Persistence of D.D.T. and Benzene Hexachloride in Soils

Acid and alkaline soils, both alone and mixed with 2 % of D.D.T. or 2 % of benzene hexa-chloride (mixed isomers, containing 10% of the γ-isomer) have been exposed outdoors or subjected to controlled leaching in the laboratory. Residual insecticide has been estimated at intervals by a method involving dehydrohalogenation, and determinations have also been made of chloride content of soil, chloride leached and pH.
Results showed that both D.D.T. and benzene hexachloride were very stable in the soils, about 95 % of the former and 80 % of the latter being recoverable after 18 months. Very little chloride was leached during this period. The residual insecticide exhibited marked toxicity towards woodlice.
Eighteen months after treatment the benzene hexachloride soils prevented root growth of germinating seeds, while germination and early growth were normal in the D.D.T. soils. This harmful effect of the residual benzene hexachloride was still apparent when 1 part of the treated soil was mixed with 99 parts of the control soil (representing a concentration of less than 0–002 % of the γ-isomer).     

THE PRACTICAL CONTROL OF WIREWORM BY γ-BENZENE HEXACHLORIDE ('GAMMEXANE'): COMPARISONS WITH DICHLORODIPHENYLTRICHLORETHANE (D.D.T.)

Benzene hexachloride containing 13% of the insecticidally active gamma isomer known as 'Gammexane' has been used successfully in a considerable number of field trials in the control of wireworm. On heavily infested land the effective dosage rates associated with an appreciable reduction in wireworm population, and giving a marked improvement in plant establishment and substantial increases in yield, range between 1 and 6 lb./acre (2–12 oz./acre of Gammexane), on oats and wheat. The effective dosage rates vary and depend upon whether the insecticide is combine-drilled, broadcast, or applied as a seed dressing.
Although D.D.T. applied by similar methods was associated with similar reductions in wireworm population, the use of this insecticide resulted in smaller yield increases.     

THE CONTROL OF WIREWORM BY GAMMA BENZENE HEXACHLORIDE: THE DEVELOPMENT OF A SEED DRESSING FOR CEREALS

Gamma benzene hexachloride has been used successfully as a seed dressing in field trials for wireworm control. For application to cereals at 2 oz./bushel, the optimum concentration of γ-isomer was 20–30 % in a dressing which advantageously included an organomercurial seed disinfectant.
Risks to germination and plant growth were thoroughly explored in the field. The 20 and 30 % dressings were safe; over-strength dressings containing 50 or 70 %γ-B.H.C. did not reduce grain yields significantly.
Seed dressed with 20 or 30 %γ-B.H.C. germinated normally after storage for 12 months. When seed was dressed at 4 oz./bushel with 35 %γ-B.H.C. and 1 % mercury as organomercurial, germination was delayed but total emergence was not affected.     

INSECTICIDES FOR PREVENTING BARNACLE SETTLEMENT

During the summer of 1950 experiments were made to test the use of insecticides for preventing the fouling of oyster spat collectors by the barnacle Elminius modestus.
The insecticides used were DDT, BHC (benzene hexachloride-γ-isomer) and dieldrin (hexachloro-epoxy-octahydro-dimethano-naphthalene), made up as 5% solutions and tested on egg-box collectors and quarry tiles. The tiles were used for frequent observations on settlement.
When the solutions were sprayed on to the surfaces, in sufficient quantity to give a covering of 200 mg./ft.² of active insecticide, none of them interfered with either barnacle or oyster settlement.
When the test surfaces were dipped in the solutions, DDT and BHC prevented barnacle settlement almost completely, while dieldrin reduced it by approximately 50%. Settlement of Ostrea edulis was also reduced on the treated surfaces.
Urea-formaldehyde resins made up as varnishes, to which DDT or BHC had been added, were also tested. A varnish incorporating 20% by weight of DDT provided an effective anti-fouling compound which lasted at least 3 months and completely prevented barnacle settlement.
The possibility of insecticides dissolving into the water and inhibiting barnacle growth on adjacent surfaces is discussed.     

