THE TOXICITY OF SOME INSECTICIDES TO FIFTH-INSTAR NYMPHS OF THE DESERT LOCUST

The toxicities of the insecticides γ-BHC, diazinon, dieldrin, DNC, heptachlor and parathion to fifth-instar hoppers of the desert locust were determined. Parathion and dieldrin were the most toxic, followed in descending order by heptachlor, γ-BHC, diazinon and DNC. The resistance of the hoppers to γ-BHC and DNC changed appreciably with age within the instar.
The effects of some factors which might influence the resistance of the insects were examined and are discussed.     

THE EFFECT OF BODY WEIGHT ON THE RESISTANCE TO INSECTICIDES OF THE LAST-INSTAR LARVA OF DIATARAXIA OLERACEA L., THE TOMATO MOTH

At a constant temperature of 24° C. the final larval instar of Diataraxia oleracea lasts about 10 days, during which its resistance to DDT and γ-BHC as contact insecticides progressively increases up to the 5th or 6th day. It then suddenly decreases, this coinciding with cessation of feeding and the beginning of prepupal formation.
Between the 2nd and the 6th days the gross body weight of the last-instar larva increases from about 0.27 to 0.65g. Under the conditions of the experiments, the LD50 of parathion, as a stomach poison, was linearly related to body weight; on the same basis TEPP was slightly less, and lead arsenate, slightly more, toxic to the larger than to the smaller larvae. However, DDT as a stomach or contact insecticide, and γ-BHC as a stomach poison were notably less toxic to the larger larvae. For example, the increase in LD50 for an increase in larval body weight of × 2 was about × 11 for DDT as a stomach poison and about × 12 as a contact insecticide.
The order of effectiveness of the above insecticides as stomach poisons for the last-instar larva of D. oleracea was parathion > DDT > γ-BHC > TEPP = lead arsenate. Zinc fluoarsenate and rotenone were relatively non-toxic. Larvae of D. oleracea were repelled by food leaf treated with an extract of natural pyrethrins.     

THE USE OF SEED DRESSINGS CONTAINING γ-BHC IN THE ESTABLISHMENT OF SUGAR-BEET SEEDLINGS

From 1949 to 1952 field trials were made to determine the effect of seed dressings containing γ-BHC, with and without the addition of organic mercurial compounds, upon the establishment of sugar-beet seedlings. Most of the trials were made in fields where no serious pest problems were anticipated. The 1949 trials established the concentration of γ-BHC non-phytocidal to sugar-beet seedlings. Later trials tested the effect on pre- and post-singling plant populations of dressings applied to natural or rubbed seed sown at standardized rates. Parallel tests of dressed seed were made on farms representing a variety of soil types, It was found that the phytotoxiCity of γ-BHC varied with season and soil type, but that a dressing containing 40 % was usually safe. In these trials, the benefits from seed dressing were, as a rule, slight. Generally the combined mercury-γ-BHC seed dressing gave the best pre-singling stand of plants. Most of the improvement was attributable to the organic mercury rather than to the γ-BHC, but where pest attacks occurred, γ-BHC gave marked improvements in stand. Wireworm appeared to be the chief pest controlled: control of pygmy mangold beetle was only partial.     

Effect of prostaglandin F2 alpha (PGF2 alpha) on sources of progesterone and pregnancy in intact, ovariectomized and hysterectomized 90-100 day pregnant ewes.

