Spodoptera Exempta Research Articles

Response of Spodoptera exempta (Walk.) larvae to simulated field spray applications of acylurea insect growth regulators with observations on cuticular uptake of acylureas

AbstractThe acylurea insect growth regulators flufenoxuron (‘Cascade®’) and teflubenzuron (‘Nomolt®’) were applied to maize plants and/or larvae of the armyworm, Spodoptera exempta (Walk.) at volumes equivalent to medium volume (MV; 250 litre ha−1) and ultra‐low volume (ULV; < 1.0 litre ha−1, VMD = 50 μm) sprays at rates ( ≪ 10 g a.i. ha−1) at or below currently recommended field rates. The Egyptian cotton leafworm, S. littoralis was examined for comparative purposes on Chinese cabbage. One‐day‐old third‐instar larvae (L3) of S. exempta sprayed (MV) with either compound (1 and 10 g ha−1), and confined on similarly treated maize leaves for 48 h, showed a high level of response after 48 h (87–100% effective mortality), with 100% mortality after 120 h. Exposure of sprayed L3 to treated plants for 6 h was only slightly less effective. When only larvae were sprayed, the higher rate for both compounds gave 97% mortality after 120 h. The response rate of one‐day‐old L3 S. littoralis was generally slower but was similar to that of S. exempta after 120 h. When plants and larvae were sprayed at relatively low densities (22–45 drops cm−2) with undiluted ULV formulations, L3 S. exempta showed a greater response to flufenoxuron (50 g litre−1) than to teflubenzuron (25 g litre−1) at 48 h but all larvae were effectively dead (93–100% actual mortality) after 120 h. Similar results were obtained with L5 S. exempta. When only larvae were sprayed (23–25 drops cm−2), equivalent concentrations (25 g a.i. litre−1) of diluted flufenoxuron and cypermethrin ULV formulations gave 87 and 90% mortality respectively with L3 S. exempta after 120 h, although the latter compound acted more rapidly. The diluted flufenoxuron was more toxic than its undiluted formulation at similar spray densities. L3 and L5 S. exempta and L3 S. littoralis showed a similar level of response to undiluted flufenoxuron and teflubenzuron. Little or no difference in toxicity was found for topically applied flufenoxuron and teflubenzuron against L3 S. exempta and S. littoralis. Accumulation of [14C]flufenoxuron appeared to increase progressively over 6 h in both species, while that of [14C]teflubenzuron reached a peak after 1 h. After 6 h, there were relatively greater amounts ( > 2‐fold) of radioactivity in flufenoxuron‐treated than in teflubenzuron‐treated larvae. Such differences may account for the greater speed of action observed with the former compound in some experiments. The potential of flufenoxuron and teflubenzuron for the control of S. exempta is discussed with particular regard to the significant contact activity and reasonably rapid response time (effective mortality at 48 h) shown by these compounds at field rates.

Speed of action and toxicity of acylurea insect growth regulators against Spodoptera exempta (Walk.) and Spodoptera littoralis (Boisd.) larvae: Effect of inter‐moult age

AbstractUltra‐low volume (ULV) spray bioassays at droplet densities (20–80 drops cm−2) corresponding to field deposits were used to determine the efficacy of two acylurea insect growth regulators, teflubenzuron (‘Nomolt®’) and flufenoxuron (‘Cascade®’) against three different age groups of third‐instar Spodoptera exempta and Spodoptera littoralis larvae. While no response (mortality and/or abnormal moulting with impaired ability to feed) was observed with one‐day‐old larvae until 48 h after treatment, two‐day‐old larvae showed some response (27–93% abnormal moulting and 3–10% mortality when larvae were sprayed; 80–100% abnormal moulting and up to 83% mortality when larvae and plants were sprayed) after 24 h and up to 100% mortality at 120 h. Studies with non‐feeding, pre‐moult larvae showed that cuticular uptake of acylureas was sufficient to affect an appreciable proportion of larvae after 24 h, with up to 100% mortality at 120 h. More detailed studies with pre‐moult S. littoralis larvae showed that, while a few larvae which moulted between 1 and 5 h after treatment showed abnormal moulting to the L4 stage, a much larger proportion of larvae which moulted 6–20 h after treatment were affected. Previous studies with S. exempta have shown that different larval instars show similar levels of sensitivity to acylureas. The present work suggests that, while the age distribution within instars has little influence on the end‐point mortality of acylureas, it can profoundly modify the speed of response, the majority of larvae within an instar being effectively controlled at the moult following treatment. The significance of these observations in relation to the crop protection activity of acylureas against field populations of Spodoptera larvae is discussed.

