Comparative Study of the Morphology of the Ovipositor of Platygaster diplosisae

We studied the morphology of the ovipositor of Platygaster diplosisae (Hymenoptera: Platygasteridae) and Aprostocetus procerae (= Tetrastichus pachydiplosisae) (Hymenoptera: Eulophidae), two parasitoids associated with the African rice gall midge (AFRGM), and Orseolia oryzivora (Diptera: Cecidomyiidae). Scanning electron microscope techniques were used for this study. The ovipositor of P. diplosisae was short (40 μm), and most of the sensillae found on it were mechanoreceptors and located on the distal portion of the 3rd valvulae. These sensillae may be involved in selection of an egg or larval host. The shortness of this ovipositor may be an adaptation to a host whose egg envelope thickness is not more than 0.7 μm. The ovipositor of A. procerae was 30 times (1.2 mm) the length of the P. diplosisae ovipositor. It was not only well equipped with mechanoreceptive sensillae, but these sensillae were very diverse and distributed along the length of the valvulae. The 10 denticulations of the lancet of this ovipositor allow this parasitoid to exploit hosts that are not otherwise readily accesible. These two parasitoids share the same resource by infesting different life stages of the host. The ovipositor of each species of parasitoid enhanced resource sharing, due to its length and its sensillae type and distribution

Estimation of Rice Yield Losses Due to the African Rice Gall Midge, \u3ci\u3eOrseolia oryzivora\u3c/i\u3e Harris and Gagne

The African rice gall midge, Orseolia oryzivora Harris and Gagne (Diptera: Cecidomyiidae), is an important pest of rice, Oryza sativa, in Burkina Faso as well as other countries in West and East Africa. In spite of its importance, little is known regarding the relationship between gall midge populations and grain yield losses. To determine yield losses, the gall midge was reared in cages, and adult midges were placed on caged plants of the rice variety ITA 123 at different population levels. The seven treatments consisted of different numbers of insects infested on the plants: 0 insect pairs (noninfested check), and 1, 5, 10, 15, 20, or 25 midge pairs/cage. The loss in yield in relation to the noninfested control was highly positively correlated (R2 = 0.81) with the percentage of gall midge damaged tillers. The infestation by the insect on the plants resulted in the compensatory production of tillers which developed in response to the gall midge damage, but the compensation was not sufficient to make up for the loss of yield due to the damaged tillers. Yield loss ranged from 0% in the control to 65.3% in the treatment with 25 pairs of adults. One percent of tillers damaged resulted in 2% grain yield loss

Nesidiocoris tenuis in Burkina Faso: Distribution, predatory capacity and insecticide sensibility

Tuta absoluta (Lepidoptera: Gelechiidae) is a worldwide invasive insect species, considered a major pest of tomato. It has recently established in Burkina Faso, where chemical control remains the only affordable option to limit damage. Nesidiocoris tenuis (Hemiptera: Miridae) is commercialised as a biological agent to control this pest in other parts of the world. But no literature is available on this predator in Burkina Faso. Therefore, in this study, we (1) scoured the country to determine its distribution and abundance in tomato fields, (2) verified its ability to consume T. absoluta eggs in two scenarios: the first one where N. tenuis has to search for the eggs on the plants and the second one in Petri dishes where the eggs are placed and N. tenuis could consume the eggs at will (3) measure the susceptibility of both insects to insecticides (two synthetic insecticides, three bio-bacterial insecticides and eight plant extracts) using the IRAC 022 method. It appears that, N. tenuis was found in 13 regions of the country with very interesting densities in some tomato fields (up to 80 individuals / m2). All stages of N. tenuis consume T. absoluta eggs and the number of eggs consumed depends on the stage of development and mode of egg delivery. When he has to look for some on the leaves, the adults find about 20 eggs to consume per day, while for an availability and consumption at will of eggs, he consumes about 45 eggs per day. Abamectin, emamectin benzoate, spinosad, spinetoram were very toxic for both T. absoluta and N. tenuis. In contrast, biopesticides including Bacillus thuringiensis, neem oil, Cleome viscosa, Ocimum basilicum and Cassia occidentalis were found to be compatible with N. tenuis while controlling T. absoluta. Based on our results, we recommend that through training for growers, they can be shown the importance of N. tenuis in the management of T. absoluta. We therefore recommend the use of biopesticides in combination with N. tenuis in the control of T. absoluta in Burkina Faso.Production Durable Intégrant la Recherche (ProDuIRe

Estimation of Rice Yield Losses Due to the African Rice Gall Midge, \u3ci\u3eOrseolia oryzivora\u3c/i\u3e Harris and Gagne

The African rice gall midge, Orseolia oryzivora Harris and Gagne (Diptera: Cecidomyiidae), is an important pest of rice, Oryza sativa, in Burkina Faso as well as other countries in West and East Africa. In spite of its importance, little is known regarding the relationship between gall midge populations and grain yield losses. To determine yield losses, the gall midge was reared in cages, and adult midges were placed on caged plants of the rice variety ITA 123 at different population levels. The seven treatments consisted of different numbers of insects infested on the plants: 0 insect pairs (noninfested check), and 1, 5, 10, 15, 20, or 25 midge pairs/cage. The loss in yield in relation to the noninfested control was highly positively correlated (R2 = 0.81) with the percentage of gall midge damaged tillers. The infestation by the insect on the plants resulted in the compensatory production of tillers which developed in response to the gall midge damage, but the compensation was not sufficient to make up for the loss of yield due to the damaged tillers. Yield loss ranged from 0% in the control to 65.3% in the treatment with 25 pairs of adults. One percent of tillers damaged resulted in 2% grain yield loss

La variabilité pluviométrique et ses impacts sur les rendements et les surfaces cultivées dans le bassin arachidier de la région de Thiès (Sénégal)

This study aims to analyze the impacts of rainfall variability on agricultural yields in the groundnut basin of the Thies region. Rainfall variability and declining rainfall volumes are characteristics of the groundnut basin in the Thies region, as they are in other Sahelian countries. There has been a significant water deficit in the study area since the 1970s. This deterioration in rainfall conditions has impacted the socio-economic activities of the population, particularly agriculture. A statistical analysis (Pettitt break test, drought index, ten-year rainfall trend) of rainfall and agricultural data from 1961-2016 revealed an irregular spatio-temporal distribution of rainfall volumes. This study also shows a weak correlation between rainfall and agricultural yields. Therefore, annual rainfall volumes alone do not determine yields. Yields of millet, cowpea, and cassava varied only slightly during the 1970s despite the drought, in contrast to groundnuts, which declined in all three departments of the Thies region because of the drought. Other factors include dry spells, seed quality, soil fertility, crop predators, etc. The different sensitivity of crops to drought in Thies contributes to choosing the best options for successful adaptation