Circadian rhythm changes in toxicity of the insecticide dieldrin on larvae of the migratory locust Locusta migratoria migratorioides.

Circadian changes in toxicity of the insecticide dieldrin were documented in the larvae (fifth stage) of the migratory locust, Locusta migratoria migratorioides. Insects were housed under light (L): dark (D) = 12:12, with L from 0800 to 2000 h. Topical applications of dieldrin at fixed clock hours, with doses ranging from 0.1 to 8 micrograms/gm body weight, were carried out in a series of experiments on male and female larvae. Twenty-four h after dosing, mortality was recorded to quantify the median lethal dose (LD50) values with reference to time of treatment. Experiments were performed during February, early and late June, and August. Larvae were more susceptible to dieldrin when dosed during the night rather than during the day [analysis of variance (ANOVA); p less than 0.05]. Moreover, female larvae were less susceptible to dieldrin than were male larvae (ANOVA; p less than 0.05). Cosinor analysis revealed circadian rhythms in susceptibility-resistance to the insecticide in all experiments except no. 2. Toxicity was found to be greatest during the nighttime. Cosinor analysis of pooled data of the four experiments documented circadian rhythmicity to toxicity of dieldrin in female but not in male larvae. Regardless of sex, the timing of least susceptibility (greatest resistance and highest LD50 value) to the insecticide, dieldrin, was around 1500.     

Insecticide resistance gene frequencies in Anopheles sacharovi populations of the Çukurova plain, Adana Province, Turkey

In Turkey, the mosquito Anopheles sacharovi has been under field selection pressure sequentially with DDT, dieldrin, malathion and pirimiphosmethyl over a period of 30 years for the purpose of malaria control. In 1984, the field population of An.sacharovi in the malarious Cukurova plain of Adana Province contained an altered acetylcholinesterase-based resistance gene giving broad spectrum resistance against organophosphorus and carbamate insecticides. The cross-resistance spectrum from this mechanism conferred resistance to malathion but not to the organophosphorus insecticide pirimiphos-methyl. Over the 6 years that pirimiphos-methyl has been applied for malaria vector control in this area, the frequency of the altered acetylcholinesterase resistance gene has declined, although in 1989 and 1990 it was still present at measurable frequencies in An.sacharovi from Cukurova. In addition to the acetylcholinesterase resistance mechanism there is evidence of an increased level of glutathione S-transferase in some of the An.sacharovi populations tested. This is known to be correlated with DDT resistance in other anophelines. In Turkish An.sacharovi, DDT resistance and elevated glutathione S-transferase occur in the same populations at similar frequencies. The continued prevalence of resistance to DDT and dieldrin, long after the 1971 cessation of DDT spraying for malaria control in Turkey, suggests that the DDT resistance gene has insufficient reduced fitness associated with it to have been lost from the field population during the past two decades. The implications of the slow decline in resistance gene frequencies in this field population are discussed in relation to mathematical models for managing resistance.     

Genetic linkage between malathion and dieldrin resistance in Anopheles arabiensis

A strain of Anopheles arabiensis resistant to both malathion and dieldrin was crossed and backcrossed to a susceptible strain. The progeny were tested on each insecticide in turn. Less than 50% mortality in the second insecticide exposure among the backcross progeny indicated linkage between the resistance genes. In a backcross of A. gambiae X A. arabiensis hybrids a recombination rate of 7.5% was observed. A Y-translocation strain of A. arabiensis showed less than 2.8% recombination between the resistance genes. It is impossible to confirm the genotype of apparent recombinants using existing stocks, but the two resistance mechanisms are biochemically distinguishable. If the two genes are very closely linked, linkage disequilibrium could influence the consequences of switching to malathion spraying after dieldrin resistance has evolved.     

Should DDT be banned by international treaty?

The insecticide DDT has been an effective and affordable means of malaria control in many countries, but pressure for its use to be banned is mounting. Here, Chris Curtis and Jo Lines take a critical look at evidence that links house spraying by DDT with harm to the environment and human health, and stress the need for resources for alternatives to DDT to be made available to countries that would be affected by a DDT ban.     

