A COMPARISON OF HIGH AND LOW VOLUME SPRAYS FOR CONTROL OF THE BEAN APHID, APHIS FABAE SCOP. ON FIELD BEANS

Insecticides were sprayed in different amounts of water to control Aphis fabae Scop. attacking spring-sown field beans. The single application of each insecticide was timed to coincide with the end of aphid migration from the winter host to the crop. A tractor-mounted row-crop hydraulic sprayer was used.
In one experiment seven different insecticide sprays were compared at high volume (in 140 gal. of water per acre); the most effective were nicotine at 22.4 oz. of active constituent per acre, demeton at 5.6 oz. and demeton-methyl at 11.2 oz.
A further comparison was made of five insecticides for each of which a selected dose of active ingredient was applied in 60 gal. (medium volume) and in 10 gal. of water per acre (low volume). The amount of insecticide retained on the plant following the low-volume application was not less than that from the medium-volume spray; the efficiency of A. fabae control was not affected by the volume sprayed except with malathion which did better at the medium volume. The systemic insecticides demeton-methyl at 6 oz. of active constituents per acre, the related compound 4741 at 3 oz. and fluoroacetamide at 3 oz. stopped the aphid numbers from rising above a peak of eight per plant compared with 230 per plant for malathion (low volume) at 12 oz. 2400 per plant for lindane at 6 oz. and 3550 per plant for check treatments sprayed with wetter only. Grain yields ranged from around 4 cwt. per acre on check treatments to around 27 cwt. per acre on plots sprayed once with the systemic insecticides. There was a curvilinear relationship between grain yield and log number of A. fabae per plant.     

WIND DIRECTION AND THE INFESTATION OF BEAN FIELDS BY APHIS FABAE SCOP.

Bean fields are often attacked by Aphis fabae very heavily along the edges: and on a field at Rothamsted in 1948 the sides facing the wind during the primary migration had more colonies than those in the lee of the crop (Johnson, 1950). Additional observations on the distribution of colonies were made on six bean fields at Sutton Bonington in 1950–2.
At Rothamsted in 1948 it was assumed that the more numerous colonies on the windward sides of the field followed a heavier deposition of primary migrants there, though the migrants themselves were not observed on the crop. In 1950–2 the locations of primary migrants, as well as of colonies, were recorded in three out of the six fields observed.     

INFESTATION OF A BEAN FIELD BY APHIS FABAE SCOP. IN RELATION TO WIND DIRECTION

The wind direction during the primary migration of Aphis fabae Scop, gave a plausible explanation of the infestation pattern round the edge of a bean field; but it is emphasized that other factors are involved whose effects have not been adequately-assessed in this preliminary survey.     

A TRADE-OFF FOR HOST PLANT UTILIZATION IN THE BLACK BEAN APHID,APHIS FABAE

Many studies on insect herbivores have sought to find trade-offs between utilization of alternate host plants, both to understand the prevalence of specialization and to appreciate the likelihood of sympatric speciation due to disruptive selection. To date, few studies have found trade-offs. Seventy-seven clones of the black bean aphid, Aphis fabae, were collected from field sites in East Anglia, U.K., over an area of about 10,000 km². These clones exhibit a trade-off in fitness between two alternative hosts, broad bean and nasturtium. This pattern is maintained in the F2 generation. The predominance of broad bean in the area, the fact that clones were only sampled from one of these two hosts, and the absence of “master-of-all-trades” genotypes after recombination all point to the importance of antagonistic pleiotropy rather than linkage disequilibrium in maintaining this trade-off. It is concluded that this population presents strong evidence for a fundamental trade-off for host utilization.     

