摘要:

SUMMARYThe effects of predation by carabid and staphylinid beetles and birds (blue‐ and great‐tits) on mature larvae of the codling moth Cydia pomonella were investigated in a field experiment. The number of predatory beetles on the ground beneath eight of 16 apple trees was reduced by an insecticide spray, and tits were excluded from the trunks and lower branches of eight trees by means of Terylene netting. Beetles had no significant effect on survival of larvae on trees, but only 8% of larvae survived to adulthood on trees exposed to blue‐ and great‐tits, whereas on trees protected from them 48% survived. Larvae were taken rapidly by the tits from the time larvae first built cocoons in summer and, by the time the majority of larvae had emerged from apples in late summer or autumn, tits had removed most from cocoons beneath flakes of bark glued to trees. Thus tits fed on larvae mainly in summer and autumn. On trees protected from tits, 8% of mature larvae were killed by fungi, of which Verticillium lecanii was most important. It was calculated that, of the larvae maturing in apples, 44% failed to build cocoons on the trees, 47% were taken by tits, then 1% were killed by fungi. Larvae failing to build cocoons on trees may build them on the ground. Of larvae in cocoons planted on or in the ground in 1975, only one (0.3%) persisted through the winter; 98.6% disappeared, and 1.1% were found dead, covered by fungi; in 1976, all larvae disappeared by December. Larvae disappeared even in the absence of predators, and are thought to have moved in response to damp ground con

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1978.tb02620.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARYTwo field strains of the German cockroach Blattella germanica (L.) were collected in England from survivors of treatments with bendiocarb wettable powder, and bred in the laboratory. These and a laboratory susceptible strain were compared by a tarsal contact method to test for resistance to bendiocarb, fenitrothion and dieldrin. The field strains after exposure to the insecticide for 24 h were resistant to bendiocarb in terms of mortality by factors of 5.6 and 6.2 at the LC50level, but at the LC95level the resistance factors were only 1.7 and 2.0; however knockdown resistance was detected, with resistance factors at the KD50level of 10.6 and 8.1. At shorter exposure times of 5 min and 60 min, 2–20% of cockroaches from the field strains survived 55 or 110 mg bendiocarb/m2; there were no survivors from the susceptible strain. Some cockroaches from the field strains were able to recover from knockdown after and during exposure to 110 mg bendiocarb/m2. Both field strains showed some resistance to dieldrin; however, there was no resistance to fenitrothion. When all three strains were exposed to 55 mg fenitrothion/m2for 5 min, all the insects were knocked down within 3 h, and all had died within 96 h. There was no recovery from knockdown to fenitrothion or dieldri

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1978.tb02621.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARYThe development and spread of maize rust from an inoculated circular plot was studied during 1975. Results from a Burkard volumetric spore trap sited in the centre of the inoculated plot showed that the daily peak urediniospore concentration in the atmosphere occurred at about 1300 h. During the season atmospheric urediniospore concentration increased to a plateau and later decreased mainly through lack of host material.The spread of the pathogen away from the inoculated plot was related to the increase in atmospheric urediniospore concentration and warm temperatures. Disease gradients along the eight major compass directions demonstrated the influence of wind on the spread of the pathogen. As the season progressed gradients tended to flatten because of secondary spread of the pathogen.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1978.tb02622.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARYIn glasshouse experiments with plants in pots, applications of potassium chloride to the soil at 0.5 g/plant, 4 days before inoculation with Puccinia striiformis, decreased the severity of yellow rust on several winter wheat cultivars in comparison with untreated plants. Conversely, yellow rust was encouraged by applications of sodium nitrate. Sodium chloride in solution (8.6 g/l) reduced yellow rust when applied to the soil at the rate of 20 ml/plant but not when it was sprayed on to the leaves.In small‐plot field experiments, sodium and potassium chlorides applied to the soil as dry powders in the spring at rates of 376, 1130 or 2260 kg/ha, significantly decreased the severity of yellow rust on most of the winter wheat cvs examined at each rate. The chlorides at these rates did not adversely affect the overall growth or yield in the absence of yellow rus

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1978.tb02623.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARYGel filtration and chromatographic separation of soil extracts gave three fractions which induced formation of chlamydospores by Fusarium solani f. sp. phaseoli. Depletion of nutrients had a similar effect.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1978.tb02624.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARYThe incidence of Phoma exigua var. foveata and Polyscytalum pustulans in dry soil and dust from potato stores was assessed at 10 farms in Scotland producing virus‐tested stocks of seed potatoes derived from stem cuttings (VTSC). Samples were collected on three occasions during 1976: during the storage period (February‐March), soon after the potatoes were planted (May) and just before the new crop was lifted and stored (August‐October). Both pathogens were detected at all three sampling times but P. exigua var. foveata was more frequently detected at the last one than P. pustulans. Soil and dust from various sites within the stores, such as floors, ledges, graders and boxes, were contaminated by these pathogens. Propagules of both pathogens remained airborne for at least 12–17 min after the floors were swept.P. exigua var. foveata remained viable for at least 16 months in dry soil from tuber surfaces stored at 4–6°C. When VTSC tubers were dusted before planting with a dry store soil contaminated by P. exigua var. foveata the gangrene potential of the progeny tubers was much greater than that from untreated tubers or from tubers treated with an uncontaminated soil. The role of inoculum surviving in dry soil is discussed in relation to reinfection of V

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1978.tb02625.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARYBenomyl and benodanil, applied to tobacco seedlings before transplanting, reduced sore shin infection. Benodanil was the more effective, sometimes restricting damage to 5% of the surface area of the buried portion of stems, compared with 50–60% in untreated plants. The fungicides were applied either as a seedbed drench or a root‐stem dip. The dip method used less fungicide and was generally more effective than the drench at equal concentration but was less practical. Benodanil was over three times as active as benomyl against Rhizoctonia solani in liquid cult

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1978.tb02626.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARYStrains within field populations of barley powdery mildew (Erysiphe graminis f. sp. hordei) varied greatly in their response to ethirimol. Each strain remained stable whether the fungicide was present or not, and no evidence for adaptation was obtained. Strains of intermediate sensitivity were the most frequent within the pathogen population, and these also dominated model populations maintained in the laboratory. Ethirimol eliminated sensitive strains from laboratory mixtures, and increased the relative fitness of insensitive ones, but not sufficiently to oust the intermediate strains. Mildew from treated field plots was less sensitive than that from untreated plots, but only early in the epidemic. Insensitivity was not related to the level of ethirimol used and, at four times the rate used commercially, insensitive strains were no more frequent than at lower rates. As the complexity of mildew populations increased, changes in ethirimol sensitivity in response to selection became less pronounced, and it is suggested that strains of intermediate sensitivity to ethirimol exert a stabilising effect within natural populations. This could alter if the fitness of insensitive strains were to increase, perhaps through recombination. Consideration should be given to the effect ethirimol might have on the composition of the pathogen population if applied when sexual recombination occurs, and to the role ascospores play in disease development.

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1978.tb02627.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARYHypochoeris mosaic virus (HMV) is common in Hypochoeris radicata (‘cat's ear’) in western Canada. It infected 10 of 53 mechanically inoculated species in five of twelve families, but was not transmitted by aphids or through seed or soil. Sap from infected Nicotiana clevelandii was sometimes infective after dilution to 10‐1and occasionally 102, after 10 min at 45 but not 50°C, and after 1 but not 2 days at 20°C. Infectivity of crude nucleic acid extracts from infected leaves was rapidly abolished by RNase but not by DNase.Host sap contained very few rod‐shaped particles or particle fragments mostly 21.0–22.5 nm in diameter, and up to 420 nm long but with predominant lengths of 120–140 and 240–260 nm. Many rods in purified virus preparations were less than 240 nm long, and the majority were c. 140 nm or shorter. The particles had a helical substructure with a pitch of 2.58 nm and contained a single type of protein of estimated mol. wt 24.5 × 103.HMV showed no serological relationship to eight morphologically similar viruses (beet necrotic yellow vein, broad bean necrosis, barley stripe mosaic, peanut clump, potato mop‐top, Nicotiana velutina mosaic, wheat soil‐borne mosaic and defective strains of tobacco mosaic). It is probably a hitherto und

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1978.tb02628.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SUMMARYPlum pox virus (PPV) was detected by ELISA throughout the year in extracts of root, bark, fruit, flowers and leaves of Prunus species; extracts from healthy plants gave negligible background reactions. In the summer, ELISA values obtained with extracts from infected leaves were variable but samples extracted at 1:50 (w/v) could have been diluted a further five to 110 times before reaching the limit of detection. Using a single antiserum the virus was detected in several hundred trees, suggesting that there was little antigenic variation.PPV was unevenly distributed in leaves and shoots and commonly occurred in only a few branches of an infected tree although it was frequently present in suckers growing from the roots. Virus was detected in the only three trees known to be infected in random leaf samples taken from 530 1‐yr‐old trees, but some infected trees were missed in samples taken from older trees and from a 7‐yr‐old rootstock hedge. The main practical use of ELISA for PPV is therefore as a sensitive and highly reliable confirmatory test which greatly facilitates control of the disease by the prompt destruction of infecte

ISSN:0003-4746    

DOI:10.1111/j.1744-7348.1978.tb02629.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY