Untreated Plots Research Articles

Preliminary Evaluation of Onion Bulb and Tobacco Leaf Extracts for Insect Control and Yield of Cowpea in the Southern Guinea Savanna of Nigeria

The study evaluated the effects of onion (Allium cepa) bulb and tobacco (Nicotiana tabacum) leaf extract on the insect pests and yield components of cowpea. The extracts were tested on number of the flower thrips, Megalurothrips sjostedti Trybom, the pod-sucking bug, Clavigralla tomentosicollis Stal, the pod borer, Maruca vitrata (F.) and cowpea aphid, Aphis craccivora Koch. Also evaluated were the dry seed weight, 100-seed weight, pod length, number of pods per plant, number of seeds per pod, pod load, pod damage and pod evaluation index. Field experiment was conducted in the Faculty of Agriculture, University of Ilorin, Ilorin, Nigeria. Plots were laid out in a randomized complete block design with three replications. Treatments included 10% (w/v) of each of onion bulb and tobacco leaf extracts, synthetic insecticide (Cypermethrin 1 L/ha) and untreated control. Results revealed that cowpea treated with the plant extracts had significantly (p<0.05) lower insect pest population than plants in untreated plots which suffered greater insect pest attack. However, plots treated with Cypermethrin produced significantly higher number of seeds per pod than other treatments. Nevertheless, tobacco leaf extract produced significantly (p<0.05) heavier 100-seed weight than other treatments including the control. It could be concluded that the plant extracts had potential to replace the synthetic insecticide for control of insect pests of cowpea, thus ensuring environmental safety.

Evaluating Coastal Douglas Fir Growth Responses to Nitrogen Application Using Tree Ring Chronologies

Dendrochronology is a technique that can be applied as a retrospective monitoring (RM) approach to evaluate the performance of nutrient application in forest ecosystems. Applying the RM approach across operations lacks experimental controls, which may adversely affect accuracy and precision of estimates due to greater mismatches in stand conditions between treated and untreated plots. To test the rigor of the RM approach, we collected increment cores of coastal Douglas fir (Pseudotsuga menziesii var. menziesii) at eight sites of an experiment where stands were fertilized in 1971. First, we tested the approach under ideal conditions by sampling from treated and untreated plots of the experiment. Second, we tested the approach using newly established surrogate control (SC) plots, which differed in ecological site classification from those of the treated plots to understand how robust the approach was to mismatches in conditions between treated and untreated samples. We hypothesized that detrending ring width would mitigate error in responses to nutrient application resulting from mismatches in site classification. Within the experiment, the approach indicated an average increase of 15% (5% to 26%, p < 0.05) growth response to operational doses of urea. Different responses were found when the analysis relied on SC plots. Detrending low-frequency variation in ring widths eliminated differences in results arising, at least in part, to mismatches in site class. However, it also reduced the growth response using the experimental control plots to 10%. Dendrochronology with detrending shows promise in the ability to mitigate variation introduced by mismatches in ecological site classification that may occur in operational monitoring. Based on these results, we see potential to implement RM with operations to evaluate and optimize stand selection criteria.

A Biopesticides and their impact on brinjal Jassid (Amrasca biguttula biguttula Ishida)

Brinjal (Solanum melongena) is a precious and nourishing vegetable grown worldwide in tropical and subtropical climates. Jassid (Amrasca biguttula biguttulaI.) (Hemiptera: Cicadellidae),of which nymphs and adults suck the cell sap from the underside of the brinjal leaves resulting in curling and affecting the photosynthesis process. The present study aimed to study the effectiveness of biopesticides and their impact on jassid and its natural enemy in different seasons. The field experiment arranged in randomized block design includes six biorational insecticides such has (T1)-Spinosad 45 % SC @ 0.4ml/l, (T2)-Neem Seed Kernel Extract(NSKE) 1% @ 2ml/l, (T3)-Beauveria bassiana 1x 108 @ conidia/ml @ 10ml/l, (T4)-Metarhizium anisopliae1x 108 conidia/ml @ 10ml/l, (T5)-Verticillium lecanii 1x108 conidia/ml @ 10ml/land (T6)-Untreated plots replicated in four times. It is resulted that all the biorational pesticides performed significantly better than the control. However, among the treatments, application of (T3)-Beauveria bassiana 1x108 conidia/ml @ 10 ml/l and (T2)-Neem Seed Kernel Extract (NSKE) 1% @ 2 ml/l was found to have significantly better results against jassid,during Rabi(2021) and Kharif season (2022) respectively. For predatory coccinellids,(T2) - Neem Seed Kernel Extract (NSKE) 1% @ 2 ml/l and(T1)-Spinosad 45 % SC @ 0.4ml/l were found to be better compared to other treatments in Rabi and Kharif season. This research will help to understand the importance of biopesticides with eco-friendly approaches to manage jassid.

