摘要:

SUMMARYSublethal doses of dieldrin were topically applied to individuals of the mosquitoAedes aegyptiL., and the effects on feeding, egg laying and mortality observed. The highest dose of dieldrin (0·0075 μg./insect) stopped the feeding of 2‐ to 3‐day‐old blood‐fed females. Egg laying continued up to 96 hr. after treatment but then dwindled and finally stopped. Lower doses induced diminished responses and the lowest amount of insecticide applied (0·0016 μg./insect) had no effect.Females (1–2 days old) were treated with 0·0060 μg./insect. Of the survivors, very few fed on subsequent days and only a small number of eggs were laid by them. Dieldrin apparently had no effects on the viability of the progeny from the treated adults.It is concluded that the insecticide primarily affects feeding; egg laying and longevity suffer a

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03722.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYThe influence on the toxicity of insecticides of the site of topical application on the insect's body has been studied, withAlphitobius laevigatusbeetles as the test insects. Four toxicants,n‐valone (2‐n‐valeryl 1,3‐indandione), DDT, dieldrin, and allethrin were used in solution in a non‐volatile mineral oil, Shell Risella 17 (R17).To facilitate the interpretation of the results of the toxicity tests, the spread of oil after application to different sites was followed. R 17 oil was marked with a fluorescent material and its spread over beetles was observed under ultra‐violet light. Doses of 0·05 μl. spread over considerable areas of cuticle from most of the sites of application, though doses of 0·02 μl. spread rather less. The greatest spread occurred after dosage between the front coxae, and the least after that on the pronotum. Although the areas of wetted cuticle overlapped following application to different sites, there were possibly quantitative differences in distribution not detectable with the method used. For experimental work applications to the mesoscutellum and hind coxae were the easiest.Toxicity tests for nine sites of application were done, using fixed doses. During and after treatment on the pronotum, elytron, or tarsi, beetles were held in wire loops to prevent their shedding any of the dose. After treatment on the other sites, the beetles were kept in groups running freely within containers. The site of application influenced slightly but significantly the toxicity ofn‐valone DDT, and allethrin, but scarcely at all that of dieldrin. Generally the first three toxicants were most toxic when applied on or near the prothorax.The toxicities of the applications made to the mesoscutellum and hind coxae were examined in more detail, varying the doses. Pairs of parallel probit‐log‐dose lines fitted satisfactorily responses for the two sites, concentration of toxicant and volume of solution being varied in respective experiments with each toxicant. Combining these results with those from the first paper of this series indicates that the respective probit planes in log‐concentration and log‐volume for the two sites were parallel.From the toxicity experiments as a whole, it appeared that the toxicant was at most about 1·9 times as effective on the ‘most sensitive’ si

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03723.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYFive experiments were made on sandy loam containing 12% clay, infested with potato‐root eelworm. Methyl bromide at 89 g./10 sq.ft. killed most eelworms, induced most increase of ammonia‐nitrogen and gave the largest yield of ware potatoes. Metham‐sodium diluted and mixed into the soil at normal dose (35 ml. active material/10 sq.ft.) and half dose, dazomet at 29 g. active material/10 sq.ft. mixed into the soil and methyl isothiocyanate injected at 23 ml. active material/10 sq.ft. were more effective than injected metham‐sodium or D‐D, except when D‐D was applied at 70 ml./10 sq.ft. to soil at 20° C. Methyl bromide, metham‐sodium, dazomet and methyl isothiocyanate controlled weeds in the weeks immediately following treatment.Assays of live eggs, hatched larvae, larvae in roots or cysts formed on the root‐mat of potato indicator plants and counts of nematodes free in the soil all selected the same treatment as the most effective. More new cysts formed in the treated plots than in untreated controls because intensive eelworm attack in untreated plots limited root growth and prevented larvae developing into cysts. To produce a good yield of ware potatoes it was necessary to reduce the eelworm population by 90%.None of the commercial treatments damaged the haulms or tainted the tubers, though spring treatment 7 weeks before planting may have depressed yields slightly. Of many experimental compounds tested, only 1,2,3,‐tribromopropane and chloro‐bromopropene (CB

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03724.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARY4‐Amino‐4′‐hydroxyazobenzene and particularly some of its ring‐substituted derivatives are efficient seed protectants for the control ofPythium ultimumon peas. They are also active againstTilletia carieson wheat, but are ineffective against four other seed‐ or soil‐borne pathogenic fungi. A possible mode of action of the compounds is suggested. Mammalian toxicity data for 4‐amino‐4′‐hydroxyazobenzene and its 3′,5′‐dimethyl and 2,3′,5′‐

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03725.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYExperiments in the greenhouse with surface‐active agents for control of apple and barley powdery mildews indicated that cationic compounds were of particular interest. On barley, significant protective disease control was given only by agents providing good wetting; on apple, even good wetting was not necessarily followed by good protection. Didecyldimethylammonium bromide (DDAB) and domiphen bromide were among the most effective agents, giving a high degree of protection at 0·05%; curative action on apple was extremely good even at 0·025%, especially by DDAB. The latter was outstanding among many fungicides for protection of strawberry foliage against powdery mildew in the greenhouse, but more prolonged protection was given by lime sulphur or dinocap in a late‐season field trial.DDAB caused no damage on foliage of any of these three host species, except on strawberry where a non‐ionic agent was also included in the formulation. But disease control was reduced when certain cationic agents, including DDAB, were used to formulate several pure fungitoxicants, e.g. captan or dodine