Persistence and distribution of insecticidal seed-dressings for control of the wheat bulb fly, Leptohylemyia coarctata

Samples of plants and soil from two experimental sites, one clay loam and one peaty loam, were analysed chemically to try to explain differing results with γ-BHC and dieldrin seed-dressings applied to control wheat bulb fly on different soil types, and to suggest reasons for patchy plant stands and occasional failure to control the pest. Seed dressed with dieldrin yielded more than untreated seed on both sites, whereas seed treated with γ-BHC yielded as much as seed treated with dieldrin on the clay site, but it yielded less than untreated seed on peat. The chemical analyses showed that the poor performance of γ-BHC on the peat site could not be explained by its failure to persist, because the soil still contained considerable quantities of γ-BHC at the time of insect attack. Possible reasons may be sorption of the poison by organic matter making it less available, and deeper sowing, permitting larvae to reach the plants without prolonged contact with the insecticide. Bayer 38156 (O-ethyl S-p-tolyl ethyl phosphonodithioate) and trichloro-nate (O-ethyl O-2,4,5-trichlorophenyl ethyl phosphonothionate) persisted in soil long enough and were sufficiently toxic to wheat bulb fly to suggest that organophosphorus compounds might provide alternatives to chlorinated hydrocarbon insecticides for control of the fly. Analyses made on seeds dressed at the laboratory for the experiment showed that the amounts of insecticide on seeds were smaller than expected and that the amounts on individual seeds differed greatly. Of ten samples of seeds dressed commercially with y-BHC, three carried very little insecticide, and the variations in the other seven samples were greater than with experimentally applied dressings.     

Global impact of biotech crops: environmental effects, 1996-2010

This paper updates the assessment of the impact commercialized agricultural biotechnology is having on global agriculture, from some important environmental perspectives. It focuses on the impact of changes in pesticide use and greenhouse gas emissions arising from the use of biotech crops. The technology has reduced pesticide spraying by 443 million kg (-9.1%) and, as a result, decreased the environmental impact associated with herbicide and insecticide use on these crops [as measured by the indicator the Environmental Impact Quotient (EIQ)] by 17.9%. The technology has also significantly reduced the release of greenhouse gas emissions from this cropping area, which, in 2010, was equivalent to removing 8.6 million cars from the roads.     

博落回生物碱对蝗虫成虫毒力试验简报

目的:测定博落回生物碱对蝗虫成虫的毒力作用,为利用药用植物提取物杀灭蝗虫的无公害防治提供参考。方法:用文献法提取博落回果实中的生物碱,制备博落回生物碱溶液;采用喷雾法将博落回生物碱溶液喷施于蝗虫成虫;进行了博落回生物碱溶液对蝗虫成虫的田间小面积试验;用计算机软件SPSS11.5进行统计学分析。结果:在96小时内,博落回生物碱对蝗虫成虫的LD50为29.568mg/L,95%可信限为2.5563～69.473mg/L。田间小面积施药3天后,每平方米内虫口减退达90%左右,持效时间7天。结论:博落回溶液对蝗虫成虫具有一定的杀灭作用。     

EXPERIMENTS ON THE MODE OF ACTION OF DIELDRIN SEED-DRESSINGS AGAINST SEEDLING ATTACK BY THE LARVAL FRIT FLY, OSCINELLA FRIT L

Experiments with dieldrin seed-dressings were done to see whether the conditions favouring their action against wheat bulb fly larvae apply also to frit fly.
Experiments with oats and wheat in boxes and a small field trial with oats showed that fewer newly hatched larvae were killed when dieldrin-treated seed was sown deeply than when sown 1/4 - 1/2 in. deep; shallow sowing probably puts the insecticide where the larvae are likely to meet it before they attack the plant. Kill was never complete even with dieldrin applied at almost forty times more than the highest rate normally used. This is partly because some larvae hatch from eggs on the plant and these, unlike those from soil eggs, can enter the shoot without touching the seed dressing.
Even in the most favourable circumstances (large doses of dieldrin applied to the shallow-sown seed and the plant at the one-leaf stage at the time of attack) there was little evidence that frit fly larvae are killed inside the shoot by systemic action of dieldrin translocated from the seed. This is not because the pales which normally surround the oat seed impair the uptake of insecticide, or because of any other factor specific to oats. Frit fly larvae also survived in wheat from seed dressed with doses of dieldrin that can kill almost all wheat bulb fly larvae by systemic action. Possible reasons for this difference are discussed.     

Dieldrin-resistant cabbage root fly in England

The existence of dieldrin resistance in Erioischia brassicae has been investigated in the main areas in England and Wales where brassicas are grown for human consumption. Dieldrin-susceptible and dieldrin-resistant flies were collected and bred as separate strains in the laboratory. In toxicity tests adult flies were treated with topically applied doses of insecticide in microdrops of cellosolve, and larvae were dipped in solutions of insecticide in 70% acetone and 30% water. Adults of the laboratory resistant strain showed a high level of resistance to dieldrin and aldrin and a lower level of resistance to γ-BHC. There was no cross-resistance with chlorfenvinphos or diazinon. Larvae of the resistant strain were shown to be resistant to dieldrin. Dieldrin resistance has been found in four areas in southern England, but not in a fifth major area, and resistant flies did not increase as rapidly in some areas as others. Sufficient migration of flies appeared to take place to produce similar percentages of resistant flies over areas of several square miles, but considerable differences were found in fly populations about 10 miles apart. It is suggested that the speed of development of insecticide resistance is affected by the proportion of brassica crops which are treated in an area, the amounts of insecticide applied to individual crops, and hence the insecticidal pressure applied to the E. brassicae population.     

Cost-comparison of DDT and alternative insecticides for malaria control

In anti-malaria operations the use of DDT for indoor residual spraying has declined substantially over the past 30years, but this insecticide is still considered valuable for malaria control, mainly because of its low cost relative to alternative insecticides. Despite the development of resistance to DDT in some populations of malaria vector Anopheles mosquitoes (Diptera: Culicidae), DDT remains generally effective when used for house-spraying against most species of Anopheles, due to excitorepellency as well as insecticidal effects. A 1990 cost comparison by the World Health Organization (WHO) found DDT to be considerably less expensive than other insecticides, which cost 2 to 23 times more on the basis of cost per house per 6 months of control. To determine whether such a cost advantage still prevails for DDT, this paper compares recent price quotes from manufacturers and WHO suppliers for DDT and appropriate formulations of nine other insecticides (two carbamates, two organophosphates and five pyrethroids) commonly used for residual house-spraying in malaria control programmes. Based on these 'global' price quotes, detailed calculations show that DDT is still the least expensive insecticide on a cost per house basis, although the price appears to be rising as DDT production declines. At the same time, the prices of pyrethroids are declining, making some only slightly more expensive than DDT at low application dosages. Other costs, including operations (labour), transportation and human safety may also increase the price advantages of DDT and some pyrethroids vs. organophosphates and carbamates, although possible environmental impacts from DDT remain a concern. However, a global cost comparison may not realistically reflect local costs or effective application dosages at the country level. Recent data on insecticide prices paid by the health ministries of individual countries showed that prices of particular insecticides can vary substantially in the open market. Therefore, the most cost-effective insecticide in any given country or region must be determined on a case-by-case basis. Regional coordination of procurement of public health insecticides could improve access to affordable products.     

Pesticides for locust control.

The factors influencing the choice of insecticides for locust control are effectiveness, safety in use, relative cost, and the formulations available. The relative importance of these factors varies with the scale of control. In small scale control by farmers safety and simplicity are paramount and a BHC dust is commonly used, but in large scale control operations by specialized organizations more toxic formulations ultra-low-volume (u.l.v.) concentrates and methods of application requiring considerable skills can be used. The remarkable effectiveness of dieldrin as a stomach poison appears to be due to its conversion to photodieldrin after application. Cases of poisoning following large scale control operations are rare, and fatalities in man unknown. Alternatives to organochlorine insecticides include fenitrothion, already recommended and used on a large scale against adults. Against nymphs the correct dosage of fenitrothion would cost nearly 11 times as much as that of dieldren. Recent experimental work with new insecticides has included safety tests with domestic animals and measurements of persistence. 1 microgram deposits of cyanofenphos, decamethrin and mecarphon, as well as of dieldrin and photodieldrin, on wheat seedlings left in the open under tropical conditions for two days, killed 80% or more first instar nymphs of the Desert Locust which fed on them.     

Optimum timing for integrated pest management: Modelling rates of pesticide application and natural enemy releases

Many factors including pest natural enemy ratios, starting densities, timings of natural enemy releases, dosages and timings of insecticide applications and instantaneous killing rates of pesticides on both pests and natural enemies can affect the success of IPM control programmes. To address how such factors influence successful pest control, hybrid impulsive pest-natural enemy models with different frequencies of pesticide sprays and natural enemy releases were proposed and analyzed. With releasing both more or less frequent than the sprays, a stability threshold condition for a pest eradication periodic solution is provided. Moreover, the effects of times of spraying pesticides (or releasing natural enemies) and control tactics on the threshold condition were investigated with regard to the extent of depression or resurgence resulting from pulses of pesticide applications. Multiple attractors from which the pest population oscillates with different amplitudes can coexist for a wide range of parameters and the switch-like transitions among these attractors showed that varying dosages and frequencies of insecticide applications and the numbers of natural enemies released are crucial. To see how the pesticide applications could be reduced, we developed a model involving periodic releases of natural enemies with chemical control applied only when the densities of the pest reached the given Economic Threshold. The results indicate that the pest outbreak period or frequency largely depends on the initial densities and the control tactics.     

常用杀虫剂噻虫嗪及其4种混配制剂对中华蜜蜂的生存风险分析

噻虫嗪及其混配制剂是防治刺吸式口器害虫的常用药剂,但对中华蜜蜂的生存风险尚未明确。在实验室条件下通过模拟中华蜜蜂授粉期间农药暴露的3种方式(蜂体接触、取食接触、植株接触),评估了噻虫嗪及其4种混配制剂,在田间最高推荐剂量下对中华蜜蜂采集蜂的毒性。结果表明,无论哪种暴露方式,噻虫嗪及其混配制剂均显著影响中华蜜蜂采集蜂的生存,且噻虫嗪混配制剂毒性高于单剂。在直接喷洒蜂体处理中,25%噻虫嗪·异丙威可湿性粉剂表现出最高毒性,其致死中时间(LT_(50)值)为1.23 h;在摄入和接触植株残留处理中,40%氯虫·噻虫嗪水分散粒剂和25%噻虫嗪·异丙威可湿性粉剂均表现出最高毒性,LT_(50)值分别为2.09、6.75 h和2.15、6.77 h。在3种暴露方式下,25%噻虫嗪水分散粒剂的LT_(50)值分别为6.50、17.24和8.90 h,明显低于对照。因此建议蜜蜂授粉期间禁止施用噻虫嗪及其混配制剂,为更好地推进蜜蜂授粉与绿色防控技术的研究与示范提供安全保障。     

Dieldrin and diazinon resistance in populations of the Australian sheep blowfly, Lucilia cuprina, from sheep-grazing areas and rubbish tips

Populations of L. cuprina collected from adjacent sheep-grazing areas and rubbish tips in Victoria (Mansfield and Warrnambool) and New South Wales (Lismore) were tested for resistance to the insecticides diazinon and dieldrin. Populations from sheep-grazing areas had a significantly higher diazinon Rop-1 allele frequency than those from adjacent tips with the Victorian populations being more resistant than those from Lismore. Victorian sheep and tip populations had similar gene frequencies at the dieldrin resistance locus, but the Rdl allele frequency was significantly greater in the population at the tip than in the population from the sheep-grazing area at Lismore. The Rdl allele is at a higher frequency in flies from the Lismore area than in Victorian populations. The results at both loci are explained by a balance of selection and gene flow between sheep and tip populations and by selective differences between geographical areas. The exceptionally high frequency of the dieldrin Rdl allele in populations at the Lismore tip may be partially explained by the use of dichlorvos for fly control. Dosage mortality curve and genetic analyses suggest that dichlorvos (an organophosphorus compound) may select at the dieldrin resistance locus. Possible mechanisms for this are discussed. The consequences of genetic differentiation between L. cuprina populations within a region for an autocidal control program are considered.     

The effect of hepatic microsomal monooxygenase induction on the metabolism and toxicity of the organophosphorus insecticide chlorfenvinphos

The induction of rat liver microsomal monooxygenase by pretreatment of rats with dieldrin affords a 10-fold protection against the acute toxic effects of the organophosphorus insecticide, chlorfenvinphos. Metabolism studies were carried out to confirm that the protection was due to an enhanced rate of detoxification (via oxidative deethylation). At low doses of chlorfenvinphos (2.5 mg · kg^?1), dieldrin pretreatment caused minimal changes in the metabolic profiles. However, at a higher dose (13.2 mg · kg^?1), giving clinical signs of intoxication in the control animals, the dieldrin pretreated rats produced 5 times more deethylchlorofenvinphos than did the control animals. The results support the conclusion that the effect of enzyme induction on the metabolism of substrates of that enzyme are dosedependent. Alterations in metabolism, therefore, are not an automatic consequence of enzyme induction.     

Malaria eradication in Calabria, residual anopheles and transmission risk]

The paper is from a presentation at the meeting "La malaria in Calabria" (Cosenza, Italy, May 3, 1997) held to celebrate the half centenary of the antimalaria campaign (1947-1952) that eradicated the infection from the region. While Plasmodium falciparum had already disappeared in 1950, P. vivax persisted and the last autochtonous case was documented on the river Esaro in 1955. From the records of that time, it is clear that malaria eradication was achieved in the presence of important vector densities, as shown by larval surveys. Indoor DDT spraying, acting through the insecticide irritant effect, mainly avoided the house resting by the vector and forced the exposure of the mosquito to the outdoor environment where the lower mean temperatures eventually proved instrumental in destabilizing the parasite's life cycle. It is stressed that insecticide resistance never arised in the Anopheles vector populations of Calabria, in spite of at least ten years of continuous indoor spraying with an excellent overall coverage. This is expected in the absence of important selection pressures at the larval breeding sites and whenever the impact of the house spraying on the vector is due mainly to the insecticide irritant effect rather than to a direct imagocidal effect.     

Effect of deltamethrin spraying on the sandfly populations in a focus of American cutaneous leishmaniasis.

The effect of deltamethrin of the sandfly population in a focus of American Cutaneous Leishmaniasis in Viana, Espírito Santo State is described. The phlebotomine population density was determined inside and outside houses during a one year period in a treated and untreated area. The results showed a significant reduction in the number of sandflies inside houses in the treated area compared with both the untreated area and the same area before spraying. Despite having a residual action for 12 months after spraying the insecticide was ineffective outside houses. It is concluded therefore that deltamethrin is an efficient insecticide for reducing the number of phlebotomine sandflies inside houses.     

DETERMINATION OF THE RESISTANCE OF LOCUSTS TO DNC IN RELATION TO THEIR WEIGHT, AGE AND SEX

Experiments have shown that the resistance of adults of the desert locust ( Schistocerca gregaria ) and the African migratory locust ( Locusta migratoria migratorioides ) to DNC applied as a contact poison to the ventral surface of the abdomen is directly related to their body weight, irrespective of age or sex.
Varying the site of application of the insecticide had little effect on the susceptibility of the insects except when the dose was applied to the wings or femur, these being less effective sites of entry for the poison.
Increasing the post-treatment temperature from 25 to 36°C. had no noticeable effect on mortality, but the speed of action of the insecticide was much increased.     

A pilot study to control Lutzomyia umbratilis (Diptera:Psychodidae), the major vector of Leishmania braziliensis guyanensis, in a peri-urban rainforest of Manaus, Amazonas State, Brazil

In the second half of 1980, 112 (or ca. 16%) of the inhabitants of the new settlement of S?o José, city of Manaus, contracted cutaneous leishmaniasis whilst clearing their properties of terra firme rainforest. With the aid of SUCAM, the authors carried out a pilot study to investigate the feasibility of reducing populations of Lutzomyia umbratilis, the local silvatic vector of Leishmania braziliensis guyanensis, by spraying insecticide on its favoured diurnal resting sites, the bases of the larger forest trees. Most manvector contact is at these resting sites and, therefore, it was encouraging to record a marked reduction of the tree-base populations of L. umbratilis for 21 days following just one application of D.D.T. emulsion in an area 200m square. Most of the treated trunks were not occupied by L. umbratilis for at least eleven months. Suggestions for extending the pilot study are made, and the need for collaboration with a clinical team is emphasized. Leishmania b. guyanensis is the aetiological agent of "pain bois", which is hyperendemic from French Guiana to central Amaz?nia. In the absence of proven vaccines or methods of vector control, some simple methods for limiting transmission of Le. b. guyanensis to man are listed.     

Discharges of pesticides to the Rivers Mole and Taw, their accumulation in fish flesh and possible effects on fish stocks

A discharge of aldrin and dieldrin caused mortality of salmonid fry in a hatchery. Pesticide residues in fish flesh and resulting management action are described. Differences in wild fish stock densities could be due to pesticides but other possibilities are explored. Dieldrin was widely distributed, even at control sites, at levels considered potentially dangerous to piscivores. A further point source was traced and widespread environmental contamination was observed.