Comparative studies on acylurea insect growth regulators and neuroactive insecticides for the control of the armyworm Spodoptera exempta walk

AbstractLeaf‐dip bioassays with commercial pesticide formulations were used throughout this study. Third‐instar larvae of Spodoptera littoralis were bioassayed for comparative purposes. The end‐point mortality against the third‐instar larvae (L3) of two Spodoptera exempta populations (Bangor and Gent) and a S. littoralis population (NRI) was found to occur at 72 h and 120 h for neuroactive compounds (carbamate, organophosphate and pyrethroid insecticides) and acylureas respectively. Overall, the acylureas were found to be more toxic (up to 240‐fold at the LC50 level) than the most active of the neuroactive compounds tested, the pyrethroids. This difference was greatest against S. littoralis, which was markedly less sensitive to the latter compounds. The Gent population of S. exempta was also found to be significantly less sensitive (7‐folt at LC50) to the pyrethroid, lambda‐cyhalothrin, than the Bangor strain. Two of the most toxic neuroactive and non‐neuroactive compounds, the pyrethroid, cypermethrin and the acylurea, teflubenzuron were chosen for further studies with S. exempta (Gent) and S. littoralis. Relatively little difference in the toxicity of teflubenzuron was observed against different larval instars (L2, L3 and L4) of S. exempta when compared with cypermethrin. Choice‐chamber‐experiments on feeding behaviour showed that when L3 larvae of either species were exposed to both treated and untreated leaves. teflubenzuron had no significant effect on larval distribution, the percentage of each leaf disc consumed or larval weight gain when compared with untreated controls. In contrast, a marked dose‐dependent repellent response to cypermethrin‐treated leaves was shown by S. littralis after 6 h. together with corresponding reductions in the percentage of the treated leaf consumed and in larval weight gain. Similarly, when L3 S. exempta were exposed only to pesticidetreated leaves, cypermethrin significantly reduced premoult larval weight gain, whereas tefiubenzuron had no premoult effect. However, following exposure of L3 S. exempta and S. littoralis to teflubenzuron for 48 h prior to moulting, L4 which survived the moult showed reduced weight gain compared with controls, the reduction being more pronounced on maize than on artificial diet. This antifeedant effect increased in proportion to the concentration of teflubenzuron originally administered. The effect of exposure time to teflubenzuron was examined by placing L3 S. exempta and S. littoralis on leaves treated with the approximate LC50 or LC95 dose for 6–48 h. The exposure time required to produce appreciable mortality (relative to LC values) within the treated population was found to be 24 h.

Sampling lepidopterous pests on maize in West Africa

AbstractThe spatial distribution of five lepidopterous pests, Sesamia calamistis Hampson (Noctuidae), Eldana saccharina Walker (Pyralidae), Spodoptera exempta (Walker) (Noctuidae), Mussidia nigrivenella (Ragonot) (Pyralidae), and Cryptophlebia leucotreta (Meyrick) (Tortricidae), on maize in West Africa is described using Taylor's power law and the relationship of proportion of infested plants to the mean density. All five species showed a highly aggregated distribution, with Taylor's indices of aggregation ranging between 1.23 for C. leucotreta and 1.52 for Sesamia calamistis. Enumerative and binomial sampling plans that incorporate Taylor's power law are proposed to estimate mean densities of S. calamistis, C. leucotreta and the species complex consisting of E. saccharina, M. nigrivenella and Spodoptera exempta which showed similar spatial distributions, with a predefined reliability level.

Forecasting of outbreaks ofSpodoptera exempta Wik. (Lep., Noctuidae) based on sex-pheromone trapping in the republic of Yemen

Spodoptera exempta (Wlk.) is recorded every year in the Republic of Yemen. Based on the use of pheromone traps, a very simple but effectively applicable monitoring and forecasting system was developed. Areas from which infestations have been reported and the frequency of attacks are mapped in detail. The monthly distributions and frequencies of incidence are presented in two tables. The range of recordedS. exempta moths is illustrated and the number of outbreaks for the last 32 years described.

Monitoring secondary outbreaks of the African armyworm in Kenya using pheromone traps for timing of Bacillus thuringiensis application

The arrival of male moths of the African armyworm, Spodoptera exempta Walker, was monitored in Kenya using pheromone traps. Peak trap counts were obtained during March 1989, and were concentrated in three out of nine traps distributed in small farms in an area of 625 km 2 in Lambwe valley, South Nyanza. Large numbers of egg masses were located on dry stalks of last year's cereals in wild cynodon grass situated around the crop fields. Smaller numbers were found on the underside of the first emerged leaves of maize seedlings. Few egg masses were found on millet crops. Application of a Bacillus thuringiensis preparation at a concentration of only 0.2% (w/v, which is 1 10 of the ordinary concentration used) based on a new isolate obtained from a Kenyan soil sample, directed against neonate S. exempta larvae, reduced larval population by 95%.

Control of the African army wormSpodoptera exemptawalker (lepidoptera: noctuidae) in kenyan fields with highly effective strains ofBacillus thuringiensisberliner

Good control of second and third instar larvae of Spodoptera exempta was obtained in cereal fields using spray application of powder preparations of different Bacillus thuringiensis (Bt) strains: Bt24 (var. entomocidus), IH‐A (var. aizawai) and K26–21 (new isolate). These Bt preparations also protected cereal crops from damage caused by fourth to sixth instar larvae, but lower rates of larval mortality were obtained (50%‐80%). Spray applications of Bt preparations combined with a ‘sweeping out’ operation using a Californian sweep net in grass fields surrounding susceptible crops, were shown to be effective in preventing massive migration of large larvae to the crops, especially in small farms.

Migration and meteorology: flight behaviour and the atmospheric environment of locusts and other migrant pests

Part 1 The desert locust - prototype migrant: locust control and migration - the background locust migration - facts and mechanisms biology and behaviour of the desert locust in relation to migration displacements of discrete locust populations locust migration, winds and weather on the intercontinental scale - the desert locust and synoptic meteorology locust numbers - the evidence and the problem of control the assessment of locust numbers and of control operations locusts at a low ebb - continuity of recession populations swarming and solitary phases outline of a recession - treatment of data - findings experience of recession forecasting current status of the Phase Theory. Part 2 Flight and migration in other major pests armyworms - larvae of formidably migrant moths sample of the armyworm problem - Sierra Leone 1979 trans-equatorial sequences of armyworm attack analogies with locusts establishing the timing and spacing of infestations in relation to the distribution of the moths forecasting in East Africa infestations - incursions of westerly winds and other early evidence moth flight - from circumstantial evidence to radar observations and marking/capture possible antecedents of armyworm attacks in West Africa - squall-line studies for WHO/ONCHO and other clues armyworm control - current approaches and some future possibilities spruce budworm - major forest problem of North America the background - problems of the economy and the environment budworm moth flight - observations by radar and aircraft. Part 3 Management of migrant pests - prospects and options, some suggestions: problems of the desert locust and other locusts of Africa African armyworm - prospects and options spruce budworm - prospects and options major migrant pests in China - possible new options for monitoring and control migrant pests and nuclear winter. Part 4 Ecology and evolution of insect flight and migration - some implications from findings on migrant pests survival value of systems of downwind redistribution migration - a single strategy implemented by a range of alternative tactics evolution of insect flight migration without navigation navigation in static populations - the honey-bee. Appendices Further notes on applications of meteorology in investigations of airbourne migration: 1 - some points of meteorological observation and analysis, surface and upper air 2 - problems of observation and interpretation of field/phenomena - some analogies from meteorological procedures 3 - hour-to-hour movements of individual swarms in relation to wind.

Effects of azadirachtin and aqueous neem seed extracts on survival, growth and development of the African armyworm, Spodoptera exempta

Treatment of larvae of the African armyworm ( Spodoptera exempta) with azadirachtin and aqueous neem seed extracts produced a range of adverse effects that were dose dependent. High doses of up to 10 μg per larva of azadirachtin resulted in 100% larval mortality, but this effect was delayed and prolonged. At lower doses of azadirachtin, however, inhibition and disruption of moulting was observed and larval-pupal intermediates or abnormal pupae were commonly found. Similar results were obtained with the aqueous extracts of neem seeds. The few pupae obtained from larvae treated with lower doses of the extracts (0.01 and 0.1 μg per larva) either failed to develop further or developed into adults that died during eclosion, or had frizzled, curled wings.

Progress and developments in forecasting outbreaks of the African armyworm, a migrant moth

This paper describes the development of the forecasting service since 1977 by highlighting the results of various attempts that have been directed at elucidating the origins of primary populations of Spodoptera exempta over eastern Africa. The dates between the last outbreak of each season and the first outbreak of the next season (offseason period) provided a mean number of days for estimating dates of potential onset of primary outbreaks. The development of computer-based data processing routines (database management) and of an expert system for forecasting the occurrence of outbreaks in East Africa are described, as examples of decision-support tools in pest management.

Trade‐off between flight and reproduction in the African armyworm moth, Spodoptera exempta

ABSTRACT. The existence of a trade‐off between flight and reproduction in the migratory noctuid, Spodoptera exempta (Wlk.), was examined in experiments in which female moths were flown on flight balances and then provided with distilled water or sucrose solution. For individuals flight‐tested from the night of eclosion (night 0) through night 1 and fed only distilled water, there was a linear, negative relationship between weight‐related fecundity and flight duration. When flight was recorded through night 2, a curvilinear relationship was obtained suggesting that highly active moths suffer a smaller decrease in fecundity than predicted from its rate of decline with increasing flight duration in less persistent fliers. The hypothesis that this reflects an energetically expensive, initial phase of each flight, followed by a less costly, cruising phase is examined. Fecundity was independent of flight duration in females provided with sucrose after flight but was related to moth weight, as it was in all unflown moths. Effects of flight and feeding on longevity and mating frequency are also reported.There is a clear trade‐off between flight and fecundity in S.exempta which is only evident in moths denied access to a source of carbohydrate after flight. The results indicate the importance of nectar sources in the field in allowing restoration of lipid reserves depleted during migratory flight. An important implication of this conclusion is that lipid is the resource limiting to fecundity in this species and not protein as is generally supposed for leaf‐feeding insects. This might be expected in highly active species as lipid is the resource for which the energetically expensive functions of flight and reproduction must compete.

Onset and spread of an African army worm upsurge

Abstract. 1. Onset and spread of the severe outbreaks of African armyworm, Spodoptera exempta (Walk.), over Ethiopa, Kenya, Tanzania and Burundi in late 1984 have been analysed in relation to trap and weather records.2. Although first outbreaks in each country appeared progressively further south, winds on the best estimated dates of moth concentration and egg laying blew from directions precluding moth movements between them.3. Such independently developing outbreaks are called ‘primary’ to distinguish them from any ‘secondary’ outbreaks that may develop from them.4. Parent moths giving rise to all seven areas of primary outbreaks were derived from low‐density populations that had persisted through the dry season, probably near the coast of East Africa.5. Primary outbreaks developed on the south‐eastern sides of individual rainstorms over the highlands, most likely because windborne moths were concentrated there by convergent winds.6. Of the secondary outbreaks within Kenya, Tanzania and Burundi, most were derived from only one area of primary outbreaks in Kenya, which were therefore critical for effective control of spread; the paucity of other secondaries was presumably due to a lack of timely rainstorms or other concentrating mechanisms.

Identification and field testing of additional components of female sex pheromone of African armyworm,Spodoptera exempta (Lepidoptera: Noctuidae)

Ovipositor washings from virgin femaleSpodoptera exempta (Walker) (Lepidoptera: Noctuidae) were analyzed by high-resolution gas chromatography (GC) linked to a male electroantennogram (EAG). GC retention times of the two major EAG responses observed were consistent with their assignment as (Z)-9-tetradecenyl acetate and (Z,E)-9,12-tetradecadienyl acetate, as previously identified. However, three other EAG responses were also noted that had GC retention times consistent with (Z)-9-tetradecenal, (Z)-9-tetradecen-1-o 1, and (Z)-11-hexadecenyl acetate. The components were present in the ratio of 100∶5∶1.5∶3.5∶4, respectively. Further analysis of the ovipositor washings by GC linked to a mass spectrometer (GC-MS) confirmed these findings and indicated the presence of a sixth component consistent with (Z)-11-tetradecenyl acetate present at 2 % of the major component. In field tests carried out in Kenya, (Z)-11-hexadecenyl acetate was the only newly identified component to enhance the catch of the original two-component mixture when presented in their natural ratio. The addition of (Z)-9-tetradecen-1-ol reduced catch, while (Z)-9-tetradecenal and (Z)-11-tetradecenyl acetate had no apparent effect.

Varying durations of arrested oocyte development in relation to migration in the African armyworm moth, Spodoptera exempta (Walker) (Lepidoptera: Noctuidae)

AbstractThe rate of oocyte development in Spodoptera exempta (Walker) was investigated in the laboratory and in the field in Kenya. Stages and rates of development were examined in relation to moth size and timing of mating and oviposition. The stage of oocyte development was established by measuring the widths of the second or third oocyte at the distal end of one ovariole. Data from moths of known age showed that oocytes were partially developed at eclosion and that a linear progression in development occurred up to 30 h after emergence, by which time the oocytes had reached approximately half their mature size. Oocyte development continued unbroken in some moths up to the time of oviposition on the second night after emergence, whilst the remainder arrested oocyte development for a varying number of days. Mating occurred after midnight, but only once the oocytes had reached a certain size, irrespective of whether development was continuous or arrested. In the latter case, this stage was reached immediately after development resumed. Oviposition usually occurred the night after mating, mainly around midnight and with a second peak towards dawn. The dawn peak derived from mature moths which mated and oviposited on the same night. It is suggested that moths arrest oocyte development to minimize wing loading during migration and that, since moths stay in arrested development for varying lengths of time (thought to be genetically regulated), dispersal is greatly enhanced.

Interactions between Grazers and a Cyanogenic Grass, Cynodon plectostachyus

Grasses exhibit many traits that have been attributed to selective pressures by grazers. These include vegetative growth from an intercalary meristem, prostrate growth form, perennial lifestyle, high nutritional content, and inducible secondary compounds. However, alternative selection pressures, that do not include grazers, have been proposed for these traits. Extreme manifestations of all these traits were found in a grass from African savannas (C. plectostachyus (K. Schum.) Pilger.), which is remarkably well adapted to extreme herbivory: 1) Heavy grazing and trampling by large mammals increases the relative abundance, and by inference the fitness, of C. plectostachyus. 2) The grass exhibits marked morphological plasticity, depending on the intensity of previous grazing and trampling, but productivity is unaffected. 3) C. plectostachyus is exceptionally nutritious compared with other co-occurring grass species. 3) Both vertebrate and invertebrate (Spodoptera exempta, Lepidoptera, Noctuidae) grazers feed preferentially on species in the genus Cynodon. 4) Defoliation is more potent than are abiotic factors that induce cyanogenesis in C. plectostachyus, suggesting that the trait evolved as a herbivore deterrent. Circumstantial evidence suggests that, after defoliation by army worm larvae (S. exempta), levels of cyanide in the leaves of C. plectostachyus were high enough to kill cattle, but S. exempta larvae are not affected by cyanide. Therefore, interactions between grass and grazer can be beneficial or antagonistic, depending on the degree of defoliation. The combination of extreme tolerance of intense herbivory, and the complexity of interactions with grazers suggests (but does not prove) that large herbivores have strongly influenced the evolution of C. plectostachyus. However, the relationship between this grass and grazeres is not obligatory, at least in ecological time, and cannot be termed mutualistic in the strict sense that each is exclusively dependent on the other.

Insect antifeedants: a behavioural and electrophysiological investigation of natural and synthetically derived clerodane diterpenoids

AbstractNatural and synthetic clerodane diterpenoids were assayed behaviourally and electrophysiologically as antifeedants against larvae of Spodoptera exempta (Walker), S. littoralis (Boisduval), S. frugiperda (J. E. Smith), Heliothis armigera (Hübner) and H. virescens (F.). The constitution of the decalin ring and the furofuran side chain were found to have an important antifeedant effect. A correlation of behavioural and electrophysiological responses of the species of Spodoptera revealed aspects of their neural codes and provided some insight into the receptor mechanisms that may operate in individual neurones. The oligophagous S. exempta was more susceptible than the polyphagous species.

The development of enzymes involved in flight muscle metabolism in Spodoptera exempta and mythimna separata

1. 1. The activities of PFK, HK, GDH, CAT, HOAD, GIDH and CS were measured in the bodywall muscles of final instar larvae and in the thoraces of female Spodoptera exempta and Mythimna separata in the pupal stage and throughout adult life. Activities were compared in moths starved or fed sucrose solution from emergence. 2. 2. The activity profiles of the enzymes are considered in relation to the moths' capacity for prolonged flight and reproductive status. 3. 3. In S. exempta there is a rapid rise in the activity of PFK, HK and GDH associated with adult eclosion, suggesting that glycolysis is important at this time. The activities of these enzyemes in starved moths and those fed sucrose suggests that glycolysis may continue to have a role in flight muscle metabolism throughout adult life. 4. 4. The results are consistent with previous reports that lipid is the major source of energy fuelling prolonged flight in both species although the increase in the activity of CAT early in the adult life of sucrose-fed S. exempta appears to reflect lipid synthesis rather than flight potential. Changes in HOAD activity appear more closely associated with flight potential. 5. 5. Only CAT and HOAD showed any indication of a fall in activity associated with the onset of reproduction and probable cessation of prolonged flight. This result further supports the evidence for the utilization by both species of carbohydrate to fuel short flights which occur throughout life and of lipid to fuel prolonged, migratory flights in the pre-reproductive period.

Migration and low population density in armyworm (Lepidoptera: Noctuidae) life histories

Field and laboratory evidence now suggests that the African armyworm, Spodoptera exempta, is specifically adapted for survival at low population densities, providing a new basis for understanding the significance of its phase polyphenism and migratory strategy. This conclusion allows deductions to be made as to the expected extent of displacement of flying moths from low and, when they occur as a result of impeded or inadequate dispersal of parent moths, high density populations. The proposed migratory strategy which depends on the genetic determination of flight potential also provides a framework for interpreting observed patterns of armyworm outbreaks through the season and in relation to rainfall. Traits associated with a low-density, “armyworm” strategy are shared by other Noctuids which may have similar life histories.

Use of pheromones in crop and stored products pest management: control and monitoring

Pheromones have been successfully used on a large scale for control of pink bollworm, Pectinophora gossypiella, by mating disruption in Egypt and Pakistan using various slow release formulations. Similar formulations are being developed for control of other cotton bollworms, Earias insulana and E. vittella. Small-scale trials are in progress to evaluate pheromone formulations for control of sugar-cane borers, Chilo sacchariphagus and C. auricilius in Mauritius and India, and the tropical warehouse moth, Ephestia cautella, as a pest of stored cocoa in Brazil. Traps baited with the pheromone of the African armyworm, Spodoptera exempta, have been extensively used in Eastern and Southern Africa as the basis of a forecasting system of pest incidence.

The use of biogeographical techniques in the study of migrant noctuid moths

The use of biogeographical techniques for monitoring, mapping and predicting seasonal changes in the distribution of migrant noctuid moths in a country or region, can lead to timely and effective control of infestations of the larvae of international pest species like the African armyworm, Spodoptera exempta (Wlk.); the American bollworm, Heliothis armigera (Hub.); the Black cutworm, Agrotis ipsilon (Hufn ); the cotton leafworm, Spodoptera littoralis (Boisd.) etc., and hence to the protection of crops and pasturelands. Methods of data collection include the establishment of national and regional networks of monitoring devices such as light and pheromone traps, and the introduction of regular or periodic standard procedures for recording, reporting and assessing infestations of larvae. Techniques for collecting and analysing the data include the use of: (a) dots, circles or similar marks on topographic or weather maps to plot the occurrence of moths and/or larvae at the latitudes and longitudes of outbreak sites, followed by the dates when infestations were confirmed; (b) numerical symbols (e.g. 1–12 for January to December) on the above maps in order to summarize periodic (e.g. monthly) shifts in the distribution of populations within or across neighbouring countries; (c) colour codes or other graphic symbols to plot maps of pest distribution and migration over the required time-scale, followed by the study of appropriate synoptic weather charts, particularly streamline wind charts showing surface and low-level wind convergence zones over the distribution areas. Successful application of these techniques have included studies of changes in the distribution and migration of: (a) A. ipsilon worldwide; (b) Desert locust in Africa and Asia; (c) S. exempta in Africa and S.W. Arabia etc. In the 1981/82 outbreak season, for example, dots (•) were used to map out and date south-to-north displacement of populations of S. exempta across eastern Africa from Tanzania to Ethiopia between November 1981 and June 1982; while in 1980/81, numbers (1–12 for January-December) were plotted to summarize outbreaks developing between Ethiopia and Tanzania. Successful monitoring and assessment of mass movement of moths between Tanzania, Kenya and Uganda early in the 1981/82 season, for example, enabled the Armyworm Forecast Service to issue accurate forecasts for the first cross-border migrations of moths between the three countries from the second week of February 1982, leading to effective control of larvae to save cereal crops, sugar-cane and pasture grasses in East Africa.