The sorghum shootfly, Atherigona seccata Rondani, is the main species of Atherigona attacking cultivated and wild species of Sorghum in Africa and Asia. The past 55 years' research on the pest has produced means for its management. The bionomics of A. soccata are well known and are being applied for its cultural control by adjusting planting dates. Natural enemies of the shootfly are few and their biology little known. The systemic insecticide carbofuran as a seed and seed furrow treatment provides effective fly control where the cost-benefit is favorable. Sources of host plant resistance to shootfly have been recognized for about 35 years. Incorporation of this resistance in high yielding varieties through plant breeding should be more rapid now that the mechanisms of resistance and their inheritance, through additive gene action, are better understood. These resistance factors include non-preference for oviposition, antibiosis and recovery through tillering.

The morphology and function of the trifoliate organ of five species are studied. Two examples are given where the ultrastructure of this organ assists the interpretation of speciation. The movement of the trifoliate organ during the courtship of Atherigona laevigata and its position during copulation is briefly described. A simple (A. seccata) and a complex (A. conigera) organ are described in detail, with emphasis on structure and function of the sensilla, and surface microsculpture. The A. hancocki-group organs are described and possible functions are suggested for these unusual structures. A distinct population is separated from the A. lineata species complex. A group of three species A. steeleae, A. secrecauda and A. matilei are confirmed to have a close, natural relationship.

Trichoid, basiconic and campaniform sensilla have been observed on the ovipositor and tarsi of the sorghum shootfly, Atherigona seccata Rondani. The ovipositor of A. seccata comprises abdominal segments 6–9, with most of the trichoid sensilla located on the ninth segment. Two olfactory pegs each are located on the paired leaflets of the ninth segment. Sensilla on the tarsi include long and short basiconic sensilla and campaniform sensilla located near the anterior margin of the last tarsal segment.

The sensory organs on the head capsule of the larva were studied by light, scanning and transmission electron microscopes. Four types of sensory receptors were observed on the cephalic lobes. They consist of four knob-shaped sensilla, two styloconic sensilla, two campaniform sensilla, and eight basiconic sensilla.

This paper describes the results of extensive rearing of shootfly species of the genera Atherigona and Acritochaeta from cultivated and wild Gramineae in Andhra Pradesh, India. Nineteen fly species were recorded from 41 graminaceous species including cultivated sorghum. Atherigona soccata, an important pest of sorghums in the Old World tropics, was reared from 22 host plants. Only cultivated and wild species of sorghum were important as hosts of this pest species. It was observed that alternative host Gramineae were of minor importance in the ‘carryover’ of Atherigona soccata through the off season, but the irrigated sorghum grown for fodder could be an important source of flies.

In general, shootflies of a particular species usually favored one graminaceous host above others. The numerically dominant fly reared from wild Gramineae was Atherigona falcata, which was recorded on 17 hosts, including sorghum. Other common species in Gramineae were Atherigona pulla, Atherigona oryzae, Atherigona punctata and Atherigona atripalpis, all of which were also reared in very low numbers from sorghum. Five new species of Atherigona were reared; three of these will be described shortly.

As an important measure for increasing grain production, hybrid sorghum has been cultivated in the whole area of the Peoples Republic of China since 1970. Over the past 10 years the sorghum shootfly has gradually become the worst pest of sorghum in several places in the southern parts of China. In 1973, some regions of Gung Dong, Gui Chou and Gung Xi Provinces were affected by the shootfly with a rate of 30% for the heavier damage, and a few even exceeding 90%.

A total of 1584 young sorghum plants showing typical ‘dead-heart’ symptoms were collected from the field at weekly intervals in 1978 and 1979. From these emerged adult flies belonging to eight families and 17 genera. Members of six of the families are scavengers, while those of the remaining two, Muscidae and Chloropidae, are phytophagous, causing primary or secondary damage to the plants. Three hundred and seventy-five Atherigona soccata adults emerged, representing only 23.7% of the damaged plants. This contrasts with previous records that rate Atherigona soccata as the most important source of ‘dead-heart’ damage in young sorghum plants. Other shootflies perhaps of similar importance, also reared from the plants included Oscinella spp. (986), Scoliophthalmus spp. (344) and Anatrichus erinaceus (160). There were a few other less abundant species.

The numbers of probable parasites and predators of the shootflies that emerged were insignificant, when compared with the extent of damage and the numbers of the shootflies. Damage caused by the shootflies to the early plantings was low and insignificant, reached a peak in mid-season and remained high until the cessation of rain at the end of the season.

The sorghum shootfly was first recorded as a pest in the central rainlands, causing losses of up to 25% in local varieties and 25–62.5% in introduced varieties. The pest has also been recorded in the Northern, Khartoum and Equatorial provinces.

In the Sudan, more than one species of Atherigona attack cereals, Atherigona soccata being the most dominant species. Sorghum plants attacked by the shootfly flower and ripen at different times.

A study of the biology of the shootfly showed that the incubation period of the egg was 2–3 days, the pupation period was 6–8 days and the duration from egg to adult was 17 days. The closer the eggs were laid to the leaf blade, the better the chances of the shootfly causing ‘dead-heart’ symptoms. The mortality of the first-instar larva was highest in the first 24 hr. The incidence of the shootfly coincided with rainfall and lower temperatures.

In a selection programme, Combine Kafir 60 had the lowest infestation level, compared to Sudan Grass, Abu Sabein and Feterita Gadarif varieties.

In Upper Volta the sorghum shootfly is considered dangerous in the case of late and staggered sowing or resowing due generally to irregular rainfall in the beginning of the rainy season. When using fish meal as bait in two different traps, one placed in a humic area and another in a dry area, we followed over a period of 2 years the dynamics of the sorghum shootfly populations at Farako-Bâ. Twenty-two different species of the genus Atherigona (Rondani) were identifed, of which the commonest was A. soccata (Rondani).

Some wild hosts of the sorghum shootfly were also identified. Attention is drawn to the importance of the pest in the case of extensive cultivation of irrigated sorghum in the managed valleys of the country.

Field and laboratory observations revealed that the placement of eggs of the sorghum shootfly, Atherigona soccata, among sorghum stems tended to be random or slightly aggregated rather than regular, which suggests that the site of oviposition by a female is little or not determined by the presence of other eggs already laid. The possible effects of this type of distribution on the mortality of the first-instar larvae are briefly discussed.

Surveys were conducted in two different ecological zones (semi-arid and arid) of Kenya to monitor egg, larval and pupal populations of the sorghum shootfly, Atherigona seccata, on a wild host, Sorghum arundinaceum. Populations were found to be usually higher on wild sorghum than on local varieties of Sorghum bicolor, the cultivated host. During dry periods, shootfly eggs and larvae were still found on wild sorghum, especially in moist areas such as beds of temporary streams or river banks. Population levels seem to be related primarily with the availability of susceptible stems, which in itself is determined by rainfall, soil conditions, density of other vegetation and by the phenology and the distribution of the host plant, Sorghum arundinaceum, being a pioneer species which colonizes recently disturbed areas and is subsequently replaced by other grass species. Since no evidence of the existence of an aestivation diapause has been found, it is reasonable to assume that Sorghum arundinaceum is a major reservoir for A. seccata, especially during the dry season.

The assumption was made that for a complete understanding of the feeding behaviour and nutrition of Atherigona soccata larvae on various cultivars of sorghum, it was necessary to investigate the relationship between plant chemicals occurring in resistant sorghum plants and the digestive enzymes of larvae. However, at least an introduction to the anatomical organization of the alimentary canal of larvae is needed to understand the digestion and absorption of food taken from resistant and susceptible sorghum lines.

The present preliminary investigation was undertaken to determine qualitatively some of the enzymes present in the gut and salivary glands of the third instar by locating enzymes histochemically on polyacrylamide gels.

Movement, feeding behaviour and growth of larvae of the sorghum shootfly, Atheriyona saccata, were studied under controlled conditions on a susceptible sorghum variety, CSH-1. The time of hatching coincided with the presence of moisture on the leaf, a condition favourable to movement of the larvae to the base of the leaf. Cutting of the central shoot at its base by the larva caused the symptom referred to as ‘dead heart’. The three larval instars are described and changes in the cephalopharyngeal skeleton discussed.

Movement of the larva to the base is not due to positive geotaxis. Larvae in plants placed horizontally to the ground did not develop normally and a high mortality resulted. The larvae are strongly cannibalistic inside the host-plant but not outside of it. The first-instar larvae do not migrate from one plant to another, but the third instars may do so if the source of food is exhausted.

The use of fish meal and detergent water has been shown to be simple, economic and reliable for sampling of shootfly populations. Various mixtures of fish meal with other ingredients were evaluated. The most potent mixture was fish meal-yeast-ammonium sulphide, but generally fish meal alone was adequate and the most readily available attractant. The attractance of fish meal was found to be related to its degradation; it increased from the first to the third or fourth day, and then decreased. The chemicals responsible for the attractance of fish meal have yet to be identified, but in all probability they may be the amines resulting from biodegradation of the meal.

This paper includes a description of the internal reproductive system of the female sorghum shootfly, Atherigona saccata, as well as studies on egg maturation and survival, and effects of mating and/or presence of the male on egg maturation, fecundity and fertility. The number of ovarioles per female ranged from 20 to 47. A. seccata exhibits autogeny, but carbohydrate is essential for egg production and survival. Nutritional deficiency led to a high incidence of oocyte resorption. A mixture of baker's yeast and sugar was a better adult food than brewer's yeast and glucose. Sorghum (cereal) aphid honeydew was a nutritious adult food. Shootflies provided with sorghum aphid honeydew showed an acceleration of vitellogenesis, a decrease in the frequency of oocyte resorption and a shortening of the preoviposition period. Egg maturation does not seem to be influenced directly by mating or by the presence of males. The continuous presence of the male also has no significant effect on fecundity. Shootfly females seem to mate only once and this single mating ensures fertilization of eggs laid even long after mating.

Sorghum (Sorghum bicolor) is an important food crop, especially of the semi-arid areas of Asia and Africa. One of the major constraints affecting the popularity of high-yielding hybrids and varieties is their extremely high susceptibility to insect pests.

Painter (1951) has reviewed in detail the work done on resistance in sorghum to the chinch bug (Blissus leucopterus), corn leaf aphid (Aphis maidis) and sorghum midge (Contarinia sorghicola). In the last decade and a half considerable work has been done on resistance to the shootfly (Atherigona seccata), stem borer (Chilo partellus) and sorghum midge (Contarinia sorghicola). By conducting multilo-cation screenings of world germplasm under natural and artificial infestation conditions, not only have promising sources of resistance been identified but a number of them have been utilised in crossing programmes to develop high-yielding resistant cultivars. Some sources with multiple resistance have also been identified.

The mechanisms of resistance in sorghum to the major pests have been investigated. It is seen that the mechanisms are generally complex and the observed field resistance is the total reaction of several components. There are several leads available which justify further intensive work, especially on identifying naturally occurring plant products associated with antibiosis mechanism.

From field screening of two international nurseries of the sorghum shootfly (Atheriaona saccata), seven promising cultivars were selected for investigating the mechanism(s) of resistance. These cultivars were IS 1054, IS 1082, IS 2146, IS 2195, IS 2312, IS 3962 and IS 5613. CSH-1, a hybrid variety from India, was used as a susceptible control. Results from observations on larval development and mortality and the longevity and fecundity of resulting females when released on either CSH-1 or the parent cultivars are reported.

Mortality among the first-instar larvae was very high on IS 2146 followed by IS 2312 and IS 5613. IS 2146, IS 3962 and IS 2312 sustained the least growth of larvae. The larvae in these cultivars were often confined to the upper region of the central shoot.

The survival rate of flies from IS 2146 was very low, and the longevity was significantly reduced in the case of flies from IS 2146 and IS 2195. The preoviposition period was significantly longer when flies were released on IS 1082 and IS 2312. Fecundity of the flies did not differ significantly when released on CSH-1; however, it was significantly reduced when released on parent cultivars in all cases except IS 1054. It is concluded that IS 2146 possesses strong antibiosis for the sorghum shootfly followed by IS 2312 and IS 5613.

The behaviour of shootfly resistance is examined over the Fl, F2, F3 and advanced generations. The Fl is almost intermediate between two parents with an added heterotic advantage of a lower ‘dead-heart’ percentage. Resistance shows partial dominance under low to moderate shootfly infestation but this relationship may shift under heavy infestation conditions.

The resistance is polygenic in nature and governed by additive genes. In the absence of host immunity, gradual accumulation of favourable genes is possible by line breeding from R × I and I × I crosses by selecting 1 SD below the population mean. Selection for multiple characters limits the genetic advance for shootfly resistance—resulting in 0- 5% selection intensity and relatively less resistant but high yielding desirable progenies. Multilocation tests enable the selection of varieties stable for shootfly resistance.

The biology of the sorghum shootfly, Atherigona soccata Rondani, was studied at the Corn and Sorghum Research Centre, Thailand. The preoviposition period is 3–5 days long. The females deposited a mean of 238 eggs with an average incubation period of 3 days. The larval development required an average of 7.8 days, and the pupal stage was 7.1 days long. The adults were reared with ordinary sugar, yeast and water. The females lived an average of 30 days and the males 20 days.

Carbofuran granular formulation is still the leading product for the control of the shootfly at the Research Centre. The application rate in the seed furrow is 0.45–0.60 kg a.i./ha with a row spacing of 75 cm. Furadan® 30ST, an emulsifiable formation of carbofuran, can also be used as a seed dressing at a rate of 20 cm3/kg of seeds. Counter®, another soil systematic insecticide, has been found effective in controlling the sorghum shootfly.

A modification of the ICRISAT trap for the sorghum shootfly is described. The trap may be effective in reducing the fly population.

The introduction of high yielding sorghum hybrids in the mid-1960s indicated that the new cultivars were highly susceptible to insect pest attack. Use of chemicals for the control of the snootily, Atherigona soccata (Rondani), became necessary to realise a full yield potential.

This paper briefly reviews the earlier work on conventional foliar sprayings and dustings of the available insecticides which generally failed to give an effective control of the shootfly.

Work carried out in the early 1960s showed that the application of phorate, disulfoton, aldicarb and carbofuran granules in the soil at the time of sowing was very effective in controlling the pest. Recently two more insecticides, viz. isofenphos and fensulfothion have been found to be equally effective. However, the cost of applying these insecticides is rather high.

Seed treatment with carbofuran at 5 parts a.i. per 100 parts of seed proved to be highly effective and economical. It is now being widely used by farmers in the major sorghum growing area of the country. It has been found that dosage of carbofuran can be further reduced by using a 6:4 mixture of treated and untreated seed.

Trials have been conducted to determine the residues of effective insecticides in the soil and in plants at different intervals. Investigations have also been carried out to establish the correlation between the residues of different insecticides in plants and their efficacy in controlling the shootfly. A future strategy for the chemical control of the shootfly is outlined.