Effects of Planting Density and Nitrogen Fertilization on the Growth of Forage Rice in Reclaimed and General Paddy Fields.

The purpose of this study is to identify the different effects exerted by planting density and nitrogen fertilization on high-salinity reclaimed paddy fields (RPF) and general paddy fields (GPFs), and to find the amount of fertilization and the planting density suitable for the growth of forage rice in each paddy field. Nitrogen fertilization with high-salt and low-salt soils, an untreated control plot, treatment with 200 kg/ha, 300 kg/ha, and 400 kg/ha, and planting densities of 30 cm × 10 cm and 30 cm × 16 cm, growth, and feed values were investigated. In both experimental locations, there was no significant change in the soil due to N treatment, but in the case of RPF, electrical conductivity (EC) decreased significantly from more than 5 dS/m to up to 2.87 dS/m during the yellow ripe stage due to the influence of floods and concentrated precipitation in the fields. In all soils, as both the amount of N treatment and the planting density increased, there was a proportional relationship in which the number of tillers and the dry weight also increased, with the occurrence of lodging also being increased. The dry weight, as expected, was 1.5 times higher at a planting distance of 10 cm, rather than 16 cm. In addition, in both locations, the N treatment led to an increase in the dry weight, but when N treatment reached 400 kg/ha (2.0), the dry weight decreased instead. Moreover, although there was no clear difference in feed value according to N treatment, in RPF, the neutral detergent fiber (NDF) was higher than 60%, the relative feed value (RFV) was less than 98, and the total digestible nutrient (TDN) was also low, confirming that the quality of rice was higher in GPF.

Efficacy of Eco-Friendly Bio-Pesticides against the Whitefly Bemisia tabaci (Gennadius) for Sustainable Eggplant Cultivation in Kebbi State, Nigeria

The eggplant (Solanum melongena L.) is among the vital fruit vegetables cultivated globally for its health and nutritional benefits. However, its production has been hindered by whiteflies (Bemisia tabaci G.) infestation worldwide. This study aims to assess the effect of some bio-pesticides in the control of whiteflies on eggplants under field conditions. The trial consists of seventeen (17) treatments replicated three times for 45 days. From the results obtained, neem leaf extract (60 mL/L) proved more effective against whiteflies, with 1.2 and 1.3 adults/leaf, while buttermilk and cow dung (50 mL/L) were less effective (10.1 and 10.8 adults/leaf) when compared to untreated plots (26.9 and 33.4 adults/leaf), two weeks after the third spray during the first and second trials. The highest reduction (%) in whitefly population was found using neem leaf extract (95.7 and 96.1%) and cow urine (85.8 and 96.1%), with cow dung and buttermilk exhibiting the least overall averages (65.9 and 62.3%), two weeks after the third spray during the respective trials. Neem extract and cow urine were more effective among the treatments examined and, thus, recommended to be incorporated into control strategies of whiteflies for the improved production of eggplants in the area.

A Study of the Toxic Effect of Plant Extracts against Philaenus spumarius (Hemiptera: Aphrophoridae).

The meadow spittlebug Philaenus spumarius (Hemiptera: Aphrophoridae) is distributed in several habitats worldwide and has been recently recognized as the main vector of Xylella fastidiosa subsp. pauca. This bacterium has been associated with olive quick decline syndrome (OQDS) in the Salento Peninsula (Italy) and is responsible for extensive desiccation and die-off of olive trees. Current OQDS management strategies include the control of P. spumarius populations, mainly through the removal of weed hosts and insecticide treatments. In addition to the mandatory phytosanitary measures, the demand for new strategies compatible with integrated pest management is increasing. In this study, laboratory biological assays were performed to assess the potential toxic effect of vegetal formulations against P. spumarius adults. Two formulations were tested at different concentrations: Form A, an emulsion of 10% hot pepper-infused oil (Capsicum annuum subspecies Cayenna in olive oil) and Arabic gum in an aqueous solution of extracts of Salvia guaranitica, and Form B, an aqueous solution of extracts of Taxus baccata. Both Form A and B showed to be toxic against P. spumarius compared to the water control. The mean percentage of spittlebug mortality obtained with Form A one hour after treatments was dose-dependent; the lethal dose values were 0.13% (LD25), 0.36% (LD50), and 0.85% (LD75). At the same time, no significant differences in mortality rate were observed between the 0.75% treatment and the treatments with deltamethrin (about 90%). The mean percentage of spittlebug mortality obtained with Form B ranged from 21% to 53% one hour after treatment, but these values were significantly lower than those obtained with deltamethrin. The effectiveness of Form A on the P. spumarius population was also evaluated in the field. The averages of captures in the three experimental blocks were 1.8/trap for treated and 7.7/trap for untreated plots, and the spittlebug populations significantly decreased after treatments. Based on these results and the literature data, we hypothesize that the effectiveness of Form A is the result of the synergistic effect of all its components. No symptoms of phytotoxicity were recorded on olive trees treated with Form A, and the number of P. spumarius specimens collected on these plants was much lower than on untreated plants. These results suggest the potential use of Form A in the protection of olive trees. This vegetal formulation can thus be considered as a valid alternative to chemical insecticides for the control of the main vector of X. fastidiosa and could be integrated into a sustainable management system for OQDS.

Maintaining an open landscape: Comparison of management methods for semi-natural grasslands: A Swedish multi-site study

Traditional management of semi-natural grasslands by grazing or annual mowing is not always feasible and the current study set out to evaluate alternative management methods. At eleven locations in southern Sweden, block experiments were conducted evaluating seven treatments in 5 m*20 m plots: grazing, annual mowing, annual spring burning, mowing every third year, mechanical removal of woody plants, herbicide control of woody plants, and untreated control. After approximately 13 years, trends for woody plants and species richness, and the occurrence of management-dependent plant species, low-grown species, and pollinator-attracting plant species were analysed. Overall, the annual mowing and grazing treatments resulted in fewer woody plants, the highest species richness, and more management-dependent, low-grown, and pollinator-attracting species. The untreated control plots showed the opposite effect, whereas less intense management (annual burning, mowing every third year, and mechanical and chemical treatments of woody plants) showed mixed and often intermediate effects. Compared to grazing and mowing, less intense management methods do not constitute long-term management alternatives to preserve typical features of species-rich grasslands. However, they may be short-term alternatives at sites where the recruitment of woody species is absent or rare. However, to prevent the encroachment of woody species, less intensive management might be a better long-term alternative at more productive sites with slow or inhibited woody species recruitment.

Field and Management Factors Can Reduce Potato Early Blight Severity: an Observational Study on Farms Combined with Field Trials in Southern Sweden

Alternaria solani is causing early blight and thereby yield reduction in the potato production. The pathogen is today mainly controlled by fungicide applications. The severity of early blight can vary largely among fields. The aim of this study was to gain understanding of what field and management parameters are the most important for early blight severity to create more farm-specific fungicide treatment recommendations. Over three seasons, 2019–2021, 52 field plots were observed at farms in southern Sweden. In each field a 24 m × 24 m plot was left untreated against early blight. However, late blight fungicides were applied. The disease severity was scored twice in the untreated plot and information about various soil/plant parameters and farmer’s management was collected from each field. In addition to the observational study, field trials were performed in 2021 and 2022, evaluating the effect of potassium fertiliser levels on severeness of infection. We found that the soil composition was of significant importance for the severity of infection, in particular the sand, clay, and potassium content. The early blight severity was directly positively correlating with a high sand content. Low levels of leaf potassium increased the severity of early blight infection, and this observation was confirmed in field trials where different levels of potassium fertiliser were applied. Further no reduction in disease severity was observed with a four-year crop rotation. With knowledge about field and management factors that influence disease, field-specific recommendations can be developed supporting an integrated pest management strategy for early blight to reduce and optimise the fungicide usage.

Optimal treatment against Athelia rolfsii rot in processing tomatoes using pesticide and rootstock against key stages of the disease

The soilborne fungus Athelia rolfsii (synonym Sclerotium rolfsii) causes stem or collar rot in tomato (Lycopersicon esculentum Mill.). We aimed to develop an optimal treatment for A. rolfsii in processing tomatoes in Israel through an understanding of the key developmental stages of the plant that are susceptible to disease development. We tested two approaches: best timing for pesticide application, and grafting onto a tolerant rootstock. The fungus attacked processing tomatoes at two stages: (i) immediately after planting, when the root neck is attacked and the young plant wilts, and (ii) in the last month of growth, when the humidity under the foliage increases, temperatures are high, and the root neck, shoot and fruit, which are lying on the ground, are susceptible to pathogen attack. The number of infected plants was significantly reduced after incorporating azoxystrobin at 2.5 and 5 L a. i./ha in the soil preplanting, and applying the combination fungicide Nativo (a.i. tebuconazole and trifloxystrobin) at 0.75 kg/ha in the drip-irrigation system (chemigation) once, 60–90 days after planting. This treatment enhanced total yield by up to 35.2% and marketable yield by up to 33.7% relative to untreated plots. Grafting to a resistant rootstock significantly reduced plant wilting in the first weeks of growth to less than 1% of the plants, and enhanced fruit yield up to four fold. In soil with a history of infestation, A. rolfsii infection should be treated during the plants’ susceptible stages: preventive azoxystrobin treatment preplanting, and a single treatment of Nativo later on to prevent infection and decay, especially for late harvest; grafting to a resistant rootstock can also reduce infection in the early stages of growth and enhance yield. In this study, we show for the first time that A. rolfsii infection in processing tomato can be dramatically decreased with minimal pesticide application against key stages of the disease and rootstocks.

Glycerin‐based dispensers of fir oil reduce response of Asian citrus psyllid, Diaphorina citri, to citrus odours

AbstractThe Asian citrus psyllid, Diaphorina citri Kuwayama, transmits the bacterial pathogen associated with huanglongbing, a fatal citrus disease. Alternatives to insecticides for D. citri management are being explored, given the development of insecticide resistance and the lack of efficient biological controls. Essential oils as pest repellents have shown some efficacy in laboratory and field evaluations; however, lack of an effective dispenser for field deployment has prevented their application. In this investigation, we evaluated glycerin‐based dispensers releasing fir (Abies spp.) oil as repellents for D. citri. In olfactometer tests, glycerin dispensers loaded with fir oil at 20% w/w repelled psyllids from citrus odours but did not cause repellency at lower loading dosages. Field evaluations were conducted with dispensers at the 20% loading dosage based on laboratory results. In open‐air cage bioassays, fewer psyllids alighted on trees treated with 2 dispensers per tree than on control trees. Similarly, fewer psyllids were found on mature lime trees in homeowner landscapes treated with 4 dispensers per tree compared to paired control trees. In small plot experiments in commercial grapefruit, psyllid infestation of young leaf flush shoots was reduced in plots treated with at least 250 dispensers/ha compared to untreated control plots. Our results indicate that these glycerin‐based fir oil dispensers can reduce infestation of citrus by D. citri. However, the efficacy observed within replicated small plots of citrus grown in monoculture was judged insufficient to manage this vector as a stand‐alone treatment. Larger scale evaluations at higher loading dosages of fir oil and/or in combination with other management tools are warranted based on the outcomes of these initial experiments.

Use of Selected Chemical and Biological Insecticides to Control Lepidopteran Pests of Maize Fields in Central Côte d'Ivoire

Control of lepidopteran larvae, the main pests in maize fields, has become necessary since the appearance and spread of Spodoptera frugiperda. The study was carried out at the Institut National Polytechnique Houphouët-Boigny in Yamoussoukro (Central Côte d’Ivoire). The study aimed to determine the effectiveness of three chemical - Viper 46 EC (Acetamiprid 16 g/l and Indoxacarb 30 g/l), K-Optimal 35 EC (Lambdacyhalothrin 15 g/l and Acetamiprid 20 g/l) and Ampligo 150 ZC (Chlorantanlipol 100 g/l and Lambdacyhalothrin 50 g/l) - and one biological insecticide Bio-Elit (Azadirachtin, Salanin, Nimbin and Melandriol) on lepidopteran larvae in maize fields using a randomized complete block design with five treatments and three repetitions. Data on insect identification, plant infestation, damage, and yield were collected. Insects’ identification was based on morphology using identification keys. Plant damage was assessed by visually estimating the plant health status (unattacked and attacked plants). Grain dry weight was used to estimate field yield. The encountered maize field insects belonged to 10 orders: Heteroptera, Hymenoptera, Homoptera, Coleoptera, Diptera, Dictyoptera, Odonata, Orthoptera, Dermaptera, and Lepidoptera. Five lepidopteran pest larvae have been recorded. Three of them were classified as minor pests (Eldana saccharina, Ostrinia nubilalis, and Helicoverpa zea), one as important (Sesamia calamistis), and one as a major pest (Spodoptera frugiperda). On untreated plots, more than 76% of plants were moderately to heavily attacked. However, on treated plots, plants showed isolated to moderate attacks. Insecticide sprayings controlled pest populations, reduced damage, and increased yield. The yields obtained on untreated plots (2.26±0.21 t/ha) were lower than those on treated plots (3.29±0.11 to 3.60±0.09 t/ha). The yield increase rate ranged from 45.74 to 59.63%. The best control was recorded with Ampligo (59.63%) and Bio-Elit (50.83%) compared to Viper (49.41%) and K-Optimal (45.74%). Therefore, the alternating use of synthetic or biological insecticides, which are not very toxic for humans and the environment but are effective on insect pests, increases the effectiveness of the control and provides a positive response to the problem of pest resistance while protecting the environment.

Evaluation of variable doses of tachnid fly, <i>Sturmiopsis inferens</i> for the management of <i>Sesamia inferens</i> under field conditions in rice and wheat

Evaluation of variable doses of tachnid fly, Sturmiopsis inferens for the management of pink stem borer, Sesamia inferens under field conditions in basmati rice (var. Pusa Basmati 1121) and wheat (var. HD 2967) was carried out at a farmer’s field in Ludhiana. Two intervals, i.e. one at 10 days and the other at 15 days were followed for releasing different doses (75, 100, 125 and 150 gravid females/ha) of S. inferens during August-October in rice and November-December in wheat. In case of Basmati rice, the minimum incidence of Sesamia inferens was recorded in treatment where a higher dose of 150 gravid females per ha was released (1.05 % DH at 75 DAT, 1.09 % WE), which was significantly at par with the dose of 125 gravid females per ha. The untreated control plot observed the highest incidence of Sesamia inferens (1.81% DH, 2.11% WE). The observations on grain yield revealed that higher doses of 125 and 150 per ha were significantly superior (37.90-38.41 q/ha) while doses of 100 and 75 per ha were at par with each other (36.35 and 36.91 q/ha, respectively) and minimum grain yield was recorded in untreated plots (34.73 q/ha). In the case of wheat, the minimum incidence was recorded in a treatment where a higher dose of 150 gravid females per ha was released (1.49% DH at 45 DAS, 1.28% WE), which was significantly at par with the dose of 125 gravid females per ha (1.66 % DH at 45 DAS, 1.50% WE). The untreated control plot observed the highest incidence (2.48 % DH at 45 DAS, 2.65% WE). The higher doses of 125 and 150 per ha were significantly superior in terms of grain yield (46.68-47.17 q/ha), while doses of 100 and 75 per ha gave a yield of 45.41 and 44.13 q/ha, respectively.

Cultural control methods improve management of leafhopper vector of X-disease

X-disease, caused by the phytoplasma ‘Candidatus Phytoplasma pruni’, is currently threatening Pacific Northwest (USA) stone fruit (Prunus) production, particularly sweet cherry (P. avium). There is no cure, and infected fruit remain unmarketable throughout the tree's life. Management efforts focus on reducing transmission through infected tree removal and frequent chemical applications to control the leafhopper vectors. The increase in chemical inputs has broken down stone fruit integrated pest management techniques and is neither economically nor environmentally sustainable. To investigate sustainable vector management, we assessed the efficacy of two long-lasting cultural management techniques, kaolin clay (Surround WP) and reflective plastic geotextile (Extenday), to deter leafhoppers from trees and prevent population growth within orchards. These methods were tested against untreated control plots in Washington State commercial stone fruit blocks in 2021 and 2022. Colladonus montanus reductus (Van Duzee) was the most abundant leafhopper vector species captured in both years. In cherry blocks, Extenday consistently reduced C. m. reductus densities by 80–90%, while kaolin clay caused a 45–50% reduction in leafhoppers, but only when they were abundant (more than 10 leafhoppers per trap). Sticky cards placed at varying heights revealed that kaolin clay caused C. m. reductus to be proportionally more abundant near the ground cover than in the tree canopy regardless of overall population density. The combination of reducing C. m. reductus density and shifting their distribution into the ground cover demonstrates both plastic geotextiles and kaolin clay provide effective post-harvest strategies for X-disease vector management.

Effect of Acibenzolar-S-Methyl on severity of Fusarium wilt and fruit yield of two tomato cultivars

Tomato wilt caused by Fusarium oxysporum f.sp. lycopersici (Fol) is one of the limiting factors to tomato production in the whole world because of its negative effect on the fruit yield of tomato. The study investigated the application of Acibenzolar-S-Methyl (ASM), a plant activator that stimulates plants’ defence mechanisms, at different concentrations (0, 25, 35 and 45 mg/L) on two tomato genotypes (Delila and Kerewa) using drenching method. Factorial experiments were laid out in a randomized complete block design and completely randomized design in both field and the screenhouse, respectively. Results showed that the application of ASM significantly reduced (p≤0.05) disease severity. At 9 weeks after transplanting Delila recorded severity scores of 3.00 and 3.33(screenhouse) and 0.33 (field) while Kerewa had severity scores of 1.33 and 1.50 (screenhouse) and 0.33 (field) when ASM was apllied at 35 and 45 mg/L concentrations, respectively. These values were significantly lower (p≤0.05) than those recorded in untreated plots. Delila yielded 151.23 and 151.73 kg/ha (screenhouse), and 754.70 and 795.8 kg/ha (field) while Kerewa yielded 109.60 and 124.03 kg/ha (screenhouse) and 601.10 and 279.8 kg/ha (field) when ASM was apllied at 35 and 45 mg/l concentrations, respectively. Yields in both screenhouse and the field were significantly higher (p≤0.05) than yields in the untreated control plots. The study concluded that application of ASM at 35 and 45 mg/L to tomato could enhance its resistance which would translate to fruit yield increase.

Effects of post-fire application of straw mulch strips on soil erosion, soil moisture and vegetation regeneration in European dry heathlands in NW Spain

Applying mulch to severely burned soils is common practice in fire-prone areas such as the NW Spain. Mulch that provides >80% cover can reduce post-fire soil erosion by up to 90%; however, this level of cover can sometimes be difficult to achieve in remote areas due to the logistic constraints. Although application of mulch strips is a possible alternative approach, there is no information available about the effectiveness of this technique. Such information is critical in protected areas where mulch application can modify the recovery of natural vegetation by altering the soil moisture regime.In this study, the effects of the application of 20 m wide straw mulch strips on soil erosion, soil moisture and vegetation recovery were assessed during the first year after a high-severity fire that occurred in September 2020 in two European dry-heathland areas.During the first year after the fire, the mean sediment yields in the untreated plots were 18.5 Mg ha−1 and 33.8 Mg ha−1, respectively at the Lobios and Vilariño study sites. Although the straw mulch strips reduced soil erosion by >70% on average, erosion rates remained high at both sites. Soil moisture contents in mulch-treated areas were significantly higher than in untreated areas during spring and summer.Mulching affected vegetation recovery in different ways, i.e., it had neutral to positive effects, depending on the study site. No alteration in species composition was observed in either of the sites as a result of treatment application.In summary, the reduction in soil erosion after the application of straw mulch strips covering 67% of burned soil under the conditions of the present study under the conditions of the present study reduced a 70–75% of soil erosion after a high-severity wildfire.

Mechanical forest restoration treatments stimulate understory plants in the Colorado Front Range

Restoration efforts are underway in dry conifer forests across the western United States to increase their resilience to wildfire and other disturbances. Because such treatments typically decrease overstory density and homogeneity, they can also drive changes in the understory plant community. Past studies of post-treatment changes in understories have found variable results over short time frames and across regions, highlighting the need to study longer-term, region-specific responses. We investigated whether mechanical restoration treatments benefited understory plants in dry conifer forests of the Colorado Front Range, and what biotic and abiotic variables modified understory plant responses in treated areas. We analyzed data collected 1–2 years pre-treatment, 1–2 years post-treatment, and 4–6 years post-treatment in 168 plots, which were distributed across 8 sites and 16 pairs of treated and nearby untreated areas. Treatments were implemented by removing trees with heavy machinery or hand tools (i.e., thinning). By the time treatments were 4–6 years old, native understory plant cover was 1.7 times higher in treated compared to untreated plots, and native richness was 1.1 times higher. Heightened cover and richness values in treated plots were not driven by a single native plant functional group, but by a large portion of the native community; long-lived, graminoid, vegetatively spreading, and non-vegetatively spreading plants all had higher cover in treated plots, while short-lived, long-lived, forb, graminoid, and non-vegetatively spreading plants had higher richness in treated plots. Non-native plants showed 3.1 times higher cover and 4.4 times higher richness in treated compared to untreated plots at 4–6 years post-treatment, but were present at very low levels (e.g., ≤ 0.5% mean cover in either treatment). Greater native plant cover and richness at 4–6 years post-treatment were associated with lower overstory basal areas that resembled 19th-century forest structural conditions for the landscape. Contrary to expectations, a long-term measure of moisture availability (i.e., 30-year average climatic water deficit) was not a strong predictor of native cover or richness in treated plots 4–6 years post-treatment; rather, they were better predicted by moisture availability during the spring months prior to sampling. Overall, the consistent and enduring stimulation of cover and richness of native understory plants after mechanical treatments, with only limited invasion from non-native species, illustrates the important benefits of ongoing restoration activities in dry conifer forests of the Colorado Front Range.

Effects of Soil and Water Conservation Practices and Slope Gradient on Selected Soil Physicochemical Properties in Ejersa Watershed, Toke Kutaye District, Ethiopia

This study was conducted to assess the effects of soil and water conservation practices and slope gradients on selected physicochemical properties of soil at Ejersa Watershed based on a total of 18 composite soil samples collected and analyzed using standard laboratory procedures. The values of pH, electrical conductivity, cation exchangeable capacity, organic carbon, organic matter, total nitrogen, and available phosphorus determined in soil samples collected from conserved and nonconserved plots were 6.4 and 6.16, 40.26 mS/m and 15.12 mS/m, 33.51 meq/100 g and 21.56 meq/100 g, 2.66% and 2.24%, 4.58% and 3.86%, 0.24% and 0.15%, and 29.45 ppm and 17.68 ppm, respectively. Soil pH, electrical conductivity, moisture, total nitrogen, and available phosphorus were significantly different ( p < 0.01 ) between treated and untreated plots and among the slope classes. Values of soil organic carbon and organic matter showed significant differences ( p < 0.05 ) between land types but not among the slope classes. Soil cation exchange capacity showed significant difference ( p < 0.05 ) between land types as well as among the slope classes. Relatively, higher values of many of the physicochemical parameters were recorded in samples collected from the treated land and lower slopes which might be attributed to the deposition effects of the conservation practices and decline in the rate of soil erosion.

Prediction of Site Index and Age Using Time Series of TanDEM-X Phase Heights

Site index and stand age are important variables in forestry. Site index describes the growing potential at a given location, expressed as the height that trees can attain at a given age under favorable growing conditions. It is traditionally used to classify forests in terms of future timber yield potential. Stand age is used for the planning of management activities such as thinning and harvest. SI has previously been predicted using remote sensing, but usually relying on either very short time series or repeated ALS acquisitions. In this study, site index and forest stand age were predicted from time series of interferometric TanDEM-X data spanning seven growth seasons in a hemi-boreal forest in Remningstorp, a test site located in southern Sweden. The goal of the study was to see how satellite-based radar time series could be used to estimate site index and stand age. Compared to previous studies, we used a longer time series and applied a penetration depth correction to the phase heights, thereby avoiding the need for calibration using ancillary field or ALS data. The time series consisted of 30 TanDEM-X strip map scenes acquired between 2011 and 2018. Established height development curves were fitted to the time series of TanDEM-X-based top heights. This enabled simultaneous estimation of both age and site index on 91 field plots with a 10 m radius. The RMSE of predicted SI and age were 6.9 m and 38 years for untreated plots when both SI and age were predicted. When predicting SI and the age was known, the RMSE of the predicted SI was 4.0 m. No significant prediction bias was observed for untreated plots, while underestimation of SI and overestimation of age increased with the intensity of treatment.

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.