Field performance of the parasitoid wasp, Trichogrammatoidea armigera (Hymenoptera: Trichogrammatidae) following releases against the millet head miner, Heliocheilus albipunctella (Lepidoptera: Noctuidae) in the Sahel

The effectiveness of the egg parasitoid Trichogrammatoidea armigera Nagaraja (Hymenoptera: Trichogrammatidae) in controlling Heliocheilus albipunctella de Joannis (Lepidoptera: Noctuidae), a major insect pest of pearl millet in the Sahel was assessed during two consecutive years in Niger on-station and on-farm conditions. We found that released T. armigera were able to find and parasitize host eggs within pearl millet fields both onstation and in farmers’ fields. On-station releases of T. armigera led to an average 4.86-fold increase in T. armigera parasitism compared to control fields, where no parasitoids were released. Likewise, on-farm releases of T. armigera led to up to 5.31-fold more egg parasitism by T. armigera in release fields than in control. Our results suggest the effectiveness of T. armigera and lays the groundwork for using T.armigera in augmentative biological control of H. albipunctella in the Sahel

Parasitism of Locally Recruited Egg Parasitoids of the Fall Armyworm in Africa

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is an insect native to the tropical and subtropical Americas that has recently spread to Africa, where it predominately attacks maize, sorghum and other plant species. Biological control is an environmentally friendly way of combatting the pest and contributes to an integrated pest management approach. In Africa, several trichogrammatid parasitoids and Telenomus remus Nixon (Hymenoptera: Platygastridae) have been found parasitizing eggs of the FAW. In Niger, the egg parasitoids encountered include Trichogrammatoidea sp. (Hymenoptera: Trichogrammatidae) and Telenomus remus Nixon. Parasitism of the FAW eggs by the two egg parasitoids was assessed in the laboratory, followed by field testing on sentinel eggs. In the laboratory, T. remus parasitized on average 78% of FAWeggs, compared to 25% for Trichogrammatoidea sp. Telenomus remus was able to parasitize egg masses that were fully covered with scales, while Trichogrammatoidea sp. parasitized only uncovered egg masses. On-farm releases of T. remus in sorghum fields caused up to 64% of FAW egg parasitism. Parasitized eggs yielded viable progeny, which can contribute to FAW egg parasitism build-up during the cropping season. Our findings lay the groundwork for the use of T. remus in augmentative releases against FAW in Africa

Gestion intégrée de Maruca vitrata (FABRICIUS, 1787) et Megalurothrips sjostedti (TRYBOM, 1908), deux insectes ravageurs majeurs du niébé au Niger

Le niébé, Vigna unguiculata (L.) Walp. est la principale légumineuse cultivée au Niger. C’est une culture d’importance économique, sociale et alimentaire. Sa productivité est faible eu égard entre autres à la forte pression des bioagresseurs. La gestion intégrée des ravageurs est l’une des stratégies adoptées pour accroître la productivité du niébé. L’objectif de l’étude est de proposer un système de gestion intégrée de Maruca vitrata et de Megalurothrips sjostedti, principaux ravageurs du niébé au Niger. L’essai est conduit sur deux différentes variétés du niébé: la TN5-78 et la KVX908-1. Le dispositif expérimental utilisé est un split plot avec quatre traitements et quatre répétitions. Le résultat du suivi des effectifs des deux insectes a montré une prédominance de Megalurothrips sjostedti par rapport à Maruca vitrata sur la TN5-78 (607,25 et 15,25 individus, respectivement). Il en est de même sur la KVX908-1, avec respectivement 307,25 et 17,5 individus. La comparaison de la densité des populations des ravageurs étudiés, montre qu’elle est plus faible dans les parcelles traitées au Super-Diforce par rapport aux parcelles traitées avec le Neem et la préparation virale (MaviNPV). Dans l’ensemble, le dispositif permet de réduire de façon significative la densité de Maruca vitrata et de Megalurothrips sjostedti. L’efficacité de la stratégie se traduit par l’obtention des rendements de 1,02 à 2,169 t/ha pour la variété TN5-78 et 1,96 à 3,06t/ha pour la KVX908-1.Mots clés : Lutte intégrée, Maruca vitrata, Megalurothrips sjostedti, Vigna unguiculata, MaviNPV, Neem, insecticide chimiqu

The parasitoid Trichogrammatoidea armigera Nagaraja (Hymenoptera: Trichogrammatidae) is a potential candidate for biological control of the millet head miner Heliocheilus albipunctella (de Joannis) (Lepidoptera: Noctuidae) in the Sahel

