Study on Socially Harmless Controlling Technologies on White Grubs
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White grubs after winter were treated by socially harmless controlling technologies in different conditions. The result showed that the urea had a obvious controlling effect on it, and its adjusted accumulative mortality rates was 81.35%. The temperature had a significant influence on bacteria and fungi,the effects were not obvious at lower temperature. The Beauveria brongniartii (Bbr) had a higher virulence and the effect at steady temperature was better than at normal temperature.Keywords:
Beauveria
White (mutation)
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Abstract The chloronicotinyl, imidacloprid, and the thianicotinyl, thiamethoxam, are effective insecticides against white grubs when applied as preventative treatments during or immediately after egg laying. Their efficacy sharply declines when the grubs reach late‐instar stage. As both imidacloprid and thiamethoxam act on post‐synaptic nicotinic acetylcholine receptors and modify insect behavior, we hypothesized that the two compounds will interfere with overwintering behavior of scarabs, thus reducing their ecological fitness and exposing them to increased winter mortality. We tested this hypothesis by applying the two compounds curatively against late second‐instar and early third‐instar Popillia japonica and Cyclocephala borealis grubs in turfgrass. Imidacloprid provided control of P japonica equivalent to the most widely used curative organophosphate, trichlorfon, by 14 days after treatment, but thiamethoxam had no affect. In contrast, both imidacloprid and thiamethoxam caused significant reductions in C borealis populations. Both insecticides altered the overwintering behavior of P japonica by significantly reducing the normal downward movement of grubs in October. Halofenozide, an ecdysone agonist, also caused rapid mortality of the late second‐instar C borealis equivalent to trichlorfon, but had no affect on P japonica . In another experiment on a site naturally infested with entomopathogenic nematodes, the exclusive treatment of third‐instar P japonica with imidacloprid resulted in no significant mortality in the autumn (up to 15 days after treatment), but caused a significant reduction in the survival of overwintered grubs. There was an increase in the numbers of grubs infected with nematodes in the imidacloprid and trichlorfon treatments compared with control, but these differences were significant only for trichlorfon. These results indicate that imidacloprid can effectively control late second‐instars of both P japonca and C borealis and can significantly reduce survival of overwintered third‐instar P japonica by altering their normal overwintering behavior. © 2001 Society of Chemical Industry
Overwintering
Popillia
Neonicotinoid
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Bassiana
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To explore the pathogenesis of infection with Heterorhabditis bacteriophora in white grubs, the activity of phenoloxidase(PO) and carboxylesterase(CarE) in hemolymph, as well as protein and trehalose content, between infected grubs and control were observed. The change tendencies of the PO and CarE activities in infected grubs were similar. At 24, 12, 36 h after infection, the PO activities in the 2nd instar larvae of Holotrichia oblita Faldermann, H parallela Motschulsky and Anomala corpulenta Motschulsky reached maximum and were significantly higher than each control(P0.05), respectively. Similarly, after 48, 36, 48 h of infection, CarE activities in the three white grubs ran to maximum respectively, significantly higher than control(P0.05). The protein content in hemolymph of 3rd instar A. corpulenta larvae increased greatly after 20 h of infection then decreased dramatically at 28 h. The trehalose content reached the highest at 20 h, and lowest at 28 h. These changes were significant difference against the control(P0.05). Taken together, it indicated that H. bacteriophora could affect the immune system and metabolic processes in white grubs. These results laid a foundation for further analysis of pathogenesis of infection with H. bacteriophora in white grubs.
Heterorhabditis bacteriophora
Hemolymph
Carboxylesterase
White (mutation)
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In order to obtain the optimal treatment conditions of Beauveria bassiana on Asias halodendri,the death of Asias halodendri larvae imposed to Beauveria bassiana were tested under different temperatures and humidities.The results showed that:(1) At 31 ℃,Beauveria bassiana showed the best lethal effect on Asias halodendri larvae,the corrected mortality rate was as high as 77.78% in 5 d,and the muscardine cadaver rate was 46.67%.The lethal rate was the highest and the LT50 value was 0.121 d.These data were better than the other groups evidently.At higher or lower temperature,the infected effects were weakened.(2)When relative humidity(RH)was higher than 90%,Beauveria bassiana showed the best lethal effect on Asias halodendri larvae,the corrected mortality rate and muscardine cadaver rate was 100% and 63.33% respectively,the lethal rate was the highest and the LT50 value was 1.017 d.When RH was relatively lower,the corrected mortality rate and muscardine cadaver rate decreased evidently.
