and pesticide toxicity levels. In this study, the interaction of different temperatures (15, 20, 25, and 30 °C) in the photoperiod (16L:8D h) was investigated on the toxicity of spiromesifen on the adult TSSM. Then the levels of α-esterase and glutathione S-transferase activity were measured. The highest LC50 was recorded at 15 °C after 24 h (LC50 = 21.269 mg ai/l), and the lowest value corresponds to 30 °C after 48 h (LC50 = 0.860 mg ai/l). The level of toxicity also increased with a temperature increase, so the toxicity was recorded 3.6 folds higher at 30 °C compared to 15 °C. The α-esterase and glutathione S-transferase activity also increased with an increase in the temperature, but this increase was significant only for esterase activity. The relationship between temperature and the power of pesticide toxicity in areas with different daily and controllable temperature changes can effectively provide a valuable proposal to reduce pesticide consumption and increase the efficiency of pest control.

The two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae) is one of the most important pests of many crops worldwide. Combined tactics for pest management have a significant special effect on reducing pesticide use and maintaining the activity of natural enemies, which is the main objective of IPM programs. The effect of low-lethal concentrations of Eforia (24.7 SC, Syngenta Co.) at LC5, LC15, and LC25 were investigated on biological parameters of Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) under laboratory condition at 25 ± 1 °C, 70 ± 5% RH and 16:8 (L: D) h. The data were analyzed based on a two-sex life table procedure. The results showed that Eforia caused a significant reduction in fecundity (Control: 37.17; LC25: 23.04 eggs/female) and total life span (Control: 42.67 days; LC25: 24.65 days). The net reproductive rate (R0) was 22.31, 20.12, 15.14, and 14.98 eggs/individual, respectively, at control, LC5, LC15, and LC25. The maximum and minimum values for the intrinsic rate of increase (r) were recorded to be 0.17 (Control, LC5, and LC25) and 0.15 (LC15) day-1 for the treated mites. Based on the results, the application of low lethal concentrations of Eforia harms some biological parameters of this predatory mite, and the results of this study showed that Eforia may not be applied for the control of T. urticae pest together with A. swirskii.

Several phytophagous insect pests are known to attack okra, Abelmoschus esculentus (L.) Moench in the field. However, information on the fruit-damaging species and the effective time for insecticide application(s) is still scanty. Field experiments were conducted in 2017 and 2018 to identify the categories of damage inflicted on okra fruits by associated insect herbivores and to ascertain the phenological growth stage in which insecticide applications will significantly reduce insect-induced fruit damage and improve crop yield. Treatments consisted of the application of Cypermethrin 20EC at two-week intervals on NHAe47-4 variety of okra during the vegetative stage (VGS), reproductive stage (RGS), VGS + RGS, and no spray (control). The setup was in randomized complete blocks with four replicates. Results showed that incisions, feeding lesions, localized discolorations, bumps, distortions, and larval exit holes are the major fruit damage symptoms caused by field insect pests of okra. Generally, fruit damage was significantly reduced, while fruit yield was higher in plots that received insecticide sprays at vegetative and reproductive stages than in the control. Fruit production increased significantly by 56.9–69.6% and 57.7–73.1% in 2017 and 2018 in treated plots compared to control, respectively. Fruit damage was reduced by 37.5-92.5% (2017) and 44.6–94.6% (2018), and fresh fruit yield of okra was increased by [58.8–75.0% (2017) and 63.1-76.1% (2018)]. We conclude that an effective field management strategy for insects associated with okra fruit damage should include potent control tactics at the crop's vegetative and reproductive growth stages.

Two chalcidoid parasitic wasps (Hym.: Chalcidoidea) of two lepidopterous pests on willow trees, Salix spp., were collected in Tehran and Alborz provinces, Iran. Ooencyrtus populicola Myartseva, 1995 (Hym.: Encyrtidae) and Colpoclypeus florus (Walker, 1938) (Hym.: Eulophidae) were reared on Ceruravinula (L., 1758) (Lep.: Notodontidae) and Nycteola asiatica (Krulikovsky, 1904) (Lep.: Nolidae), respectively. Ooencyrtus populicola is a parasitoid of egg and C. florus is an ectoparasitoid of larval stage. Ooencyrtus populicola is a new record for Iran, but C. florus was previously reported as a parasitoid of an unknown leaf-roller larva.

Diasemiopsis ramburialis and Nomophila noctuella are moths from Spilomelinae (Lepidoptera: Crambidae) with an overlapping feeding period on Azolla spp. in northern Iran. Due to some morphological similarities, immature stages often lead to confusion. A five-year study conducted in laboratory and natural environments revealed that, despite these morphological similarities, distinct characteristics in both morphology and behavior can facilitate their primary identification in the field. Diasemiopsis ramburialis eggs, and first instar larvae are opaque to pale orange, while those of N. noctuella are pale to creamy. Additionally, the last instar larvae of D. ramburialis feature orange head capsules with smaller body sizes and tend to pupate near the feeding site. In contrast, Nomophila noctuella's last instar larvae have black head capsules, larger body sizes, and pupate at a distance from the feeding site. Both species exhibit shelter-building behavior, binding Azolla spp. leaves together using silken webs to create protective enclosures. However, D. ramburialis larvae construct more robust shelters and produce more webs. They primarily remain within these shelters and navigate through web-formed corridors. On the other hand, N. noctuella larvae prefer to move along the feeding site margins within corridors formed by bound-up leaves and display a more wandering behavior. The study's findings indicate that Azolla spp. serves as the primary host plant for D. ramburialis, while N. noctuella appears to choose its host plants randomly.

This study aimed to investigate the oviposition behavior, distribution, and host plants of Orosanga japonica (Hemiptera: Ricaniidae) in Guilan province, Iran. Random sampling was conducted across various locations within Guilan province. Adult insects typically emerge in late July and deposit their eggs from early August to mid-September. This species prefers laying eggs on young shoots and leaf midribs of various plants, from annual herbaceous species to shrubs. This oviposition behavior can lead to stem desiccation. Additionally, the females' oviposition behavior, sap-sucking activities on stems, and the potential transmission of pathogenic fungi can cause substantial damage to host plants. This research provides information regarding the distribution of pest egg masses across several host plants. Our findings revealed that the mean number of egg masses per twig was higher on chinaberry, averaging 13.75, than on bitter orange, elm trees, and mulberry. The longest average egg mass length, measuring 16.1 mm, was observed on mulberry. Furthermore, this study confirmed the presence of O. japonica in 13 cities within Guilan province, including Rasht, Anzali, Amlash, Astaneh, Lahijan, Langroud, Rezvanshahr, Rudsar, Rudbar, Sowme'eh Sara, Siahkal, Shaft, and Fouman. The insect was predominantly found infesting kiwi, tea, beans, corn, eggplants, peppers, elm leaf blackberries, chinaberries, mulberries, Japanese spindles, cucumbers, citrus plants, fig-trees, rice, cabbage, and grapes.