Journal Of Crop Protection
Volume:12 Issue: 2, Jun 2023

Two independent field experiments were carried out on two sowing dates. The experimental factors included three herbicides (trifluralin, pendimethalin, and linuron) using the method of incorporation by sowing, inter-row cultivation, and control (weed-free and weed-infested). The density of weeds 45 days after sowing, applying pendimethalin, linuron, and inter-row cultivation on the first sowing date (FSD), was 26.5, 31.8, and 45.9% less than the second sowing date (SSD), respectively. On the contrary, at the flowering stage, weeds on the SSD were 59% less than the FSD, and the average weed density in applying pendimethalin and linuron was 78.7% less than their density in the weed-infested. The height of the plant and the height of the first pod from the soil surface on the FSD were 13% and 11% higher, respectively, compared to the SSD. The average number of branches per plant with experimental treatments was 37% more than the weed-infested ones. The maximum biological yield of chickpeas in the FSD and SSD was obtained by inter-row cultivation (760 g m-2) and pendimethalin (749 g m-2), respectively. On the FSD, the seed yield in applying pendimethalin was 82.5%, and its average in linuron and inter-row cultivation was 86.4% more than the weed-infested control. Also, on the SSD, the average seed yield in the three mentioned treatments was 73.6% more than the weed-infested control. However, linuron and inter-row cultivation were identified as the most appropriate treatments for weed control in the early stages of both sowing dates.

Whether fenoxaprop-p-ethyl activity could be affected by the carrier volume and whether this relationship can be affected by two types of bio-surfactants, rhamnolipid and surfactin, was assessed under greenhouse conditions. Treatments consisted of herbicide dose (0, 18.75, 37.5, 56.25, 75, and 93.75 g ha-1), spray volume (60, 120, 240, and 480 L ha-1), surfactant type above, and surfactant concentration (0, 0.125, 0.25, 0.5, 1, 2, 4, and 8x critical micelle concentration (CMC). The dry matter of sterile oat was regressed over the doses of fenoxaprop-p-ethyl to obtain a dose causing 50% sterile oat control (ED50). Without surfactant, a 38% increase in the ED50 with increasing the spray volumes from 60 to 480 L ha-1 (44.7 and 72.1 g ha-1, respectively) revealed a negative relationship between fenoxaprop-p-ethyl activity and spray volume. In other words, a low-volume spray solution, creating smaller, more concentrated spray droplets, is necessary to get the optimal action of fenoxaprop-p-ethyl. This relationship could also be observed when both surfactants were used at 0.125 to 1x CMC. At 2 to 8x CMC, the relationship mode changed from negative to neutral for rhamnolipid, while it did not change for surfactin. This study shows that, unlike surfactin, rhamnolipid worked better at a low concentration in a low-volume spray solution to get the optimal action of fenoxaprop-p-ethyl.

The cotton bollworm, Helicoverpa armigera (Hübner), is one of the most important pests of crops. Like other insects, this insect has an immune system against external threats such as various diseases, parasitoids, and chemical compounds. Phenoloxidase is a key factor in the immunity of insects and other arthropods. The present study investigated the lethal effects of four insecticides, indoxacarb, profenofos, chlorfluazuron, and hexaflumuron, and their effects on phenolic oxidase activity in cotton bollworm. Among the studied insecticides, in two bioassays (mixture of insecticide with artificial food and immersion of sugar beet leaves), Chlorfluazuron had the highest toxicity (LC50 = 1.71 and 3.11 mg ai/liter, respectively). Also, the highest phenol-oxidase activity at 24 h was for larvae treated with chlorfluazuron and hexaflumuron. Also, when treated with chlorfluazuron and hexaflumuron, the larvae fed on an artificial diet had higher phenoloxidase activity than those fed on sugar beet cultivars.

Tomato bacterial canker caused by Clavibacter michiganensis subsp. michiganensis (Cmm) is a destructive tomato disease in the world and Iran, which can seriously affect the quality of the product. An integrated management program using pathogen-free seeds and resistant cultivars is necessary for disease control. In this study, the reaction of 24 cultivars of tomato was assessed against the disease under greenhouse conditions. Inoculation of seedlings at the 4-5 leaf stage was carried out by injecting a bacterial suspension of 1 × 104 CFU ml-1 at the axil, where the petiole meets the stem. The response of cultivars to the disease was evaluated via three indices, including the time of disease onset, disease severity (DS), and the area under the disease progress curve (AUDPC). The results indicated that AUDPC positively correlated with the time of disease onset (r = 0.85) and disease severity (r = 0.86). Based on the current findings, applying different indexes in response of tomato cultivars to bacterial canker disease provides accurate information about host resistance. The AUDPC index is the most reliable as it has a high positive correlation coefficient with two other indexes. In this study, cultivars ‘Rio Grenade’, ‘King Stone’, ‘Early Urbana Y’, ‘CalJ N3’, and ‘Hyb. Firenze’ showed more resistance against the disease than other studied cultivars. Usage of the mentioned cultivars is recommended in the integrated management program of tomato bacterial canker disease.