Pearl millet, Pennisetum glaucum (L.) R. Br., is a crop grown throughout West Africa, especially in the Sahel. Pearl millet is the major staple food for the population of the Sahel, particularly for household use. It is one of the world’s most resilient drought-tolerant cereal crops, surviving even in the poorest soils in the driest regions and in the hottest climates. Despite this extreme climatic adaptation, pearl millet suffers from many biotic constraints, including insect pests (Nwanze and Harris, 1992). Among these, the stem borer (MSB) Coniesta ignefusalis (Hampson) (Lepidoptera: Crambidae) and the millet head miner (MHM) Heliocheilus albipunctella (de Joannis) (Lepidoptera: Noctuidae) are the major chronic insect pests of millet in the Sahel, including Niger. The MSB develops on many species of the Poaceae family; in the Sahel, it develops 2–3 generations per year on pearl millet during the rainy season and diapauses in leftover pearl millet stems during the rest of the year (Youm et al., 1996). The damage from C. ignefusalis is due to the feeding of developing larvae in millet stalks; first generation larvae cause dead hearts and stand loss, while the second and third generations cause lodging, disruption of the vascular system, and inhibition of grain formation (Harris, 1962; Youm et al., 1996). The MHM is a univoltine and monophagous species, which develops on millet in the Sahel during the rainy season between July and October and spends the remainder of the season in diapause in the soil (Gahukar et al., 1986). Infestations of H. albipunctella are more severe in the drier zones of the Sahel (Nwanze and Harris, 1992). The damage from H. albipunctella is due to larvae that feed on the panicle and prevent grain formation (Nwanze and Harris, 1992). Almost every year, outbreaks of the MHM are observed in the Sahel, especially on millet planted early or earlymaturing cultivars, while millet planted later or late-maturing cultivars is more affected by MSB (Gahukar et al., 1986; Youm et al., 1996). Both insect pests inflict significant yield losses ranging from 15% to total crop failure for C. ignefusalis (Harris, 1962; Ajayi, 1990) and from 40% to 85% for H. albipunctella (Gahukar et al., 1986; Krall et al., 1995)..

Native parasitoids recruited by the invaded fall army worm in Niger

Surveys of fall army worm Spodoptera frugiperda (J. S. Smith) on maize and sorghum in Niger revealed the occurrence of egg parasitoids (Trichogrammatoidea sp., Trichogramma sp., and Telenomus sp.), egg-larval parasitoids (Chelonus sp.), and larval parasitoids (Cotesia sp., and Charops sp.)

Economic feasibility of an augmentative biological control industry in Niger

Farmers in Niger are vulnerable to high millet yield losses due to the millet head miner, Heliocheilus albipunctella De Joannis (Lepidoptera: Noctuidae), for which pest control options are limited. Researchers have developed a procedure to multiply and spread an augmentative biological control agent Habrobracon hebetor Say (Hymenoptera: Braconidae) which is effective in limiting millet yield losses due to the pest. This study assesses the economic viability of small businesses to produce and sell biological control agents. It analyzes the profitability of the businesses under alternative pricing regimes given estimated costs to produce and distribute biological control agents. The economic assessment provides budget analysis for potential businesses and discusses options for scaling, price setting, and organizing. Our study suggests that the small H. hebetor industry should turn a profit in Niger at relatively low prices for the biological control agents of $3.00-$4.00 per bag with 15 bags needed per village. Competitive wages are achievable for the businesses that sell to at least 13 villages. Each business would hire three workers from late May to late August. Commercialization of H. hebetor would generate opportunities for wide geographic distribution of the technology on a sustainable basis in Niger

Farmers’ knowledge, perceptions and management of the moringa tree defoliator, Noorda blitealis Walker (Lepidoptera: Crambidae), in Niger

Moringa oleifera Lam. is a commercial crop in Niger consumed as a leafy vegetable on daily basis in urban areas. Its production is, however, hampered by a defoliator pest, Noorda blitealis Walker for which farmers lack a practical management approach. For this, a structured questionnaire was used to interview individual Moringa farmers (n = 120) in two producing areas (Maradi and Tillaberi) to assess farmers’ knowledge of N. blitealis, their perceptions, and management practices in Niger. Among the biotic constraints they faced, 70% of farmers ranked N. blitealis Walker as the most critical pest of Moringa. In the two regions, all the interviewed farmers could describe N. blitealis damage symptoms; however, only 21–25% of farmers were able to describe some of the development stages of N. blitealis. According to farmers, the perceived yield losses ranged from 4 to 99% across the regions, with the highest losses being recorded in the September–November production period. Farmers’ knowledge of N. blitealis and their management practices were not significantly associated with their socioeconomic profiles. Farmers in both regions relied primarily on synthetic insecticides (60–80%) to control N. blitealis damage, although most farmers misused them (unsuitable molecules, excessive applications, or no attention to preharvest interval). Interestingly, some farmers relied only on sole neem sprays (3–5%) or alternate sprays of synthetic insecticides with neem sprays (15% of farmers in Maradi). Some farmers (10–17%) prune the trees to prevent N. blitealis infestation, while other farmers (3–7%) release chickens into their fields to feed on the N. blitealis caterpillars. These results indicate a crucial need to train farmers in terms of basic knowledge regarding the pest’s biology and develop an integrated pest control approach that will minimize synthetic insecticides