A single dose of 8 or 16 mg of PGF2 alpha per 58 kg body weight was injected intramuscular into intact, ovariectomized or hysterectomized 90-100 day pregnant sheep in three separate experiments. Both doses of PGF2 alpha decreased the weights of the corpora lutea (P less than or equal to 0.05) and the concentration of progesterone in ovarian venous plasma at 72 hr (P less than or equal to 0.05) compared to the 0 hr sample within treatment groups and to control ewes at 72 hr in intact and hysterectomized pregnant ewes. In hysterectomized pregnant ewes, progesterone in jugular plasma declined (P less than or equal to 0.05) from 0 to 72 hr but never fell below 4 mg/ml and this decrease in progesterone after 8 or 16 mg PGF2 alpha was greater than in control hysterectomized ewes (P less than or equal to 0.05). There was a significant decrease in progesterone over time in jugular or uterine venous plasma in the presence of absence of the ovaries in 90-100 day pregnant ewes (P less than or equal to 0.05) but the profiles of progesterone were not different between vehicle and PGF2 alpha-treated ewes (P greater than or equal to 0.05). Uterine venous progesterone never declined below 30 ng/ml in the presence or absence of the ovaries and there was a significant quadratic increase (P less than or equal to 0.05) in uterine venous progesterone toward the end of the 72 hr sampling period indicating an increase in steroidogenic activity of the placenta. PGF2 alpha did not affect the number of abortions in intact or ovariectomized pregnant ewes (P greater than 0.05). Thus, the corpus luteum of sheep at 90-100 days of pregnancy is functional and responsive to PGF2 alpha, placentomes are functional but do not appear to be responsive to the doses of PGF2 alpha tested and PGF2 alpha was not an abortifacient over the 72 hr treatment period.     

PROTECTION OF SORGHUM AGAINST SOIL FUNGI, SOIL PESTS AND COVERED SMUT BY COMBINED INSECTICIDE-FUNGICIDE SEED DRESSINGS

Treatment of sorghum ( Sorghum vulgare ) seed with fungicide dressings controlled covered smut ( Sphacelotheca sorghi ), the major disease of sorghum in the Sudan, and usually resulted in appreciably better stands. In the Sudan Gezira, powder dressings containing 20–40%γ-benzene hexachloride (γ-BHC) applied at the rate of 1g./1b. of seed effectively protected sorghum seedlings from root attack by chafer grubs ( Schixonycha sp.) and significantly increased stands and yields. No certain evidence of this effect was obtained with dolichos bean ( Dolichos lablab ) or groundnut ( Arachis hypogaea ), and the different responses shown by these plants as compared with sorghum are attributed largely to differences in seed germination and root system. An application rate of 0·08 %γ-BHC/seed was sometimes slightly but appreciably phytotoxic to sorghum in the field and more markedly so in greenhouse experiments. A powder containing 25% thiram and 20%γ-BHC applied at the rate of 1g./1b. of seed is recommended as the standard seed dressing for sorghum in the Sudan.     

Effects of the organophosphate insecticides diazinon and parathion on bobwhite quail embryos: skeletal defects and acetylcholinesterase activity

Bobwhite quail eggs were injected at 48 or 72 hr of incubation with various doses of the organophosphate (OP) insecticides diazinon or parathion and the embryos were examined after an additional 48 hr of incubation by both histological and cartilage-staining methods. Bobwhite embryos did not display the notochordal folding or vascular enlargement reported for OP-injected chicken embryos. Cartilage staining of embryos injected with insecticide at 72 hr of incubation and recovered at day 12 of incubation revealed severe shortening and contortion of the vertebral axis, as well as tibiotarsal, rib, and sternum defects. Parathion was more potent in causing skeletal defects than diazinon. No type I defects (micromelia, parrot beak) were detected. Radiometric acetylcholinesterase (AChE) assays of whole embryo homogenates were performed for day 6, 9, and 12 diazinon-injected and control embryos. Diazinon effected drastic reductions in AChE activity. Although the AChE and axial skeletal responses of bobwhite embryos to OP injection are similar to those reported in the literature for other species, some major differences in the bobwhite response were noted: namely, the absence of notochordal folding in the young bobwhite embryo and the absence of type I defects at day 12. These differences suggest that further studies with the bobwhite quail would be useful in clarifying the mechanisms involved in OP-induced teratogenesis.     

STUDIES OF THE TOXICITY TO WORKER HONEY-BEES (APIS MELLIFERA L.) OF CERTAIN CHEMICALS USED IN PLANT PROTECTION

Laboratory techniques are described for the estimation of the stomach poison, direct and residual film contact poison and fumigant poison effects of chemicals to adult worker honey-bees.
The toxicity of eleven chemicals used in plant protection has been investigated by these methods. The order of effectiveness as stomach and contact poisons was: parathion, TEPP, γ-BHC, dieldrin, aldrin, chlordane, o , o -diethyl- o -ethylmercaptoethyl thiophosphate (constituent of Systox), bisdimethylamino fluorophosphine oxide, toxaphene and the sodium salts of 2:4-D and MCPA: as residual films, dieldrin, aldrin, γ-BHC, parathion, chlordane, and o , o -diethyl- o -ethylmercapto-ethyl thiophosphate (constituent of Systox); toxaphene, TEPP and bisdimethylamino fluorophosphine oxide had no measurable effect; as fumigants, dieldrin, γ-BHC, aldrin, parathion, and chlordane; the remainder had no measurable effect.     

Toxicity of A Novel Neonicotinoid Insecticide Paichongding to Earthworm Eisenia fetida

Traditional neonicotinoid insecticides are used worldwide. Paichongding (IPP), as a novel neonicotinoid pesticide, has been widely used in China. However, the ecotoxicity of IPP to non-target invertebrates in soil ecosystem has not been reported yet. In this study, acute toxicity of IPP to earthworm Eisenia fetida, as well as the antioxidant response after IPP exposure, was evaluated. In the filter paper contact test, the LC₅₀ at 24 hr and 48 hr for IPP were 14.98 μg/cm² and 7.59 μg/cm², respectively. In artificial soil test, the LC₅₀ (lethal concentration) at 14 days and 28 days for IPP were 541.07 mg/kg and 238.51 mg/kg, respectively. The LC₅₀ of IPP is much higher than that of traditional neonicotinoid insecticides. However, earthworm body weight assessment demonstrated that the growth of earthworm was inhibited by extended exposure to IPP at sublethal doses. The activities of antioxidative enzymes superoxide dismutase and catalase in earthworms were significantly induced after IPP exposure. Malondialdehyde, a biomarker of lipid peroxidation, was also increased after IPP exposure. Although the results indicated that IPP had potentially adverse effect on earthworms, its toxicity was much lower than traditional neonicotinoids.     

INSECTICIDAL CONTROL OF PAEDOGENETIC CECID LARVAE IN MUSHROOM BEDS

γ-BHC, incorporated at 50 p.p.m. in mushroom compost during the last turn of composting delayed the reproduction of paedogenetic cecid larvae without reducing the yield of mushrooms. Other insecticides were less satisfactory as they either did not control the larvae, were not sufficiently persistent or decreased the yield. Large cecid populations did not depress yields on normal composts but a proportion of the larvae migrated on to the sporophores, thus reducing the value of the crop.     

Determination of the resistance of locusts to γ-BHC and diazinon in relation to their age, sex and weight

The relation between body weight and resistance to γ-BHC and diazinon was studied in experiments using the desert locust ( Schistocerca gregaria ) and the African migratory locust ( Locusta migratoria migratorioides) .
In all experiments with Schistocerca , resistance was proportional to weight within any one age and sex group. Resistance to diazinon (per unit body weight) decreased with age, that of the males at a faster rate than that of the females. Against γ-BHC the insects showed a nearly twofold increase in resistance about 1 week after fledging.
Within groups of Locusta the resistance to diazinon was found to be independent of weight, but the resistance to γ-BHC was dependent on weight. Similarly the resistance to diazinon at different ages after fledging was independent of age but resistance to γ-BHC increased with age.     

THE PENETRATION OF THE INSECT CUTICLE BY DDT AND RELATED COMPOUNDS

The penetration of pp -DDT and some related compounds into grain weevils has been studied by a micro-analytical technique.
Grain weevils were exposed to filter papers, impregnated with the chemical under test, for periods varying from a few hours to several days. The chemical removed by washing the insects with cold methanol, which was not expected to dissolve anything which had penetrated below the wax layer of the epicuticle, was described as being 'outside' the insect; that which remained was extracted with ether after grinding the insects with anhydrous sodium sulphate and recorded as being 'inside' the insect. By plotting the amounts 'inside' and 'outside' after varying times of exposure a picture of the rate of penetration of these compounds was obtained.
The results are discussed in relation to similar curves published earlier for isomers of benzene hexachloride. The major difference revealed is the very slow penetration of pp -DDT compared with γ-BHC. This is ascribed to the vapour effect of γ-BHC which has a vapour pressure much greater than that of pp -DDT.     

Influence of pH treatments on survival of Escherichia coli O157:H7 in continuous cultures of rumen contents

The pH (i.e., 5.5, 5.75, 6.0, 6.25, 6.5, 6.75, 7.0, and 7.25) effect on Escherichia coli O157:H7 in an artificial rumen model was investigated. Eight fermenters were inoculated with bovine rumen fluid and were supplied with a diet (75 g of dry matter daily in 12 equal portions [every 2 hr]) containing similar forage-to-concentrate ratio. After an adaptation period (i.e., 3 days for adjusting the rumen fluid [pH 6.2] microbial population to the test pH and 4 days for adjustment to the diet at the test pH), each fermenter was inoculated with 10(9) cells of E. coli O157:H7. Samples were collected hourly for 12 hr and every 2 hr for an additional 12 hr and were analyzed by flow cytometer. E. coli O157:H7 could not be quantified after 24 hr, and detection was only possible after enrichment. Because the pathogen could not be detected 5 days postinoculation (i.e., Day 13), the fermenters were reinoculated with E. coli O157:H7 on Days 17 and 22. E. coli O157:H7 numbers decreased from 10(6) to 10(4)/ml of fermenter contents in a quadratic (P < 0.05) fashion over the 24-hr sampling period, and the rate of reduction was slower (P < 0.05) for pH 7.0 than for other pH treatments. Results suggested that E. coli O157:H7 population were decreased by competitive exclusion and were not affected by culture pH.     

Toxicity of four systemic neonicotinoids to adults of Anoplophora glabripennis (Coleoptera: Cerambycidae)

As part of the ongoing evaluation of different systemic insecticides for prophylactic treatment of trees, responses of the beetle Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae) to different doses of four systemic neonicotinyl insecticides were studied. Adult beetles were provided with twigs or leaves of trees treated with different concentrations of imidacloprid to evaluate the toxicity of the insecticide through ingestion or contact or through both. Adult beetles also were provided with twigs of host plant treated with clothianidin, dinotefuran, and thiamethoxam to establish dose response of the beetle to these insecticides. Levels of individual insecticides in twigs and leaves were determined by using the "parent" method with high-performance liquid chromatography, and these levels were compared with the applied concentrations to determine their relationship. The LC50 values for detected level of each insecticide in twigs was 5.1 ppm at 24 h, 2.9 at 48 h, and 1.9 ppm at 72 h for imidacloprid; 1.1 ppm at 72 h for clothianidin; 2.2 ppm at 72 h for dinotefuran; and 1.0 ppm at 72 h for thiamethoxam. Our results indicate that mortality of adult beetles resulted not only from the ingestion and contact toxicity but also possibly from the antifeedant effect of imidacloprid.     

ACUTE ETHANOL EXPOSURE DECREASES THE ANALGESIC POTENCY OF MORPHINE IN MICE

Chronic (7 days), forced ethanol drinking can decrease the analgesic potency of opioid agonists in mice. In the present study, the effect of short-term ethanol treatment was examined using forced ethanol access and ethanol injection protocols. Mice were given forced access to 1, 3 or 7% (v/v) ethanol for 24 hr and then tested for s.c. morphine analgesia using the tailflick assay. Controls had access to water. Another group of mice was injected i.p. with 2.5 g/kg ethanol or water 4 times over a 21 hr period and tested 3 hr after the final injection for morphine analgesia. Other mice were injected once i.p. with 1, 2 or 3 g/kg ethanol or water and tested 24 hr later using the tailflick. In the forced access study, ethanol dose-dependently decreased morphine's analgesic potency with the highest dose (7%) producing a 1.6-fold shift in the ED₅₀. This decrease in morphine potency was similar to that found in a related study using 7% ethanol for 7 days (1.8-fold shift). Repeated ethanol injections significantly reduced the analgesic potency of morphine (1.9-fold shift), whereas, a single injection of 1, 2 or 3 g/kg ethanol did not alter the potency of morphine. Control studies indicated that neither 24 hr water nor food deprivation affected morphine potency. Overall, these data show that sustained exposure to ethanol over a 24 hr period will dose-dependently decrease morphine's analgesic potency. © 1998 Elsevier Science Inc.     

Degradation of chlorinated hydrocarbons by Clostridium sp. isolated from lindane-amended,flooded soil

Summary A Clostridium sp., isolated from flooded soil amended with lindane (γ-BHC), decomposed methoxychlor, γ-BHC and heptachlor in that order under anaerobic condition. During the bacterial degradation of ring-labelled C¹⁴-γ-BHC, there was a net loss of radioactivity from the reaction mixture. Release of C¹⁴O₂ during the degradation of C¹⁴-γ-BHC was negligible. Methane was not detected as an end product of γ-BHC breakdown. re]19720406     

Response of adult parasitoids ofBemisia tabaci (Hom.: Aleyrodidae) to leaf residues of selected cotton insecticides

The contact toxicity of eight insecticides to adults of four parasitoids of the sweetpotato whiteflyBemisia tabaci was evaluated in the laboratory. Two common Texas species,Eretmocerus sp. andEncarsia pergandiella Howard, and two exotic species,Eretmocerus mundus Mercet from Spain andEncarsia formosa Gahan from Greece were tested. Insecticides, applied as sprays to greenhouse-grown cotton plants at recommended rates were amitraz (Ovasyn^®), azinphosmethyl (Guthion^®), bifenthrin (Capture^®), buprofezin (Applaud^®), cypermethrin (Ammo^®), methyl parathion and thiodicarb (Larvin^®), with a water control. Parasitoid adults were confined on discs cut from leaves (1) sprayed the same day and (2) sprayed two days previously. Survival in both treatments was measured two and four days following exposure. Significant differences in toxicity were detected among the insecticides. Buprofezin was not toxic to any of the four parasitoids. When caged on leaves sprayed two days previously, only amitraz of the remaining compounds allowed significant general parasitoid survival after two days.E. mundus exhibited the greatest overall tolerance to insecticides, with 40% or more surviving 48 hr after confinement on leaves sprayed with amitraz, thiodicarb and cypermethrin. Survival was generally much reduced after 96 hr. In a separate test, fresh residues of endosulfan (Thiodan^®) were highly toxic at the two rates tested, but two day old residues at the lower rate allowed 76.7% survival ofE. mundus and 35% survival ofE. pergandiella after 48 hrs.     

Rumen Bacterial and Protozoal Responses to Insecticide Substrates

Insecticides containing organophosphate, chlorinated hydrocarbon, and carbamate were tested with bovine ruminal ingesta fractions. Rumen bacteria exposed to insecticide levels of 0 to 500 ppm in rumen fluid for 4 hr were inoculated into rumen fluid-starch feed extract medium. No apparent significant bacterial count inhibitions were noted. Also, when insecticides were used as carbon sources at concentrations of 500 ppm in carbohydrate-limited media, no increases in bacterial counts were indicated. Warburg manometric data showed that paraffin oil-Triton X-155 preparations of dimethoate, Diazinon, lindane, Thiodan and Sevin stimulated gas production in holotrich protozoa. Entodinium simplex, an oligotrich, produced less gas with insecticide substrates per unit of dry weight than did an Isotricha sp. Rumen bacteria and plant debris fractions from ruminal ingesta provided with insecticides did not give increased manometric responses over the endogenous control vessels. Washed suspensions of I. intestinalis produced volatile fatty acids in excess of the endogenous suspensions when provided insecticide substrates. Thiodan dissimilation by I. intestinalis was followed colorimetrically with 15% loss in substrate in 1 hr of incubation at 39 C. Diazinon-C¹⁴ substrate uptake was demonstrated with suspensions of E. simplex and I. intestinalis. Rumen ciliates are suggested as a possible means for screening out useful insecticides susceptible to microbial dissimilation for use on forage and other cattle-feed crops.     

