Intraspecific Host Discrimination and Superparasitism in Telenomus remus (Nixon), an Egg Parasitoid of Spodoptera frugiperda (J. E. Smith)
Telenomus remus (Nixon) is an important egg parasitoid of Spodoptera frugiperda (J. E. Smith), a major invasive pest. In order to clarify the intraspecific host discrimination and the superparasitism of T. remus, the self-recognition (same individual) and conspecific-recognition (different individual) ability to recognize the hosts eggs parasitized at different time intervals were determined, and the superparasitism rate of single and multi-female T. remus under different host density were also investigated. The results showed no superparasitism in T. remus , either self-recognition or conspecific-recognition. After a single female T. remus parasitizing for 24 h at different parasitoid-egg ratios, the percentage of 1st instar larvae of T. remus in S. frugiperda eggs was less than 100%, and only one was found in each host egg. With multi-female T. remus and sufficient hosts, and when parasitoid-egg ratios were 1:100, 2:200, 4:400, 6:600 and 8:800, the percentage of unparasitized host eggs were 52.8%, 67.2%, 63.2%, 53.6% and 51.2%, respectively, and the percentage of host eggs with one 1st instar larva were 47.2%, 32.8%, 36.8%,46.4% and 48.8%, respectively. With multi-female T. remus and insufficient hosts, and when parasitoid-egg ratios were 2:20, 3:21, 4:20, 7:21 and 20:20, the parasitism rates of T. remus were 60.0%, 83.0%, 95.0%, 94.0% and 96.0%, respectively, and the superparasitism rates were 11.0%, 38.0%, 64.0%, 73.0% and 92.0%, respectively, the average number of 1st instar larva of T. remus in a single host egg were 0.4, 0.6, 1.1, 1.3 and 2.1, respectively, and the maximum number were 3.0, 4.0, 5.0, 6.0 and 12.0, respectively. The results show that T. remus has the ability of self and conspecific-recognition, the superparasitism of a single female T. remus does not depend on host density. When the host is sufficient, the superparasitism of multi-female T. remus does not occur, but when the host is insufficient, the parasitism and superparasitism rate, the average and maximum number of 1st instar larvae in a single host egg increase with the increase of parasitoid-egg ratios. The parasitoid-egg ratio of 4:20 is suitable for propagation of the wasp because it produces high parasitism rate, low superparasitism rate, and low internal competition.
Isolation, Identification and Control Effect of Strain ZF510 on Bacterial Soft Rot of Chinese Cabbage
Soft rot of Chinese cabbage is a serious bacterial disease caused by Pectobacterium brasiliense. Currently,,there are few effective products for the control of bacterial soft rot in vegetables. In order to screen biocontrol bacteria with good antagonistic effect against Chinese cabbage bacterial soft rot, this study isolated a strain of beneficial bacteria ZF510 from the rhizosphere soil of cabbage. Through morphological observation, physiological and biochemical characteristics, and multi-gene phylogenetic tree analysis, as well as pot experiments to verify the control effect of the antagonistic strain on Chinese cabbage bacterial soft rot. The results showed that the strain ZF510 was Pseudomonas donghuensis, which produced protease during the metabolic process, and had the ability to synthesize IAA, iron-loving and phosphorus-dissolving ability. Through the analysis of bacteriostatic spectrum, it was proved that strain ZF510 had significant antagonistic effects on seven pathogenic bacteria such as Pectobacterium brasiliensis and Xanthomonas campestris pv. campestris. The dichotomous dish method was used to determine that the volatile substances had inhibitory effects on the three pathogenic fungi of Rhizoctonia solani, Didymella bryoniae and Stemphylium solanacearum. The results of pot experiment showed that the symptoms of bacterial soft rot of Chinese cabbage inoculated with strain ZF510 were significantly reduced, and the control effect reached 44.56%. In summary, strain ZF510 has great potential for biological control and application prospects.
Bionomics and the Control of the Tea Stick Thrips, Dendrothrips minowai Priesner
The tea stick thrips, Dendrothrips minowai Priesner, is one of the most important sucking pests in tea plantations in China. Both D. minowai adults and nymphs feed on fresh and tender leaves, causing leaves to turn curling, brittle and scorched and finallyfall off, which seriously affect the growth of tea plants and the quality of tea products. In this paper, we reviewed the biological and ecological characteristics of D. minowai such as their morphological characteristics, identification method, geographical distribution, damage symptoms, individual development and life cycle, as well as genetic differentiation. In addition, we also summarized the research progress in the management of D. minowai. At the same time, we suggest that the basic research of the olfactory mechanism and the green prevention and control strategy such as monitoring, mass trapping and the use of pathogenic resources in prevention and control of the pest be accelerated. The review provides a theoretical basis and technical support for the integrated pest management of the thrips.
