THE EFFECT, ON OYSTER SPATFALL, OF CONTROLLING BARNACLE SETTLEMENT WITH DDT

During the summer of 1955 experiments were made with DDT to control barnacle fouling of oyster spat collectors. Results showed that effective control of barnacles on artificial collectors doubled the yield of oyster spat. Shell cultch treated in the same way gave less conclusive results, partly because of the poor spatfall experienced.
Oyster spat on treated artificial collectors were approximately 40% bigger, at the end of 2 1/2 months, than those on controls. Evidence from shells, however, indicated that DDT initially inhibited the growth of oyster spat. Apparently spat become stunted in natural conditions, because they are unable to compete effectively for food with the dense barnacle populations. Competition amongst barnacles themselves also causes stunting.
The dense population of Elminius modestus on the east coast oyster grounds may have a long-term effect on both the yield and growth of oysters.     

粉剂防治粘虫Pseudaletia separata (Walker)研究

粘虫Pseudaletia separata(Walker)是粮食作物的毁灭性害虫,也是全国农业发展纲要(修正草案)所规定要消灭的八大害虫之一。粘虫在大发生时为害面积很广,虫体发育迅速,食量很大,过去多采用人工器械捕打办法,但不能澈底解决问题,尤其在作物密植的情况下,捕打也发生了困难,常因捕打时将作物践踏而引起损失,因此要求在发生时应用化学防治方法,以达到迅速消灭为害之目的。     

昆虫神经毒素的研究:各种神经毒剂引起毒素的产生

用五类(七种)神经毒性的杀虫药剂,对美洲(虫非)蠊测定了它们能否引起血淋巴中毒素的产生。DDT、溴氰菊酯及六六六均能引起血淋巴中毒素的产生,而E605、西维因、巴丹及杀虫脒均无此效果。纸层析及薄层层析,用标准样品(酪氨酸、酪胺、苯乙胺、L-亮氨酸及异戊胺)作比较,测定了这一产生的血淋巴中的毒素乃是酪胺,或主要是酪胺。增效试验,证明了杀虫脒与DDT或溴氰菊酯合用时,能增加酪胺的产量。讨论了这一毒素产生的条件,以及这一毒素有可能不是单一成分,而是几种单胺及氨基酸的复合物,但酪胺为其主要成分。     

Sensitivity of the alga Scenedesmus acutus to some pesticides.

Indoor cultures of the green alga $\text{Scenedesmus}$$\text{acutus}$ were tested for sensitivity to varying concentrations of seven insecticides and three fungicides. The growth rates of the organisms were considerably reduced by BHC and DDT analogues even at low concentrations of 500 ppb and 1 ppm. Lindane above 5 ppm and Technical BHC and DDT at 100 ppm were lethal to this alga. Of the three fungicides, TMTD (Tetra Methyl Thiurum Disulfide) was most toxic resulting in death of the culture at 10 and 100 ppm. Blitox (Copper-oxy chloride) and Zineb (Zinc Ethylene-Bis dithiocarbamate) considerably retarded growth at all concentrations. This alga was more sensitive to Lindane, BHC (Technical), DDT and TMTD. The growth rate appeared to be influenced by the concentration of pesticide present in the algal culture. As $\text{Scenedesmus}$$\text{acutus}$ is being considered as a source of Single Cell Protein (SCP) for human consumption, knowledge on the sensitivity of this alga to pesticide contamination will be useful.     

The Control Of Blowflies Infesting Slaughter-Houses

Field experiments on the control of blowflies have been carried out at a large slaughter-house which was heavily infested both by flies breeding on the premises and by those attracted from surrounding districts.
The control of breeding by admixture of a larvicide with slaughter-house refuse proved to be impracticable. Although a single treatment of the surface of refuse was ineffective, daily applications of DDT or BHC markedly reduced the degree of infestation and killed some emerging adults.
The introduction of a scheme for rotational storage and collection of refuse and a general improvement in sanitary conditions, together with a daily application of 5% DDT dust to refuse and nearby vegetation, resulted in the prevention of breeding on the premises and a very considerable reduction in the adult population.
Results of experimental applications are compared with those obtained in practice using unskilled labour.     

Insecticide susceptibility levels of Anopheles gambiae s.l. in the area of Ouagadougou, Burkina Faso

Tests to evaluate the susceptibility level in Anopheles gambiae s.1. from Ouagadougou and two nearby villages have been carried out. Anopheles gambiae s.1. larvae from Ouagadougou showed complete susceptibility to organophosphates and carbamates, and adults showed low-level resistance to DDT. Nine percent survival of adult An. gambiae s.1. to one-hour exposure of 4% DDT was observed in samples from Zagtouli village while in those from Koubri village, where dieldrin also was tested, resistance to both organochlorine insecticides was detected.     

THE CONTROL OF BLOWFLIES INFESTING SLAUGHTER-HOUSES

A field experiment has been conducted to control blowflies which fell as mature larvae from railway wagons carrying domestic refuse and infested the soil at the sidings of a refuse collecting and sorting depot.
The surface of the soil was treated so that the insects were exposed to insecticide both as migrating larvae and newly emerged adults. Dusts and emulsions of DDT and BHC were compared on the basis of equal cost. A method was evolved for obtaining quantitative measurements of the effectiveness of the treatments by trapping flies emerging from the soil.
DDT was more effective than BHC, dusts were more effective than emulsions, and small quantities applied twice weekly were more effective than a correspondingly heavy dose applied monthly. DDT dust applied twice weekly was estimated to have killed 79.7% of larvae and pupae and 95.7% of emerging adults: overall control was 99.1%. Equally high control was maintained when the method was adopted as a routine measure by the local authority.     

Reduction of barnacle recruitment on micro‐textured surfaces: Analysis of effective topographic characteristics and evaluation of skin friction

This study investigates five designed micro‐textured surfaces and their effects on barnacle fouling and hydrodynamic drag. Three of the micro‐textures were developed in the present study and evaluated together with two commercial riblet films. All micro‐structures were arranged as longitudinal grooves with different profile depths, widths and angles of inclination. In field tests the recruitment of the barnacle Balanus improvisus on micro‐textured surfaces and smooth controls was evaluated. All micro‐textured surfaces reduced recruitment, and the most efficient texture reduced recruitment by 98%. For some micro‐textures the reduction of recruitment declined as settlement intensity increased. In a correlative analysis, the trigonometric inclination of the micro‐structures explained most of the recruitment reduction. The steepest angle of inclination caused a massive reduction in barnacle settlement. Surface micro‐structures may affect the boundary‐layer flow and the hydrodynamic drag (skin friction) of the surface. The skin friction was empirically measured in a flow channel using a sub‐set of the tested micro‐textures. The measurements of skin friction showed that the orientation of the microstructures is important, with a minimum friction when the grooves are parallel to the flow. For one of the micro‐textures the skin friction was ca 10% lower compared to a hydraulically smooth surface. It is concluded that, depending on the flow speed, micro‐textures will not significantly increase skin friction when arranged parallel to the flow, even at moderate protrusion through the viscous sub‐layer.     

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.     

Settlement Dynamics of the Encrusting Epibenthic Macrofauna in Two Creeks of the Caeté Mangrove Estuary (North Brazil)

The epibenthic encrusting fauna of 2 creeks of the Caeté mangrove estuary, northern Brazil, was studied over a 13 month period using collectors fixed at 2.5 and 3.5 m above the creek bottom and in which upper and lower sides of ceramic and wooden panels were used as settlement substrates. The number of individuals of the most abundant organisms (barnacles, oysters and mussels) settling per panel was determined each month, for each substrate type, panel orientation and height above creek bottom. The barnacle, Fistulobalanus citerosum has a peak settlement period during the wet season whereas both peaks in the numbers of settlers of the oyster Crassostrea rhizophorae were recorded during the dry season and such discrete temporal patterns in settlement have also been observed for barnacles and oysters in other mangroves and estuaries. In contrast to other studies, settlement of the mussel Mytella falcata was generally low during the study period and may be related to over-exploitation of stocks in the region. Overall, settler density was usually greater on the underside of ceramic panels close to the creek bottom, similar to results of other studies of epibenthic settlement in diverse habitats.     

THE SYSTEMIC INSECTICIDAL ACTION OF CERTAIN COMPOUNDS OF FLUORINE AND OF PHOSPHORUS ON PHAEDON COCHLEARIAE FAB.

Four compounds— bis dimethylaminophosphonous anhydride (schradan), bis (dimethylamino)fluorophosphine oxide ( dimefox ), diethyl paranitrophenyl phosphate ( paraoxon ) and sodium fluoroacetate ( acetate )—have been tested against the mustard beetle, Phaedon cochleariae Fab. When the four compounds are compared by a direct contact technique in which insects can also imbibe some of the test solutions, or the insects are caged with foliage which has been dipped and then dried, the order of toxicity to adults and larvae was found to be Paraoxon > acetate ≏ dimefox > schradan.
The paraoxon is very much more toxic than the other compounds. In all cases the adults are more resistant than the larvae.
When the insecticides are applied systemically the order of toxicity changes to Paraoxon > dimefox > acetate ≏ schradan because the acetate causes the plants to wilt and less of it is absorbed. Both paraoxon and dimefox give complete kills of adult Phaedon which is the most resistant stage, at practical concentrations.
When the insecticides were applied to the outer leaves and translocated to the inner untreated leaves an effect was observed with the dimefox and paraoxon after numerous application, but with a single application very inconsistent results were obtained.
It is concluded that schradan and the acetate are ineffective systemically against Phaedon. The dimefox and paraoxon are very effective, but because of their high mammalian toxicity they would require very careful handling in practice.     

Surface wettability as a determinant in the settlement of the barnacle Balanus Improvisus (DARWIN)

Several studies have shown that the initial surface wettability, is of importance in the settlement of macrofouling larvae such as barnacles, bryozoans and hydroids in the field as well as in laboratory assays. In this study we present results from laboratory assays using hydrophilic and hydrophobic polystyrene (PS) and cyprid larvae of Balanus improvisus (Darwin). The results obtained differ markedly from those reported for the barnacle Balanus amphitrite (Darwin), where a high surface wettability seemed to be preferred for settlement. Our results show that a surface with intermediary wettability (hydrophilic PS) reduced settlement by 38% as compared to surfaces of low wettability (hydrophobic PS) during an 8-day period. During the experiment, the wettability in the hydrophilic PS dishes was not significantly changed as measured by advancing contact angle with mQ water. Over an 8-day period wettability of the hydrophobic PS dishes approached that of the hydrophilic PS surfaces. We further conducted experiments with highly hydrophilic and highly hydrophobic methylsilane-treated glass surfaces with known chemistry. In this experiment, the settlement of cyprid larvae was completely inhibited by the high wettability surfaces. Contact angle measurements revealed that the wettability during the length of the experiment of the hydrophilic glass surfaces was not significantly altered. We conclude by these experiments that even an intermediate wettability can significantly affect the overall settlement success of the barnacle B. improvisus. The mechanism by which the settlement is impeded might be biologically mediated through the recognition by cyprid larvae of the molecular composition of the surface when the cyprid reverts to the settlement phase, i.e. when swimming behaviour is abandoned in favour of surface exploration, or it is mediated by physicochemical forces acting between the surface and the larval body or the larval antennules.     

SYSTEMIC INSECTICIDAL ACTION OF NICOTINE AND CERTAIN OTHER ORGANIC BASES

Nicotine and nicotine salts are taken up by the roots of plants from solutions, and when 0.01–0.001 % nicotine is used the plants become toxic to Aphis fabae and to Pieris brassicae larvae and can be shown to contain nicotine. The results with Phaedon cochleariae adults and larvae are less satisfactory. No systemic action is observed when the nicotine is watered on to soil in which plants are growing and no nicotine can be detected in the plants. Apparently the nicotine is decomposed in the soil.
When applied several times to the upper surface of a bean leaf nicotine kills aphids on the underside. There is some evidence that nicotine can be translocated further through the plant following leaf applications, but the toxic action at any distance is very weak in the plants used in the present experiments and can only be produced by frequent applications of rather concentrated nicotine solutions. Leaf absorption and subsequent translocation has not been observed with nicotine salts.
The various organic bases, including some piperidine phosphonites and allied compounds tested, are of very little interest as contact or systemic insecticides against aphids.     

Adult Prey Neutralizes Predator Nonconsumptive Limitation of Prey Recruitment

Recent studies have shown that predator chemical cues can limit prey demographic rates such as recruitment. For instance, barnacle pelagic larvae reduce settlement where predatory dogwhelk cues are detected, thereby limiting benthic recruitment. However, adult barnacles attract conspecific larvae through chemical and visual cues, aiding larvae to find suitable habitat for development. Thus, we tested the hypothesis that the presence of adult barnacles (Semibalanus balanoides) can neutralize dogwhelk (Nucella lapillus) nonconsumptive effects on barnacle recruitment. We did a field experiment in Atlantic Canada during the 2012 and 2013 barnacle recruitment seasons (May–June). We manipulated the presence of dogwhelks (without allowing them to physically contact barnacles) and adult barnacles in cages established in rocky intertidal habitats. At the end of both recruitment seasons, we measured barnacle recruit density on tiles kept inside the cages. Without adult barnacles, the nearby presence of dogwhelks limited barnacle recruitment by 51%. However, the presence of adult barnacles increased barnacle recruitment by 44% and neutralized dogwhelk nonconsumptive effects on barnacle recruitment, as recruit density was unaffected by dogwhelk presence. For species from several invertebrate phyla, benthic adult organisms attract conspecific pelagic larvae. Thus, adult prey might commonly constitute a key factor preventing negative predator nonconsumptive effects on prey recruitment.     

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.     

Investigations into mechanisms responsible for seizures induced by chlorinated hydrocarbon insecticides: the role of brain ammonia and glutamine in convulsions in the rat and cockerel

Abstract— Seizures were produced in adult female rats and in cockerels (Gallus domesticusL.) after the intracarotid administration of four structurally-unrelated chlorinated hydrocarbon insecticides. The temporal relationship of the course of the convulsions to levels in whole brain of ammonia and glutamine was examined. High levels of brain ammonia occurred in rats and cockerels poisoned acutely with lindane, dieldrin, heptachlor and DDT. The intensity of convulsions and other neurological signs coincided with and were directly correlated with the increases in brain ammonia, whereas interictal periods were associated with decreased levels of ammonia. In both species the order of drug toxicity was lindane > dieldrin > heptachlor > DDT. Significantly elevated levels of brain glutamine were induced in the cockerels after administration of all four insecticides. In contrast, increased levels of glutamine in rats were found only in those intoxicated with lindane and dieldrin. Although the ammonia-binding mechanism (conversion of free ammonia into glutamine) was saturated throughout the experiments in both the rats and cockerels, the latter were more resistant to ammonia toxicity by virtue of being able to convert free ammonia into glutamine more efficiently than rats. These data, together with data reported by others, lead to the conclusion that the four structurally-unrelated chlorinated hydrocarbon insecticides probably induced convulsions in both species by a common mechanism, involving interference with the production and/or utilization of ammonia.     

Inhibition of common fouling organisms by marine bacterial isolates ith special reference to the role of pigmented bacteria

Two questions of relevance to the establishment of marine biofouling communities were addressed, viz (1) what is the frequency with which bacterial strains isolated from living and inanimate surfaces in the marine environment show inhibitory activity against the settlement of common fouling organisms, and (2) is the antifouling bacterium, D2, an inhabitant of different marine waters, and how unique is this bacterium, in its mode of action against different target organisms? With respect to the first question, ninety three marine bacteria isolated from various rock surfaces from the marine environment were tested against larvae of Balanus amphitrite and spores of Ulva lactuca. Settlement assays against the diatom Amphora sp. were also performed on 10 of these strains. Nine bacterial isolates were shown to be inhibitory against larval settlement and eight of these strains were also inhibitory against algal spores. Altogether 16 strains were inhibitory against the settlement of algal spores while none of the bacterial strains inhibited diatom settlement. With respect to the second question, D2, a dark green pigmented bacterium, isolated from an adult tunicate off the Swedish west coast, has been found to be a very effective inhibitor against common fouling organisms. In order to see if this bacterium can be found in other marine waters, bacteria from living surfaces of marine plants and animals from waters around Sydney, Australia, were isolated and screened for inhibitory activity against barnacle larvae. Seventy four percent of the 23 plant isolates were shown to be inhibitory against larval settlement while only 30% of the 23 isolates from marine animals reduced settlement. Twenty two of the isolates from different seaweeds were dark pigmented and 20 of these strains inhibited settlement of barnacle larvae and algal spores. Three of the strains showed the same phenotypic expression as D2, and the results indicate that these strains may be D2 or closely related strains, suggesting that D2 may be a common inhabitant in the marine environment.     

THE ACTION OF COPPER IN ANTIFOULING PAINTS

Experiments on the number of barnacle cyprids found on plane surfaces and on the surface of small pits coated with compositions containing different amounts of cuprous oxide show that the presence of copper does not deter the cyprids from attempting to settle. Copper-oxide paints do not inhibit settlement appreciably; their efficiency as antifouling agents is caused by the toxic action of copper on cyprids and young spat after initial attachment.
The cementing of the shell to the substratum in young barnacles which have survived metamorphosis appears to be hindered by the presence of copper paints so that they are easily dislodged.     

Barnacle Settlement on Hydrogels

Settlement of cultured Balanus amphitrite cyprid larvae was tested on different non-solid hydrogel surfaces. Gels consisting of alginate (highly anionic), chitosan (highly cationic), polyvinyl alcohol substituted with light-sensitive stilbazolium groups (PVA-SbQ; very low cationic) and agarose (neutral) were applied in cell culture multi-well plates. Polystyrene served as a solid surface reference. Preliminary experiments were performed to determine whether any substances leaching out of the gels could inhibit barnacle settlement. Whilst leachate from the gels revealed no toxicity towards Artemia salina nauplius larvae, PVA-SbQ in solution at and above a concentration of 0.4 ppm inhibited B. amphitrite cyprid settlement. Gels were therefore washed to avoid such effects during further testing, and toxicity and settlement tests with B. amphitrite nauplii and cyprids, respectively, applied to verify that washing was effective. Settlement was tested directly on the different test materials, followed by a quality test of non-settled larvae. All gels inhibited barnacle settlement compared to the polystyrene controls. Gels consisting of 2.5% PVA-SbQ or 0.5% agarose showed promising antifouling properties. Although some settlement occurred on 2.5% PVA-SbQ gels, metamorphosis was clearly inhibited. Only 10% of the larvae had settled on 0.5% agarose gels after 8 d. Less than 40% settlement occurred on alginate gels, as well as on 2% chitosan gels. Quality testing showed that the majority of remaining non-settled larvae in all gel experiments were able to settle when offered a suitable solid substratum.     

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.