Bassiana
Beauveria
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In this study, the effect of temperature and humidity on the virulence of a Beauveria bassiana isolate, SCAU-BB01D, to Phaedon brassicae, a serious insect pest of cruciferous vegetables in South China, was studied in the laboratory. The mortality of P. brassicae was significant lower at temperature of 17℃ and 29℃ than at other temperatures. At temperature of 23℃, the mortality of adult on the 14th day after treatment reached its highest, 95.60%. For 2nd instar larvae the highest mortality (96.00%) was obtained at both 23℃ and 26℃ on the 10th day after treatment. The pathogenicity of B. bassiana to P. brassicae was enhanced as relative humidity increased. When relative humidity (RH) was increased from 50% to 100%, adult mortality 14 days after treatment was enhanced from 55.70% to 88.80% and 2nd instar larvae mortality 10 days after treatment was enhanced from 62.00% to 96.00%. At 17, 20, 23, 26, and 29℃, the LT50 values were 13.63, 10.27, 8.05, 8.87 and 12.41 days for adults, arid 6.06, 5.72, 4.90, 4.86 and 6.73 days for 2nd instar larvae, respectively. LT50 values at RH of 50%, 60%, 70%, 80%, 90% and 100% were 12.97, 10.97, 10.13, 9.79, 9.14, 8.29 for adults and 7.68, 6.92, 5.76, 5.57, 5.48, and 4.82 days for 2nd instar larvae, respectively. Therefore, temperatures between 23-26℃ and RH higher than 80% were the most suitable conditions for promoting infection of B. bassiana to P. brassicae.
Bassiana
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Macrosiphum roswomm is one of the most serious pests on Rosaceae. However,biological control of M. roswomm with Beauveria bassiana still remains unreported. The patho genicity and greenhouse control effect of B. bassiana strain isolated from M. roswomm on aphid nymphs and adults,and the survival of B. bassiana on rose leaves were studied. The results showed that,under the same conditions,aphid mortality increased with increasing spore concentration.At the spore concentration of 108 spores / m L,the highest cumulative mortality was 99. 3% in 5 days; the pathogenicity for adults and the third instar nymphs was much higher than the first instar nymph. Under different temperature and humidity,the highest mortality was discovered at the condition of 25 ℃,and the infection mortality rate increased with the increasing of the environment humidity; the highest infection mortality in greenhouse was 94%. These results indicated that B. bassiana has a good potential in biological control of M. roswomm.
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Beauveria
Heterorhabditis bacteriophora
Animal ecology
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Beauveria
Entomopathogenic fungus
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The bacterial suspension of Beauveria bassiana( Bals.) Vuill with different concentrations have been used to infect the larvae and adults of bark beetles indoors,and the death rate of larvae and adults have risen with raising the concentration. Under the same conditions,Beauveria bassiana have infected the larvae easier than the adults,and the lethal time of larvae are shorter than the adults. The bark beetles have been controlled with brushing and injecting bacteria outdoors. The results of controlling bark beetles with injecting bacteria of 0. 1 hundred million spores / mL and one hundred million spores / mL were higher than brushing. There was no obvious difference between two kinds of controlling methods when the concentration reached up to ten hundred million spores / mL. Through 3-year continuous monitoring,in non- controlled area,the number of plant with insects and the insect density were relatively stable,with a higher insect density. In chemical controlling area,the numbers of plant with insects and the insect density had a large fluctuation. Compared with the chemical controlling area,the controlling result was effectively and continuously in controllin area with Beauveria bassiana,but the controlling effect disappeared after two years basically.
Bassiana
Beauveria
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[Objective]Effects of host’s environmental humidity on pathogenicity of Beauveria bassiana during white muscardine epidemic were studied to provide references for adopting proper treating and controlling measures to eliminate the influence of white muscardine on silkworm production . [ Method ] White muscardine silkworm bodies collected from Xiangzhou County of Guangxi were used to investigate their changes in different humid environment and pathogenicity every 15 days. [Result ]White muscardine silkworm bodies were observed at temperature of 25 ℃ in 60%, 75% and 90% RH environment, respectively. The results showed that there was a close relationship between humidity and survival ability of Beauveria bassiana. In storage environment of 60% RH, silkworm bodies remained intact and hard with yellowish white conidium clearly seen on 60 d. The pathogen activity went down progressively at increasing humidity. Those three treatments all had strong pathogenicity of Beauveria bassiana to 2nd -instar of silkworm during the first 30 days. Their LT50 was 2.915, 3.071 and 5.222 d, respectively. At 60%-75% RH, Beauveria bassiana still had strong toxicity to silkworm on 45-60 days, while at 90% RH, conidium number dramatically fell on the 45th d, hence its pathogenicity could not be detected. [Conclusion]Within 60 days, pathogenicity rate of Beauveria bassiana to silkworm was high, therefore it was useful to reduce reinfection of Beauveria bassiana by removing the diseased silkworm body timely and inactivating body pathogenicity.
Bassiana
Beauveria
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