The bioactivity of the aqueous extracts of the leaf of Tetrapleura tetraptera against the wheat storage pest, Rhyzopertha dominica, on stored wheat grains was investigated in laboratory conditions. T. tetraptera leaf extracts were added to 20.0 g of grains at 25.0 mg/l, 50.0 mg/l, and 100.0 mg/l to assess contact toxicity, damage assessment, reproductive performance, and repellency ability. Results showed that the extracts were toxic to the insects. The leaf extracts applied at 100.0 mg/l significantly caused the highest mortality of 94% after 21 days. It also repelled almost 90% of the insects and inhibited adult emergence up to 98%. The 100.0 mg/l of the leaf extract further offered protection of nearly 99% of the wheat grains against insect damage compared to the control. This study revealed that leaf extracts of T. tetraptera can be used to control R. dominica in stored grains efficiently, and its incorporation into traditional storage pest management is strongly recommended in developing countries

Temperature and water potential are the main determinants of the seed germination of plant species. Experiments were conducted to quantify the seed germination response of two sterile oat Avena sterilis subsp. ludoviciana (Durieu) Nyman biotypes susceptible and resistant to acetyl coenzyme A carboxylase inhibitor herbicides under six temperature regimes (5, 10, 15, 20, 25, and 30 °C), and five levels of drought stress (0.0,-0.3, -0.6, -0.9, and -1.2 MPa). The base temperature of seed germination in both biotypes was affected by drought stress. The base temperature changed from no stress to maximum stress in the susceptible biotype from 3.24 to 7.15 °C and in the resistant biotype from 3.12 to 7.43 °C. Thermal times required for 50% germination of the seed population at sub-optimal temperatures was increased from 26.2 to 87.8 °C day in the susceptible biotype and from 28.8 to 90.6 °C day in the resistant biotype. Increasing the temperature from 5 to 30 °C decreased the constant hydrotime from 10.92 to 1.66 MPa in the susceptible biotype and 11.52 to 1.98 MPa in the resistant biotype. The hydrothermal time constant for susceptible and resistant biotypes was 28.6 and 31.1 MPa. According to the hydrothermal time model, the herbicide-resistant biotype (-0.858 MPa) seeds require more water potential than the susceptible biotype (-0.905 MPa) to germinate at higher temperatures. Based on the parameters of the models, the germination response to temperature and water potential was similar in both susceptible and resistant biotypes. Consequently, maximum emergence of both biotypes is possible at 15 °C and without water stress conditions.

In an in silico investigation, genome sequences of three RNA viruses were identified in the crown imperial Fritillaria imperialis L. transcriptome dataset. Sequence comparison and phylogenetic analyses revealed that these three novel viruses belong to the genus Amalgavirus. They were tentatively named Crown imperial amalgavirus (CIAV), Iranian amalgavirus (IrAV), and Koohrang amalgavirus (KAV). The RNA-dependent RNA polymerases (RdRps) of CIAV, IrAV, and KAV showed 69.53%, 42.26%, and 37.46% amino acid sequence identities with the homologous RdRp of the most closely related virus, respectively, suggesting that they are novel viruses. Also, the conserved motifs of RdRp were detected in the RdRp of each CIAV, IrAV, and KAV. Genomes of both CIAV and IrAV were complete and contained two overlapping Open Reading Frames (ORFs). A + 1 programmed ribosomal frameshifting (PRF) motif, which matches the conserved amalgaviruses consensus sequence UUU_CGN was found at the ORF1/ORF2 boundary of CIAV and IrAV. The current study reports three novel viruses for the first time from crown imperial, and these findings enrich our understanding of new plant dsRNA virus species, which may also be helpful for the study of amalgaviruses.

Rhizoctonia root rot caused by Rhizoctonia solani is one of the critical factors influencing bean plants' yield. This study investigates the effects of some biofertilizers for controlling R. solani and their impact on the growth parameters of bean plants in the greenhouse. Biofertilizers, Funneliformis mosseae (F. mos), vermicompost (Verm), and mealworm frass (Meal), were used in a completely randomized design with five replications. Compared with diseased control, biofertilizers applied separately or in combination, reduced disease severity (except Meal) and disease incidence (except Verm). The combination of Meal + Verm had the best effect on both indices. All biofertilizer treatments increased the dry root weight (except Verm and F. mos + Meal + Verm), fresh root, and foliage weight. Also, root length, and dry foliage weight was increased only in combination treatments, and stem length in Meal + Verm and F. mos + Verm. The highest growth of foliage parameters, root length, and fresh and dry root weight was observed in Meal + Verm, F. mos + Verm, and F.mos + Meal, respectively. The highest mycorrhizal colonization was in F. mos and F. mos + Verm. Therefore, combinations of biofertilizers had better effects on the plant growth and inhibition of Rhizoctonia root rot. The tested biofertilizers and their combinations could be considered as promising tools for reducing the use of chemicals and enhancing sustainable agriculture and disease management. The appropriate timing and application rates for these biofertilizers must be determined accurately during field experiments.