Stenodiplosis Sorghicola Research Articles

Understanding the Impact: Insect Pests of Millets and their Consequences on Yield Loss

Millets, crucial cereal crops in many regions, face significant threats from various insect pests, leading to substantial yield losses. Insect pests such as stem borers, leaf folders, aphids, midges, bugs, caterpillars, and termites inflict damage at different growth stages of millet plants. Stem borers like Chilo partellus and Sesamia inferens bore into stems, impairing structural integrity, while leaf folders such as Cnaphalocrocis medinalis create folded leaf shelters for feeding, causing extensive tissue damage. Aphids such as Rhopalosiphum maidis and shoot bugs like Peregrinus maidis extract sap, resulting in wilting and stunting of plants. Millet midges like Geromyia penniseti and Stenodiplosis sorghicola target reproductive structures, leading to grain abortion and reduced yield. Earhead pests like Cryptoblabes gnidiella and Helicoverpa armigera feed on developing grains, causing significant losses in quality and quantity. Additionally, termites like Odontotermes spp. and Microtermes spp. damage roots and stems, disrupting nutrient and water uptake causing plant death. Understanding the biology and ecology and implementing appropriate pest management strategies are crucial for mitigating yield losses and ensuring millet production sustainability.

Effects of insecticides and cultivars on panicle-feeding insect pest infestations and grain yield of sorghum (Sorghum bicolor (L.) Moench) in northern Ghana

BackgroundPanicle-feeding insects are a challenge in sorghum (Sorghum bicolor (L.) Moench) cultivation but most farmers do not protect the crop. Here, the effects of pest management in different sorghum cultivars on grain yields and the financial returns after protecting the crop from panicle-feeding insects was studied.ResultsThere were significant insecticide treatments × cultivars/genotypes interaction effects for Stenodiplosis sorghicola, Clavigralla tomentosicollis, Nezara viridula, Dysdercus fasciantus and Riptortus dentipes. Generally, pest infestations were higher in the untreated control compared to K-Optimal- or NSO-treated sorghum. Infestations were also higher in compact-headed cultivars (Dorado and Kapaala) compared to those with open heads (CSSOR 08-V01 and CSSOR 10-V07). Damage was approximately 1.7-fold higher in the untreated controls than in NSO or K-Optimal. Grain yields were about 14% higher in NSO or K-Optimal treated sorghum than in controls. Gross margins were between 16- and 35-fold higher in protected sorghum compared to the untreated ones.ConclusionThese findings suggest that an effective integrated pest management strategy for sorghum farmers must comprise cultivars that do not have compact heads, and the use of about two sprays of NSO or a synthetic pyrethroid when high numbers of panicle-feeding insects are observed during the growing season. Judicious use of insecticides and the “right” cultivar will improve the profitability of sorghum farmers with gross marginal returns that are at least 15-fold higher than that obtained by farmers who adopt only good agronomic practices without insecticide sprays.

Principal component analysis of early generation sorghum lines for yield-contributing traits and resistance to midge

ABSTRACT Sorghum (Sorghum bicolor L. Moench) is a staple food crop in Niger. Its production is constrained by sorghum midge (Stenodiplosis sorghicola Coquillett 1898) and by the use of low-yielding, local sorghum varieties. To improve sorghum productivity, farmers need high-yielding and midge-resistant sorghum cultivars. The objective of this research is to evaluate genetic diversity among sorghum inbred lines for yield, yield-contributing traits, and resistance to midge. Two-hundred and eighty-two lines (280 recombinant inbred lines plus two checks) were evaluated at two experimental sites in Niger. An alpha (0.1) lattice design with two replications was used to conduct the trial. Principal component analysis was used to determine the relationship between grain yield and resistance to midge. The first three principal components (PC) accounted for 56.22% of the total genotypic variation. Based on the similarity of traits within and between members of clusters, genotypes were divided into 18 clusters. Genetic variability was present for the traits under study in the tested germplasm. Hybridization of midge-resistant genotypes from different clusters should be able to yield new genotypes combining high yield and other desirable yield-contributing traits.

First record of Stenodiplosis sorghicola on sorghum in Greece

In October 2007, the sorghum midge Stenodiplosis sorghicola (Coquillett) (Diptera: Cecidomyiidae) was recorded for the first time in Greece. Its occurrence was noticed in an experimental sorghum cultivar at Aliartos, near Athens, in Viotia region. Information on its morphology, biology and distribution is given.

Cost-Benefit Analysis of Sorghum Midge,Stenodiplosis sorghicola1(Coquillett)-Resistant Sorghum Hybrid Research and Development in Texas

Sorghum, Sorghum bicolor (L.) Moench, is important to the economies of Texas and the U.S. Sorghum midge, Stenodiplosis sorghicola (Coquillett), attacks flowering sorghum, causing substantial loss of grain every year. Sorghum midge-resistant genotypes are available for use in breeding programs to develop agronomically superior sorghum hybrids. Estimated yield loss caused by sorghum midge varied between 94.2 and 890.8 and 12.9 and 188.8 kg/ha if sorghum midgesusceptible and resistant hybrids, respectively, were grown. Yield saved by using a resistant hybrid was 48.1 (45.3 kg/ha) to 96.7% (702.0 kg/ha). Benefits accrued during a 25-year period were 66.7, 99.9, and 319.8 million (in 1984 constant dollar) at 1, 5, and 15% compounding/discounting rates, respectively. The corresponding accruable costs were $4.3, 6.7, and 23.4 million. Net present value was positive and cost-benefit ratio was less than one, indicating investment in developing a sorghum midge-resistant hybrid was profitable. Depending on the interest rate, a dollar invested in research and development of a sorghum midge-resistant hybrid would generate $13.6 to 15.7.

HISTORICAL PERSPECTIVE ON DRUG-PLACEBO DIFFERENCES: IMPLICATIONS FOR GENERALIZABILITY OF RESULTS AND FUTURE TRIAL DESIGN

Studies on tritrophic interactions involving sorghum genotypes, midge (Stenodiplosis sorghicola) and the predominant parasitoids (Aprostocetus spp.) at ICRISAT Asia Center were conducted using three midge resistant (ICSV 745, ICSV 89058 and IS 10712) and three susceptible (Swarna, CSH 9 and ICSV 112) genotypes during the post-rainy (1992/93) and rainy (1993) seasons. A. coimhatorensis, the predominant parasitoid during post-rainy season, preferred mid-late midge larvae for parasitization, while A. gala, which was predominant during the rainy season, preferred early-mid larval stages. Variations in the preference of A. coimbatorensis and A. gala for the developmental stage of their host larvae indicate good prospects for the biological control of sorghum midge populations. There were significant differences in parasitization level of midge by Aprostocetus spp. between resistant and susceptible sorghum genotypes, and season. Higher parasitization was observed on susceptible genotypes than on resistant ones during both post-rainy and rainy seasons. However, the level of parasitization was greater in post-rainy than in rainy seasons. There was also evidence of higher midge infestation in rainy than in post-rainy seasons. Susceptible genotypes attracted more parasitoids because of high levels of midge infestations. Low parasitoid density in midge resistant sorghum under glasshouse and field conditions was associated with low midge infestations in these genotypes. However, parasitoids were always associated with their host in spite of low midge densities in resistant genotypes. The present study revealed that the interaction between host plant resistance and parasitoids of sorghum midge would thus be synergistic and complementary and could result in successful integration of these two important pest management tactics.

Host-plant resistance and biopesticides: ingredients for successful integrated pest management (IPM) in Australian sorghum production

There are two major pests of sorghum in Australia, the sorghum midge, Stenodiplosis sorghicola (Coquillett), and the corn earworm, Helicoverpa armigera (Hübner). During the past 10 years the management of these pests has undergone a revolution, due principally to the development of sorghum hybrids with resistance to sorghum midge. Also contributing has been the adoption of a nucleopolyhedrovirus for the management of corn earworm. The practical application of these developments has led to a massive reduction in the use of synthetic insecticides for the management of major pests of sorghum in Australia. These changes have produced immediate economic, environmental and social benefits. Other flow-on benefits include providing flexibility in planting times, the maintenance of beneficial arthropods and utilisation of sorghum as a beneficial arthropod nursery, a reduction in midge populations and a reduction in insecticide resistance development in corn earworm. Future developments in sorghum pest management are discussed.

Economic Injury Levels for Sorghum Midge, Stenodiplosis sorghicola1,and Corn Earworm, Helicoverpa zea2, Feeding on Panicles of Sorghum, Sorghum bicolor

Abstract Sorghum midge, Stenodiplosis sorghicola (Coquillett), and corn earworm, Helicoverpa zea (Boddie) are important insect pests of sorghum, Sorghum bicolor (L) Moench. Both pests feed on the developing kernel and directly reduce grain yield. Economic injury levels (EIL) that respond to pest management costs, commodity values and pest density are developed for each pest based upon published reports on grain loss per insect stage and stage-specific mortality. The economic injury level for sorghum midge is M = C 33,256 / V F where M = mean number of adult sorghum midge per flowering panicle, C = cost of management to control sorghum midge per unit area ($/acre), V = market value per unit of production ($ per 100 lbs of sorghum grain), and F = number of flowering panicles per acre. The EIL for sorghum midge is expressed as the number of adult sorghum midge per flowering panicle because only flowering panicles are susceptible to oviposition by sorghum midge females. Corn earworm larval stage must be consi...

Seasonal incidence of Stenodiplosis sorghicola (Coquillett) (Diptera: Cecidomyiidae) and its parasitoids on Sorghum halepense (L.) Pers. in south‐eastern Queensland, Australia

Abstract To quantify the role of Johnson grass, Sorghum halepense, in the population dynamics of the sorghum midge, Stenodiplosis sorghicola, patterns of flowering of Johnson grass and infestation by sorghum midge were studied in two different climatic environments in the Lockyer Valley and on the Darling Downs in south‐eastern Queensland for 3 years. Parasitism levels of S. sorghicola were also recorded. In the Lockyer Valley, Johnson grass panicles were produced throughout the year but on the Darling Downs none were produced between June and September. In both areas, most panicle production occurred between November and March and infestation by S. sorghicola was the greatest during this period. The parasitism levels were between 20% and 50%. After emergence from winter diapause, one to two generations of S. sorghicola developed on S. halepense before commercial grain sorghum crops were available for infestation. Parasitoids recorded were: Aprostocetus diplosidis, Eupelmus australiensis and two species of Tetrastichus. Relationships between sorghum midge population growth rate and various environmental and population variables were investigated. Population size had a significant negative effect (P < 0.0001) on population growth rate. Mortality due to parasitism showed a significant positive density response (P < 0.0001). Temperature, rainfall, open pan evaporation, degree‐days and host availability showed no significant effect on population growth rate. Given the phenology of sorghum production in south‐eastern Queensland, Johnson grass provides an important bridging host, sustaining one to two generations of sorghum midge. Critical studies relating population change and build‐up in sorghum to sorghum midge populations in Johnson grass are yet to be performed.

Effect of soil burial depth and wetting on mortality of diapausing larvae and patterns of post‐diapause adult emergence of sorghum midge, Stenodiplosis sorghicola (Coquillett) (Diptera: Cecidomyiidae)

Abstract In south‐eastern Queensland, Australia, sorghum planted in early spring usually escapes sorghum midge, Stenodiplosis sorghicola, attack. Experiments were conducted to better understand the role of winter diapause in the population dynamics of this pest. Emergence patterns of adult midge from diapausing larvae on the soil surface and at various depths were investigated during spring to autumn of 1987/88–1989/90. From 1987/88 to 1989/90, 89%, 65% and 98% of adult emergence, respectively, occurred during November and December. Adult emergence from larvae diapausing on the soil surface was severely reduced due to high mortality attributed to surface soil temperatures in excess of 40°C, with much of this mortality occurring between mid‐September and mid‐October. Emergence of adults from the soil surface was considerably delayed in the 1988/89 season compared with larvae buried at 5 or 10 cm which had similar emergence patterns for all three seasons. In 1989/90, when a 1‐cm‐deep treatment was included, there was a 392% increase in adult emergence from this treatment compared with deeper treatments. Some diapausing larvae on the surface did not emerge at the end of summer in only 1 year (1989/90), when 28.0% of the larvae on the surface remained in diapause, whereas only 0.8% of the buried larvae remained in diapause. We conclude that the pattern of emergence explains why spring plantings of sorghum in south‐eastern Queensland usually escape sorghum midge attack.

Variation in inheritance of resistance to sorghum midge, Stenodiplosis sorghicola across locations in India and Kenya

Sorghum midge [Stenodiplosis sorghicola (Coquillett)] is an important pest of grain sorghum, and host plant resistance is one of the important components for the management of this pest. We studied the inheritance of resistance to this insect involving a diverse array of midge-resistant and midge-susceptible genotypes in India and Kenya. Testers IS 15107, TAM 2566, and DJ 6514, which were highly resistant to sorghum midge in India, showed a greater susceptibility to this insect in Kenya. The maintainer lines ICSB 88019 and ICSB 88020 were highly resistant to sorghum midge in India, but showed a susceptible reaction in Kenya; while ICSB 42 was susceptible at both the locations. General combining ability (GCA) effects for susceptibility to sorghum midge for ICSA 88019 and ICSA 88020 were significant and negative in India, but such effects were non-significant in Kenya. The GCA effects of ICSB 42 for susceptibility to sorghum midge were significant and positive at both the locations. The GCA effects were significant and positive for Swarna, and such effects for IS 15107 and TAM 2566 were negative at both the locations. GCA effect of DJ 6514 were significant and negative in India, but non-significant and positive in Kenya; while those of AF 28 were significant and positive during the 1994 season in India, but significant and negative in Kenya. Inheritance of resistance to sorghum midge is largely governed by additive type of gene action. Testers showing resistance to sorghum midge in India and/or Kenya did not combine with ICSA 88019 and ICSA 88020 to produce midge-resistant hybrids in Kenya. Therefore, it is essential to transfer location specific resistance into both parents to produce midge-resistant hybrids.

Effect of sorghum resistant to Stenodiplosis sorghicola (Coquillett) (Diptera: Cecidomyiidae) on oviposition and development of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Abstract Helicoverpa armigera oviposition preference for, and larval development on sorghum hybrids with differing resistance to sorghum midge, Stenodiplosis sorghicola, were investigated. When H. armigera larvae were fed seed of resistant and susceptible hybrids in the laboratory there were no differences in larval and pupal sizes or the rate of development. The same result was recorded when larvae fed on panicles on plants in a glasshouse. On some sampling occasions, significantly more eggs were laid on panicles of resistant hybrids in the field. This occurred when plants were in plots and also in a mixed planting. Midge‐resistance status did not affect levels of egg parasitism. In a field study using recombinant inbred lines between a midge‐resistant and a midge‐susceptible line, no relationship was found between level of resistance and oviposition of H. armigera. We conclude that, although midge‐resistant hybrids are sometimes preferred for oviposition by H. armigera, the resistance per se does not determine this preference. Egg survival, larval survival, development and resultant damage are not significantly affected by the midge‐resistance status of the host.

Environmental factors influence the expression of resistance to sorghum midge, Stenodiplosis sorghicola

Host plant resistance is an effective means of controlling sorghum midge (Stenodiplosis sorghicola). We studied the influence of environmental factors on expression of resistance to sorghum midge in three midge-resistant and two midge-susceptible genotypes. Midge-resistant lines AF 28, ICSV 197, and TAM 2566 suffered 8.8 to 17.3% damage across seven so wings compared to 25.6%damage in ICSV 112, and 69.4% damage in CSH 5. Susceptibility of the midge-resistant lines (AF 28, ICSV 197, and TAM 2566) decreased with an increase in open pan evaporation, maximum and minimum temperatures, and solar radiation; while the midge-susceptible lines (ICSV 112 and CSH 5) showed a poor interaction with these factors. Midge damage in ICSV 197 showed a negative correlation with minimum temperature and relative humidity and positive correlation with sunshine hours,while the reverse was true for CSH 5. Grain growth rate between 0 and 3 days after anthesis was lower in crops sown on 1st October, when AF 28 and ICSV 197 suffered maximum midge damage. Maximum and minimum temperatures and maximum relative humidity influenced the moisture content of the grain, grain growth rate, and sorghum midge damage. There was considerable variation in genotype × environment interaction for expression of resistance to sorghum midge,and the implications of these results have been discussed in relation to development of sorghum cultivars with resistance to this insect.

DNA sequence variation in the ITS‐1 rDNA subunit and host relationships in sorghum midge, Stenodiplosis sorghicola (Coquillett) (Diptera: Cecidomyiidae), in Australia

AbstractSequence variation in the internal transcribed spacer (ITS‐1) ribosomal DNA subunit was examined for sorghum midge obtained from introduced and native hosts in south‐eastern and central Queensland. No variation was observed relative to host plant or geographical distance for midges collected from two introduced hosts, grain sorghum (Sorghum bicolor) and Johnson grass (S. halepense); however, sequence differences were observed between midges from introduced and native hosts and among midges from a single native host, slender bluegrass (Dichanthium affine). No evidence was observed of introduced midges on native hosts, or vice versa. These results agree with previously hypothesised host distributions for native and introduced midges in Australia, and expand the sample of introduced hosts to include Johnson grass. They suggest that Stenodiplosis sorghicola, the principal midge infesting grain sorghum, is also the most common species on Johnson grass. This confirms that Johnson grass plays a role in the population dynamics of S. sorghicola and suggests that midges originating from Johnson grass may influence levels of infestation in grain sorghum.

Compensation in grain weight and volume in sorghum is associated with expression of resistance to sorghum midge, Stenodiplosis sorghicola

Sorghum midge, Stenodiplosis sorghicola (Coquillett) is one of the most important pests of grain sorghum worldwide. We studied the inheritance of resistance to sorghum midge and compensation in grain weight and volume in panicles of sorghum hybrids and their parents under uniform infestation (40 midges per panicle for two consecutive days). Sorghum midge damage ranged from 8.2 to 82.4% in the maintainer lines (B-lines) of the females parents (A-lines), and 9.0 to 67% in the male parents (restorer lines). Hybrids involving resistant × resistant parents were highly resistant, while those involving resistant ×susceptible and susceptible × resistant parents showed moderate susceptibility. Susceptible × susceptible hybrids were susceptible. Compensation in (percentage increase) grain weight and volume in midge-infested panicles of midge-resistant parents and their F1 hybrids was greater than in midge-susceptible parents and hybrids. General combining ability effects for midge damage, and grain weight and volume were significant and negative for the midge-resistant females (ICSA 88019 and ICSA 88020), whereas those for the midge-susceptible females (ICSA 42 and 296A) were significant and positive. However, the reverse was true in case of compensation in grain weight and volume. Inheritance of compensation in grain weight and volume and resistance to sorghum midge is controlled by quantitative gene action with some cytoplasmic effects. Resistance is needed in both parents to realize full potential of midge-resistant hybrids.

Mechanisms and diversity of resistance to sorghum midge, Stenodiplosis sorghicola in Sorghum bicolor

Sorghum midge, Stenodiplosis sorghicola (Coquillett) is the most important pest of grain sorghum worldwide, and plant resistance is an important component for the control of this pest. To identify sorghum genotypes with diverse mechanisms of resistance to sorghum midge, we studied oviposition, larval survival, and midge damage in 27 sorghum midge-resistant genotypes, and a susceptible check under greenhouse conditions. Observations were also recorded on floral characteristics and compensation in grain mass. Of the 28 sorghum genotypes tested, 19 showed high levels of antixenosis to oviposition as a component of resistance, and had 80% midge damaged spikelets in QL 12 - the susceptible check. Genotypes showing resistance to sorghum midge have smaller glumes than the susceptible check, QL 12. However, IS 7005, IS 18653, and ICSV 745 have relatively large sized glumes, but suffered 20% compensation in grain mass when the panicles were reduced to 250 spikelets and infested with 10 or 25 midges per panicle. There is considerable diversity in sorghum genotypes showing resistance to sorghum midge. Genotypes with diverse combination of characteristics associated with resistance to sorghum midge can be used in breeding programs to broaden the genetic base and increase the levels of resistance to this insect.

Flowering events in sorghum in relation to expression of resistance to sorghum midge, Stenodiplosis sorghicola

Sorghum midge (Stenodiplosis sorghicola Coquillett) is an important pest of grain sorghum, and host plant resistance is one of the most effective means of controlling this pest. Several studies have shown that resistance to sorghum midge is associated with short and tight glumes, faster rate of grain development, and tannins. However, some recent studies suggested that time of flowering is the principal component of resistance to sorghum midge. Therefore, we conducted a series of experiments under laboratory and field conditions on the flowering behaviour of a diverse array of midge-resistant and midge-susceptible genotypes to quantify the contribution of time of flowering in genotypic resistance to sorghum midge. Time of flowering under field and laboratory conditions did not show any differences between midge-resistant and midge-susceptible genotypes. Time to maximum flowering varied considerably between the rainy and the post-rainy seasons. Under field conditions, most of the spikelets in the midge-resistant lines opened between 0000 and 0400 h, while most of the spikelets in the susceptible check, CSH 1, opened at 0200 h. Under light and dark conditions in the laboratory, most of the spikelets opened at 0300 h in all genotypes, irrespective of their level of resistance to the sorghum midge. However, flowering events continued for a longer period under dark conditions outside the laboratory. There were no differences in oviposition in panicles on the midge-resistant genotype, ICSV 745, infested between 0200 and 0600 h, and significantly more eggs were laid in spikelets of the susceptible check, CSH 1, than in the midge-resistant, ICSV 745, at all infestation times. The peak oviposition was recorded at 0945 h irrespective of the level of resistance to sorghum midge, and significantly more eggs were laid in the spikelets of CSH 1 and Swarna than in ICSV 745 and ICSV 197. There was no evidence of change in the susceptibility of sorghum midge-resistant genotypes when infested at different times in relation to time of flowering. Therefore, flowering behaviour of sorghum genotypes seems to play little role in genotypic susceptibility to sorghum midge.

Inheritance of resistance to the panicle-feeding bug Eurystylus oldi and the sorghum midge Stenodiplosis sorghicola in sorghum

A study of the inheritance of sorghum resistance to head-bug Eurystylusoldi and midge Stenodiplosis sorghicola has been conducted from anF1-based complete diallel involving four parental lines (namely head-bugresistant Malisor 84-7 & 87W810, and susceptible S 34 & ICSV 197).The trial was conducted at Samanko, Mali, under both natural and artificialhead-bug infestation, in one date of sowing (DOS) in 1995 and two DOSin 1996. Head-bug visual damage scores (under both types of infestation)were indicated and analyzed in all these trials. Head-bug numbers underartificial infestation on the two DOS of 1996, and midge damage scoreunder natural infestation on the second DOS of 1996 were recorded. Allfour parents confirmed their expected level of resistance to head-bugs,while ICSV 197 confirmed its resistance to midge. Diallel analyses showedthat general combining ability (GCA) and thus additive gene effects werevery important in the inheritance of resistance to both pests. Specificcombining ability and maternal effects were generally of minor importance.Mean performance of the parents and their GCA effects were linked, whichsuggests high heritability. Head-bug resistant parents, Malisor 84-7 &87W810, with high per se resistance and negative GCA shouldtherefore be used in breeding for resistance to this pest, while for a similarreason, ICSV 197 should be used in breeding for midge resistance. Resultsconcerning independance between resistance to head-bugs and to midge,are also discussed.

Artificial infestation of sorghum spikelets with eggs of Stenodiplosis sorghicola (Coquillett) (Diptera: Cecidomyiidae) by water injection

AbstractA technique for artificially infesting sorghum spikelets with eggs of sorghum midge is described and compared with natural oviposition achieved in a glasshouse cage trial. This technique was developed to facilitate antibiosis resistance related studies of midge biology, and to overcome the reduced and inconsistent oviposition achieved in sorghum lines that contain ovipositional‐antixenosis resistance. Injecting an aqueous suspension of exactly two midge eggs between the glumes of individual sorghum spikelets using a micropipette produced consistent, low egg densities across five lines of varying resistance (0.8–1.2 eggs per spikelet; 50–70% infestation), while water injection of four to six eggs per spikelet in the same lines produced high and consistent egg densities (two to three eggs per spikelet; > 80% infestation). In contrast to both of the water‐injection treatments, natural oviposition within the same five lines produced inconsistent egg densities, even when midge densities were adjusted to account for the variable levels of ovipositional antixenosis present in each line (one to four eggs per spikelet; 40–80% infestation). A bioassay was also conducted to determine the effect of suspending midge eggs in water on egg hatch, neonate survival and fitness. Aqueous suspensions of midge eggs stored for 4 h at room temperature produced 79% egg hatch. However, aqueous egg suspensions refrigerated at 4°C for 1–7 days reduced egg hatch (41–64%), lowered larval longevity and reduced maximum movement of neonate larvae. No eggs hatched after 14 days of refrigerated storage.

Incidence and distribution of the sorghum head bug, Eurystylus oldi Poppius (Heteroptera: Miridae) and other panicle pests of sorghum in West and Central Africa

L'incidence et la distribution de la punaise du sorgho, Eurystylus oldi Poppius (Heteroptera Miridae), et des autres ravageurs du panicule du sorgho ont ete evaluees de 1985 a 1994 en stations de recherches et en parcelles paysannes, en Afrique de l'Ouest et Centrale (AOC). Labondance maximale du miride a ete observee pendant le stade pâteux. L'abondance du miride etait plus importante sur les cultivars ameliores que sur les sorghos guineens locaux a longues glumes, aussi bien en stations de recherches qu'en parcelles paysannes. Les degâts sur graines etaient moderes a severes bien que les fermiers ignoraient la plupart du temps ces insectes et leurs degâts potentiels car ils restent caches dans les panicules. Les degâts provoques par le. moucheron du Sorgho (Stenodiplosis sorghicola Coq.) etaient tres importants dans les parcelles paysannes au Burkina Faso, au Niger et au Nigeria. La mouche du sorgho Atherigona soccata Rond., le foreur des tiges Busseola fusca Fuller, les criquets, le cercopide Locris rubens Erichson, Campylomma spp., Creontiades pallidus Ramb., les chenilles de la noctuelle Helicoverpa armigera Hub., Pyroderces simplex Wlsm. et Eublemma gayneri Roths etaient egalement des ravageurs responsables de degâts sur sorgho dans la zone prospectee. On suggere que les futures investigations pour l'amelioration de la culture du Sorgho en OAC pourraient porter sur le developpement de cultivars resistants au miride du Sorgho. (Resume d'auteur)