Optimization of Fermentation Conditions of Streptomyces sp. SS9-1 and Its Control Effect on Tomato Gray Mold
A strain of Streptomyces ciscaucasicus SS9-1 was isolated from rhizosphere soil samples of Aconitum pendulum Busch in our laboratory before. The antifungal activity test showed that the strain SS9-1 had a good inhibitory effect on Botrytis cinerea, the pathogen of tomato gray mold. In order to further improve its antifungal effect on tomato gray mold, the fermentation medium formula and fermentation conditions of SS9-1 were optimized by single factor test and orthogonal test. Then the fermentation filtrate was tested for its antifungal effect and pot control efficiency on tomato gray mold. The results showed that the optimal fermentation medium of strain SS9-1 was as follows: starch soluble 4%, KNO3 1%, yeast extract powder 0.25%, NaCl 0.2%, MnCl2·4H2O 0.002%. The optimum fermentation conditions were as follows: liquid volume 150 mL, inoculation rate 3%, initial pH 8.0, fermentation temperature28℃, fermentation time 7 d. Plate confrontation test showed that the mycelium of B. cinerea was swelled and deformed after being affected by the fermentation filtrate. It also had a strong inhibitory effect on the germination of B. cinerea spores, and the germination inhibition rates of were 97.83% and 96.07% after 12h and 24h of treatment, respectively. In addition, in the pot experiment, the control efficiency of the fermentation filtrate of strain SS9-1 reached 98.43%, which was obviously higher than that of the pesticide control, 40% pyrimethanil SC 500 times dilution. After the fermentation filtrate was diluted 50 times, the control efficiency was still 71.11%. In conclusion, the strain SS9-1 has a good biological control effect on tomato gray mold, and has the application value and potential as a biocontrol agent.
Population Dynamics and Spatial Distributions of Jujube Gall Midge and Predatory Natural Enemies in Jujube Orchards of Southern Xinjiang
Jujube gall midge Dasineura jujubifolia is an important pest in jujube orchards in Xinjiang. Clarifying population dynamics and spatial distributions of the jujube gall midge and its related predatory natural enemies in orchards is important for the management of the gall midge. In this study, population dynamics of jujube gall midge adults and larvae, predatory natural enemies in jujube orchards, as well as leaf damages caused by gall midge larvae were investigated in Aksu area in southern Xinjiang, in 2021 and 2022. Densities of gall midge larvae, predatory natural enemies, and degrees of leaf damage were analyzed in relation to directions of the jujube tree. Our results showed that the gall midge mainly occurred in May and June, with two population peaks. Larvae started feeding on jujube leaves one week later following the occurrence of adults, and adults of the next generation emerged after two or three weeks. Predatory natural enemy species were dominated by lady beetles and lacewings, with low population density during the whole growing season. Gall midge larvae caused serious damage in May and June, with young leaf damage rate of 6.2%—17.8% and bearing branch damage rate of 11.0%—33.8%. No direction-related biases were detected in population densities of gall midge larvae, predatory natural enemies, or the damage degree of jujube leaves. The damage degree of jujube leaves was positively correlate with the density of gall midge larvae. Results of population dynamics and distributions of the jujube gall midge and predatory natural enemies in jujube orchards in Aksu area of southern Xinjiang provide a scientific basis for the control of jujube gall midge.
Inhibitory Effect of Fusarium lateritium Pa2 against Strawberry Gray Mold
Strawberry gray mold caused by Botrytis cinerea is one of the most destructive diseases in strawberry cultivation, which seriously reduces the edible and economic value. In this study, "Hongyan" strawberries were used as experimental materials to determine the effects of Fusarium lateritium Pa2 on the inhibitory activity and control of gray mold pathogen, as well as the effects on the pathogenesis-related genes expression levels of strawberry fruit. The results showed that strain Pa2 had significant antifungal activity against B. cinerea. The supernatant of strain Pa2 could damage the mycelial cell membrane of B. cinerea, leading to leakage of cell contents. The results of inoculation experiments indicated that the control effects of strain Pa2 on strawberry leaves gray mold and strawberry fruits gray mold were 79.13% and 54.29%, respectively. In addition, the strawberry fruits pathogenesis-related genes FaPR1, FaPR4, and FaGR increased by 19.05, 24.64, and 3.69 times at 24 hours post treatment with supernatant of strain Pa2, respectively. In conclusion, the F. lateritium strain Pa2 is a new biocontrol resource for controlling strawberry gray mold.