Assessing the performance of pea and lentil at different seeding densities as trap crops for the management of wireworms in spring wheat

Wireworms, the larvae of click beetles (Elateridae), are difficult to manage due to their habitats and behaviour. Wireworms pose a major threat to the wheat crop in the north‐western USA. Seed treatment with neonicotinoids, biological control management and some cultural controls are recommended to manage these pests. Trap cropping is an emerging way to manage wireworms. In strawberry and potato crops, trap cropping has been found effective at attracting wireworms away from the principal crop. An earlier study in the Golden Triangle area of Montana found that pea and lentil could be effective trap crops for managing wireworms in spring wheat. In the present study, experiments were conducted at two locations. The effectiveness of peas and lentils as trap crops with wheat at different seeding densities was assessed [pea at 0, 4, 8, 16 seeds/sq.ft. or 0, 43, 86, 172 seeds/sq.m.; lentil at 0, 6, 12, 18 OR 0, 65, 130, 194 seeds/sq.m.; both with wheat at 0, 11, 22, or 28 seeds/sq.ft. or 0, 120, 230, 300 seeds/sq.m.] in a randomized design where all three crops were intercropped. Both trap crops were found to be effective in protecting wheat at standard seeding rates of 8 seeds/sq.ft. for pea and 12 seeds/sq.ft. for lentils. At these seeding rates, higher numbers of wireworms were found to be attracted to the trap crop, resulting in higher yield (7%–10%) of the associated spring wheat plant stands at 22 seeds/sq.ft. To develop an effective trap crop strategy, the pea–wheat and lentil–wheat spatial patterns that are possible need to be assessed in further field trials. Proper design and evaluation of the cost–benefit ratio of pea and lentil as trap crops are likely to produce good results for wheat crops in Montana.     

A TECHNIQUE FOR THE BIOLOGICAL EVALUATION OF INSECTICIDAL AEROSOLS

The development of a technique for testing insecticidal aerosols produced from pressure dispensers is described. The method of rearing the test insect, Musca domestica L., is given in detail.
Both free-flying and caged flies were exposed in a room of 1194 cu. ft. Six insecticidal solutions were selected for test.
The biological efficiency of each aerosol was judged on the time required to paralyse 50% of the test insects (KD 500) and on the percentage kill obtained in 24 hr. Statistical analysis of some of the estimated figures for KD 500 showed a standard error of 4–5% of the mean.
The effects of temperature, of distribution and of dosage of the aerosol on the results were investigated.
Free-flying flies were preferred, mainly because of better replication of results.
The technique adopted is described as a specification and suggestions are made for its practical application.     

EXPERIMENTS ON SPRAYING WITH DDT TO PREVENT THE FEEDING OF SCOLYTUS BEETLES ON ELM AND CONSEQUENT INFECTION WITH CERATOSTOMELLA ULMI

Experiments were done for three years on street elms at Folkestone and Aldenham to repeat American work on the use of insecticidal sprays to prevent feeding by Scolytus beetles, which carry Ceratostomella ulmi , the cause of elm disease. Although the fungus can remain alive in the older annual rings of an infected tree, active disease usually results from fungus freshly introduced by Scolytus. Thus spraying is of value on infected, as well as uninfected elms.
The results of the experiments supported American conclusions that DDT was superior to benzene hexachloride. A 1.5% solution of DDT in miscible oil gave reasonably good, but not perfect, control, and was much superior to solutions made from DDT in the form of a dispersible powder.
Spraying of trees 20–30 ft. high cost over £1 per tree per year, which is considered prohibitive, except for small trees of special amenity or sentimental value.     