Activity of conventional and reduced-risk insecticides for protection of grapevines against the rose chafer, Macrodactylus subspinosus (Coleoptera: Scarabaeidae)

Abstract:  Bioassays were conducted to compare the residual toxicity and leaf protection activity of conventional broad-spectrum and reduced-risk insecticides against the rose chafer, Macrodactylus subspinosus . Insecticides were applied to a Vitis labrusca (F.) vineyard and residues were aged for 1, 3 or 7 days before leaves were collected and exposed to beetles in no-choice tests. Azinphosmethyl caused rapid knockdown and mortality for up to 1 week after application, with 1-day-old residues providing 95.6% protection against feeding, dropping to 51.6% when residues were a week old. Fenpropathrin caused mortality and knockdown after beetles had been exposed to fresh residues for 72 h. Although these effects diminished as residues aged, this compound provided the best protection of leaves against beetle feeding, with 77.9% reduction in feeding compared with the control after 7 days of aging in the vineyard. Of the reduced-risk insecticides, imidacloprid caused the greatest initial mortality and knockdown of beetles, providing protection against feeding that was equivalent to azinphosmethyl. Exposure to azadirachtin caused a low level of knockdown and mortality when residues were 1- and 3-days old. Protection against feeding was also low, lasting for only 3 days. Beetles were minimally affected by capsaicin and kaolin, with mortality and knockdown seen only when beetles were exposed to 1-day-old residues for 72 h. Foliage protection from these compounds was minimal, with between 10 and 15% reduction in feeding injury. Results are discussed in relation to development of semi-field bioassay methods for evaluating reduced-risk insecticides, and the management of M. subspinosus within grape pest management programs.     

CONTROL OF SEED-BED LOSSES OF GROUNDNUTS BY SEED TREATMENT

Fungicide treatment of groundnut ( Arachis hypogaea L.) seed usually reduced seed-bed losses and improved emergence, plant populations and yields of this crop when cultivated under rain in the sandy soils of Kordofan (west-central Sudan) or under irrigation in the alkaline clay soils of the Gezira. These beneficial effects were greatest with slightly damaged seeds, such as would occur with machine sowing, but were present even when selected undamaged seed was sown by hand; they were attributed to protection against a number of soil micro-organisms, including Aspergillus niger van Tieghem, A.flavus Link and Rhizopus spp. Agrosan GN (organo-mercurial, 1% mercury equivalent) or 50% thiram powder, both applied at the rate of 1 g./lb. of seed, are suggested as suitable dressings for groundnut sowing seed in the two areas studied. Combined fungicide-insecticide dressings containing up to 40% by weight of γ-BHC did not control a late attack of wilt, due to root attack by cockchafer grubs ( Schizonycha sp.), which developed some 8 weeks after sowing in the Gezira.     

Effect of an oxadiazine, indoxacarb, on the biochemical composition of ovaries in the German cockroach

Conventional insecticides have been widely used to control cockroaches but these insects have developed resistance to several compounds. Safer insecticides with a low toxicity such as oxadiazine have been advanced: indoxacarb (30% WG) is designated to be a reduced-risk insecticide and is considered as an organophosphate replacement. Insecticidal activity occurs via blockage of the sodium channels in the insect nervous system. In a first series of experiments, the toxicity of different concentrations (15, 20, 25 and 30 ppm) administrated by topical application to newly emerged adults was studied on the German cockroach Blattella germanica, and the LC50 and LT50 values were determined. In a second series of experiments, the compound was applied at its LC50 and LC90 over a period of 6 days, and the effects on the biochemical composition of ovaries (proteins, carbohydrates and lipids) during the adult life (2, 4 and 6 days) were examined.