Effects of Cold Storage of the Parasitized Host Pupae on Aceratoneuromyia indica (Silvestri)
Aceratoneuromyia indica (Silvestri) is a highly effective parasitoid of tephritid pests. With the aim to establish the optimal cold storage conditions and facilitate the application of the parasitoid, the effects of different cold storage treatments on A. indica were studied. The results showed that age of the parasitized host pupae, temperature and duration of cold storage had significant effects on the emergence rate of A. indica, but had no significant effects on the ratio of females emerging from the parasitized host pupae and the number of host pupae parasitized by individual F1 females. The four stages of the host pupae parasitized by A. indica were suitable to be cold stored at13 ℃for 7 d, and there was no significant difference in the biological parameters between each of the treatments and the control. The host pupae at 3 d and 6 d after parasitization have the potential as the medium and long-term cold storage pupae. The results of this study are of significance for the low temperature storage for scale-up of A. indica population size before mass release.
Isolation, Identification and Control Effect of Antagonistic Bacteria on Common Bacterial Blight of Common Bean
Common bacterial blight of common bean is one of the most widespread common bean diseases inHeilongjiangProvincein recent years. In severe cases, it can lead to large-scale yield reduction of common bean and affect grain quality. In order to explore the biocontrol bacteria resources of common bacterial blight of common bean, an antagonistic strain B2 with significant inhibitory ability on common bacterial blight of common bean was isolated and screened from the rhizosphere soil of healthy common bean. Based on microscopic observation, physiological and biochemical characteristics determination combined with 16S rDNA and gyrB sequence analysis, the strain B2 was identified as Bacillus velezensis. The antibacterial ring diameter of the strain B2 against Xanthomonas axonopodis pv. phaseoli (Xap) and Xanthomonas fuscans subsp. fuscans (Xff) were19.3 mmand21.8 mm, respectively. In the pot experiment, the control efficacy of strain B2 against Xap and Xff were 55.42% and 67.77 %, respectively. The determination of defense enzyme activity and malondialdehyde content in bean leaves showed that strain B2 could significantly increase the activities of SOD, POD, CAT and PPO in bean leaves and reduce the content of malondialdehyde. Its indicating that strain B2 could induce plant defense response to resist pathogens. In conclusion, strain B2 has good development and application potential in the biological control of common bacterial blight of common bean which caused by Xap and Xff.
Effects of fluG Gene Knockout on Sporulation in Metarhizium anisopliae
The fungal gene fluG is involved in the regulation of conidial generation. However, the role of fluG in the entomopathogenic fungus Metarhizium anisopliae is rarely reported. To investigate the role of fluG in M. anisopliae, we constructed a mutant strain of M. anisopliae with fluG knocked out by DNA homologous recombination to analyze its effect on the sporulation characteristics. The target vector pDHt/sk-fluG-Ben was constructed by using benomyl resistance gene ben as selective marker and sequence of fluG gene flanks as homologous arms. The target vector was transformed into the protoplasts of M. anisopliae by PEG mediating, and the resistant transformants of benomyl were obtained. According to the test of target genes and marker genes, the mutant strains of M. anisopliae with fluG knocked out were determined. Phenotypic analysis showed that the fluG mutant still maintained benomyl resistance after 5 generations of subculture. The mutant colonies looked loose and flocculent, grew significantly slower than the wild type, and could not or only produce a very small number of conidia. These results indicate that the knockout of fluG gene affect the development of the strain and prevent conidia formation, showing fluG an important gene in the regulation of spore-producing of M. anisopliae. This study establishes the basis for further elaborating the regulation mechanism of M. anisopliae conidiation.
Effects of Different Formulations of Artificial Diet on the Biological Characteristics of Coccinella septempunctata Adults
The effects of artificial diet formulation on the adults of Coccinella septempunctata were determined for the purpose of further optimization of the preparation of the artificial diets of C. septempunctata by feeding C. septempunctata adults with two formations, i.e., dry-wet separation (DWS) and microcapsulation (MCS), of artificial diets and measuring the feeding frequency, food intake, mating frequency, oviposition frequency, and eggs deposition. The results showed that the feeding frequency of C. septempunctata adults on the DWS diet (0.72 insects/min) was significantly lower than that on the MCS diet (1.58 insects/min), but the feeding amount on the DWS diet (0.04 g/pair) was significantly higher than that on the MCS diet (0.01 g/pair). There was no significant difference in the mating frequency of C. septempunctata between the two groups. The oviposition frequency and egg deposition in the DWS diet group were 19.00% and 23.40 eggs/female, respectively, significantly higher than the values of 1.00% and 2.40 eggs/female in the counterpart, respectively. In general, the adults of C. septempunctata can feed on both formulations of artificial diet, but the dry-wet separation diet is better than the microcapsule diet.