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03726.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYThe severity of banana fruit‐spot (‘speckle’), caused byDeightoniella torulosa, in plantations having abundant leaf trash was greater than in relatively trash‐free plantations. Experimental de‐trashing reduced disease severity to a level at which it ceased to be of commercial importance. Aerial application of fungicides did not control disease, but direct spraying of bunches was effective. Plastic bags put on bunches shortly after ‘shooting’ also provided good control of speckling. Relative costs of various control measures are discussed and associated practical difficulties pointed out. De‐trashing two or three times a year appears to be the cheapest and most p

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03727.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYInoculation of pine stumps with oidia ofPeniophora giganteadirectly after felling gives good protection againstFomes annosus.With the largest inoculum ofF. annosusspores likely to occur naturally, a dosage of 1 × 104oidia suffices for stumps having a wood‐diameter of 16 cm.P. giganteaenters the lateral roots of inoculated stumps and tends to check advance ofF. annosusin any tissues infected at the time of felling; it also replaces this fungus to some extent, Lignin is rapidly decomposed and sporophores are generally produced within a year. Suspensions may conveniently be applied by a compressed air sprayer. Owing to the selectivity of freshly cut stumps, contamination of the suspension is not a serious hazard.If widely used, the method would necessitate large‐scale production of suitable inoculum sources. For most of the experimental work undertaken the inoculum was derived from wood‐block cultures ofP. giganteastored in polythene bags, but for routine use a more compact source would be preferable. A method is described for preparing tablets which, when dissolved in IOO ml. water, yield suspensions containing up to 1 × 106viable oidia per ml.: if kept at 10° C. they should each provide inoculum for more than a hundred stumps over a storage period of 10–20 weeks.The relative merits of inoculation and chemical treatment for control ofF. annosusin pine stumps are briefly discussed and other possible applications of stump inoculation ar

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03728.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYInduction of disease symptoms and water loss from detached shoots placed in cell‐free filtrates from cultures ofVerticillium albo‐atrumand dilute solutions of substances of high molecular weight have been studied. There was no difference between the effect of these solutions on resistant and on susceptible plants. Freezing and heating decreased the effect of culture filtrates in reducing water loss and causing wilt. Solutions of pectic substances as dilute as 30 p.p.m. induced wilting and were 30 times as effective as solutions of certain polysaccharides in reducing water loss. Filtrates from pectate cultures had a very high polygalacturonase activity and when diluted up to 250 times induced typical disease symptoms in leaves of cut shoots in 70 hr.; this property was lost on autoclaving.No difference was found in the composition of xylem exudates from resistant and susceptible plants. Filtrates from cultures on a synthetic plant‐sap medium to which insoluble plant material from resistant and from susceptible plants had been added were found to have different effects on cut shoots; this may depend on the different polygalacturonase activities of these filtrates.Studies on water loss from shoot‐inoculated resistant and susceptible plants showed that the water loss/fresh weight was reduced to almost the same extent in resistant and susceptible shoots, despite the fact that resistant plants developed only mild symptoms of disease. Resistant plants were found to be more drought‐resistant than susceptib

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03729.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYAn isolate ofVerticillium albo‐atrumvirulent on tomato produced polygalacturonase abundantly in suitable culture media. Secretion was greatly stimulated by pectic substances, and by organic, as compared with inorganic sources of nitrogen. Degradation of polypectate by culture filtrates decreased sharply when only about 25% of available glycosidic linkages had been hydrolysed.Cellulase (Cx) activity of culture filtrates was relatively much lower and no cellulase (Cx) activity was detected.The fungus produced pectic and cellulolytic enzymes when grown on sterilized pieces of tomato stem.Culture filtrates liberated reducing groups from insoluble plant material and there was some evidence that this depended on the activity of pectic enzymes.Polygalacturonase was strongly adsorbed by plant material but was eluted readily with O·2M‐NaCl.When dilute solutions of polygalacturonase were taken up by tomato cuttings only a relatively small proportion could be recovered from the tissues by treatments which removed enzyme adsorbed by plant tissue. This indicates inactivation of the enzyme by living pieces of stem, but extracts from healthy and infected stems did not inactivate polygalacturonasein vitro.Polygalacturonase was detected in extracts from the stems of root‐ and shoot‐inoculated plants. It was shown that the activity in these extracts was of the order to be expected from the activity of filtrates from cultures on media suitable for production of polygalacturonase.In all respects tested, the material from resistant Loran Blood and susceptible Ailsa Craig plants reacted in the same way with pectic and cellulolytic

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03730.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

SUMMARYMost leaf‐scar infections of cherry trees are caused by bacteria washed from the leaf surfaces in rain. In estimates made from three young orchards in four different seasons the numbers ofPseudomonas mors‐prunorumon the leaf surfaces of the cherry variety Napoleon during the autumn were consistently higher than those on the more resistant variety Roundel, the ratio on occasion exceeding three to one. The amount of leaf surface inoculum and the number of cankers on each variety increased progressively with the age of the trees, but both were unrelated to the severity of leaf‐spot infection, which fluctuated widely from year to year. The possibility of epiphytic growth by the pathogen and the relationship between inoculum potential and ‘field’ resistance of the varieties are

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1963.tb03731.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY