Le présent travail étudie les effets induits par 4 paramètres agrométéorologiques (la pluviométrie, la température, l’humidité relative et l’insolation) sur la dynamique des populations larvaires de M. vitrata dans les fleurs et les gousses de niébé, Vigna unguiculata (L.) Walp. en milieu réel. Au total, 8 traitements (dates de semis) répartis dans un dispositif de bloc aléatoire complet à quatre répétitions ont été utilisés pour l’essai. L’évolution du nombre moyen des populations larvaires de M. vitrata de chaque date de semis en rapport avec les quatre paramètres agrométéorologiques a été considérée. Par la régression multiple, nous avons observé que les 4 paramètres du milieu ont influencé la variation totale de la population de cet insecte dans les fleurs et gousses pour 24 % et 16 % respectivement. Il a été enfin observé qu’il existe une corrélation significative au niveau des fleurs (p = 0,005 et r = 0,33) et également au niveau des gousses (p = 0,04 et r = 0,26) entre la dynamique des populations de M. vitrata et la pluviométrie. Cette dernière est donc le facteur qui gouverne la relation sur l’ensemble des facteurs climatiques au niveau des fleurs et des gousses.Mots clés : Effets, Maruca vitrata, paramètres agrométéorologiques, niébé, Sud du Bénin.

The Sunn pest, Eurygaster integriceps Puton (Hemiptera; Heteroptera; Scutelleridae), is the most damaging insect pest of wheat and barley in countries of West Asia with infestations spreading over 15 million ha in the affected area. The aim of these studies was to develop methods for bioassaying the responses of E. integriceps to volatile signals from live insects and host plants and also to collections of volatiles from the insects. In a slow-speed windtunnel with the bugs confined in longitudinal channels, there was some evidence for attraction of female bugs to male bugs on wheat seedlings and for repellency of females by female bugs on the seedlings. Bugs were found to move most easily along tubular devices 3-5 mm dia, and they are probably negatively geotropic and positively phototropic. A vertical Y-tube, linear-track olfactometer was developed which allowed comparison of responses of bugs to two stimuli in terms of number responding and time taken to respond. Females did not respond to volatiles from wheat or wheat with live conspecific males, but were attracted to wheat with live females. Males were not attracted to volatiles from wheat or wheat with live bugs of either sex. Females were significantly attracted to wheat with volatiles collected from male bugs on Porapak when an amount equivalent to 19.2 bug hr was used but not with one quarter this amount. More females went to the arm with odor from wheat and vanillin (1 µg) than to the arm with odor from wheat only, but the difference was not significant with the number of insects used. A preliminary experiment indicated that females were repelled by a blend of synthetic components of the metathoracic gland exudate. The significance of these results in terms of mate location in this species is discussed

Eurygaster integriceps Puton (Hemiptera; Scutelleridae) is the most damaging insect pest of wheat and barley in countries of West Asia. This study aimed to characterize vibratory signals produced by male and female E. integriceps and to investigate the role of these signals in intraspecific communication, both in the presence and absence of odor signals from the insects. The male consists of short chirps repeated at regular intervals with a call rate of 4.6 chirps/sec, mean chirp duration of 0.085 sec and inter-chirp interval 0.17 sec. When approached, a second male typically produces a distinctive agonistic call or rivalry in which chirps are repeated at a much faster rate of 10.4/sec. Females occasionally call spontaneously, but they are much more likely to do so in response to male calling song, or indeed when any other conspecific is nearby. The female song structure does not differ from the male calling song in its chirp rate, although it is generally produced at lower amplitude and the vibratory movements generating the calls are not always evident. Typically the chirp rate increases as the male gets close to the female, and once mounted with genitalia engaged, vibratory signals subside. A Y-track bioassay system was developed and when vibratory signals produced by live insects were used as source, male bugs were significantly attracted to signals from both females and males. Females were not attracted to signals from either sex. When recorded signals were used as source, rather different results were obtained in that females were significantly attracted to signals from males and males were not attracted to signals from males or females. In the presence of odor collected from male bugs on Porapak, females showed no preference for vibratory signals from live males or the recorded signal. The role of vibratory signaling in mate location in this species and the interaction of these signals with production of volatiles are discussed.

Cowpea Vigna unguiculata (L.) Walp. is an important component in mixed cropping systems that are appropriate to the agro-ecological characteristics of the West African savannah. However, the contribution of cowpea to overall productivity of the systems is reduced by a number of insect pest species. Compared with the humid zone, important features of insect pests in the savannah region include: (i) a tendency towards higher pest incidence during the limited growing period, (ii) a more advantageous situation for generalist and migratory pests in the scanty and unstable vegetation and (iii) lower mortality inflicted by parasitoids on the pest populations. The key pests of cowpea of importance in the West African savannah are the legume flower thrips Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae), the legume pod borer Maruca vitrata (Fabricius) (Lepidoptera: Crambidae) and the pod-sucking bug Clavigralla tomentosicollis Stål (Hemiptera: Coreidae). To control these insects in a sustainable manner, pest management practices such as the use of resistant cowpea varieties, mixed cropping systems, botanical and reduced risk insecticides, and biological control assisted by pest monitoring have been developed. Nevertheless, no single component is effective when used alone, but specific combinations can work synergistically. This paper highlights recent progress in integrated pest management strategies for cowpea in cereal-based cropping systems in the West African savannah.

In previous work successful trapping of the legume podborer, Maruca vitrata Fabricius (Lepidoptera: Pyralidae), was accomplished using a synthetic pheromone blend consisting of (E,E)‐10,12‐hexadecadienal, (E,E)‐10,12‐hexadecadienol, and (E)‐10‐hexadecenal in a 100 : 5 : 5 ratio. In the present work, experiments were conducted in cowpea fields in Benin to compare different trap designs, and other aspects of the lures. A water‐trap made from a plastic jerry‐can was found to be superior to commercial funnel‐ and sticky‐trap designs, and 120 cm was the optimum height for captures. Generally, lures consisted of polyethylene vials containing 0.1 mg of pheromone. Results showed that shielding the lures from the adverse effects of sunlight with aluminium foil did not increase trap catches of M. vitrata. The degree of isomeric purity of the (E,E)‐10,12‐hexadecadienal and (E,E)‐10,12‐hexadecadienol blend components, in the range 73–99%, had no significant effect on captures, while lures of 80% isomeric purity showed no loss of effectiveness for up to 4 weeks. Similar results were observed with lures from a commercial source containing 0.46 mg of pheromone in the blend ratio 100 : 11 : 6 and 95% isomeric purity. Residue analysis showed that vial lures exposed for 2 weeks in the field still contained 73% of the initial amount of (E,E)‐10,12‐hexadecadienal, compared to rubber septa dispensers, which only retained 22%. Females comprised 11–50% of total catches, confirming earlier, unexpected results for synthetic lures. The observations that effective traps can be made from locally available plastic containers, and that pheromone blend composition and purity are not critical, should reduce costs and improve the feasibility of traps as practical monitoring tools for M. vitrata.

The legume podborer, Maruca vitrata (syn. M. testulalis) (F.) (Lepidoptera: Pyralidae) is a pantropical pest of legume crops. Sex pheromone was collected by gland extraction or trapping of volatiles from virgin female moths originating in India, West Africa, or Taiwan. Analysis by GC-EAG and GC-MS confirmed previously published findings that (E,E)-10,12- hexadecadienal is the most abundant EAG-active component with 2–5% of (E,E)-10,12-hexadecadienol also present. At least one other EAG response was detected at retention times typical of monounsaturated hexadecenals or tetradecenyl acetates, but neither could be detected by GC-MS. Laboratory wind-tunnel bioassays and a field bioassay of blends of (E,E)-10,12-hexadecadienal with (E,E)-10,12-hexadecadienol and a range of monounsaturated hexadecenal and tetradecenyl acetate isomers indicated greatest attraction of males was to those including (E,E)-10,12-hexadecadienol and (E)-10-hexadecenal as minor components. In subsequent trapping experiments in cowpea fields in Benin, traps baited with a three-component blend of (E,E)-10,12-hexadecadienal and these two minor components in a 100:5:5 ratio caught significantly more males than traps baited with the major component alone, either two-component blend, or virgin female moths. Further blend optimization experiments did not produce a more attractive blend. No significant differences in catches were found between traps baited with polyethylene vials or rubber septa, or between lures containing 0.01 and 0.1 mg of synthetic pheromone. Significant numbers of female M. vitrata moths, up to 50% of total catches, were trapped with synthetic blends but not with virgin females. At present there is no clear explanation for this almost unprecedented finding, but the phenomenon may improve the predictive power of traps for population monitoring.