Assessment of Acacia dealbata as green manure and weed control for maize crop

Acacia dealbata Link is one of the main invasive species in southwestern Europe and a resource with potential value for agriculture. Our objective was to assess the value of A. dealbata vegetative aerial biomass used as green manure and as a tool for weed control in maize crops through three sequential experiments. In 2017, an experiment was carried out with acacia green manure vs inorganic fertilization of pots sown with a field corn and a sweet corn hybrid with strong and weak nutrient demand, respectively. Nutrients were not released from acacia green manure at an appropriate timing, and maize suffered nutrient deficit. In 2018, a pot experiment was made outdoors incorporating acacia green manure at different times before maize sowing, and we found that a 4-month period was required for maximum nutrient release from acacia green manure. In 2019, an early and a late-field experiments were performed by incorporating acacia green manure 4 months before maize sowing. Physiological and agronomic data were recorded in maize, along with soil data, for all years, and weed data the last year. Altogether, most effects and interactions between genotype or environment and fertilization treatment were not significant, and some deficiencies caused by acacia green manure fertilization depend on genotype and environment. Incorporation of acacia green manure 4 months before maize sowing partially controlled weeds and replaced inorganic fertilization. However, deficiencies should be corrected with additional weed control practices and fertilization treatments, according to the nutrient demand of the crop and the soil environment.

First report of Curvularia leaf spot of field corn, caused by Curvularia lunata, in Mississippi

In July 2021, foliar symptoms characterized by small, circular, light brown to tan lesions (0.5 to 3 mm diameter) with reddish-brown margins were observed on field corn (Zea mays L.) in two commercial fields in Hinds and Marion counties, Mississippi. Disease severity ranged from 2 to 15% on observed leaves. Symptomatic leaves were sealed in plastic bags, stored on ice, and transferred to the laboratory. Lesions were cut into small sections (≈4 mm2) and surface-sterilized with 70% ethanol for 30 s then rinsed with sterile water. Sterilized sections were transferred to potato dextrose agar (PDA) amended with chloramphenicol (75 mg/liter) and streptomycin sulfate (125 mg/liter) and incubated at 25°C in the dark for 7 days. Gray to brown-black colonies with orange margins and melanized, curved conidia with three transverse septa were observed microscopically (Fig. 1; ×400). Conidia measurements ranged from 15 to 25 μm in length and 7.5 to 12.5 μm in width (x̄= 20 × 9.8 μm; n= 44). Colony and conidia morphology were consistent with previous descriptions of Curvularia lunata (Wakker) Boedijn (Mabadeje 1969; Ellis 1971). Pure cultures were obtained, and DNA was extracted from 9-day old cultures. Two isolates (TW003-21; TW008-21) were selected for sequencing of the internal transcribed spacer (ITS) region using ITS4 and ITS5 primers. The 530-bp consensus sequences were deposited in GenBank under the accession No. OK095277 and OK095278. BLASTn queries of NCBI GenBank showed that the sequences shared 100% identity with C. lunata isolate DMCC2087 from Louisiana (MG971304) and isolate CX-3 from China (KR633084). A pathogenicity test was performed on V4/V5 stage corn plants (Progeny 9114VT2P) grown in 10.2 cm pots in the greenhouse. Plants were transferred to a growth chamber one-week prior to inoculation. The two isolates were grown on amended PDA for 14 days at 25°C and an inoculum suspension was prepared for each isolate by rinsing culture plates with 2 ml of autoclaved reverse osmosis (RO) water amended with Tween 20 (0.01%) and re-suspended into 40 ml of RO water containing Tween 20. The final concentration was adjusted to 2.6×105 conidia/ml (TW003-21) and 2×105 conidia/ml (TW008-21). Ten corn plants were sprayed with 10 ml of inoculum suspension for each isolate using a Preval sprayer with a CO2 canister, and 10 plants were sprayed with water containing Tween 20 only. Plants were incubated in a growth chamber at ≈79% relative humidity and 25°C. Foliar symptoms including small, circular, and tan lesions, similar to those observed in the field, developed 3 days after inoculation. No symptoms were observed on control plants. Following incubation, symptomatic leaves were collected and C. lunata was re-isolated as described above. Colony, spore morphology and DNA sequences from inoculated plants were consistent with the original isolates as described above. The disease has been recently reported in Louisiana (Garcia-Aroca et al. 2018), Kentucky (Anderson et al. 2019), and Delaware (Henrickson et al. 2021). Although Curvularia leaf spot has been observed sporadically in MS corn fields since 2009 (Allen, personal communication), to our knowledge, this is the first official report of the disease in MS. While this disease has been more frequently encountered in MS, the economic impact associated with C. lunata is currently unknown. References Anderson, N. R., et al. 2019. Plant Dis. 103:2692. Chang, J., et al. 2020. J. Integr. Agr. 19:551-560. Ellis, M. B. 1971. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew, England, p. 452-458. Garcia-Aroca T., et al. 2018. Plant Health Prog. 19:140. Henrickson M., et al. 2021. Plant Dis. First Look. Mabadeje, S. A. 1969. Trans. Br. Mycol. Soc. 52:267-271. † Indicates the corresponding author. E-mail: [email protected]

