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The fall armyworm (FAW), Spodoptera frugiperda is a real threat to food security. It is able to totally destroy the cereal crops in a country. It can cause famine in Sub-Saharan Africa where cereals are subsistence crops. Reported in Africa in 2016, the FAW succeded to colonize 47 countries in one year. Its migration capacities wich are of around 100 km per night can allow it have fully infest a country like Senegal (ca 200 000 km²) in less than a week. The FAW is very difficult to fight because resistant to several insecticides. Invasive species often invade a new environment without their natural enemies, which promotes their multiplication and damage to crops. To estimate the generation number per year and evaluate the impact of biological control of indigenous natural enemies on the FAW, larvae were collected in maize fields and monitored in the laboratory. The results show that the development cycle of S. frugiperda takes 25 days on average, that is to say fifteen (15) generations per year. The study confirms the presence of three species of native natural enemies, a nematode Hexamermis sp. and two Hymenopterans Chelonus sp. and Campoletis sp. detected for the first time in West Africa on FAW larvae. The overall parasitism rate is 25.8%. These native natural enemies are a very promising means of control against FAW populations. The introduction of agricultural techniques to promote the maintenance and the proliferation of the FAW auxiliaries is an alternative to the use of pesticides.

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In Senegal, damage caused by insect pests is a major obstacle to seasonal stability and an increase in cabbage production. Little is known about the spatial and temporal distribution of cabbage pests, which makes the design of management recommendations to small-scale farmers challenging. The objectives of this study were to: (i) evaluate the status of insect pests observed in cabbage farmers’ fields; (ii) give information on the spatial and temporal distribution of key pests and (iii) assess the effect of temperature, insecticide applications, and host crop abundance on their incidence. A total of 116 cabbage fields were monitored for insect pests and related damage over four crop cycles, from October 2012 to May 2014, in the main vegetable producing area of Senegal (Niayes). The diamondback moth Plutella xylostella (L.) was by far the most important pest present in all the fields and with high levels of incidence (37.1% infested plants), particularly in the latter part of the dry season in the South of Niayes (50% infested plants). The cabbage webworm Hellula undalis (F.) was mainly observed in the early dry season in the south of Niayes, with an incidence of up to 12.5% infested plants. More surprising was the detection of the tomato fruit worm Helicoverpa armigera (Hübner), with damage of up to 9.4% of cabbage heads. The incidence of sucking pests such as whiteflies Bemisia tabaci (Gennadius), or aphids (including Lipaphis pseudobrassicae (Davis, 1914), Myzus persicae (Sulzer) or Brevicoryne brassicae (L.)) was generally low. The incidence of P. xylostella increased significantly with the number of insecticide applications, indicating that control deployed by growers was ineffective. The incidence of H. undalis did not depend on the number of insecticide applications, but significantly increased with host crop abundance and decreased with temperature. This study is a first step towards developing alternative pest management strategies in the framework of sustainable vegetable production systems.

Biotic factors (including insect pests) constrain field-grown tomato production in Senegal. However, little information is available on the identity and life system of key pests. The objectives of this study were to: (i) update key pest records of field-grown tomato in the central vegetable-producing area along the northern coast of Senegal, known as the Niayes area; (ii) map their spatial and temporal incidence and (iii) understand insecticide use by growers to control the pests. A total of 98 tomato fields distributed in three zones along a north–south transect in the Niayes area were monitored over four crop cycles from 2012 to 2014. As expected, the tomato fruitworm Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) was the most destructive pest with an occurrence of 92% in sampled fields (90/98) and up to 38% damaged fruits in one field at the time of sampling. The proportion of damaged fruits did not differ among zones, but was significantly higher in the early dry season compared to the late dry season. The invasive tomato leafminer Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) was detected in 53% of sampled fields (52/98), mainly in the south of the Niayes area in the late dry season. Because of their ability to adapt to unstable environment and insecticides, this insect pest assemblage is a new challenge that farmers have to deal with while decreasing their use of broad-spectrum insecticides.

Monitoring of the evolution of insecticide resistance in the field is crucial to prevent pest control issues. The present study was conducted to assess insecticide resistance status of the fruitworm, Helicoverpa armigera (Hübner) (Lepidoptera, Noctuidae), the most destructive pest of field-grown tomato in Senegal. A sample of 11- 15 field populations were monitored for their susceptibility to abamectin, deltamethrin, and profenofos, using a standard leaf-dip bioassay method. Resistance ratios ranged from 1- to 30-fold to abamectin (4/15 populations with RR>10), 7- to 112-fold to deltamethrin (11/12 populations with RR>10), and 1- to 29-fold to profenofos (3/11 populations with RR>10). This indicates that resistance evolution to deltamethrin was widespread among field populations of H. armigera. However, an increasing trend of resistance to deltamethrin was observed from the South to the North of Niayes. Susceptibility to abamectin and profenofos was generally high but showed that resistance might be evolving within some populations. In addition, signs of cross-resistance to abamectin were detected, suggesting possible metabolic resistance mechanisms already selected in pyrethroid-resistant populations. The recorded high levels of pyrethroids resistance are a concern for the control of H. armigera in Senegal as the country is being currently embarking into economic expansion of tomato cropping systems. © 2020 International Formulae Group. All rights reserved. Keywords: Insecticide resistance, pyrethroids, avermectins, OPs, Helicoverpa armigera, West Africa

No abstract

Potato (Solanum tuberosum L.) is one of the important vegetable crops in Senegal with the potential to improve the national food supply and economic benefits to smallholder producers. Experiment was conducted from November 2015 to March 2016 to assess the impact of cut seed tubers and pre-germination on seed tuber storage conditions on potato tubers yield. Four treatments were used for experiment. Pre-plant seed treatments were (T1) 136 whole seed tubers 45-55 g then pre-germinated; (T2) 68 cutted tubers 22-28 g then pre-germinated; (T3) 68 pre-germinated seed tubers then cut 22-28 g; (T) 136 whole seed tubers 45-55 g not pre-germinated (maintained 4 °C). Plants grown from whole and pre-germinated seed tubers had significantly higher yield and more number of secondary stems per plant, when compared to cut and or no pre-germinated seed (P < 0.001). Daughter tubers produced from cut seed resulted in higher small size potato tubers than those from whole seed (P < 0.001). However, no significant difference was found on potato seed emergence. Our results indicated a clear advantage to plant whole and pre-germinated seed potatoes with the aim of producing healthier daughter tubers and increasing yields.Keywords: Seed potato, whole seed, pre-germination, Niayes, Senegal.