Insecticide Combinations Research Articles

Bio-efficacy of Selected New Generation Insecticides and Azadirachtin against Legume Pod Borer (Maruca vitrata) Infesting Cowpea

In the present study, various combinations of newer generation insecticides and azadirachtin were tested and among them, chlorantraniliprole followed by flubendiamide and novaluron followed by emamectin benzoate were found to be equally effective in reducing the inflorescence and pod damage by Maruca vitrata in cowpea. The treatments in which botanicals were alternated with insecticides i.e., azadirachtin followed by chlorantraniliprole and azadirachtin followed by novaluron were found to be on par in efficacy with chlorantraniliprole followed by flubendiamide and novaluron followed by emamectin benzoate. Natural enemy population i.e., wasp, spider and coccinellids was more in plots received no insecticide sprays. Next to these, azadirachtin included treatments have recorded more natural enemy population. In insecticides sprayed plots, wasps were not noticed but spiders were found here and there. High yield was recorded in the treatment, chlorantraniliprole followed by flubendiamide with high BC ratio followed by novaluron followed by emamectin benzoate. Treatments in which azadirachtin was alternated with newer insecticides, BC ratio was slightly lower than the chemicals alone sprayed treatments. However, combining the sprays of novel insecticides with azadirachtin was proved to be ecologically safe as these treatments supported natural enemy population.

Impact of Biopesticides Applied Alone and in Combination with Insecticides Using Drone and Taiwan Sprayer on Beneficial Fauna in Rice Ecosystem

Aims: To evaluate the impact of biopesticides and insecticides applied via drones and taiwan sprayers, on beneficials in rice cultivation. Study Design: Randomized Block Design (RBD). Place and Duration of Study: The present study was conducted at the Agricultural Research Station, Kampasagar, Nalgonda, during the kharif, 2023. Methodology: The beneficial populations, specifically coccinellids and spiders, were monitored after two consecutive sprays. The population counts were recorded by following standardized sampling methods. Results: The analysis of results revealed that mean coccinellid populations ranged from 3.33 to 6.67 per ten hills across treatments, with the highest population observed in the untreated control (T19), followed by Bacillus thuringiensis var. kurstaki 0.5% WP and insecticide combination treatments applied via drone. Spider populations demonstrated similar trends, with means ranging from 4.33 to 6.50, indicating non-significant differences across treatments. Drone spraying demonstrated better consistency in preserving natural enemy populations, likely due to precise droplet deposition and reduced pesticide drift. Conclusion: The study underscores the potential of drone technology as an eco-friendly, efficient application method, enabling better conservation of beneficial fauna in rice ecosystems.

Herbivory and allelopathy contribute jointly to the diversity-invasibility relationship.

Although herbivory and allelopathy play important roles in plant invasions, their roles in mediating the effect of plant diversity on invasion resistance remain unknown. In a 2-year field experiment, we constructed native plant communities with four levels of species richness (one, two, four, and eight species) and used a factorial combination of insecticide and activated carbon applications to reduce herbivory and allelopathy, respectively. We then invaded the communities with the introduced plant Solidago canadensis L. One year after the start of the experiment, there was no statistically significant net effect of species richness on biomass of the invader. However, a structural equation model showed that species richness had a positive direct effect on invader biomass that was partially balanced out by a negative indirect effect of species richness via increased light interception. In the second year, the relationship between invader biomass and species richness was negative when we analyzed the treatment combination with herbivory and allelopathy separately. Therefore, we conclude that joint effects of herbivory and allelopathy may play major roles in driving the diversity-invasibility relationship and should be considered in future studies.

The potential of insecticides and genetically modified soybean in the control of Spodoptera frugiperda (J. E. Smith, 1797) (Lepidoptera: Noctuidae)

Brazil is the largest soybean producer in the world, and soybean is the most important crop in the country. The use of genetically modified soybean expressing Bt proteins represents a significant milestone in insect pest management in this crop. However, the isolated use of these biotechnologies is not sufficient to control Spodoptera frugiperda larvae, thus the use of insecticides in seed treatment becomes essential. Therefore, the objective of this study was to assess the efficiency of controlling S. frugiperda larvae through insecticides applied to seeds and different biotechnologies in soybean cultivation. The experiments were conducted in a laboratory, following a completely randomized block design in a factorial scheme with twelve treatments, consisting of combinations of soybean cultivars and insecticides in seed treatment. The mortality and foliar consumption of first and third instar S. frugiperda larvae were evaluated. Based on our studies, it was possible to verify that ciantraniliprole is an excellent molecule for controlling first and third instar S. frugiperda larvae. The biotechnology Intacta 2 Xtend, Cry1A.105/Cry2Ab2/Cry1Ac, and the insecticide ciantraniliprole protected soybean against damage caused by S. frugiperda larvae.

Sugar feeding in triatomines: a new perspective for controlling the transmission of Chagas disease.

Introduction: Triatomines are vectors of Trypanosoma cruzi, the etiological agent of Chagas disease. Currently, there is no vaccine against this disease. Thus, control of the insect vector population is the main strategy available to reduce the number of cases. Triatomines are considered obligate hematophagous, but different alternative feeding behaviors were described, such as haemolymphagy or plant feeding. Methods: To determine the preference for sugar feeding in nymphs and adults of Rhodnius prolixus, the insects were exposed a piece of cotton containing bromophenol blue plus sucrose. In addition, we offered several sugars for different species of triatomines, and tested sugar meals as a route of delivery of insecticides in first-instar nymphs of R. prolixus. The effect of sugar feeding on the physiology of these different species of triatomines was recorded. Results: First instar nymphs ingested sucrose more strongly than other stages, and showed high mortality rates. In different species of triatomines, sucrose induced an ingestion, but engorgement varied according to the species. R. prolixus nymphs showed an indiscriminate intake of various sugars, with very different physiological effects. Furthermore, ingesting different combinations of insecticides + sugar significantly reduced insect survival. Discussion: In summary, we described for the first-time sugar feeding as a widespread behavior in several species of triatomines, and the possibility of the use of toxic sugar baits for the control of these vectors. The knowledge of feeding behavior in these insects can be fundamental for the development of new strategies to control Chagas disease.

The combined effect of sublethal concentrations of insecticides and local entomopathogenic nematode isolates on larval and pupal stages of Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae)

The black cutworm (BCW), Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae), is an economically significant pest affecting numerous crops and turf grasses. Despite employing various methods, such as chemical and biological control, to mitigate this pest, the efficacy of these methods often fails to reach the desired level. Hence, the integration of diverse strategies is a key to sustainable management. In this study, we assessed the toxicity of four insecticides (indoxacarb, pyridalyl, lufenuron, and methoxyfenozide) and three local EPN isolates (two isolates of Heterorhabditis indica and one of Heterorhabditis bacteriophora) in targeting the fifth instar larval (L5) and pupal stages of BCW. After demonstrating their potential use in BCW control, we explored the combined use of sublethal concentrations of insecticides (LC15 or LC30) alongside the LC20 values of EPNs. The findings revealed that lufenuron and methoxyfenozide, when combined with EPNs, exhibited a synergistic effect on the L5 stage of BCW, whereas the same combination displayed antagonism on pupae. On the other hand, the combination of indoxacarb and pyridalyl with EPNs demonstrated a synergistic effect on the pupal stage of BCW. These results highlight the potential of employing a combination of insecticides and EPNs at sublethal concentrations to control BCW effectively. This approach shows promise for designing sustainable pest management strategies within the framework of integrated pest management (IPM).

Environmental exposure patterns to 94 current-use pesticides in women of reproductive age who are preparing for pregnancy

Current-use pesticides (CUPs), including insecticides, fungicides, and herbicides, are extensively employed in agriculture to manage pests, diseases, and weeds. Nonetheless, their widespread application raises significant concerns regarding potential impacts on human health, particularly with reproductive health. This study focuses on exploring the landscape of CUP exposure among pre-pregnancy women. Based on a cohort study comprising 354 pre-pregnancy women of reproductive age in Beijing, China, we measured the concentrations of 94 CUPs in serum and conducted an in-depth analysis of exposure profiles, health risks, and contributing factors. The results revealed that the serum of pre-pregnancy women was contaminated with CUPs, of which the median concentrations ranged from 0.114 (fenamiphos-sulfone) to 61.2 ng/L (mefenacet). Among the 94 CUPs, 54 exhibited detection rates higher than 50 %, including 26 insecticides, 14 fungicides, and 14 herbicides. The exposure concentration profile highlighted that the insecticides contributed 56 % to the total CUP concentration percentages, with organophosphate insecticides being the primary contributors within this category (63.0 %). The average daily intake (ADI) of CUPs ranged from 2.23 to 16,432.28 ng/kg, while diflubenzuron had the highest ADI. Health risk assessments showed that exposure to a combination of total insecticides or herbicides poses a moderate risk for 15.8 % and 30.2 % of women, with mefenacet being the most significant, which showed moderate hazard in 29.4 % of participants. The overlap analysis showed that methiocarb-sulfone, diflubenzuron, and mefenacet were the dominant pesticides. In addition, maternal age, annual income level, smoking, and vitamin B12 supplementation were associated with serum CUP concentrations. Our study contributes a novel and comprehensive exposure profile of CUPs in pre-pregnancy women in northern China, providing valuable insights for evaluating the potential consequences of pre-pregnancy exposure on reproductive health. SynopsisWe provided a comprehensive exposure landscape, health effects, and influential factors of 94 current-use pesticides among pre-pregnancy women in China.

Quality assessment of soybean seeds submitted to industrial seed treatment and stored in a natural and controlled environment

Seed quality is a limiting factor in the search for high soybean yields. However, fungi and insect pests can negatively interfere with their performance, and industrial seed treatment (IST) is a tool used to minimize the attack of pathogens and pests. The treated seeds are often stored until sowing, which can lead to a reduction in their quality. This work aimed to evaluate the physical and physiological quality of soybean seeds submitted to IST, with subsequent storage in a natural and controlled environment. The experiment was conducted in a split-split-plot design in a completely randomized scheme (time x storage systems x IST) with four replications. Soybean cultivar 55I57RSF IPRO was subjected to IST with fungicide (metalaxyl-M, thiabendazole, and fludioxonil) and insecticide (thiamethoxam and cyantraniliprole), combined or not with polymer and dry powder, with subsequent storage in a controlled and natural environment. The moisture content, thousand-seed weights, germination, first germination count, germination speed index, accelerated aging, seedling length, dry matter transfer, and emergence sand test were evaluated. IST did not affect the moisture content and weight of a thousand seeds. However, storage in a controlled environment provided a greater reduction in moisture content and a smaller reduction in the weight of a thousand seeds. IST negatively affected germination, first germination count, germination speed index, and accelerated aging test. IST negatively affected plant length, except in the treatment where only insecticide was applied. The dry mass transfer was negatively affected but with less intensity in seeds subjected only to the application of insecticide or fungicide and the combination of insecticide, fungicide, and polymer. Seed emergence in the sand was negatively affected by all treatments. Regardless of the treatments, all responses evaluated showed a reduction throughout storage, with greater intensity in seeds stored in the natural environment.

Efficacy of Insecticidal Spray Schedules Against Sucking Insect Pests on Chilli

A field experiment was conducted at the research farm, Agricultural Research Station, Department of Entomology, College of Agriculture, Ummedganj, Agriculture University, Kota during rabi 2020- 21. Bioefficacy of selected insecticides was evaluated against sucking insect pests viz., aphid (Aphis gossypii Glover), whitefly (Bemisia tabaci Gennadius) and mite (Polyphagotarsonemus latus Bank) on chilli (Capsicum annuum L.). This study revealed that, among the treatments tested, the combination of insecticides as per spray schedule, treatment T1 (acetamiprid 20 SP @ 100 g/ ha + ethion 50 EC @ 1500 ml/ ha followed by imidacloprid 17.8 SL @ 125 ml/ ha + propargite 57 EC @ 1500 ml/ ha followed by buprofezin 25 SC @ 300 ml/ ha + fenazaquine 10 EC @ 1250 ml/ ha followed by fipronil 5 SC @ 1000 ml/ ha + spiromesifen 240 SC @ 400 ml/ha followed by chlorantraniliprole 18.5 SC @ 150 ml/ ha) was found significantly most effective against aphid, whitefly and mite population up to 15 days after treatment.

Preparation and indoor virulence determination of a temperature-sensitive insecticide against Zeugodacus cucurbitae (Coquillett).

Zeugodacus cucurbitae (Coquillett) is an important fruit and vegetable pest, especially in high-temperature seasons. In our previous research, we developed a temperature-sensitive sustained-release attractant for Z. cucurbitae, that not only can control the release rate of cuelure according to the temperature change, but also shows an excellent trapping effect on Z. cucurbitae. To further enhance the killing effect of the temperature-sensitive attractant on Z. cucurbitae, this study proposed using it in combination with an insecticide to prepare a temperature-sensitive insecticide for Z. cucurbitae. Based on the controlled release technology of pesticides, a temperature-sensitive Z. cucurbitae insecticide was developed by using PNIPAM gel as a temperature-sensitive switch to carry both cuelure and insecticide at the same time. In addition, the lethal effect of different pesticides on Z. cucurbitae were tested by indoor toxicity test, and the best pesticide combination was screened out. The temperature-sensitive insecticide prepared in this study not only had excellent thermal response and controlled release ability, but also enhanced its toxicological effects on Z. cucurbitae because it contained insecticides. Among them, combining thiamethoxam and clothianidin with the temperature-sensitive attractants was the most effective, and their lethality reached more than 97% against Z. cucurbitae. This study is not only of great practical significance for the monitoring and controlling Z. cucurbitae, but also provides theoretical basis and reference value for the combination of temperature-sensitive attractant and insecticide.

The Synergistic Effect of Lemongrass Essential Oil and Flometoquin, Flonicamid, and Sulfoxaflor on Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae): Insights into Toxicity, Biochemical Impact, and Molecular Docking.

The whitefly, Bemisia tabaci (Genn.), is one of the most dangerous polyphagous pests in the world. Eco-friendly compounds and new chemical insecticides have gained recognition for whitefly control. In this study, the toxicity and biochemical impact of flometoquin, flonicamid, and sulfoxaflor, alone or combined with lemongrass essential oil (EO), against B. tabaci was studied. In addition, a molecular docking study was conducted to assess the binding affinity of the tested compounds to AchE. Based on the LC values, the descending order of the toxicity of the tested compounds to B. tabaci adults was as follows: sulfoxaflor > flonicamid > flometoquin > lemongrass EO. The binary mixtures of each of the tested compounds with lemongrass EO exhibited synergism in all combinations, with observed mortalities ranging from 15.09 to 22.94% higher than expected for an additive effect. Sulfoxaflor and flonicamid, alone or in combination with lemongrass EO, significantly inhibited AchE activity while only flonicamid demonstrated a significant impact on α-esterase, and none of the tested compounds affected cytochrome P450 or GST. However, the specific activity of P450 was significantly inhibited by the lemongrass/sulfoxaflor mixture while α-esterase activity was significantly inhibited by the lemongrass/flometoquin mixture. Moreover, the lemongrass EO and all the tested insecticides exhibited significant binding affinity to AchE with energy scores ranging from -4.69 to -7.06 kcal/mol. The current findings provide a foundation for utilizing combinations of essential oils and insecticides in the integrated pest management (IPM) of B. tabaci.

The Management Strategies against Maize Stem Borer, Chilo partellus (Swinhoe) on Maize (Zea mays L.): A Review

The research provides updated information on the effect of different insecticides and biopesticides against maize stem borer (Chilo partellus Swinhoe) were carried out at different areas by different scientists. Combining Imidacloprid and Trichogramma chilonis resulted in significantly decreased leaf injury m-2 (1.32) and dead hearts (4.16%) in several trials done in different agroclimatic zones. With maximum grain yield (39.5 q/ha), imidacloprid + Karanj oil significantly reduced dead heart (2.8%), plant infestation (14.1%), stem tunneling (2.7%), and number of exit holes per plant (0.6). Results of the field bio-efficacy study showed that at, Chloropyrifos 50% + Cypermethrin 5% @2500 g.a.i./ha recorded significantly lower larval populations (1.18 larvae per plant) and a lower percentage of plant damage (9.00%). As per the findings this study suggests the percentage infestation and larval population of Chilo partellus can be minimized by the application of combinations of insecticides and biopesticides.

Resistance management and integrated pest management insights from deployment of a Cry3Bb1+ Gpp34Ab1/Tpp35Ab1 pyramid in a resistant western corn rootworm landscape.

In Nebraska USA, many populations of western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, now exhibit some level of resistance to all corn rootworm-active Bacillus thuringiensis Berliner (Bt) proteins expressed in commercial hybrids. Therefore, a study was conducted in northeast Nebraska from 2020-2022 to reevaluate current corn rootworm management options in continuous maize (consecutive planting for ≥2 years). Results from on-farm experiments to evaluate a standard soil-applied insecticide (Aztec® 4.67G) in combination with non-rootworm Bt or rootworm-active Bt pyramided maize (Cry3Bb1 + Gpp34Ab1/Tpp35Ab1) are reported within the context of WCR Bt resistance levels present. Corrected survival from Bt pyramid single-plant bioassays (<0.3, 0.3-0.49, >0.5) was used to place populations into 3 resistance categories. Variables evaluated included root injury, adult emergence, proportion lodged maize, and grain yield. Key results: A composite analysis of all populations across resistance levels indicated that addition of soil insecticide to Bt pyramid significantly reduced adult emergence and lodging but did not significantly increase root protection or yield. Within and among resistance category analyses of root injury revealed that the Bt pyramid remained highly efficacious at any non-rootworm Bt root injury level when resistance was absent or low. When corrected survival was >0.3, mean Bt pyramid root injury tracked more closely in a positive linear fashion with mean non-rootworm Bt root injury (rootworm density x level of resistance interaction). Similar trends were obtained for adult emergence but not yield. Mean Bt pyramid root injury rating was <0.75 in most populations with Bt resistance, which contributed to no significant yield differences among categories. Results are discussed within the context of IPM:IRM tradeoffs and the need to reduce WCR densities in this system to decrease the impact of the density x resistance interaction to bridge use of current pyramids with new technologies introduced over the next decade.

Efficacy of Some Insecticides in Combination with Neem on Rice Planthoppers

A field experiment was carried out during kharif 2020, at the Agricultural College Farm, Bapatla to evaluate the efficacy of some insecticides in combination with neem against rice planthoppers in direct seeded rice crop. The results showed that triflumezopyrim 10.6SC @ 25g a.i. ha-1 was the most effective treatment against both brown planthopper Nilaparvata lugens (Stål) and white backed planthopper Sogatella furcifera (Horváth) with 73.61 and 77.69% reductions over untreated control, respectively at 5 DAT. The other effective treatments were dinotefuran 20SG @ 40 g a.i. ha-1 and pymetrozine 50WG @ 150 g a.i. ha-1 with 70.14 and 66.44% reduction of N. lugens and 71.89 and 69.66% reduction of S. furcifera, respectively over untreated control at 5 DAT. Neem formulation 1500 ppm revealed the lowest efficacy with 34.95 and 36.19% reduction of N. lugens and S. furcifera over the untreated control at 5 DAT.

Combination Insecticide Treatments with Methoprene and Pyrethrin for Control of Khapra Beetle Larvae on Different Commodities.

Trogoderma granarium Everts, the khapra beetle, is a serious pest of stored products throughout the world. Larvae pose a significant threat to stored products because they feed on >100 different commodities, possess the ability to enter facultative diapause, and are difficult to detect. Control methods for T. granarium include fumigation, contact insecticides, trapping, and insecticide-incorporated packaging. The objective of this study was to determine the residual efficacy of two insecticide formulations (methoprene + deltamethrin + piperonyl butoxide synergist Gravista® and methoprene + deltamethrin, DiaconIGR®Plus). These insecticides were evaluated on three stored product commodities, corn, wheat, and brown rice, by exposing T. granarium larvae during a 12-month testing period. Both formulations significantly reduced adult emergence on corn and wheat for 12 months and on brown rice for up to 6 months. Adult emergence was highest at month 12 for corn (8.41%), and brown rice (85.88%), and month 9 for wheat (39.52%), treated with DiaconIGR®Plus or Gravista®, respectively. A biological index used to measure the development of exposed larvae on the treated grain from the larval stage (low values) to adult emergence (high values) was lower (fewer adults) on corn and wheat compared to controls. Despite differences in formulations, each of these grain protectants could be utilized by stored commodity managers to protect commodities during storage and transportation for T. granarium when and if this pest is detected at USA ports of entry.

Exploring Newer Molecules With Novel Modes of Action For The Management of The Invasive Maize Fall Armyworm, Spodoptera frugiperda (J.E. Smith)

Maize is affected by more than 30 insect pests and the recent attack by the invasive fall armyworm Spodoptera frugiperda has been a serious concern to maize growers all over the country. Being polyphagous with a wider host range, the pest necessitates the use of insecticides in the hitherto unsprayed maize ecosystems of the country. Evaluation of newer insecticides against fall armyworm revealed that, the combination insecticide, chlorantraniliprole 9.3% + lambda cyhalothrin 4.6%ZC registered lesser infestation after first round of spraying. However after two rounds of spraying, emamectin benzoate 5%SG, spinetoram 11.7%SC, chlorantraniliprole 18.5%SC, flubendiamide 480%SC and chlorantraniliprole 9.3% + lambda cyhalothrin 4.6%ZC were on par in their efficacy in reducing the fall armyworm infestation, though emamectin benzoate and flubendiamide treated plots registered comparatively higher yields. With respect to B:C ratio, emamectin benzoate and chlorantraniliprole 18.5%SC registered comparatively higher BC ratio followed by flubendiamide 480%SC, spinetoram 11.7%SC and chlorantraniliprole 9.3% + lambda cyhalothrin 4.6% ZC. Thus the above insecticides can be used in maize ecosystems to effectively tackle the fall armyworm menace.

Bio-efficacy of different newer pre-mixed insecticide combinations against okra aphids

Bio-efficacy of different newer pre-mixed insecticide combinations against okra aphids

Management of khapra beetle, Trogoderma granarium Everts, using binary combinations of chitin synthesis inhibitors and inert dusts

Control of Trogoderma granarium is difficult due to its high tolerance to all common insecticides. This problem can be partially overcome using binary combinations of insecticides with other control measures and products. In this study, three chitin synthesis inhibitors (CSIs), chlorfluazuron (CH), hexaflumuron (HE) and lufenuron (LU), and three inert dusts, diatomaceous earth (DE), zeolite (ZE) and kaolin (KA) and their combinations were assessed on stored wheat for the control of T. granarium. The three CSIs were tested at 2.5 and 5.0 mg/kg and the three inert dusts at 500 and 1000 mg/kg. The mortality of T. granarium larvae was counted after 7 and 14 days. The adult emergence (F1 progeny) from treated larvae was examined after 30 days, while F2 progeny and wheat weight loss were recorded after 80 days of exposure. The results showed that the treatments of wheat grains with individuals and combinations of CSIs and inert dusts caused remarkable mortality of T. granarium larvae after 14 days of exposure. Also, the combinations of CSIs and inert dusts were significantly more effective than those of products alone. The combinations (5.0 mg/kg of CH + 1000 mg/kg of DE and 5.0 mg/kg of LU + 1000 mg/kg of DE) induced a complete larval mortality after 14 days. Furthermore, individual and binary combinations decreased the adult emergence (F1 and F2 progeny) from T. granarium larvae and the complete inhibition of progeny was obtained in the treatments with CH or LU alone or with their combinations with the three inert dusts. After 80 days of exposure, all individual and binary treatments of CSIs and inert dusts particularly CH and LU, induced a complete wheat protection with weight loss of 0.0%. Our findings indicate that the binary combinations could be successfully applied in IPM strategies of this invasive insect species.

Results of testing of the efficacy of sublethal concentrations of bacterial-chemical insecticides combinations against cabbage moth larvae

Using chemical pesticides has adverse effects on the environment and humans. Bacterial preparations may provide an alternative to chemical pesticides. The study aims to test different combinations of sublethal concentrations of bacterial and chemical preparations against cabbage moth larvae. During 2020-2022 different combinations of sublethal concentrations of bacterial (Lepidocide) and chemical (Arrivo, Voliam Flexi, Proclaim Fit) preparations were tested in laboratory and field conditions, against cabbage moth young larvae (stage I-II). The combinations of insecticides with bacterial and chemical sublethal concentrations show high biological efficiency against the cabbage moth larvae. No statistical difference was found between the efficiency indicators of the combined and standard chemical (Arrivo, Voliam Flexi, Proclaim Fit) options and the significance level was generally between 2.0 and 5.9 %, showing that the results of the scientific experiments are reliable.

Heterotroph removal alters the difference in plant biomass among plant species compositions in systems with different N availability

ABSTRACT We studied the effects of heterotroph removal on the relationship between species composition and plant biomass in systems with different N availability. Two understory herb species (Ophiopogon bodinieri and Lophatherum gracile) were grown in monocultures and mixture, and heterotroph removal treatments (control, insecticide, fungicide, and fungicide-insecticide combination) were performed on each plant species composition in systems without or with N addition. Results showed that (1) in systems without N addition, the plant biomass of O. bodinieri monoculture was higher than that of the mixture under insecticide and fungicide-insecticide treatments, but this difference disappeared in systems with N addition. (2) In systems without N addition, fungicide and insecticide application increased leaf area but decreased root length and root tips of O. bodinieri monocultures. In systems with N addition, fungicide and insecticide application increased root tips of O. bodinieri monocultures and root diameter of mixtures. (3) In systems without N addition, fungicide and insecticide application increased the soil pH of O. bodinieri monocultures. In systems with N addition, fungicide application decreased the soil K concentration of O. bodinieri monocultures. Our findings suggest that heterotroph removal alters the difference in plant biomass among plant species compositions in systems with different N availability.