Observations on the Population Dynamics of the Red Locust, Nomadacris septemfasciata (Serville), in its Outbreak Areas.

1968 ◽  
Vol 5 (3) ◽  
pp. 751
Author(s):  
G. F. Burnett ◽  
C. W. Stortenbaker
Keyword(s):  
Population Dynamics ◽  
Nomadacris Septemfasciata ◽  
Red Locust ◽  
Outbreak Areas

Enumerating Populations of Adults of the Red Locust, Nomadacris septemfasciata (Serville), in its Outbreak Areas in East and Central Africa

1958 ◽  
Vol 49 (2) ◽  
pp. 273-285 ◽  
Author(s):  
C. C. Scheepers ◽  
D. L. Gunn
Keyword(s):  
Total Population ◽  
Central Africa ◽  
Nomadacris Septemfasciata ◽  
Natural Mortality ◽  
Red Locust ◽  
Frequency Distributions ◽  
Moving Vehicle ◽  
The North ◽  
Outbreak Area ◽  
Outbreak Areas

SummaryA method is described of estimating the total numbers and frequency distributions of adults of the Red Locust, Nomadacris septemfasciata (Serv.), in outbreak areas of hundreds of square miles, based upon counting the numbers that fly up in a two-yard strip in front of a moving vehicle. The method has proved itself valuable for indicating both immediate and future requirements for killing the locusts, but it requires refining for some research purposes.By this method, the importance has been clearly shown of the process of congregation of scattered adult locusts in forming emigrant swarms that could start a plague. The locusts do not congregate but actually disperse just before laying eggs.The total population in part (189 sq. miles) of the North Rukwa Outbreak Area (a self-contained area of 253 sq. miles) in Tanganyika Territory has been followed for four years. There are indications that a small migrant swarm contains 5–10 million locusts, that a total population in the whole of the North Rukwa Outbreak Area of 20 million locusts is unlikely to yield a migrant swarm, but that 50 million locusts could readily do so.In 1953, after poor rains, no natural mortality was detected between July and October by the assessment methods described. In 1957, after good rains, natural mortality of 70–90 per cent. was revealed by the same methods, although the dry season was not fully covered by the assessments.

Field trials with a presistent stomach insecticide against populations of the red locust, Nomadacris Septemfasciata (Serv.), in an outbreak area

1963 ◽  
Vol 54 (2) ◽  
pp. 349-359 ◽  
Author(s):  
G. J. W. Dean
Keyword(s):  
Standard Method ◽  
Field Trials ◽  
Nomadacris Septemfasciata ◽  
Mosaic Pattern ◽  
Tall Grass ◽  
Red Locust ◽  
Total Cost ◽  
Outbreak Area ◽  
Outbreak Areas ◽  
The Cost

In its potential outbreak areas in Northern Ehodesia and Tanganyika, sexually immature populations of adults of Nomadacris septemfasciata (Serv.) tend to concentrate in the islands of grass that remain unburnt after the annual fires that occur during the dry season. The locusts use the tall grasses as roosting sites and descend in the daytime to feed on adjacent short grasses, where these occur as constituents of an internal mosaic within the islands, or, in the case of islands composed wholly of tall grasses, on the fresh grass-shoots on the burnt-over ground surrounding them.Two methods are described whereby emulsified solutions of dieldrin were applied in the Central Bukwa plain, Tanganyika, in 1960 as a stomach poison at dosages of 2·9 and 4·5 oz. active ingredient per acre from aircraft to the whole of individual islands showing the internal mosaic pattern (4 trials) or at 2·9, 4·5 and 8·2 oz. per acre to a swath 20 or 40 yd. wide around the perimeter of tall-grass islands (8 and 4 trials, respectively). Results were assessed by counting the numbers of locusts flushed by a vehicle driven along strips parallel to one another and 0·1 mile apart, and checked by counts of dead locusts. Mortality reached at least 90 per cent, within four days, at either dosage, following the first method, and 21–89 per cent, within 14 days following the second, being significantly greater at the higher dosages but not with the wider swath.These results are compared with those obtained in preceding years by the standard method of applying DNC from aircraft at 20 per cent, in oil as a contact insecticide; in the latter case, the cost of insecticide was more per acre sprayed, but less per 1,000 locusts killed because the density (5 locusts per sq. yd. of grass island) in the trials was greater than in those using dieldrin (1 per 3 sq. yd.). Even so, when dieldrin was used, many more locusts were killed per sortie flown, and the total cost (of flying plus insecticide) per island was much less, and per 1,000 locusts killed very much less, than in the standard method, which nevertheless has to be used against mobile swarms because DNC is quick acting.

Assessing the size of populations of adults of the red locust, Nomadacris septemfasciata (Serv.), in their outbreak areas by means of a helicopter

1966 ◽  
Vol 56 (4) ◽  
pp. 715-723 ◽  
Author(s):  
P. M. Symmons
Keyword(s):  
Central Africa ◽  
Early Morning ◽  
Rotor Blades ◽  
Nomadacris Septemfasciata ◽  
Red Locust ◽  
Outbreak Area ◽  
South Central ◽  
Outbreak Areas ◽  
Considerable Length ◽  
On Line

Populations of the red locust, Nomadacris septemfasciata (Serv.), can build up to large numbers in certain of the grass plains of south-central Africa. Adult populations are always under-dispersed, and estimates of their size can be made economically only by counting the locusts flushed on line traverses of considerable length. It is necessary, in such traverses, to determine the width of the strip swept, the proportion of the locusts in it that are flushed, and the accuracy with which these are counted. Investigations into the use of a three-seat Hiller helicopter for this purpose were carried out in south-west Tanzania in 1964–65. It proved possible to cause virtually all the locusts in a strip the width of the rotor blades to rise ahead of the machine, provided it was flown at a height of about 10 ft. and at less than 10 m.p.h. and neither in the early morning nor in the late evening. A comparison of estimates of the size of the population in a 1-sq.-mile plot made by Land-Rover traverses with those made by helicopter, both when the traverse strip was marked on the ground and when it was assessed from within the helicopter, showed no evidence of systematic errors in estimating from the helicopter either the number of locusts flushed or the width of strip. Further, two observers simultaneously counting locusts rising from one strip achieved very similar results. Thus, estimation of the size of a complete outbreak-area population by means of a helicopter is clearly possible.

The assessment of the size of populations of adults of the red locust, Nomadacris septemfasciata (Serville), in an Outbreak Area

1963 ◽  
Vol 54 (3) ◽  
pp. 549-569 ◽  
Author(s):  
P. M. Symmons ◽  
G. J. W. Dean ◽  
C. W. Stortenbeker
Keyword(s):  
Standard Error ◽  
Large Scale ◽  
Considerable Proportion ◽  
Nomadacris Septemfasciata ◽  
Random Errors ◽  
Red Locust ◽  
Moving Vehicle ◽  
Outbreak Area ◽  
Outbreak Areas ◽  
Valid Estimate

Estimates of the size of populations of the red locust, Nomadacris septemfasciata (Serv.), in their outbreak areas have been made in Tanganyika from counts of adults caused to fly up by the approach of a slowly moving vehicle. For research purposes it was desirable both to improve and estimate the accuracy of such assessments. For control purposes it was desirable to devise an objective aerial assessment technique which could be used in areas where ground methods were either impracticable or expensive. The errors involved in both ground and air estimates can be divided into those concerned with the ratio of locusts counted in the sample area to those actually present, and those concerned with the distribution of the locusts.It was found that a Land-Rover moving at five miles an hour, with the wind blowing from a rear quarter, flushed a high and virtually constant proportion of locusts during most of the day and in the most important grasses of the Rukwa outbreak area, throughout the dry season. Variation in locust density and in the state of the grass had little effect, if any, on the value of the equivalent strip (e), i.e., a strip whose width is such that the number of locusts in it is equal to the number flushed by the vehicle in a strip equal in width to its own. The change with time, and thus presumably with locust behaviour, in the value of e, estimated as recommended, was small but significant.Counts by various observers in one vehicle gave similar results and it seems likely that, even with high numbers, there was no systematic mis-estimation. This is almost certainly true for counts of under a hundred locusts flushed per 0·1 mile. With upwards of one thousand 0·1-mile counts in each assessment, it is believed that the random errors due to mis-counting of the locusts flushed will be negligible.The locusts are always distributed in an over-dispersed manner, consequently normal techniques for ascertaining the standard error of estimate cannot be used. Three assessments were made by the methods recommended, using a grid of two-mile squares; in one case, where the distribution was very gregarious, the most densely populated sector was more intensively sampled. The standard error of assessments laid out in this way was estimated. The method of analysis overestimates the standard error to some degree. Alternatively, the standard error resulting from the nature of the locust distribution can be computed for assessments where the 0·1-mile counts can be shown to be distributed log-normally.Provided the population assessment is carried out under the conditions stipulated above, the additional errors will be minor. The effect of such errors will be likely to be so small that the estimated standard error, derived from the lognormal or assessment-grid analysis, may be regarded as a valid estimate of the standard error of the population estimate.An attempt was made to estimate populations of the red locust in part of an outbreak area from locusts flushed by a ‘ Prospector ’ aircraft. The trials suggested that, given a clear rear view, red locusts which were flushed could be identified as such. Further, the number of locusts flushed could be counted at low densities, and it is thought likely that a reasonably objective technique could be developed for estimation at higher densities.Flushing appeared to be most effective at an aircraft height of 20 ft. or less and when the direction of flight was with the wind. However, the majority of locusts present failed to take off and the proportion which did rise varied very greatly. The spraying of concentrated ammonia under pressure increased the efficiency of flushing.A large-scale comparison of air and ground assessments suggested that, under the prevailing conditions, a considerable proportion of the locusts could be flushed only from the dense concentrations. At all densities the proportion of locusts which the aircraft caused to rise was a small fraction of those present. With flushing of such a low level of efficiency, little idea could be obtained of the size of the locust population at a moderate or low density.

The Habits and control of the Red Locust in outbreak Areas and elsewhere

1947 ◽  
Vol 37 (3) ◽  
pp. 331-379 ◽  
Author(s):  
A. P. G. Michelmore
Keyword(s):  
Special Reference ◽  
Large Scale ◽  
Social Conditions ◽  
Control Methods ◽  
Relative Efficacy ◽  
Red Locust ◽  
Ecological Economic ◽  
Outbreak Area ◽  
Outbreak Areas ◽  
And Control

The best way of preventing locust outbreaks is to control them at their source. After a description of those habits of the Red Locust that have a direct bearing on control, an account is given of some of the results of three years' experience of control of this species in an outbreak area. The methods used in Rukwa are described in detail, and attention is drawn to their relative efficacy, advantages and difficulties. A number of other methods are also referred to and their values discussed. Control methods are considered with special reference to conditions in Rukwa and other outbreak areas, and in relation to large scale campaigns against large outbreaks. Conclusions on the relative values of the various methods are summarised below. These values depend both on the habits of the locusts and on the ecological, economic and social conditions of a country in which a campaign is to be waged. It must not be assumed that conclusions about control methods reached with one locust or in one country necessarily apply to another locust or another country.

Operational Aspects of Locust Control

1966 ◽  
Vol 70 (672) ◽  
pp. 1077-1081
Author(s):  
D. Yeo
Keyword(s):  
Schistocerca Gregaria ◽  
Locusta Migratoria ◽  
Broad Band ◽  
Central Africa ◽  
Nomadacris Septemfasciata ◽  
Red Locust ◽  
Migratory Locust ◽  
Locusta Migratoria Migratorioides ◽  
The World ◽  
Locust Control

The crops of every continent of the world have been devastated from time to time by locusts or grasshoppers. To mention three major locust species, the Desert Locust (Schistocerca gregaria Forsk.) has caused havoc in a broad band of the world stretching from East Pakistan to Senegal and from the Mediterranean to Central Africa, the Red Locust (Nomadacris septemfasciata Serv.) has infested East, Central and Southern Africa, and the African Migratory Locust (Locusta migratoria migratorioides Rch. and Frm.) has plagued most of Africa south of the Sahara.What happens in one part of a plague area can significantly affect the situation in others and locust control is therefore an international problem, requiring international co-operation. Many of the threatened areas are countries where standards of living are not high and local agriculture is a mainstay of the economy; the regions are often inhospitable and lack modern roads, aerodromes and lines of communication.

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