Untreated Plots Research Articles

Insecticidal activity of <i>Ricinus communis L.</i> seed extract against <i>Spodoptera frugiperd</i>a J.E. Smith under laboratory and field conditions

Insecticidal activity of the aqueous extract of the castor seed (Ricinus communis L.) against the Fall Armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), one of the worst pests of maize crop, was assessed under laboratory and field conditions. In laboratory, the larvicidal activity of three concentrations of the extract that are 150 g/l, 200 g/l and 250 g/l and their effects on the development of FAW were evaluated through direct exposure and ingestion tests. The field experiment consisted of a randomized block design with two extract concentrations – 200 g/l and 250 g/l – and negative control consisted of untreated plots and positive control plots were treated with Emacot (Emamectin benzoate). Results of the laboratory experiments revealed considerable larvicidal activity of the extract through the ingestion test, inducing the larvae mortality of 75.8%, 60.3% and 46.5% for the extract concentrations of 250 g/l, 200 g/l and 150 g/l respectively, whereas positive (Emacot) and negative controls (emulsified water) recorded 100% and 3.3% of the larvae mortality, respectively. The field results showed 10% and 11% of infested plants in plots treated with 200 and 250 g/l, respectively, whereas Emacot-treated plots recorded 9.5% of infested plants. Untreated plots recorded the highest infested plants of 22.5%. The two- castor seed extract concentrations 200 g/l and 250 g/l reduced about 50% of maize plant infestation by FAW, thus could be a good candidate as alternative to chemical pesticides in controlling the pest.

Creeping Bentgrass Nutritional, Morphological, and Putting Green Performance Response to Ca/Mg-Silicate Slag Liming Agent

While not classified as an essential plant nutrient, silicon (Si) assimilation following exogenous Si application has enhanced the wear resistance of cool-season turfgrass. Given this beneficial supplementation of lignin by Si reported in epidermal tissue of monocotyledonous plants, our research objective was to quantify root morphology, vegetative nutrition and vigor, soil chemistry, and putting green performance in response to split applications of pelletized liming agents rich in Si and/or Ca and Mg. Field evaluation of granular liming agent treatment, 2441 kg (ha year)−1, was conducted on creeping bentgrass (Agrostis stolonifera L. cv. Penn G-2) putting green maintained in the Mid-Atlantic US. Pelletized Ca/Mg-SiO3 slag or dolomitic limestone treatments were conducted in frequent split applications and incorporated into the upper 5 cm of the rootzone. Measurements of canopy color and density, shoot growth as clipping yield, soil pH, Si and nutrient content of clippings, and soil extractable Si were performed each season. Cumulative Ca/Mg-SiO3 application (kg ha−1) increased mean acetic acid (HOAc) extractable Si by 35 to 60 mg kg−1 and leaf Si content by 1.0 to 1.5 mg g−1. However, neither putting green canopy quality, shoot nutrient concentration, 5 to 15 cm depth root length density nor ball roll distance was improved by liming agent treatment. Liming agent-treated or untreated plots showed statistical, yet inconsistent, differences in clipping yield 4, 14, 15, 16, and 17 months from initiation (MFI). This thorough shuffling of treatment rank, resulting in identical experiment-wide means precludes the expectation of dependably superior vigor by any.

Evaluation of compost with chemical fertilizers for Irish potato (Solanum tuberosum L.) production in Debub Ari Woreda, Southern Ethiopia

Soil fertility reduction is the main problem for sustainable crop production and productivity in southern parts of Ethiopia. Integrated soil fertility management is the best choice to improve soil fertility constraints using accessible organic and chemical fertilizers. The aim of the experiment was to examine the effect of organic and chemical fertilizers on crop yield and soil fertility improvement. This experiment was conducted from 2017 to 2018 in Debub Ari district, southwestern Ethiopia. The treatments contain Control (no fertilizers), Recommended NP (69/30), 250 kg NPSB + 161 kg ha-1 Urea, 10 t ha-1 compost, and 5 t ha-1 compost + 125 kg NPSB + 80 kg Urea top dress. Potato variety ‘Belete’ became used for the experiment and was planted early in the ‘Belg’ season. The treatments were arranged in randomized complete block design with three replications. Soil sample was randomly collected before treatment application with a depth of (0-20cm) and composited into one kg of a sample. The analysis results of the initial soil sample revealed that it was sandy clay in texture, moderately acidic, low in total N, OC, CEC, and very low in available P. The analysis of variances showed significant differences among the treatments on potato tuber yield when compared to untreated plots. Potato tuber yield is increased by 32, 22, and 35% of sole use of inorganic fertilizer, compost alone, and 50% of compost + 50% of NPSB treatment, respectively, than control. The maximum tuber yield 18.7 t ha-1 was obtained from treatment 5 t ha-1 compost + 125 kg NPSB + 80 kg Urea top dress, whereas the minimum tuber yields 13.85 t ha-1 were obtained by untreated plot (without any fertilizer application). Farmers in the study area can use by selecting either recommended NP (69 N and 30 P) ha-1 or 5t + 125 kg NPSB + 80 kg urea ha-1 depending on the accessibility of labor, composting material, and cash to purchase an adequate amount of fertilizers. Int. J. Agril. Res. Innov. Tech. 13(1): 77-82, June 2023

Can fall armyworm damage decrease depending on the season, the maize hybrid, and the pesticide sprayed?

Maize is the third most important grass produced in the world after wheat and rice. Among the limitations of its production, fall armyworm, Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) is considered the most relevant pest in which corn is the main host plant. During the dry and rainy seasons of 2021-2022, lots of 1200 m2 were planted including three commercial hybrids, ADV-9139, Trueno NB-7443, and INIAP-551 in which the treatments were evaluated: T1: Sequence of insecticides (CLE) based on chlorantraniliprole, lufenuron, and emamectin benzoate. T2: Biological insecticide based on Bacillus thuringiensis (BT). T3: Methomyl-based treatment (MET). T4: Untreated plot (UP). Plant and cob damage, plant height and cob insertion, and grain yield were evaluated, and an economic analysis was performed. The least damage to plants and cobs was detected in the ADV-9139 hybrid. Regarding pesticides, CLE showed the best damage control in plants and the cobs were less damaged when CLE and BT were applied. Plant height and cob insertion height were lower in the ADV-9139 hybrid in which the highest grain yields were estimated. Plots treated with BT showed the highest increase in grain yield. The results show that the management of this voracious insect can be achieved combining the partial resistance of a maize genotype with pesticide applications with the lowest social, economic and ecological costs.

Determining the Effect of Biopesticides and Chemicals against Pod Borer [Helicoverpa armigera (L.)] on Chickpea (Cicer arietinum L.)

The field investigation was carried out in the Prayagraj district of Uttar Pradesh. The experiment was conducted in rabi 2022 at Central Research Farm (CRF), SHUATS, Naini, Prayagraj district. The field was laid in RBD with three replication and eight treatments viz., Beauveria bassiana (2×108 CFU/gram) (2 ml/liter), Metarhizium anisopliae (2×108 CFU/gram) (2 g/liter), Bacillus thuringiensis (1×109CFU/ml) (2 ml/liter), Ha NPV (1×109 POB’s/ml) (1 ml/liter), Azadirachtin 0.3EC (5 ml/liter), Spinosad 45% SC (0.5 ml/liter), Neem seed kernel extract 5% (5 ml/liter), and untreated controlled plot to check the efficacy of biopesticides against pod borer, on chickpea. The result on the efficacy of treatments the least larval population was recorded in Spinosad 45% SC (0.96) followed by Ha NPV (1.20), Bacillus thuringiensis (1×109 CFU/ml) (1.84), Beauveria bassiana (2×108 CFU/gram) (1.91), Metarhizium anisopliae (2×108 CFU/gram) (2.02), Azadirachtin 0.3EC (2.22), Neem seed kernel extract 5% (2.48) and the highest larval population of pod borer was found in control treatment (4.02). In another parameter higher yield and cost benefit ratio was recorded in Spinosad 45% SC (20.33 q/ha) (1:2.84), followed by Ha NPV (1×109 POB’s/ml) (18.60 q/ha) (1:2.59), Bacillus thuringiensis (1×109 CFU/ml) (17.65 q/ha) (1:2.46), Beauveria bassiana (2×108 CFU/gram) (15.68 q/ha) (1:2.19), Metarhizium anisopliae (2×108 CFU/gram) (14.58 q/ha) (1:2.03), Azadirachtin 0.3% EC (13.81 q/ha) (1:1.92) and Neem seed kernel extract 5% (13.58 q/ha) (1:1.89) as compared to control (10.83 q/ha) (1:1.54).

Effects of different rangeland management practices on vegetation metrics and wildlife abundance in a semi-closed ecosystem in north-central Kenya

Rangelands contribute at least 30% of terrestrial net primary productivity, making them an important part of natural ecosystems despite low and unpredictable rainfall regimes. Rangelands are sensitive to anthropogenic activities, making management interventions key to maintaining forage quality and quantity for wildlife. This study explored the effects of mowing of grasslands and carrying away (MO), prescribed grazing (PG), and unprescribed grazing (UG) on above-ground biomass, basal gaps, and wildlife abundance at Lewa Wildlife Conservancy in Meru, Kenya. Data collection was done 18 months after treatment for PG and MO, while UG was continuous. Treated blocks were selected in a systematic and random way, while adjacent untreated plots acted as controls. Blocks were divided into 100 m × 100 m grid cells using ArcMap 10.8.1, where sampling plots were drawn. T-statistics and analysis of variance (ANOVA) tests were used to test statistical significance. We found a significant reduction in the aboveground biomass between MO and its control (t = 4.886, p = 0.003) and between UG and its control (t =5.487, p = 0.007). No significant change was observed between PG and its control (t = 1.192, p = 0.287). MO increased wildlife abundance (t = -4.670, p = 0.003), while PG (t = 0.589, p = 0.583) and UG (t = -0.262, p = 0.803) showed no difference compared to their controls. The mean length of basal gaps between MO and its control decreased (t = 7.069, p = 0.001), while those between UG and its control increased (t = -4.053, p = 0.001), with no effect observed between PG and its control (t = 1.882, p = 0.061). This study recommends the use of mowing of grasslands and carrying away on rangelands as it positively influence the metrics under investigation.

Probiotic Bacteria, Anaerobic Soil Disinfestation, and Mustard Cover Crop Biofumigation Suppress Soilborne Disease and Increase Yield of Strawberry in a Perennial Organic Production System.

Black root rot complex and crown rot of strawberry caused by soilborne fungi limit sustainable strawberry production in the northeastern United States, especially in perennial systems, including matted row and plasticulture. As pathogen populations build up over time in the rhizosphere and infect the root system, feeder roots are pruned, which diminishes nutrient and water uptake and causes stunted plant growth or death. Alternative management options are needed for many organic and small growers who can't use chemical fumigants due to new regulations and potential health hazards. Strawberry plug plants were grown on beneficial microbe-inoculated or uninoculated planting mix followed by transplanting in fruiting field plots that either was biofumigated with mustard cover crop (MCC), anaerobically disinfested (ASD), or left untreated. Different combinations of plug plants and field plot treatments were used to determine the efficacy of individual treatments or synergistic effects from combination treatment. Plug plants were transplanted in pretreated plastic mulched raised beds and grown following a typical organically recommended production system. Plants grown on TerraGrow (TG)-inoculated planting mix showed enhanced plant vigor in the fruiting field compared with untreated plants. Weeds that grew through planting holes were significantly (P ≤ 0.045) suppressed in ASD plots compared with untreated plots in the first year. Plants treated with a combination treatment of TG and ASD had significantly higher fruit yield in both years (2019 and 2020), although the difference was greater in the second year. Plant vigor and survival in treated plots except MCC were also significantly higher in the second year compared with the untreated control. Suppression of pathogenic microbes and plant vigor improvement in treated plots appear to be the factors providing beneficial effects and higher net economic return. Taken together, our results suggest that a combination of beneficial microbes and ASD could be an alternative to synthetic fumigation in a perennial strawberry production system.

Efficacy and Economics of Selected Insecticides against Pod Borer [Helicoverpa armigera (Hubner)] on Cowpea [Vigna unguiculata (L.)Walp.

