摘要:

SUMMARYBecause they remained almost uncolonized by the cabbage aphid(Brevicoryne brassicae(L.)) throughout the growing season, plants of Brussels sprouts were singled out in each of 4 years, from plots heavily infested with the aphid, as possibly being resistant to attack. Clones of these plants were established from cuttings and tested in a controlled environment by inoculation withB. brassicaeand later, in the field, by natural infestation. The tests confirmed that some of the plants were resistant to the aphid, and the most resistant of those from the first year of the work proved at least as resistant as any subsequently found. The resistance was expressed as antibiosis, but in the field host non‐preference was also shown by incoming winged aphids.The possibility that biotypes ofB. brassicaemight exist, to which the resistant sprout clones were not necessarily resistant, was investigated usingB. brassicaecollected from sprouts from each of several areas in England. Eight sprout clones, seven of which were known to be resistant, and the other susceptible, toB. brassicaefrom Wellesbourne were tested with these otherB. brassicae.The results showed that biotypes of the aphid, with differing abilities to colonize respective sprout clones, existed in each area, and of the seven sprout clones resistant to the Wellesbourne aphid, only one appeared never to be fully susceptible to one or more of the other biotypes ofB. brassica

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1972.tb01266.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYThe trapping of alate aphids in emergence cages each 1 yd2(0–83 m2) over cereal crops from mid‐June to the end of July, 1964 to 1971, always revealed colonies of cereal aphids within the crop.Four species,Sitobion avenae, S. fragariae, Metopolophium dirhodumandRhopalosiphum padioccurred every year in different proportions. Alate aphids from winter wheat were most numerous in 1968 and fewest in 1967. Alatae developed slightly earlier in cages than in the field and peak catches were a few days earlier than in a nearby 12‐2 m suction trap.Cereal aphid colonies were adversely affected by bad weather in May, e.g. in 1969, and by predators. Coccinellidae (chieflyPropylea 14‐punctata)were the dominant predators in 1971 and 1968, Syrphidae in 1966, 1971 and 1968 and Chrysopidae in 1970. Parasites belonging mainly to the genusAphidiuswere numerous every year. When hyperparasites such asAsaphes vulgaris, Lygocerussp.,Conostigmussp. andPhaenoglyphissp. were abundant as in 1967, they affected numbers of aphids in the current year and increased them in the following year (1968), possibly by hindering early, heavy parasitism. Hyperparasites could have an important influence in fluctuations of cereal aphid populations from year to year. Aphids of one species or another are always present in cereal crops in sufficient numbers during the summer months to provide copious quantities of honey dew, and this is unlikely to be a limiting factor in the biology of the wheat bulb fly,Leptohylemyia co

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1972.tb01267.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYMuch sacbrood virus accumulates in the brains of infected bees, especially of drones, without causing symptoms. However, infected individuals fly earlier in life than healthy bees and most infected foragers failtocollect pollen, as do bees briefly anaesthetized with CO2. The few infected bees that gather pollen contaminate their loads with much sacbrood virus. Infection does not shorten the lives of drones, or of workers that have been deprived of pollen, but it much shortens the prolonged lives of workers that have eaten pollen. Infected workers, healthy workers deprived of pollen, and senile individuals are unable to maintain the usual metabolic rates of bees at temperatures below 35oC, or to resist chilling.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1972.tb01268.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYThe hyphomycetous fungusAphanocladiutn albumcan grow over and around uredia of the rustsPuccinia coronata, P. hordei, P. graminisf.sp.avenaeandP. reconditaf.sp.triticinawhen host plants are kept under very humid conditions, but not on such plants not infected with rusts; uredia are adversely affected and telia develop in their vicinity.Plants inoculated with these rusts and with five isolates ofA. album(one from a dead insect) showed: (1) much earlier development of telia on detached and non‐detached rusted leaves inoculated withA. albumthan on corresponding leaves not thus inoculated; (2) telial induction byA. albumin some isolates of rust species which hitherto had rarely or never produced telia; (3) precocious telial formation, in comparison with controls, whenA. albumspores were sprayed on leaves as much as 3 days before and 9 days after rust inoculation, and occasionally after uredia had already matured. As affected leaves remained green until the whole leaf became moribund, senescence is apparently not the factor inducing telia formation.The normal‐appearing teliospores of some isolates were induced to germinate, whereas others did not.Rhamnus palaestinainoculated with basidiospores of one isolate ofA. album‐treated P. coronataf.sp.avenaeproduced pycnia and fertile aecia.The importance ofA. albumas a working tool in rust research and as a possible means for biological control of rust epiphytotics is disc

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1972.tb01269.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYCocksfoot mottle (CFMV) and Phleum mottle (PMV) viruses are both transmitted by the Chrystomelid beetlesOuletna melanopaandO. lichenis.Both viruses are readily inoculated into some cereals but only CFMV has ever been found causing a natural infection, in one wheat crop. The apparent absence of these viruses from cereals in the field results from inefficient transmission by the vectors and the existence of symptomless tolerance in cereals to both viruses, especially after tillering. In cereals symptom expression is related to virus concentration, and both may be influenced by light intensity and ambient temperature.O. melanopa, which is potentially the most important vector of the viruses to cereals, moves to winter‐sown cereals only when the virus‐tolerant growth stage has been reached, and later to spring‐sown cereals when they too have commenced tillering. Whereas the spread of these viruses within grass crops is increased by cutting and grazing, cereal crops are neither cut nor commonly g