The pathogenic Metarhizium rileyi were collected from diseased Spodoptera frugiperda for the purpose of enriching the entomopathogenic fungi resource inAnhuifor green prevention and control of S. frugiperda. In this study, the strain Mr006 was identified using morphological characterization and ITS-rDNA sequence analysis, and the pathogenicity of the strain to the larvae, prepupae, and pupae of S. frugiperda and the field application efficiency were evaluated. The strain Mr006 was identified as M. rileyi and showed pathogenicity in the larvae and pupae of S. frugiperda. A spore concentration of 1×107 spores/mL achieved a corrected mortality of 91.16%, 88.38%, 70.71%, 53.03%, 22.73%, and 76.26% in the 1st to 5th instar larvae and pupae, respectively. LC50 values to the 1st to 5th instar larvae and pupae were 3.55×104, 8.23×104, 3.63×106, 4.16×107, 4.23×108 and 2.57×105 spores/mL, respectively. LT50 values is negatively correlated with spore concentration and positively correlated with larval instar. At a spore concentration of 1×108 spores /mL, LT50 values to the 1st to 5th instar larvae and pupae were 3.47, 3.94, 4.90, 6.73, 9.01 and 4.02 d, respectively. In the field at 20 days after application, the strain achieved a control of over 64% and showed a good persistence against S. frugiperda. The current results indicate the strain Mr006 is highly pathogenic to S. frugiperda and of high biological control potential for further development.
Pathogenicity and field control efficiency of Mucor hiemalis BO-1 against Bradysia odoriphaga Larvae
Mucor hiemalis BO-1 is a newly reported entomopathogenic fungus that infects Bradysia odoriphaga, a destructive root maggot. However, the pathogenicity and field control efficiency of M. hiemalis BO-1 against B. odoriphaga are unknown. In this study, we analyzed the pathogenicity of M. hiemalis BO-1 to B. odoriphaga larvae and its relation to temperature and evaluated its application value by pot and field experiments. The results indicated that M. hiemalis BO-1 was of acute pathogenicity against B. odoriphaga larvae and was as toxic as some chemical pesticides. At 3 d after treatment, the median lethal concentrations (LC50) to the 2nd and 4th instar larvae were 3.714×105 spores/mL and 4.680×106 spores/mL, respectively. Moreover, M. hiemalis BO-1 also showed pathogenic activities against B. difformis and Delia antiqua larvae. The optimal temperatures for high pathogenic activity of M. hiemalis BO-1 were 16―28 ℃, especially at 20―24 ℃. The results of pot and field experiments confirmed excellent control efficiency of M. hiemalis BO-1 against B. odoriphaga larvae, which exceeded 80% at 7 d after treatment with spore concentration of 1×107 spores/mL, the equivalence to the chemical insecticide clothianidin. In addition, M. hiemalis BO-1 exhibited high persistence in control of B. odoriphaga. Therefore, M. hiemalis BO-1 is of high perspective as a biocontrol agent against B. odoriphaga.
Identification and Mechanism of Strain X-20 for Biocontrol against Meloidogyne incognita
Meloidogyne incognita is a major pathogen that affects vegetable crops, and currently, there are limited safe and efficient biological control options available. In this study, strain X-20 was isolated from soil where root-knot nematodes were present. When tested against second-stage juveniles (J2) of M. incognita, strain X-20 exhibited a mortality rate of up to 100% after 24 and 48 hours. The strain X-20 was identified as Pseudomonas fluorescens through various methods, including morphological, physiological, biochemical and molecular biological analysis. When 1 mg/mL fermentation broth of strain X-20 was used to treat J2 of M. incognita, the nematode body showed twisted and stiff changes, and the internal tissue decomposed. After 1 hour of treatment, the fluctuation frequency of the body decreased by 47.26%, the swing frequency of head and the bending frequency of the body also changed. After 24 hours of treatment, the body length of M. incognita J2 decreased 4.68%, while the stylet length and the hyaline tail length of M. incognita J2 increased by 7.64% and 83.9%, respectively. Meanwhile, the body fluids of M. incognita J2 leaked, and its conductivity increased with the increase of treatment concentration and time. After six hours treatment with 1 mg/mL methanol extract from fermentation broth, the sugar and glycerol content of J2 body increased by 39.10%, 66.67%, respectively; While the soluble protein content of J2 body 55.73% decreased compared to the control. In conclusion, the metabolites produced by strain X-20 were found to cause body fluid leakage, disrupt the body wall and internal structure of root-knot nematodes, and affect the metabolism of sugars, lipids, and proteins, ultimately leading to the death of M. incognita.