A field trail was conducted at CRF, SHUATS, Naini, Prayagraj during Kharif season 2022. Eight treatments were evaluated against Helicoverpa armigera i.e. of Chlorantraniliprole 18.5 SC, Emamectin benzoate 5 SG, Flubendiamide 480 SC, Spinosad 45 SC, Thiamethoxam 25 WG, Lambda cyhalothrin5 EC, Indoxacarb 14.5 SC and untreated Control. Results revealed that, among the different treatments lowest larval population of cowpea pod borer was recorded in Chlorantraniliprole 18.5 SC (1.323). Lambda cyhalothrin5 EC (1.478) was found tobe the next best treatment followed by Emamectin benzoate 5 SG (1.589), Indoxacarb 14.5 SC (1.734) and Flubendiamide 480 SC (1.922).The least effective treatments were Spinosad 45 SC (2.089) where as Thiamethoxam 25 WG (2.200) was found to be least effective. The plot treated with Chlorantraniliprole 18.5 SC show highest yield (19.46 q/ha) followed Lambda cyhalothrin5 EC (17.82 q/ha) the best and most economical treatment was Chlorantraniliprole 18.5 SC (1: 3.89). Among the treatments studied, the best and most economical treatment was Chlorantraniliprole 18.5 SC (1: 3.89) followed by Lambda cyhalothrin 5 EC (1:3.67), Emamectin benzoate 5 SG (1:3.41), Indoxacarb 14.5 SC (1:2.95), Flubendiamide 480 SC (1:2.56), Spinosad 45 SC (1:2.27) and Thiamethoxam 25 WG (1:2.17) as compared to untreated control plot (1:1.60).

Study on financial assessment of rice production causing false smut disease of different varieties at farm level in Kushtia district

The present study was conducted to evaluate the false smut incidence and its effect on yield in different varieties, and to determine the financial cost, return and profitability of rice production during the year 2018–2019 in Kushtia district. The highest average farmers (65%) lost their yield 0.85 t/ha in 5 severity scale of BRRI dhan49, while Dhani Gold as hybrid variety exerted the lowest yield losses of 0.20 t/ha in 7% affected farmers. Spraying of Nativo (75 WG) 0.40 kg/ha increased the yield 34.87% over control, and Amister Top 325 SC was applied in the field that produced lower yield compared to Nativo. Tilt (250 EC) 0.45 l/ha and Folicur 0.90 l/ha also showed significant increase of yield over untreated control plot. The highest gross return of BRRI dhan39 was determined at Tk. 114753/ha with higher price and its fine quality. The lowest gross return and net return were estimated at Tk. 106958/ha and (−) Tk. 1215/ha, respectively, in Shorna cultivar due to higher incidence of false smut disease.

The effect of pre-drought mepiquat chloride management on cotton sensitivity to drought during peak water demands

Drought can substantially limit yield in cotton, and water loss in any crop is closely associated with plant growth, but studies addressing the effects of growth management on drought sensitivity are limited in cotton. We tested the hypothesis that aggressive plant growth management would decrease cotton sensitivity to drought during flowering and boll development. Cotton was grown at a field site near Tifton, GA during the 2021 and 2022 growing seasons. Treatments included mepiquat chloride (MC) strategies (aggressive and untreated) and two water availability treatments (well-watered and drought-stressed). At approximately 2 weeks after first flower, water was withheld from the drought-stressed treatment for a three-week period, and well-watered plots were kept irrigated using a regionally accepted water balance approach. Measurements throughout the season included heights, nodes, length of the fourth internode below the plant terminal, nodes above white flower (NAWF), and soil moisture. End-of-season measurements included lint yield, fiber quality, and yield component assessments. MC treatment significantly affected plant height, mainstem node number, 4th internode length, and cutout date. Soil moisture was significantly reduced during the drought stress period. Aggressive MC treated plots showed less drought-induced yield reduction than untreated in response to drought, but did not reach the same lint yield, boll density, or uniformity as well-watered, untreated plots. Aggressive MC treatment produced greater seed surface area, seed number boll-1, and boll mass. Aggressive MC management may prevent drought-induced yield reductions but penalize yield under well-watered conditions. Among the potential components driving yield, boll number per unit land area was the most important contributor. Our findings highlight the potential for aggressive MC management to mitigate drought risk, but future efforts should evaluate this possibility in a broader range of cultivars adapted for production in the southeastern United States and with the inclusion of a moderate MC treatment.

Efficacy of the Botanical Extracts, Azadirachta indica (Sapindales: Meliaceae) and Tagetes minuta (Asterales: Asteraceae) in the Control of Cabbage Insect Pests in Iringa District, Tanzania

Although botanical extracts have been widely studied globally, the efficacy of neem and Mexican marigold against cabbage insect pests is scanty. Field experiments were conducted at Kalenga and Mgera in 2022 using a randomized complete block design. Four treatments (neem, Mexican marigold, a mixture of the two extracts and untreated) were replicated three times. In Kalenga, damage levels for treated plots varied significantly from 3.33 to 9.20% and 5.0 to 18.33%, while for untreated plots varied from 37.70 to 45.85% during the rainy and dry seasons, respectively (F(3, 499) = 111.71, p < 0.05). A similar trend was recorded in Mgera, the damage levels varied significantly between treated (4.44–15.83%) and untreated plots (34.40–46.60%) (F(3, 449) = 94.23, p < 0.05). Treated plots had higher marketable cabbage yields (30.6–43.10 t/ha) than untreated plots (4.78–11.20 t/ha), which differed significantly in Kalenga (F (3, 67) = 141.79, p < 0.05) and Mgera (F (3, 67) = 53.36, p < 0.05). These extracts have shown insecticidal properties, can serve as promising candidates for further studies aimed at isolating active compounds for scaling up ecologically friendly strategies of controlling pests and improve the quality of cabbage products.

Efficacy of eco-friendly insecticides against yellow stem borer under spring rice crop ecosystem of Saptari district, Nepal

The study aimed to assess the effectiveness of eco-friendly insecticides in controlling yellow stem borer in spring rice crops of Hardinath-1 variety in Saptari district, Nepal. For this experiment, a Randomized Block Design was used with seven different treatments and an untreated control group. The treatments tested included Bacillus thuringiensis var kurtaski, Beauveria bassiana, Azadiractin 2.00%, garlic extract, tobacco extract, larvosin, and an untreated plot. The plots used were 3 × 4 meters in size and the plants were spaced 20 centimeters apart in both rows and between plants. The crop was sprayed twice, once during the vegetative stage and once during the reproductive stage, when the pest population reached a certain level. The incidence of dead heart was observed on ten randomly selected hills from each plot before and after the insecticide application, and observations on yellow stem borer incidence were recorded. Results showed that B. thuringiensis var kurtaski had the lowest dead heart infestation (0.4889%) and the minimum white head infestation (0.367%), as well as the highest mean yield (5.755mt/ha). Neembicide and B. bassiana also showed promising results.

Fruit Phenology of Two Hazelnut Cultivars and Incidence of Damage by Halyomorpha halys in Treated and Untreated Hazel Groves

Over the past decade, Halyomorpha halys has become one of the main threats to hazelnut production. Its trophic activity makes kernels inedible due to strongly detrimental effects on the organoleptic quality. Its management in Italy is still tricky due to the lack of effective native biocontrol agents and authorized and effective insecticides. A field test was performed on San Giovanni (SG) and Tonda Romana (TR) cultivars (early and late ripening, respectively) to assess the intensity of cimiciato damage with different pest management approaches (no insecticide and integrated pest management, IPM). Moreover, phenological analysis of fruits and the monitoring of stink bug species by traps and plant beating were carried out. In the untreated plots, the SG cv showed a higher cimiciato incidence with respect to the late TR cv (40% SG–NI vs. 23% TR–NI). This was probably due to the different phenological phases in which stink bugs injured the fruits. In fact, stink bug bites provoke different kinds of injuries (blanks, shriveled, and cimiciato) according to the fruit’s development period. Indeed, in the period of highest insect occurrence in the field, the fruits of the early cv (SG) were in kernel expansion, a phenological phase in which bug injuries are more likely in cimiciato defects. Lastly, the IPM did not provide sufficient fruit protection (19% SG–IPM vs. 11% TR–IPM). The interaction between the phenological development of hazelnuts and the brown marmorated stink bug represents a critical aspect in understanding and implementing effective strategies for controlling this key pest on hazelnut trees.