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1972.tb01270.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYTecnazene (up to 33 ppm) and dichloran (up to 500 ppm) had little effect on germination of spores or growth ofFusarium solaniisolated from and causing a rot of potato tubers; they also did not decrease rotting when applied to wounds later inoculated with the pathogen.Benomyl and thiabendazole (up to 500 ppm) also had little effect on spore germination but did greatly decrease growth at 5 ppm. A pronounced pink coloration developed in cultures growing slowly in the presence of benomyl; a similar though less striking effect appeared in agar cultures containing thiabendazole.Benomyl suspended in water or diluted with Fuller's earth gave good control of rotting when applied to wounds inoculated later withF. solani.Still better control was obtained with thiabendazole; dusts containing 1% a.i. substantially decreased rots and those containing 10 % a.i. gave almost complete control when applied to wounds shortly before inoculation. Thiabendazole was also very effective when used 24 h after inoculation and a fair measure of control was obtained when it was applied 24 h later.Benomyl and thiabendazole placed on apparently intact surfaces of tubers caused tissue 5 mm deep to become toxic toF. solani10 days later, and, unexpectedly, this tissue prevented spore germination.Fuller's earth alone substantially decreased rotting.The results obtained suggest that dusts containing thiabendazole have some promise for the control ofFusariumrots of potato tubers, especially of early crops.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1972.tb01271.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYExperiments at two sites in each of three seasons showed that successful control of celery leaf spot depended more on the choice of fungicide than on the number of sprays and the dates of application. Organotin fungicides gave best control of celery leaf spot and with one exception residues were not detected even when the last application was given 4 weeks before harvest rather than 6 weeks.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1972.tb01272.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYLettuce plants grown in beds of soil previously fumigated with methyl bromide accumulated water‐extractable bromide, the amount present in the tissues depending on the concentration of inorganic bromide produced in the soil by the breakdown of the fumigant. Samples of lettuce plants from commercial nursery soils fumigated with methyl bromide at rates of 1–2 lb/ 100 ft2(49–98 g/m2) gave rise to soil bromide levels of n‐6i/μg/g. The corresponding bromide concentrations in the plants ranged from i‐6 to io‐1 mg/g of dry tissue.The bromide concentrations in whole lettuce plants grown in pots of soil supplemented with 0–5 mg/g inorganic bromide, as potassium bromide, ranged up to 100 mg/g of dry tissue. Bromide taken up from the soil by lettuce plants was located mainly in the outer leaves.Lettuce was relatively insensitive to the presence of bromide in the soil; no phytotoxic symptoms were observed in plants growing in soils containing 5 mg/g inorganic bromide.Implications in relation to possible tolerance limits for the bromide content of lettuce plants

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1972.tb01273.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYIn sandy clay soil in Bedfordshire, potato cyst‐nematode(Heterodera rostochiensisWoll.) was controlled and yields of Majestic potatoes greatly increased when i‐2g aldicarb, 4‐0 g fensulphothion or 10‐3 g diazinon, disulphoton, ‘Isolan’ (i‐isopropyl‐3‐methyl‐5‐pyrazolyl dimethylcarba‐mate) or thionazin per m2were incorporated in the top soil before potatoes were planted. Diethyl phosphorothioates controlledH. rostochiensisbetter than dimethyl phosphates. One hundred and eleven g methyl bromide, 47‐6 g carbon disulphide or 45‐2 g D‐D per m2applied to the soil and covered with polyethylene sheeting greatly increased the yield of potatoes, but also increased the number of nematodes in the soil. Estimates of the number of larvae able to invade potato roots in treated soil after harvest and of cysts, total eggs or live eggs selected the same range of treatments as effective i

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1972.tb01274.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

SUMMARYWater loss from cut grass was studied to determine factors limiting the drying process.An apparatus, used to measure water loss at 28±1°C from blotting paper and from leaves and stem internodes of cocksfoot, consisted of four channels in which air speed was controlled at 25–80 cm s‐1and relative humidity at 7–68%.The maximum rate of water loss from wet blotting paper was 10500 mg water dm‐2h‐1but from leaves and stem internodes supplied with water it was less than 250 mg dm‐2h‐1. The rate of loss from both plant specimens and blotting paper was linearly related to the vapour pressure differences between the specimen and the surrounding air but was not increased when air speed was changed from 40 to 80 cm s‐1. Grass specimens supplied with water had lower rates of water loss than wet blotting paper because of tissue resistances which were calculated for(a)untreated leaf and stem specimens,(b)rubbed leaves, (c) cut leaves,(d)leaves exposed to steam for 60 s. Treatments(b)‐(d)greatly reduced tissue resistances.The rates of drying of leaves and stem internodes not supplied with water changed only slightly in response to faster air speeds but were significantly increased by treatments(b), (c),(cs)(split stems),(d)and (e) (exposure to petroleum vapour for 60 s). The most effective treatments trebled the drying rates of leaves and increased the drying rates of stem internodes by 10 times. Reductions in relative humidity had little effect on drying rate following treatments(a), (b), (c) and(d), but when treatments (cs) and (e) were given, additional significant increases in drying rates were obtained when the relative humidity was reduced.Grass specimens given the most effective treatments and dried under the most favourable conditions did not utilize the full drying capacity of the environment, for the rates of water loss from these specimens were at least three times lower than those from wet blotting paper. The results indicate that high rates of drying could be achieved at 28oC or similar temperatures if practical treatments were developed to remove or greatly reduce the high resistance to wate

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1972.tb01275.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY