Open Field Crops Research Articles

Global Invasion of Thrips parvispinus (Karny) (Thysanoptera: Thripidae) Across Three Continents Associated With Its One Haplotype

ABSTRACTThrips parvispinus (Karny) is an exotic pest that has invaded many regions around the world in the last three decades. It was first detected in Florida in 2020 on ornamental plants (Hoya and Anthurium) in greenhouses and subsequently on ornamental plants in residential landscapes (Gardenia) in 2021. However, its first report on open vegetable field crops (Capsicum) in Florida was in 2022. We conducted field surveys and genetic analysis to answer three questions: (1) Is the population of T. parvispinus that invaded Florida the same as the one that has spread globally in the last few decades? (2) Is the host expansion to Capsicum in Florida a new population or the extension of the existing population reported on ornamental plants? and (3) What are the native and invaded distribution ranges of T. parvispinus? We analysed the genetic variation in the mitochondrial gene cytochrome oxidase I (COI) to address these questions. The global genetic diversity analysis of T. parvispinus revealed 18 haplotypes (populations) worldwide based on available data, but only one population (Hap1) invaded three continents: Africa, Europe, and North America. Based on available data, the highest haplotype diversity was observed in India, suggesting India may be part of the presumed native range (South and Southeast Asian countries) of T. parvispinus. Our survey of retail plant stores across 10 Florida counties indicated that plant trade is the source of T. parvispinus in open vegetable field crops and ornamental landscape plants. The outcome of this study will assist with regulatory and management decisions of T. parvispinus in Florida and elsewhere.

Cu Concentration in Vegetable-Cultivated Soil: Comparison Between Open Fields and Protected Environments in Brazil

High copper (Cu) concentration in soils used for vegetable production is an agricultural, social and environmental issue. The excess of Cu in soil can cause toxicity in plants, reducing growth and yields. Moreover, Cu can also be absorbed and accumulated in edible organs, increasing risks for human health. This study aimed to compare Cu fractions in soils: (1) non-cultivated, natural soil (NC), (2) soils cultivated with open field crops (FCs) and (3) soils cultivated in controlled environments (CEs). The survey was carried out on 25 sites in Rio Grande do Sul (Southern Brazil), with each site containing the three types of soils described above. From these sites, the four with the highest soil Cu concentrations were selected to compare soluble (Cu-CaCl2), available (Cu-EDTA) and total (Cu-EPA) Cu. Both total and available soil Cu concentration in soil solution, in CE and FC areas were higher than in NC. At sites 23R1 (Oxisol) and 11R1 (Molisol) the soluble and available Cu content was higher in the FC environment than in CEs, and the same was observed for the total Cu content at sites 23R1 (Oxisol) and 9R1 (Molisol). Some FC soils showed total Cu concentrations higher than the limits established by Brazilian environmental legislation, being, as a consequence, potentially contaminated. Soil monitoring and cropping practices must be adopted to reduce the Cu content in soils of vegetable crops in this region.

Predation efficacy of Chrysoperla carnea on two economically important stink bugs

Larvae of the green lacewing Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) are generalist predators feeding on a range of pests in agroecosystems. Little is known about the suitability of stink bugs as prey for lacewing larvae. In the present laboratory study, the predatory efficacy of C. carnea on two economically important stink bugs, Halyomorpha halys (Stål) and Nezara viridula (L.) (Hemiptera: Pentatomidae), was evaluated at three constant temperatures (16, 21, and 26 °C) in different arenas (10-cm diameter dishes with bean pod slices or caged small bean plants). We found that second and third instars of C. carnea readily prey on the first instars of both stink bug species. However, only third instars of C. carnea could successfully kill and feed on second instars of either pentatomid. The complexity of the arena, as well as the life stage of the prey and predator influenced the predation efficacy of C. carnea on stink bug nymphs, whereas temperature did not. The observed predation rates on the early instars of both stink bugs suggest that augmentative releases of C. carnea larvae may have some potential in greenhouse crops, particularly against N. viridula infestations, whereas in open field crops their natural populations may also contribute to pest suppression within the broader predator guild.

Effect of Waterlogging on Growth and Productivity of Fruit Crops

Τhe production of fresh fruit as well as olive orchards is increasing around the world, in order to meet the global demand for both fruits and olive products. This results in the spread and establishment of fruit and olive tree cultivation in areas where they were not found before, for example, plains and lowlands prone to waterlogging. Climate change is having a significant impact on the natural environment. Agricultural open-field crops have less growth and yield under these harsh weather conditions. Nowadays, unpredictable rainfall more often exposes field crops to waterlogging on a regular basis. This is a very stressful factor which can cause a reduction in yield and even total crop elimination. In this review, the morphological and physiological parameters affected by waterlogging are developed in order to understand better how olive and other fruit crops respond to waterlogging conditions and how this affects their development and productivity. Having a better understanding of these mechanisms can help us design strategies and approaches to increase fruit crop resistance to waterlogging stress.

Cucumber under Controlled Environment Polyhouse: A Step Forward to Enhance Farmers Income

Present study was conducted to see profitability of cucumber crop when grown under polyhouse. Controlled environment crops have greater consistency and production is more reliable than uncontrolled open field crops. Technology is used to manage and manipulate the growing conditions to reduce uncertainty and optimise crop growth. Particularly, cucumber crop was uneconomical when grown under open field conditions due to its climate sensitiveness. Present study was conducted in cucumber which was being cultivated in environment-controlled poly house. The cost return analysis showed that the total cost of cultivation per 1000 m2 area was Rs. 307746 with an output value of Rs.888960 resulted in Benefit Cost Ratio of 2.89. As the poly house involves initial establishment costs besides maintenance costs every year. This component was amortized to be included in Total Fixed Cost component (TFC) of cost analysis. Similarly, the bed prepared for cucumber sowing also amortized as it lasts for five years once prepared. As most of the farmers were facing initial capital issues for establishing polyhouse, majority of farming fraternity till unable tap the full benefits of cucumber crop. By utilizing the policies of government, cucumber cultivation under poly house is economically beneficial.

Automated imaging coupled with AI-powered analysis accelerates the assessment of plant resistance to Tetranychus urticae

The two-spotted spider mite (TSSM), Tetranychus urticae, is among the most destructive piercing-sucking herbivores, infesting more than 1100 plant species, including numerous greenhouse and open-field crops of significant economic importance. Its prolific fecundity and short life cycle contribute to the development of resistance to pesticides. However, effective resistance loci in plants are still unknown. To advance research on plant-mite interactions and identify genes contributing to plant immunity against TSSM, efficient methods are required to screen large, genetically diverse populations. In this study, we propose an analytical pipeline utilizing high-resolution imaging of infested leaves and an artificial intelligence-based computer program, MITESPOTTER, for the precise analysis of plant susceptibility. Our system accurately identifies and quantifies eggs, feces and damaged areas on leaves without expert intervention. Evaluation of 14 TSSM-infested Arabidopsis thaliana ecotypes originating from diverse global locations revealed significant variations in symptom quantity and distribution across leaf surfaces. This analytical pipeline can be adapted to various pest and host species, facilitating diverse experiments with large specimen numbers, including screening mutagenized plant populations or phenotyping polymorphic plant populations for genetic association studies. We anticipate that such methods will expedite the identification of loci crucial for breeding TSSM-resistant plants.

AgriFireInfo v1.0: An Open-Source Platform for the Monitoring and Management of Open-Field Crop Residue Burning

Open-field crop residue burning (OCRB) is a widespread agricultural practice with significant impacts on regional environments and public health. The effective management of OCRB remains a challenging task that requires timely access to various forms of monitored and forecasted information. Addressing this worldwide need, an open-source platform named AgriFireInfo v1.0, which is specifically tailored to monitoring and regulating regional OCRB activities, was developed. This technical note thoroughly illustrates the platform’s architecture, major modules, and visualization processes. Through AgriFireInfo v1.0, government agencies can access timely information about the spatial distribution of fire spots and emissions as well as meteorological conditions and air quality status. AgriFireInfo v1.0 also introduces an innovative Prevention Alarming Index, designed to identify regions prone to OCRB and promote comprehensive crop residue utilization. Furthermore, it offers the burning window and crop residue yields for controlled OCRB activities and can be used to analyze shifts in farmers’ burning behaviors and intensities. Future enhancements will focus on supplying holistic information on the burning windows and burning amounts of crop residues to further facilitate refined controlled burning activities and optimize decision-making processes. The flexibility and scalability of this platform can potentially allow users to easily customize and apply it to other regions or countries.

Growth and Nutritional Responses of Zucchini Squash to a Novel Consortium of Six Bacillus sp. Strains Used as a Biostimulant

The use of biostimulants consisting of plant growth-promoting rhizobacteria (PGPR) has been rapidly expanding in horticulture in recent years. In the current study, a novel mix of six Bacillus sp. strains (B. subtilis, B. pumilus, B. megaterium, B. amyloliquefaciens, B. velezensis, B. licheniformis) was tested as a PGPR biostimulant in two experiments with zucchini squash (Cucurbita pepo L.). The first experiment took place in greenhouse soil in winter, while the second experiment was conducted in an open field during summer. In both experiments, seeds of the local landrace “Kompokolokytho” and the commercial hybrid “ARO-800” were either inoculated or non-inoculated with the PGPR biostimulant. The application of the six Bacillus sp. strains increased both the vegetative growth and the yield of zucchini squash, and these effects were associated with significantly higher shoot phosphorus levels in both experiments and both genotypes. Furthermore, at the end of the cultivation, the colony-forming units of Bacillus sp. were appreciably higher in plants originating from inoculated compared to non-inoculated seeds, indicating that the tested mix of Bacillus sp. can be successfully applied through seed inoculation. “ARO-800” produced more vegetative and fruit biomass than “Κompokolokytho” under greenhouse cropping conditions, while in the open field crop, both genotypes performed equally. Presumably, this response occurred because “ARO-800” did not express its full yield potential in the open field due to stress imposed by the high summer temperatures, while the local landrace, which is traditionally grown in open fields, may be more resilient to stress conditions frequently encountered in open fields.

Bemisia tabaci MEAM1 still remains the dominant species in open field crops in Brazil.

Among Bemisia tabaci species, the invasive MEAM1 and MED species are key agricultural pests for many crops. In Brazil, most part of B. tabaci population outbreaks were associated with MEAM1, which, since 1990s quickly spread across the entire country. Later in 2014, the MED was identified in Brazil, initially more restricted to greenhouses, but suddenly reaching new areas in the South and Southeast open regions. Thus, our objective was to investigate the geographical distribution of MEAM1 and MED on open field crops in Brazil. MEAM1 is still the predominant species on open field crops such as soybean, cotton, and tomato. The sequencing of a cytochrome c oxidase subunit I (COI) gene fragment revealed a single haplotype of MEAM1, suggesting the establishment of a single MEAM1 strain in the country. The haplotypes found for MEAM1 and MED are genetically related to the globally dispersed strains, Jap1 and Mch1, respectively. Continuous monitoring of B. tabaci species is crucial because landscape alterations, climatic changes, and pest management methods may shift the B. tabaci species distribution and dominance in Brazilian crop areas.

A planning strategy for sprinkler-based variable rate irrigation

Automated variable rate irrigation (VRI) is one of the frontiers for sustainable water use in agriculture. In this paper, we describe a planning procedure for self-propelled rain gun sprinklers, a type of equipment largely used in irrigation of open field crops thanks to its relatively low cost and easy deployment in multiple sites. The sprinkler is commanded by an information system which acquires data from remote sensors (satellite), processes vegetation indices and spatial maps describing the water need of the crop, and computes a VRI prescription map for a specific field, i.e. the water quantity to be supplied to each field sub-area. The VRI prescription map is used to compute the motion commands for a rain gun system pulled by a hose reel. The procedure is based on a sprinkler model, has been validated by simulation, and is fully automated. Experiments have shown the precision in water distribution achievable with software-controlled sprinklers and effective planning strategies.

Combined Effects of Different LED Light Recipes and Slow-Release Fertilizers on Baby Leaf Lettuce Growth for Vertical Farming: Modeling through DoE

The modern agriculture system based on open-field crops requires a lot of energy and resources in terms of soil, water, and chemicals. Vertical farming (VF) systems could be a viable alternative for some types of cultivation that are receiving interest thanks to their high modularity, optimized water and nutrients use, and LEDs employment as an energy-efficient light source. However, VF design and installation are expensive and require well-tailored optimization depending on the specific crop to increase its competitiveness. This work analyzed the effects of different combinations of NPK (nitrogen-phosphorus-potassium) slow-release fertilizers and LED-based light recipes on the growth of baby leaf lettuce (Lactuca sativa L.), taking advantage of the Design of Experiments (DoE) methodology. The type of slow-release fertilizer, its quantity measured as the number of aggregates from 0 to 6, and the type of light recipe were considered as input factors, and their possible influence on the growth of lettuce (in terms of morphological parameters) in a controlled indoor farming system was measured. Results suggest that using higher fertilizer inputs equal to six aggregates leads to an increase of average leaf area equal to 46% (from 13.00 cm2 to 19.00 cm2), while the fresh weight of lettuce increases by 65% (from 1.79 g to 2.96 g). However, the height of plants also depends on the combination of the light recipes. In particular, the separate coupling of higher inputs of two fertilizers and light recipes leads to an increase in the height of lettuce equal to 33% (from 6.00 cm to 8.00 cm).

Insecticide Susceptibility and Detoxification Enzyme Activity of Frankliniella occidentalis under Three Habitat Conditions.

Frankliniella occidentalis is a highly destructive and invasive agricultural pest that has developed resistance to a variety of insecticide classes. Different planting structures and insecticide use frequency can directly affect the resistance development of F. occidentalis. In this study, the susceptibility of three field strains of F. occidentalis, collected over one year (April to November) from three habitat conditions (facility agriculture area, FA; open field crop area, OF; agroforestry intersection area, AI), to spinetoram, spinosad, emamectin benzoate, chlorfenapyr, acetamiprid, and imidacloprid were monitored and compared. At the same time, the detoxification enzyme activity of F. occidentalis in different habitats was determined. The results showed that the susceptibility of the F. occidentalis population in FA was significantly lower than that of populations from OF and AI. Among them, the F. occidentalis population in FA had developed low levels of resistance to spinetoram (RR = 9.18-fold), emamectin benzoate (RR = 5.47-fold), chlorfenapyr (RR = 6.67-fold), and acetamiprid (RR = 7.49-fold), and had developed moderate level resistance to imidacloprid (RR = 11.67-fold), while still being relatively sensitive to spinosad. The population of F. occidentalis from OF had developed low level resistance to spinetoram (RR = 5.24-fold) but was still relatively sensitive to the other five insecticides. The resistance of F. occidentalis from AI to six insecticides was at relatively sensitive levels. The results of the enzyme activities of detoxification enzymes, including carboxylesterase (CarE), glutathione S-transferase (GST), acetylcholinesterase (AChE), and the cytochrome P450 enzyme system (CYP450), revealed that the activities of the FA population of F. occidentalis were significantly higher than those of the other two populations. The change of CarE activity in F. occidentalis was consistent with that of spinetoram resistance, indicating that CarE may be involved in the metabolic resistance of F. occidentalis to spinetoram. Among the three populations, the resistance and detoxification enzyme activities of F. occidentalis of the FA population to six insecticides were higher than those of the other two populations. Our findings, along with other strategies, are expected to help with the resistance management of F. occidentalis in different habitats.

Tillage, green manuring and crop residue management impacts on crop productivity, potassium use efficiency and potassium fractions under rice-wheat system

The conventional crop production practices including intensive tillage and open field crop residue burning in world’ largest rice-wheat system (RWS) are adversely affecting crop productivity besides deteriorating natural resources and ecosystems’ sustainability. In order to improve system productivity, potassium (K) use efficiency and apparent K balance, adoption of conservation tillage in a RWS with residue management is considered highly effective. We therefore, studied the effect of wheat straw retention and green manure (GM) in rice (main plot treatment), and tillage and rice residue management in subsequent wheat (sub-plot treatments) on crop productivity, K use efficiency and its transformation amongst different fractions of variable solubility. These results revealed that rice straw retention along with GM significantly (p < 0.05) increased the rice yields by ∼5.3–6.7% and wheat yields by ∼10.2–16.9%, compared to the conventional tillage (CT) without GM. Green manuring during the intervening period (CTRW0+GM) significantly increased the rice grain K uptake by ∼36.2% than in plots with no-GM (CTRW0). However, it increased by ∼29.8% under CTRW25+GM, compared with CTRW25-GM treatment. As compared with CTRW0, CTRW0+GM significantly increased the reciprocal internal use efficiency of K of rice by 3.8 kg Mg−1 grain yield (∼29.5%). However, CTRW25+GM increased the RIUEK of rice by 3.3 kg Mg−1 grain yield (∼22.4%), compared with no-GM (CTRW25). Although, apparent K balance was net negative for CTRW25, ZTWR100 treatments, yet there was decreased K mining of 56–262 kg K ha−1 (∼11.9–61.2%) for CTRW25 and ZTWR100 over CTRW0 and ZTWR0. The increased crop yield, K uptake and K use efficiency were significantly related to K enrichment in water soluble K, exchangeable K, non-exchangeable-K, hydrochloric acid extractable-K, lattice-K and total K fractions by ∼1.3, 3.4, 18.6, 11.0 and 34.1%, respectively due to residue retention, compared with no residue. Therefore, conventional tillage with puddled transplanted rice (CTR) with wheat residue and green manure during intervening period (CTRW25+GM), and zero tillage wheat with rice residue retention (ZTWR100) were emerged as highly valuable technological options for mitigating soil degradation effects under intensive RWS for food grains in north-western India.

Investigation of the dissipation behaviour and exposure of flonicamid and imidacloprid in open field green beans under dry climatic conditions

ABSTRACT Flonicamid and imidacloprid are insecticides that are commonly used for the protection of many annual open field crops, such as beans, against insects. Residues of these insecticides in the consumable product above the acceptable limits can cause health concerns or trade barriers; thus, the dissipation behaviour and the consumer risk assessment of flonicamid and imidacloprid residues in open field green beans were investigated. The initial concentrations were found to be 0.44 and 0.99 mg kg−1. The decline of residues followed in both cases the first-order kinetics model with half-lives of 2.3 (r2 0.912) and 2.1 (r2 0.977) days, for flonicamid and imidacloprid, respectively, while degraded almost completely after 14 days if applied according to the authorised patterns. The dietary risk assessment performed using the hazard quotient (RQ) and the EFSA PRIMo model showed no concern to consumer health with exposure values <2% of the acceptable daily intake (ADI) and <22% of the acute reference dose (ARfD) of each compound. In conclusion, the investigation of the dissipation behaviour of these compounds in green bean provides useful information to ensure safe pre-harvest intervals, acceptable dietary exposure and compliance with good agricultural practices and maximum residue levels.

A comparison of candidate banker plants for management of pests in lettuce.

Agricultural systems are often lacking in resources for natural enemies. Providing alternative prey can help natural enemies persist through periods of low pest abundance, although this approach has been rarely commercially implemented in open field crops. In this study, we tested the potential of eight plant species to provide alternative prey to natural enemies in lettuce fields over a 2-yr period. Results showed that the tested plants would not act as sources of the lettuce aphid Nasonovia ribisnigri Mosley (Hemiptera: Aphididae), the primary lettuce pest. Of the banker plants tested, barley contained high numbers of non-lettuce aphids and appeared to provide reliable habitat for hoverfly larvae. However, lettuce aphids were present on lettuce early in the season, and may have dwarfed any effects of nonlettuce aphids on natural enemy populations. Numbers of hoverfly larvae were also high in lettuce, but did not appear to track numbers of non-lettuce aphids on banker plants. In contrast, numbers of lacewing larvae were highest on plants containing high numbers of non-lettuce aphids, and predatory hemipterans appeared to be associated with numbers of thrips on banker plants. Although barley showed promise as a source of alternative aphids, it did not appear to improve pest control in the adjacent crop.

Impacts of biomass power generation on ambient air quality–evidence from China

ABSTRACT With deteriorating air pollution and climate change, generating power with cleaner technologies to meet energy demand of economic development has become a crucial policy consideration globally. Biomass power generation, despite being cleaner than coal power generation, still emits certain air pollutants that can impact ambient air quality. On the other hand, biomass power plants might mitigate air pollution by reducing open-field crop burning. With this counteracting in play, it is unclear which effect is dominant and how biomass power generation affects ambient air quality eventually. We build a unique spatially high-resolution dataset for 20-km-radius circles, considering both regions with biomass power plants and those without, to explore the impacts of biomass power generation on air quality in nearby regions. By applying panel and canonical difference-in-differences models with various model specifications and estimation strategies, we demonstrate that biomass power generation in China significantly reduces ambient annual concentrations of PM2.5, PM10, SO2, and CO. The impacts on NO2 reduction could only be observed in summer, when open-field burnings decreased substantially. The impacts on PM2.5 could be observed in both summer and fall. No seasonal pattern is observed for the reductions in PM10, SO2, and CO concentrations.

Effect of the Landscape on Insect Pests and Associated Natural Enemies in Greenhouses Crops: The Strawberry Study Case

Compared to open-field crops, the influence of the surrounding landscape on insect diversity in greenhouse crops has been poorly studied. Due to growing evidence of insect influx in greenhouses, identifying the landscape properties influencing the protected crop colonization by insect pests and their natural enemies would promote the improvement of both pest prevention and conservation biological control methods. Here, we present a field study on the effect of the surrounding landscape on the colonization of greenhouse crops by insect pests and associated natural enemies. By monitoring 32 greenhouse strawberry crops in the South West of France, we surveyed crop colonization by four insect pests and four natural enemy groups over two cultivation periods. Our results showed that the landscape structure and composition could have contrasting effects on insect colonization of greenhouse crops so there could be species-specific effects and not general ones. While the degree of openness of greenhouses and the pest management practices modulated insect diversity marginally, we also showed that seasonality represented a key factor in insect crop colonization. The various responses of insect pests and natural enemy groups to the landscape support the idea that pest management methods must involve the surrounding environment.

First report of root rot caused by Fusarium solani on roselle in Nanning, Guangxi, China.

