The index of population trend in treatment of spraying chemical insecticides was 7.20,The index of population trend would increase in 1.43 times against that in control.
The LT50 values ranged from 2 d to 5 d at the dosages of 1. 31 -16. 48 conidia/mm2. The estimated dose-effect parameter β was 1. 82. a high value for a microbial control agent and equivalent to that of some chemical insecticides.
The result showed that the effects of BtA 800x 3—12days after spray to aphid were 85.96%, 92. 98%, 91.22%, much higher than those 4 chemical insecticides.
Field application indicated that 0. 4 billion nematodes/667m2 of use amount can keep the damage rate of beet seedlings under 15.1%, this result was obviously higher than those of chemical insecticides.
ational use of chemical insecticides, protection and utilization of natural enemies. The purpose of integrated control was to heighten the benefits and effects of ecology, economics and society.
This virus belongs to subgroup B of Baculovirus, terms IcGV. Bioassay conducted in the laboratory showed that the medium lethal concentration LC_(50) was 1×10~(-4.36). Field tests showed that the mortality of the larvae may reach 86—100％ spraying with the virus suspension, the IcGV was better than the chemical insecticides Malathion.
Without chemical insecticides in vegetable fields, the index of population trend (I) of dominant insect pest decreased greatly, the control effect of natural enemies on major insect pests increased, the diversity index of arthropod increased at the same time.
The effect of chemical insecticides on the structure and diversity of arthropod communities in various vegetable fields and the restoration of their biodiversity after stopping application of chemical insecticides were studied.
When the applications of chemical insecticides were stopped in vegetable fields, the index of population trend ( I ) of dominant insect pests decreased greatly, the control effect of natural enemies on major insect pests increased, and the diversity index of arthropod increased at the same time.
When SLNPV of 10~(6)PIB/mL was added to chemical insecticides,the synergic ratio is 2.75 and 2 at the fifth day,LT_(50)is shortened by 10.472 d and 6.402 d at the seventh day.
Methods Using A,B,C,D four kinds of method for killing cockroach to each xingshisu,25K,25G,22 type,using chemical insecticides to investigate the density of cockroaches and counting the killing rates.
1. chemical insecticides: field tests of six insecticides to control alfalfa thrips shows that six insecticides gave significant control, especial 25% thiamethoxam 5000x、10000x、15000x and 1.8% abamectin 1000x, 3 days after treatment, the control level attained were 85.63~93.30%.
As the farmers gain more experience with both agronomic practices and chemical insecticides, they are likely to rely more heavily on cultural practices and less on insecticides to manage PTM.
Use of chemical insecticides has created a control problem because of the development of resistance.
By contrast cotton growers are beset with problems of pest resistance to chemical insecticides.
The compatibility of the entomopathogenic fungus Lecanicillium muscarium and chemical insecticides used to control the second instar stages of the sweetpotato whitefly, Bemisia tabaci, was investigated.
The use of both control agents might be helpful in reducing the selection pressure for resistance to chemical insecticides, thereby delaying or preventing the build-up of resistant populations in greenhouses.
The pine caterpillar is one of the most important pests of pine trees in China. Be-cause there are some disadvantages to apply chemical control of this pest, an urgentneed of using microbial methods as a supplementary measure is evident. The results ofthe preliminary test are very promising. The results are as follows: 1. The application of B. thuringiensis var. thuringiensis to control the pine cater-pillar seems to be very effective. In future it may develop into a new and powerfulweapon in pest control work....
The pine caterpillar is one of the most important pests of pine trees in China. Be-cause there are some disadvantages to apply chemical control of this pest, an urgentneed of using microbial methods as a supplementary measure is evident. The results ofthe preliminary test are very promising. The results are as follows: 1. The application of B. thuringiensis var. thuringiensis to control the pine cater-pillar seems to be very effective. In future it may develop into a new and powerfulweapon in pest control work. 2. The concentrations of the bacterial suspensions should be raised with the in-crease of larval instars. The range is approximately between 15×10~6--2.7×10~8 sporesper c.c. 3. High temperature resulted in a quick infection and death of the larvae. There-fore, the application of this method in June, July and August will give better results,though in cold and wet seasons, for example in March and April in central China, thecontrol is also effective. 4. The applications of B. thuringiensis var. thuringiensis with very dilute concentra-tions of chemical insecticides, such as 666, DDT and Diptrex, will give quicker andbetter results. This is a promising method. Dusting is valuelessly.
The European corn borer(Ostrinia nubilalis)is one of the major pest insects of grain crops in Hopei Province.In the past satisfactory control may be achieved by using granulated insecticides at the late whorl stage of the corn.But in recent years the infestation by this pest has aggravated in districts where the cultivation system has changed.This paper reports the occurrence and the integrated control of this insect in Yung-ching County,1974.The results of our study may be summarized as follows.1.Our field...
The European corn borer(Ostrinia nubilalis)is one of the major pest insects of grain crops in Hopei Province.In the past satisfactory control may be achieved by using granulated insecticides at the late whorl stage of the corn.But in recent years the infestation by this pest has aggravated in districts where the cultivation system has changed.This paper reports the occurrence and the integrated control of this insect in Yung-ching County,1974.The results of our study may be summarized as follows.1.Our field observations on the development of the European corn borer have shown that when the summer corn is sown between rows of growing wheat,the eggs of the second generation of the pest will be deposited mainly on corn plants at the tasseling-silking stage.When the summer corn is sown after the wheat is harvested as before,the eggs will be equally divided between the corn plants at late whorl stage and those at the tasseling-silking stage.This is the reason why the damage on corn by this insect at tasseling-silking stage is increased in recent years.2.Several insecticides and their mixtures have been tested and some of them are found to be good substitutes for the organochlorine insecticides used before.The effectiveness of 1%,0.5% and even 0.25% granulated E605 were found higher or a little lower than the 5% granulated DDT When 0.5% or 0.1% E605 is added to the soil granules of the white muscardine fungus(Beauveria bassiana)(1:20),the effectiveness is higher or a little lower than the 5% DDT granules respectively.0.1% and 0.2% Phoxim granules are more effective than 0.1% 666 granules.C-9140 soil granules(1:10)are as effective as 5% DDT granules.3.According to our experience the integrated control of the European corn borer in our district may include the following steps:destruction of the host plant debris in the winter,attracting and killing the adult moths by light traps,and the combined use of the fungus and chemical insecticides.
This paper reports the results of studies on the nuclear polyhedrosis virus-of the cotton bollworm Heliothis armigera.The virus was isolated in 1974 from dead boll-worms collected from cotton fields in Chinchow district of Hupeh Province.It was designated as VHA-273.It is observed that the polyhedra are hexagonal,pentahedron,cubical or irregular in shape,varying from 1.25 to 5.0 p in diameter.Serious pathological changes were in the fat-body,epidermis,tracheal matrix and other tissues of the diseased insects...
This paper reports the results of studies on the nuclear polyhedrosis virus-of the cotton bollworm Heliothis armigera.The virus was isolated in 1974 from dead boll-worms collected from cotton fields in Chinchow district of Hupeh Province.It was designated as VHA-273.It is observed that the polyhedra are hexagonal,pentahedron,cubical or irregular in shape,varying from 1.25 to 5.0 p in diameter.Serious pathological changes were in the fat-body,epidermis,tracheal matrix and other tissues of the diseased insects and the former two seemed to be the most susceptible tissues.The muscle bundles were not affected.Our bioassay showed that the susceptibility of the larvae to the NPV varied with dosage,larval instar and temperature.The first and second instars were the most susceptible stages;and their mortality rates at 1×106 PIBs/ml were 85% and 80% and the time lasting were 6 and 8 days respectively.Larvae of fifth and sixth instars were not so susceptible,especially when the temperature exceeded 33℃.Cross infections of the NPV with tobacco budworm,Heliothis assulta,was susccessful.In 1975,from July to September,field tests with the NPV to control bollworms were made in cotton fields about 102 mil's at Kung-an County of Hupeh Province.The concentrations used were 1.5×1010 PIBs/mu,3×1010 PIBs/mu and 6×1010 PIBs/mu.The results showed that the NPV was better than the chemical insecticides 1605+DDT.Combined use of the NPV with dilute sevin and Bacillus thurin-giensis suspensions were also tested;and the results were either better or as effective as the NPV or sevin used alone.The application of the NPV VHA-273 to control bollworms in the field seems promising.
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