Plant Spacing and Variety of Field Corn (Zea mays L.) Affecting Yield, Yield Components and Silage Quality

The recent increase in dairy and cattle production in Thailand has increased demand for high-quality roughage, particularly corn silage. Although there has been a great deal of research on field corn, far fewer studies have focused on corn intended as silage. This study involved a field experiment that analyzed crop management methods, focusing on plant spacing and 8 of the field corn varieties most commonly used in Thailand. The objectives were to determine which plant spacing and variety produced the best forage yield and silage qualities of corn silage. The plantings were arranged in a split-plot Randomized Complete Block Design (RCBD) with four replications. The main plot contained two spacing (75×20 and 75×25 cm2), each with subplots of 8 field corn varieties (SW5, NS2, NS3, NSX982013, TE1719, WS6437, WS6440, WS6442). All plants received the same crop management care regarding soil conditions, water, fertilization, and weeding. The results showed plant spacing did not significantly affect plant height (cm) and ears per plant, but the narrower 75×20 cm2 spacing produced the highest fresh leaf yield (13 t ha-1) and dry stalk yield (4.5 t ha-1) (p < 0.05). At 75×20 cm2 spacing, the TE1719 varietal had more ears per plant than SW5 (the check variety). TE1719 had the best fresh ear, stalk, and total biomass yield at both spacing of all the varieties. With regard to silage quality, the plant spacing did not significantly affect the CP, ADF, ADL, ash, and pH of the corn silage. The study revealed planting TE1719 varieties at 75×20 cm2 spacing is more economical for farmers because it increases forage yields without negatively affecting the nutritional value of corn silage.

Peanut Response to Preemergence Applications of Metribuzin

Herbicide-resistant Palmer amaranth is one of the most problematic weeds in agronomic cropping systems in Georgia. The wide germination window of Palmer amaranth seed allows it to emerge after field corn harvest, and if left uncontrolled, can contribute significantly to the weed seed-bank causing problems in future rotational crops. One option for a lay-by (in-crop) or post-harvest burndown application in field corn for postemergence and residual control of Palmer amaranth is metribuzin. However, the current metribuzin label prohibits peanut planting for 18 months after application. Peanut tolerance to metribuzin has not been well documented. Therefore, the objective of this research was to evaluate the tolerance of peanut to metribuzin. Field studies were conducted in 2017-2019 in Ty Ty, GA to evaluate the tolerance of peanut to various rates of metribuzin. In a RCBD with four replications, metribuzin was applied preemergence (two days after planting) at 0, 70, 140, 280, 420, and 560 g ai/ha. Rainfall in the first month after planting was 13.1, 15.9, and 11.8 cm for 2017, 2018, and 2019, respectively. Data were subjected to nonlinear regression using log-logistic analysis to demonstrate a dose-response relationship. Year by treatment interactions were significant for late season injury, so data were separated by year. However, early season injury, stand loss, and yield loss data were pooled over years. There was a direct relationship between rate and the response variables. As metribuzin rate increased, injury, stand loss and yield loss increased. Generally, visual injury, stand loss, and yield loss were negligible at rates less than or equal to 140 g ai/ha. With a targeted application rate of 280 g ai/ha and an estimated half-life of 30 to 60 days, metribuzin residues should have minimal impact on peanut grown in rotation when used in lay-by or post-harvest treatments for the prevention of Palmer amaranth seed rain in field corn.

Line × Tester Method Used to Evaluate the Inbred Lines of Field Corn

Nineteen selected lines of field corn were crossed in a line × tester method with two testers to produce 38 hybrids during rabi 2018-2019. In the following year, all the hybrids were raised along with five commercial checks in an alpha lattice design with two replications. The lines E34, BML75, BML76, BML249, BIL106, CML465, CML481 and CML487 were better among the parents, showing GCA effects for yield and other traits could be used extensively in hybrid breeding program owing to increase yield. Furthermore, based on mean, SCA effects and standard heterosis of yield value, the crosses BML75 x BIL79, E34XBIL157, BML76 x BIL157 and BML249 x BIL157 were found to be better to increase the grain yield along with other traits and play pivotal role to development of commercial hybrid.