Changes in overall and inter-variability of runoff and soil loss for a loess soil resulted from a freezing-thawing cycle.

The soil freeze-thaw process is a transition phase of soil water in cold areas that influences the soil's hydrological behavior. However, dynamic phenomena and corresponding consequences have yet to be studied adequately. Therefore, the present study was planned to comparatively analyze the effects of a freezing-thawing cycle on the hydrologic behaviors of loess soil from northeast Iran. Small-size (0.5 × 0.50m) erosion plots were subjected to a freezing-thawing cycle under governing conditions of the region of the origin soil. The plots were subjected to a freezing-thawing treatment by inducing cold air until the temperature declined to below - 20°C and lasted for 3days using a cooling compartment system and then were kept in the laboratory with an ambient temperature of above 10°C for 2days. The treated plots and untreated plots were then exposed to a simulated rainfall with an intensity of 72mmh-1 and 0.5h duration while they were placed on a slope of 20%. The results indicated that the hybrid processes of freezing-thawing and splash and inter-rill erosions significantly increased runoff generation and soil loss. The time to runoff, runoff volume, and soil loss were 1.65 times less and 1.38 and 2.90 times more, respectively, compared to those reported for the control treatment with significant differences (p < 0.006). The performance of ice lenses, freezing fronts, and the creation of near-saturation moisture after completing the cycle were identified as the most critical factors affecting the different soil behaviors under the frozen-thawed cycle.

Efficacy of Selected Chemicals and Biopesticides against Chickpea Gram Pod Borer

The field experiment was carried out in the Rabi season of 2022-2023 at Central Research Farm (CRF), Sam Higginbottom University of Agriculture, Technology And Sciences, Prayagraj. The field was replicated with three randomised block design (RBD) of eight treatments including control (water spray) viz., Indoxacarb 14.5% SC, Chlorantraniliprole 18.5% SC, Emamectin benzoate 5% SG, Emamectin benzoate 5% SG+Indoxacarb14.5% SC, Beauveria bassiana 1.5% WP, NSKE 5%, Neem oil 5% and one control plot (water spray). The maximum reduction of larval population was recorded in T3 Emamectin benzoate 5% SG (78.9%) followed by T2 Chlorantraniliprole 18.5% SC (76.2%), T4 Emamectin benzoate 5% SG + Indoxacarb 14.5% SC (68.2%), T1 Indoxacarb 14.5% SC (65.8%), T6 NSKE 5% (59.3%), T5 Beauveria bassiana 1×108CFU\G (54.7%) was found next effective treatments. Among all the treatments T7 Neem oil 5% (49.4%) was found least effective but comparatively superior over untreated plot (0%).

Evaluation of the Dynamic Tube Method for Measuring Ammonia Emissions after Liquid Manure Application

Easy and inexpensive methods for measuring ammonia emissions in multi-plot field trials allow the comparison of several treatments with liquid manure application. One approach that might be suitable under these conditions is the dynamic tube method (DTM). Applying the DTM, a mobile chamber system is placed on the soil surface, and the air volume within is exchanged at a constant rate for approx. 90 s. with an automated pump. This procedure is assumed to achieve an equilibrium ammonia concentration within the system. Subsequently, a measurement is performed using an ammonia-sensitive detector tube. Ammonia fluxes are calculated based on an empirical model that also takes into account the background ammonia concentration measured on unfertilized control plots. Between measurements on different plots, the chamber system is flushed with ambient air and cleaned with paper towels to minimize contamination with ammonia. The aim of this study was to determine important prerequisites and boundary conditions for the application of the DTM. We conducted a laboratory experiment to test if the ammonia concentration remains stable while performing a measurement. Furthermore, we investigated the cleaning procedure and the effect of potential ammonia carryover on cumulated emissions under field conditions following liquid manure application. The laboratory experiment indicated that the premeasurement phase to ensure a constant ammonia concentration is not sufficient. The concentration only stabilized after performing more than 100 pump strokes, with 20 pump strokes (lasting approximately 90 s) being the recommendation. However, the duration of performing a measurement can vary substantially, and linear conversion accounts for those differences, so a stable concentration is mandatory. Further experiments showed that the cleaning procedure is not sufficient under field conditions. Thirty minutes after performing measurements on high emitting plots, which resulted in an ammonia concentration of approx. 10 ppm in the chamber, we detected a residual concentration of 2 ppm. This contamination may affect measurements on plots with liquid manure application as well as on untreated control plots. In a field experiment with trailing hose application of liquid manure, we subsequently demonstrated that the calculation of cumulative ammonia emissions can vary by a factor of three, depending on the degree of chamber system contamination when measuring control plots. When the ammonia background values were determined by an uncontaminated chamber system that was used to measure only control plots, cumulative ammonia emissions were approximately 9 kg NH3-N ha−1. However, when ammonia background values were determined using the contaminated chamber system that was also used to measure on plots with liquid manure application, the calculation of cumulative ammonia losses indicated approximately 3 kg NH3-N ha−1. Based on these results, it can be concluded that a new empirical DTM calibration is needed for multi-plot field experiments with high-emitting treatments.