Roselle (Hibiscus sabdariffa L.) is an annual herbaceous plant in the Malvaceae family with high anthocyanin and is widely cultivated in Nanning, Guangxi of China due to its economic and nutritional importance. In August 2021, a severe root rot disease with incidence of 42.4% (860 plants in the field) was observed in roselle plants in an open-field crop in Nanning (108°33"E, 22°84"N), Guangxi, China. The roots of the diseased plants were discolored and rotten, and the xylem became black, extending along the main root to the junction of the rhizomes. The above-ground symptoms were leaf yellowing, vascular tissue browning, wilting and death. Three diseased samples were rinsed thoroughly with sterile distilled water, cut with a sterile scalpel into approximately 0.5-cm pieces, surface disinfested with 75% ethanol for one minute, rinsed 3-4 times with sterile water, and finally incubated on potato dextrose agar (PDA) at 28 °C in the dark for 3 days. Emerging colonies were transferred to new PDA two-three times until a single colony was obtained. The aerial mycelium was initially white, turning pale yellow after 5 days of growth on PDA. Microscopic observations revealed that microconidia were hyaline and ovoid with sizes of 5.13 to 15.12 and 2.50 to 4.20 μm (average 9.02, 3.32 μm, n=30). Macroconidia were falciform with 3- to 4-septate, with sizes of 19.08 to 24.35 and 4.5 to 8.00 μm (average 24.35 and 5.23 μm, n=30). The morphological characteristics of the microscopic images were identical to those described for Fusarium solani (Leslie and Summerell 2006). A representative isolate (GXRST29) was selected for DNA extraction for further characterization. The internal transcribed spacer rRNA regions (ITSs), beta tubulin gene sequence and a fragment of the translation elongation factor 1-alpha (EF 1-α) gene sequence were amplified using the primer pairs ITS1/ITS4 (Chehri 2014), Bt-1/Bt-2 (Wang et al. 2014) and EF1-F/EF2-R (O'Donnell et al. 2010), respectively. PCR products were sequenced and deposited in GenBank (accession Nos. OL314654, ON157430 and ON157431, respectively). BLASTn analysis showed that the ITS sequence had 96.99% homology with sequence of F. solani (NR 163531), and 99.26% for Fusarium cf. solani (MG775565) obtained from Homo sapiens. The beta tubulin sequence had 97.96% similarity with BLAST sequence of F. solani (MN295052.1) and EF 1-α gene had 100% identity to published F. solani (MN977912.1). The fungus was identified as F. solani. Five roselle plants at the 5-leaf stage were artificially inoculated by root dipping into a 106-107-mL-1 spore suspension of the isolated GXRST29 for pathogenicity testing. The experiment was conducted three times, and the negative controls were replaced with sterile water. Compared to the control, the growth of plants was significantly inhibited, leaves turned yellow, plants dwarfed and wilted, and roots decayed three days post-inoculation. One week post-inoculation, all plants exhibited symptoms similar to those observed in the field, and F. solani was steadily reisolated from those diseased plants, while no positive isolations were obtained in the controls. F. solani has been reported to cause root rot on roselle in Upper Egypt (Hassan et al. 2014) and lisianthus in China (Xiao et al. 2018). To our knowledge, however, this is the first report of Fusarium wilt caused by F. solani in roselle plants in Nanning, Guangxi, China, and could result in severe crop losses.

Meet Amblyseius swirskii (Acari: Phytoseiidae): a commonly used predatory mite in vegetable crops

Abstract The predatory mite, Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae), is a generalist predator feeding on multiple soft-bodied insects and mite pest species. It is a biological control agent commercially available since 2005 that has become one of the top 3 most released biocontrol predators worldwide. It is commonly used to suppress whitefly populations (Hemiptera: Aleyrodidae), thrips (Thysanoptera), and spider mites (Acari: Tetranychidae) to a lesser degree. This predatory mite has been used as part of Integrated Pest Management (IPM) programs for vegetable (e.g., peppers, eggplants, cucumbers, squash) and ornamental (e.g., roses, chrysanthemums) crops in open fields and greenhouses, and some field crops such as cotton, but it has been demonstrated to be more successful at establishing reproductive populations and suppressing pests under protected structures. Amblyseius swirskii can feed on various food resources besides prey, including pollen or honeydew. It is successful at suppressing pests when used together with low-risk pesticides, when multiple prey are available, when prey and pollen are available naturally (neighboring flowering or companion plants present), or when pollen is supplemented in the field. This predator is a good option to control pests early in the season if shelter and food resources are available for its establishment.

​Optimization of Sowing Density for Improving Fruit Yield of Tomatoes Grown in Open-field Crop

Background: Sowing density optimal is rated a less expensive solution for enhancing the output of tomato yield in the background of extending food requirements worldwide. Methods: The main objective of this study is to investigate the sowing density effect on the growth and tomato yield planted in Don Duong district of Lam Dong province, Vietnam. The study was conducted during the spring tomato crop (January to June 2020) with five different sowing densities varying from 33000 to 50000 plants/ha based on drip irrigation system supply approximately 100% of actual evapotranspiration. Result: Results pointed out that among investigated sowing densities, sowing density 45830 plants/ha obtained the optimal fruit yield (OFY) up to 87.8 tons/ha compared with different sowing densities while other observed variations as the number of bunches, fruit weight per plant and diameter were no significant difference. Based on the findings, tomato growers can sow with a density 45830 plants/ha to obtain the OFY thereby contributing to increase profits.