THE PENETRATION OF THE INSECT CUTICLE BY ISOMERS OF BENZENE HEXACHLORIDE

The penetration of the α-, β-, γ- and δ-isomers of benzene hexachloride through the insect cuticle has been studied by a micro-colorimetric technique.
Grain weevils were exposed for varying periods to deposits of pure isomers of benzene hexachloride on filter-paper. The amounts of each isomer picked up by the insects were determined as two fractions, one 'outside' representing that which could be removed by cold methanol washing, and the other 'inside' recovered after decomposing the insects with nitric acid.
The results show that the amounts of each isomer taken up by the insects are in the approximate ratio of their solubilities in hydrocarbon solvents, and that the y-isomer penetrates through the outer layers of the insect integument much more rapidly than the other three isomers tested.
On the basis of these results it is concluded: (i) that the first stage of pick-up of insecticide by the insects is simple solution of the insecticide in the outer waxy covering of the epicuticle; and (ii) that structural effects play an important part in the penetration through the insect cuticle as well as in toxic effects at the site of action.     

Radio Telemetry of the Electrocardiogram,Fitness Tests,and Oxygen Uptake of Water-Polo Players

During competitive water polo, heart rate in six subjects was monitored by cupped plastic and silver electrodes glued to the skin. Minimum rates during the game averaged 156 beats/min.; maximum rates averaged 186 beats/min. Mean maximum rate with bicycle exercise was 188 beats/min. Maximum oxygen (VO₂ max.) with bicycle exercise of 14 water-polo players was 53.3 ml./kg. Physical working capacity (PWC 170) was 1310 kilopond metres per square metre (k.p.m./sq.m.). PWC 170 correlated well with VO₂ max. in this small group (r = 0.77).Oxygen uptake was measured at three speeds of swimming and four levels of work on a bicycle ergometer. VO₂ max. of swimming was 88% of that obtained on bicycle exercise. The slope of the oxygen uptake vs. pulse rate curves was less for the swimming than for cycling, so that for a given oxygen uptake below the maximal, pulse rate was less in the swimmers. At near-maximal swimming, respiratory quotient was 0.95 compared with 1.27 for cycling, suggesting that the swimmers were underbreathing.     

THE INFESTATION OF WINTER LETTUCE BY APHIDS AND ITS CONTROL

Observations have been made on the infestation by aphids of winter lettuce at Imperial College Field Station, Slough, for the seasons 1947–8 and 1949–54. The effects of transplanting and of the use of insecticides have been studied.
Plants drilled in September where they were to mature were ready for cutting a little earlier than those transplanted in November, but in years when aphids were numerous the drilled lettuces were heavily infested and very few of them hearted.
The infestation of young crops varied from year to year; in some winters it fell to a low level, in others it increased rapidly and persisted with serious effect on the crop. In some years lettuce mosaic virus was also prevalent. The dominant aphid species was Nusonovia ribis-nigri (Mosley).
An early and persistent attack, even in the absence of virus disease, much reduced the number of hearted plants and their average weight. A late attack by winged aphids in early spring sometimes spoilt fully hearted lettuces.
Dipping the plants in nicotine solution at the time of transplanting in November reduced aphid infestation; dusting with benzene hexachloride proved more effective.
If transplanting was delayed until February or March a relatively clean crop could be produced by insecticide treatment, but losses from fungal disease were usually high.     

To Catch a Fly: Landing and Capture of Ceratitis capitata in a Jackson Trap with and without an Insecticide

Attractant-based traps are a cornerstone of detection, delimitation and eradication programs for pests such as tephritid fruit flies. The ideal trap and lure combination has high attraction (it brings insects to the trap from a distance) and high capture efficiency (it has a high probability of capturing the insect once it arrives at the trap). We examined the effect of an insecticide (DDVP) in combination with a pheromone lure (trimedlure) on capture of Ceratitis capitata using 1) digital images of surfaces of a Jackson trap analyzed via computer vision, and 2) counts of the number of flies caught in the trap and in the area under the trap. Our results indicate no significant difference in trap capture without or with insecticide (means ± SD = 324 ±135 and 356 ±108, respectively). However, significantly more dead flies were found around the trap with insecticide (92 ±53 with insecticide compared with 35 ±22 without), suggesting a possible decrease in trap efficiency due to mortality before insects enter the trap. Indeed, the average number of flies detected on all surfaces of the traps with insecticide was lower than that for lure-only (4.15±0.39 vs 8.30±1.18), and both were higher than control (no lure: 0.76 ±0.08). We found that the majority of fly sightings, 71% of the total, occurred on the inside panels of the lure-only traps, suggesting that increased efficiency of the Jackson trap may be obtained by adding a contact insecticide to those surfaces.     

THE PHYTOTOXIC EFFECTS OF D.D.T., B.H.C., PARATHION AND TOXAPHENE ON TOBACCO

No phytotoxic effect was seen following a pre-sowing spray of tobacco seed-beds with 27 lb./acre technical D.D.T. or after an application of the same material at 75.6 lb./acre to 3-week-old tobacco seedlings.
A pre-sowing application of parathion (diethyl para nitrophenyl thiophosphate) (2 % dust) at 1–8 lb. parathion per acre had no harmful effect. Used on 3-week-old tobacco seedlings at the excessive rate of 22.7 lb./acre it caused serious stunting and many deaths.
Toxaphene (chlorinated camphene: empirical formula C₁₀H₁₀Cl₈), applied as a 25 % wettable powder in a pre-sowing spray at 6-4 lb. toxaphene per acre, did not injure tobacco seedlings.
No residual phytotoxic effects appeared in beds re-sown 4 months after being treated with parathion or toxaphene at the pre-sowing doses given above.
Benzene hexachloride, applied before sowing at doses above 1.6 lb. technical B.H.C. per acre, suppressed root development in newly germinated tobacco seedlings. B.H.C. dusts used on n-day-old seedlings at 2–25 lb. technical B.H.C. per acre caused temporary distortion and stunting. Up to 11 lb./acre these symptoms were transitory: at 37.5 lb./acre many plants were killed and the remainder severely stunted. Resistance to these phytotoxic effects increased with age of plant, but 3-week-old tobacco seedlings showed considerable mortality after the application of 75.6 lb./acre of technical B.H.C.
Beds re-sown 4 months after the application of 6-4 and 12.8 lb. respectively of technical B.H.C. per acre showed no phytotoxic effect, but, as tobacco seed is sown on the soil surface, the effect of the B.H.C. may have been merely masked, and it is not safe to assume that there was no residual effect. The actual persistence of B.H.C. in the soil was not determined.
The possible mechanism of action of the B.H.C. effect is discussed.     

The effects of D.D.T. and of benzene hexachloride on bees

Laboratory and field experiments were carried out during 1946 to determine the effects of D.D.T. and of benzene hexachloride (B.H.C.)* on honey-bees and on several wild be species.
Laboratory experiments show that B.H.C. is a powerful contact and stomach poison and results of field experiments with commercial preparations confirm its danger to the foraging bee population. A few minutes' contact with treated surfaces is sufficient to cause death and blossom may remain poisonous for at least 3 days after treatment.
In the laboratory D.D.T. has a contact action at fairly high concentrations and as a stomach poison is rather more toxic than lead arsenate. In the field, commercial preparations on open blossom are apparently harmless to foraging bees.     

Pyrethroid insecticide evaluation on different house structures in a Chagas disease endemic area of the Paraguayan Chaco

Insecticide effects of deltamethrin 2.5% SC (flowable solution) on different substrates and triatomine infestation rates in two indigenous villages (Estancia Salzar and Nueva Promesa) of the Paraguayan Chaco are reported. This field study was carried out to determine the extent to which variability in spray penetration may affect residual action of the insecticide. A total of 117 houses in the two villages were sprayed. Filter papers discs were placed on aluminium foil pinned to walls and roofs in selected houses and the applied insecticide concentration was determined by high pressure liquid chromatography (HPLC). The target dose rate was 25 mg a.i./m2. The mean actual applied dose in Estancia Salazar was 11.2 +/- 3.1 mg a.i./m2 in walls and 11.9 +/- 5.6 mg a.i./m2 in roofs while in Nueva Promesa, where duplicates were carried out, the mean values were 19.9 +/- 6.9 mg a.i./m2 and 34.7 +/- 10.4 mg a.i./m2 in walls and 28.8 +/- 19.2 mg a.i./m2 and 24.9 +/- 21.8 mg a.i./m2 in roofs. This shows the unevenness and variability of applied doses during spraying campaigns, and also the reduced coverage over roof surfaces. However, wall bioassays with Triatoma infestans nymphs in a 72 h exposure test showed that deposits of deltamethrin persisted in quantities sufficient to kill triatomines until three months post spraying. Knockdown by deltamethrin on both types of surfaces resulted in 100% final mortality. A lower insecticidal effect was observed on mud walls. However, three months after treatment, sprayed lime-coated mud surfaces displayed a twofold greater capacity (57.5%) to kill triatomines than mud sprayed surfaces (25%). Re-infestation was detected by manual capture only in one locality, six months after spraying.     

Susceptibility of <Emphasis Type="Italic">Amblyomma variegatum</Emphasis> ticks to acaricides in Ghana

The susceptibility of unfed and fed stages of larvae, nymphs and adult females of Amblyomma variegatum ticks were tested using Shaws filter paper dip method against four acaricides; chlorfenvinphos and dioxathion, chlorfenvinphos, gamma benzene hexachloride and amitraz at four different concentrations including the recommended dose rates. Based on their lethal concentrations (LC₅₀ & LC₉₀) chlorfenvinphos and dioxathion combined and chlorfenvinphos alone placed first and second, respectively, in all stages except at the unfed nymphal stage where gamma benzene hexachloride topped with a LC₅₀ of 0.001629, while chlorfenvinphos and dioxathion combined and chlorfenvinphos alone had LC₅₀ of 0.001794 and 0.002258, respectively. Amitraz appeared to have a quick knock-down effect on larvae and nymphs but at the recommended dose rate, showed no mortality of the ticks at that stage. However, at a concentration of 0.040%, amitraz showed a 100% inhibition of oviposition and hatching of laid eggs. Gamma benzene hexachloride produced only 66% inhibition of oviposition while chlorfenvinphos and dioxathion combined and chlorfenvinphos alone produced 100% inhibition of oviposition at their recommended dose rates. Fed nymphs were more susceptible than the unfed nymphs. Eggs laid by engorged female ovipositing ticks, applied with gamma benzene hexachloride, hatched.This revised version was published online in May 2005 with a corrected cover date.     

Diflubenzuron inhibits reproduction of different strains of Drosophila melanogaster

Abstract  The effect of (1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)urea) insecticide – diflubenzuron – on wild type and white type fruit flies Drosophila melanogaster (Meigen, 1830) was studied. Adult insects were placed in vials with different concentrations of the insecticide in the nutrient (from 0.048 to 48 mg of diflubenzuron per 1 cm³ of the nutrient). In each case, the insects showed some mortality, which was concentration-dependant. When comparing both strains, we could observe different acute toxicities, with wild type being more resistant to diflubenzuron. However, subacute toxicity was similar within both strains. In both strains the prolonged exposure led to the extinction of the majority of the populations (>70%). Although imagoes could freely copulate, we did not observe copulating fruit flies, and we did not find either eggs or larvae in any of the exposed groups. These results indicate that genetic mutation which leads to different eye colour can also affect resistance and survival of insects in pesticide-exposed areas.     

The relative toxicity and persistence of insecticides applied as water-dispersible powders against stored-product beetles

Twelve insecticides, formulated as water-dispersible powders, were applied to strips of filter paper and their toxicities to eight species of stored-product beetles were determined. The insecticides were DDT, methoxychlor, lindane, aldrin, dieldrin, synergized pyrethrins, malathion, fenthion, Chlorthion, diazinon, trichlorphon and carbaryl. The insects were adults of Sitophilus granarius (L.), S. zeamais Mots., Tribolium castaneum (Herbst), Oryzaephilus surinamensis (L.), Rhyzopertha dominica (F.), Stegobium paniceum (L.), Lasioderma serricorne (F.), and Ptinus tectus Boield. Tables of LD 50 values are presented in terms of deposits of active ingredient between the limits investigated, namely 0.625 and 80 mg./sq.ft., for 2-day and 3-day periods of continuous exposure at 25d? C. and 70% R.H. The data give a broad view of the susceptibility of each insect species to the different insecticides, the effectiveness of each insecticide against the range of insect species, and the speed of action of the insecticides. Trichlorphon had a very low toxicity to all species except O. surinamensis and was omitted from further testing. Deposits of the remaining eleven water-dispersible powders on filter paper were stored and tested at intervals up to 16 months. This yielded information on the persistence of the formulations after application to a chemically inert substrate. Five of the insecticides-malathion, fenthion, Chlorthion, diazinon and carbaryl were then investigated for their persistence on cement, tile, whitewash on tile, wood, and sacking. This test revealed loss of effectiveness of some of the organophosphorus insecticides because of volatility or of alkalinity of the substrate, although some of the results obtained with tiles were difficult to explain. Factors such as surface activity, porosity and real surface area may have played a role, as well as the physical state of the insecticide in the formulation.     

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.     

The Morgan Recharger: a new horn fly (Diptera: Muscidae) control device for beef cattle

A 20% diazinon formulation was evaluated for control efficacy against the horn fly, Haematobia irritans (L.), in the Morgan Recharger (Morgan International Products, College Grove, Tenn.). The Morgan Recharger releases insecticide with a wicking system from an insecticide reservoir and can be attached to an animal's ear or tail. This device was most effective against the horn fly when used as an ear tag with two per head; horn fly counts did not exceed five flies per side through 8 wk. The diazinon formulation tested was released from the Morgan Recharger at a decreasing rate. The problems and potential of the Morgan Recharger as an effective horn fly control device are discussed.     

Trap position and fruit presence affect visual responses of apple maggot flies (Dipt., Tephritidae) to different trap types

Abstract:  We compared responses of apple maggot flies, Rhagoletis pomonella (Walsh), in a commercial apple orchard in Massachusetts with three different types of visual traps baited with synthetic fruit volatiles. The traps were red spheres, Ladd traps (a rectangular yellow panel between two red hemispheres) and rectangular yellow panels. Traps were placed either in optimal position (D rummond , F.; G roden , E.; P rokopy , R. J., 1984: Environ. Entomol. 13, 232–235.) or sub-optimal position (not surrounded by foliage and fruit from all sides). The study was performed over 3 years. Early in the fruiting season, when apples were small and green, red spheres followed by Ladd traps attracted more flies than yellow panels. Ladd traps were the most sensitive to trap positioning, losing effectiveness when placed in sub-optimal position. Late in the fruiting season, in years yielding crops of large red apples, red spheres in optimal position (surrounded by growing red fruit) lost some effectiveness relative to Ladd traps in optimal position. Red spheres in sub-optimal position were not similarly affected, perhaps because of the lack of fruit in the background. Red sphere performance relative to Ladd traps was re-established after removal of competing fruit from trees at harvest. Because Ladd traps are more expensive to purchase and more difficult to position, red spheres are a better option for commercial growers in eastern North America. Conceivably, loss of capturing power of red spheres because of visual competition from red apples towards harvest could be mitigated by adjusting trap positioning.