Synergistic effects of the entomopathogenic fungus Isaria javanica and low doses of dinotefuran on the efficient control of the rice pest Sogatella furcifera

The rice planthopper, Sogatella furcifera, is a piercing-sucking insect pest of rice, Oryza sativa. It is responsible for significant crop yield losses, and has developed moderate to high resistance to several commonly used chemical insecticides. We investigated the effects of the insect fungal pathogen Isaria javanica, alone and in combination with the chemical insecticide dinotefuran, on S. furcifera under both laboratory and field conditions. Our results show that I. javanica displays high infection efficiency and mortality for different stages of S. furcifera, reducing adult survival, female oviposition and ovary development. Laboratory bioassays showed that the combined use of I. javanica with a low dose (4–16 mg L–1) of dinotefuran resulted in higher mortality in S. furcifera than the use of I. javanica or dinotefuran alone. The combined treatment also had more significant effects on several host enzymes, including superoxide dismutase, catalase, peroxidase, and prophenol oxidase activities. In field trials, I. javanica effectively suppressed populations of rice planthoppers to low levels (22–64% of the level in untreated plots). Additional field experiments showed synergistic effects, i.e., enhanced efficiency, for the control of S. furcifera populations using the combination of a low dose of I. javanica (1×104 conidia mL–1) and a low dose of dinotefuran (~4.8–19.2% of normal field use levels), with control effects of >90% and a population level under 50 insects per 100 hills at 3–14 days post-treatment. Our findings indicate that the entomogenous fungus I. javanica offers an attractive biological control addition as part of the integrated pest management (IPM) practices for the control of rice plant pests.

Compositional variation in grassland plant communities

AbstractHuman activities are altering ecological communities around the globe. Understanding the implications of these changes requires that we consider the composition of those communities. However, composition can be summarized by many metrics which in turn are influenced by different ecological processes. For example, incidence‐based metrics strongly reflect species gains or losses, while abundance‐based metrics are minimally affected by changes in the abundance of small or uncommon species. Furthermore, metrics might be correlated with different predictors. We used a globally distributed experiment to examine variation in species composition within 60 grasslands on six continents. Each site had an identical experimental and sampling design: 24 plots × 4 years. We expressed compositional variation within each site—not across sites—using abundance‐ and incidence‐based metrics of the magnitude of dissimilarity (Bray–Curtis and Sorensen, respectively), abundance‐ and incidence‐based measures of the relative importance of replacement (balanced variation and species turnover, respectively), and species richness at two scales (per plot‐year [alpha] and per site [gamma]). Average compositional variation among all plot‐years at a site was high and similar to spatial variation among plots in the pretreatment year, but lower among years in untreated plots. For both types of metrics, most variation was due to replacement rather than nestedness. Differences among sites in overall within‐site compositional variation were related to several predictors. Environmental heterogeneity (expressed as the CV of total aboveground plant biomass in unfertilized plots of the site) was an important predictor for most metrics. Biomass production was a predictor of species turnover and of alpha diversity but not of other metrics. Continentality (measured as annual temperature range) was a strong predictor of Sorensen dissimilarity. Metrics of compositional variation are moderately correlated: knowing the magnitude of dissimilarity at a site provides little insight into whether the variation is driven by replacement processes. Overall, our understanding of compositional variation at a site is enhanced by considering multiple metrics simultaneously. Monitoring programs that explicitly incorporate these implications, both when designing sampling strategies and analyzing data, will have a stronger ability to understand the compositional variation of systems and to quantify the impacts of human activities.

MANAGEMENT OF RED PUMPKIN BEETLE AND FRUIT FLY IN ASH GOURD USING BIORATIONAL INSECTICIDES

Ash gourd Benincasa hispida Thumb., a cucurbit vegetable, faces frequent infestation of red pumpkin beetle and cucurbit fruit fly. Farmers in Bangladesh mainly apply conventional synthetic insecticides to protect crops from the attack of these pests. The current study was conducted in the experimental field of the Department of Entomology, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur during March 2021 to July 2021 to know the effects of five biorational insecticides, namely Biotrin (matrine), Proclaim (emamectin benzoate), Sunmectin (abamectin), Mahogany oil and Neem oil on the abundance and infestation of red pumpkin beetle and fruit fly infesting ash gourd. The insecticides were applied 3 times maintaining 7 days interval. Results showed significant reduction of the insect population compared to untreated control. Sunmectin (1.55±0.34) treated plot showed the lowest abundance of red pumpkin beetle after the 3rd spray with 65% reduction of population compared to untreated control plot. Biotrin (8.59±1.00%) treated plot showed the lowest leaf and flower infestation by red pumpkin beetle after 3rd spray, with the reduction (69% in both) over control. The lowest fruit infestation was found in Sunmectin treated plot (23.01±8.05%). The highest yield of ash gourd (17.9 T/ha) was recorded from Sunmectin treated plot which showed statistical similarity to Proclaim (16.01 T/ha) and Biotrin (15.90 T/ha) treated plots with 3.5, 2.5 and 2.6 benefit cost ratio, respectively. Therefore, it could be concluded that Sunmectin, Proclaim and Biotrin were more effective to control the infestation of red pumpkin beetle and fruit fly of ash gourd than the other tested insecticides.

Evaluation of pre-emergence herbicides for weed management and rice yield in direct-seeded rice in Cambodian lowland ecosystems

Poor weed management in direct-seeded rice (DSR) at crop establishment stage has led to the need to explore different pre-emergence herbicides to reduce weed biomass and increase DSR yield in Cambodian lowland ecosystems. This study evaluated weed and yield responses to pre-emergence herbicides (pendimethalin, pretilachlor, butachlor, oxadiazon and no application as the control) under different weed management options during the 2018 and 2019 early wet seasons in farmers’ rice fields. All pre-emergence herbicides reduced weed flora and pendimethalin was most effective in controlling the population of mainly grassy weeds. Pendimethalin significantly reduced weed dry biomass by 36.2% (21.3 ​g ​m−2) in 2018 compared with the untreated control. In 2019, weed dry biomass was significantly reduced by 46% (17.9 ​g ​m−2) with butachlor compared with the untreated plot. Pendimethalin increased toxicity in rice plants, which decreased SPAD (leaf greenness) by 44.8% and tiller numbers by 39.3% at 7 days after herbicide application (DAPH) compared with butachlor, but plants recovered from pendimethalin toxicity at 14 DAPH. In 2018, oxadiazon herbicide significantly increased grain yield by 61% (4.6 ​t ​ha −1) compared with the untreated control, but oxadiazon produced similar grain yields as pendimethalin. In 2019, there was no significant effect of pre-emergence herbicides on yield but butachlor produced the highest rice yield (3.2 ​t ​ha−1) followed by pendimethalin (2.8 ​t ​ha−1) and oxadiazon (2.7 ​t ​ha−1). Our study demonstrated that pre-emergent herbicides function differently under varying soil-water conditions in 2018 and 2019, therefore rice growers can use butachlor to control weeds in dryer soil conditions and potentially use pendimethalin to control weeds in good soil moisture conditions. This information is crucial and safe in developing appropriate strategies to manage weeds and enhancing DSR productivity in lowland ecosystems.