MOULTING RHYTHM IN THE ALIENICOLAE OF APHIS FABAE SCOP. (HEMIPTERA: APHIDIDAE) IN THE FIELD

In a natural population of alienicolae of Aphis fabae Scop, on field beans in July 1952, the frequency of moulting of the last larval instar into the alate form was usually relatively high between about 04.00 and 08.00 hr. G. M. T. This high rate was followed by a decline to a lower fluctuating rate for the rest of the day. The moulting rate at night was usually very low.
The high rate of moulting in the morning, just as the temperature is rising, may be due to acceleration of nymphal development which leads to a synchronization of moulting, much as teneral development of alatae, if accelerated, produces flight peaks during the day (Johnson, Taylor & Haine 1957): data on the relations of moulting and nymphal development to temperature are, however, insufficient for making a complete analysis along these lines.
Changes in moulting rate during the rest of the day are correlated with temperature and with time, both independently. A rise of 1°C. ambient temperature is associated with an 11.6% rise in moulting rate: a fall of 1°C. with a drop of 10.5% and a lapse of 1 hr. in time by a 5.4% drop in the rate. Sunshine and humidity show no simple correlation with moulting rate.     

AGGREGATION IN APHIS FABAE SCOP. I. AGGREGATION ON PLANTS

A study of free infestations of Aphis fabae Scop. on the leaves of its host plants, spindle and sugar beet, showed that the clustered distribution of the aphids within the boundaries of each leaf was not a matter of chance but involved active aggregation. Experiments in small leaf cages showed that aggregation could take place independently of any differences between portions of a leaf, being brought about by truly gregarious reactions between the aphids. Experiments in which walking aphids were made to encounter other live or dummy aphids fixed to leaves, showed that the gregarious reactions were of at least two kinds. The aphids both probed more often, and remained inserted for longer, near other aphids than apart from them.
It appears that the unequal distribution of aphids among the leaves of a plant is due primarily to intrinsic differences between leaves, but is aided by gregariousness, while the aggregations observed on leaves are due primarily to gregariousness, and only secondarily to differences between portions of a leaf. It is suggested that the primary function of gregariousness is to concentrate the aphids on to the best feeding sites, both among the parts of a plant, and among whole plants; that is, it acts as an aid in host selection, even with aphids which do not aggregate so compactly as A. fabae. The functions of compact aggregation and other specialized forms of gregarious behaviour remain to be discovered.     

豆蚜在不同品种扁豆上的取食行为

在温室栽培不同品种的扁豆(Dolichos lablab),采用接蚜,光暗对照,隔离饲育,离体饲育,蜡膜人工饲液饲育以及用昆虫取食行为自动测试仪对其取食行为进行测试等方法来鉴定不同扁豆品种对豆蚜(Aphis craccivora Koch)的抗性,确认紫色品种对豆蚜具有拒食作用.分离,提取了扁豆所含的色素成分并对豆蚜进行生物测定,确定扁豆的红色“色素”是抗蚜的物质基础.用进一步提纯的红色“色素”对豆蚜进行取食行为测试,得出拒食强度的初步数据.     

METHODS FOR MASS REARING AND INVESTIGATING THE HOST RELATIONS OF APHIS FABAE SCOP.

A method is described for producing some hundreds of apterous and thousands of alate virginoparous Aphis fabae every day continuously throughout the year. Broad beans are used as the host plants, in a 'production-line' arrangement of eleven ventilated breeding cages, with additional cages for starting subcultures and rearing alatae, all contained in a portion of a small greenhouse with supplementary lighting in winter. When running smoothly, the culture requires about half an hour's work by one man per day.
An 'aphid gun', being a modified type of aspirator catcher, is described, with which large numbers of aphids could be handled and counted rapidly without damaging them.
Amodified technique for host-transference experiments is described, which permits individual leaves to be compared one with another as host-units for the aphids. Two types of small metal cages are used, both easily attached to leaves in their natural positions on growing plants. One type confines the aphids to a part of a single leaf and is used mainly for determining relative reproduction rates on different leaves. The other type encloses equal areas of two different leaves between which the aphids can move freely, and is used for determining their behavioural preferences. The principles underlying the use of such cages, the experimental procedures and the interpretation of the results obtained are discussed.     

THE ANALYSIS AND RECONSTRUCTION OF DIURNAL FLIGHT CURVES IN ALIENICOLAE OF APHIS FABAE SCOP.

Experiments, in which alate aphids were marked immediately after eclosion from the last nymphal instar and observed until they took flight, gave information which, together with the measured rate of moulting and a continuous record of temperature, has been used to construct theoretical daily curves for numbers flying from a bean crop. These curves have been matched against the observed curves for the same days.
The differences between curves so constructed for a period of 17 days and the observed curves for the same period are of the same order and kind as the differences between two measured curves in different sites at the same time.
The different types of daily flight curve can thus be accounted for in terms of the rate of production of alatae by moulting, the effect of temperature on the teneral ('drying out') period and the effect of low light intensity and temperature on take-off behaviour.     

THE CHANGING NUMBERS OF APHIS FABAE SCOP., FLYING AT CROP LEVEL, IN RELATION TO CURRENT WEATHER AND TO THE POPULATION ON THE CROP

Aphis fabae Scop, flying over bean crops in the summer usually show a double peak of aerial density during the day; scarcely any flight occurs at night. The first peak is thought to be composed mainly of alatae moulted since the previous evening and the decline of the peak to their depletion as they fly away from the crop. The second peak is probably composed mainly of alatae moulted during the same day. Lack of flight at night is due partly to low temperature, partly to lack of alatae old enough to fly and probably also to low light intensity.
Contrary to expectation changes in aerial density from hour to hour are only very weakly correlated with weather factors, especially wind-speed. The total numbers in each of the two peaks do show a low but significant correlation with both wind-speed and temperature in one case, but even then only a relatively small amount of the variation in aerial numbers is associated with weather changes. Other factors, particularly rapid changes in the numbers of alatae on the crop caused by moulting, accumulation before flight and depletion by flight evidently obscure changes due simply to varying flight behaviour. Thus because of large populations on the crop, it is possible to have quite large numbers in the air even when the weather is relatively unfavourable for flight.
In addition to these observations, the relation between total numbers caught at different wind-speeds shows that most of the migration occurred in winds when the aphids could have had no control over the general direction of flight. The current view that most migration takes place only in calm weather can therefore no longer be held.     

HOST FINDING BY APHIDS IN THE FIELD: APHIS FABAE SCOP. (GYNOPARAE) AND BREVICORYNE BRASSICAE L.; WITH A RE-APPRAISAL OF THE ROLE OF HOST-FINDING BEHAVIOUR IN VIRUS SPREAD

Aphis fabae gynoparae occurred in the same large proportion in simultaneous collections of all aphids alighting and probing on, and taking off from, a host plant (spindle) and a non-host (peach), and behaved similarly when approaching and leaving them in the same conditions. Most alighters took off again from leaves of both kinds within a few minutes, staying longer and probing more times on the host. In atmospheric conditions favouring local 'hovering' instead of dispersal, flying and alighting aphids became concentrated around host plants, not through any specific attraction to them, but apparently because more aphids had accumulated upon them and were now taking off.
Brevicoryne brassicae occurred in the same large proportion in simultaneous collections of aphids alighting on a host plant (cabbage) and a non-host (sugar beet). No satisfactory evidence was found of preferential alightment on cabbage and there were indications of preferential alightment on the non-host. A very small minority of the A. fabae and B. brassicae that alighted on their hosts stayed there long enough to larviposit. This minority was rather larger among alighters late in the day, but in the absolute sense, more colonization occurred during earlier periods when more aphids arrived.
The intensely dispersive type of host-finding behaviour in Myzus persicae, A. fabae and B. brassicae may be common among Aphididae. It seems ideal for the dissemination of non-persistent plant viruses, more particularly among the less-favoured host plants of each aphid. The tendency to commensal association between virus and vector provides an ecological framework which may govern the incidence of virus-vector specificity and symbiosis.     

生物有机无机复合肥的研制与效果研究

研制了一种融微生物肥有机肥和无机肥于一体的新型复合肥料。测定结果,含微生物活菌总量为2．5亿个／g,其中固氮、解磷、解钾功能做生物活菌量达1．0亿个／g,有机干物质34．3－37．3％,含氮（N）7.8－8．9％,全磷（P2O5）5．2－5．5％,全钾（K2O）4．8—5．0％。毒性试验结果表明,该肥无毒无害,对环境不构成危害。生产过程中采取了有机物料发酵和功能微生物大量繁殖一次同步完成,添加除臭微生物、机械自动翻拌等工艺。田间试验表明,与等养分或等价格投入的化肥相比,增产9－18％,对多种经济作物品质有明显的改善作用,且有一定的改土培肥效应。