Sustainable rice production in African inland valleys: Seizing regional potentials through local approaches

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Rice-feeding insects and selected natural enemies in West Africa: biology, ecology and identification.

Arthropods destroy an estimated 18–26 % of annual crop production worldwide, at a value of more than $ 470 billion. The greater proportion of losses (13–16 %) occurs in the field, before harvest, and losses have been heaviest in developing countries. With the Earth’s human population expected to reach 10 billion by the end of the current century, raising agricultural productivity through the prevention of crop losses to pests has assumed considerable urgency. The techniques employed in crop loss assessment provide a framework useful in identifying the causes and magnitude of crop losses, and a basis for the evaluation of control options. Crop losses to arthropods have been reported to be lower in traditional than in modern, industrial agriculture, and are thought to result from the more environmentally sound and sustainable practices employed in traditional agriculture. Many of the pest problems in modern agriculture have arisen through an over-reliance on synthetic chemicals for pest control. More environmentally sound pest control practices not only are more sustainable, but may provide greater economic benefits as well. The return per dollar invested in ecologically-based biological and cultural pest controls has been estimated to range from $ 30 to $ 300, significantly higher than the $ 4 estimated for control based on synthetic pesticides. Crop losses to pests must be reduced in ways that are compatible with sustainable production, which requires pest control to be approached in a holistic manner with a focus on the entire agroecosystem. Key to averting or minimizing crop losses to pests is a commitment, by government or other entities, to collect the data, on which reliable estimates of losses are based.

Crop Losses to Arthropods

The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is an invasive insect pest attacking maize in Ghana and sub-Saharan Africa countries. Biological control will need to be an important management strategy, and a first step was to identify potential natural enemies. Sampling was conducted in different localities of the 10 regions of Ghana from May to Nov 2017. A total of 1,062 larvae were collected from 106 maize farms, and the presence of natural enemies was recorded in 18 (17.0%) farms. Among natural enemies recorded, 7 species were parasitoids: Chelonus bifoveolatus Szpligeti, Coccygidium luteum (Brull), Cotesia icipe Fernandez, Meteoridea testacea (Granger), and Bracon sp. (all Hymenoptera: Braconidae), Anatrichus erinaceus Loew (Diptera: Chloropidae), and an undetermined tachinid fly (Diptera: Tachinidae). The parasitism rate was 3.58%. Three predator species were collected: Pheidole megacephala (F.) (Hymenoptera: Formicidae), Haematochares obscuripennis Stal, and Peprius nodulipes (Signoret) (both Heteroptera: Reduviidae). The 2 most abundant parasitoids were C. bifoveolatus and C. luteum with a relative abundance of 29.0% and 23.7%, respectively, and a parasitism rate of 1.04% and 0.85%, respectively. However, C. bifoveolatus was the most dispersed parasitoid, found in 6.6% of the inspected sites within all the agroecological zones of Ghana. This species is a good candidate as a biological control agent for fall armyworm in Africa. The predator that was most abundant (46.0%) and dispersed (3.8% of the farms) was P. megacephala.

https://bioone.org/journals/florida-entomologist/volume-103/issue-1/024.103.0414/Natural-Enemies-of-the-Fall-Armyworm-Spodoptera-frugiperda-JE-Smith/10.1653/024.103.0414.pdf

Natural Enemies of the Fall Armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) in Ghana

https://www.jstage.jst.go.jp/article/jsta1957/51/2/51_2_41/_pdf

Breeding and Dissemination Efforts of “NERICA”

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 (non‐infested check), and 1, 5, 10, 15, 20 or 25 midge pairs/cage. The loss in yield in relation to the non‐infested 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 ma...

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Estimation of rice yield losses due to the African rice gall midge, Orseolia oryzivora Harris and Gagne

Populations of larvae and pupae of the African rice gall midge, Orseolia oryzivora Harris & Gagne (Diptera: Cecidomyiidae), and two parasitoids, Platygaster diplosisae Risbec and Aprostocetus procerae (Risbec)[= Tetrastichus pachy diplosisae Risbec], were recorded in replicated experiments on farmers' fields at Karfiguela, Burkina Faso in the 1992 wet season and the 1993 dry season. In each season, four plantings were made at 14-day intervals and samples taken at weekly intervals for 10 weeks. Gall midge populations in the wet season developed through three distinct phases: an initial slow increase, followed by a period of rapid increase coinciding with maximum tillering, and then a final decline. On average, the highest midge populations and highest levels of parasitism developed in the later plantings. During the dry season midge infestations were low and no parasites were detected.

Population Dynamics, Host Plant Damage and Parasitism Associated with the African Rice Gall Midge in Southern Burkina Faso

Lepidopteran stemborers (Chilo zacconius Bleszynski, Chilo diffusilineus de Joannis and Maliarpha separatella Ragonot) and diopsid flies (Diopsis spp.) are economically significant insect pests of rice in Burkina Faso. The objective of this study was to monitor damage trends and the pre-imaginal populations of these insects on two host plants, cultivated (Oryza sativa L.) and wild rice (Oryza longistaminata Chev and Roehr). The study was conducted over four consecutive rice crop seasons from 1999 to 2001 in three irrigated rice-growing locations in western Burkina Faso. Sampling of cultivated rice was conducted monthly in 1 m quadrates in 100 randomly selected farmers’ fields. Data on wild rice were collected monthly from each of the three locations using 500 tillers that were plucked at random and dissected. Results showed that in the absence of a rice crop lepidopteran stemborers and diopsid flies are able to survive on O. longistaminata, which can host the pre-imaginal populations of these insects throughout the year. Damage caused on cultivated rice varied across farmers’ fields, seasons and phenological stages of the plants. With 8% the highest average extent of ‘whiteheads’ was recorded during the dry season. These results are important elements in the design of a sustainable management strategy for these insect pests.

Seasonal abundance of lepidopteran stemborers and diopsid flies in irrigated fields of cultivated (Oryza sativa) and wild rice (Oryza longistaminata) in western Burkina Faso.

Experiments were conducted during the rainy seasons in 2003 and 2004 in central Burkina Faso to assess the importance of the African rice gall midge Orseolia oryzivora Harris & Gagne in relation to the planting date under irrigated conditions. The young midge larva feeds at the growing point of the rice tiller, which stimulates the plant to produce an oval hollow gall that prevents the plant from heading. Experiments consisted of three treatments arranged randomly within each of the four replications. Treatments were planting dates separated by 7 days. The rice cultivar planted in the experiment was FKR 14, which matures in 120 days. Nine entomological evaluations (assessment of the number of galls per hill) were performed for each planting date, starting at 25 days after transplanting (DAT) and ending at 81 DAT. Evaluations were conducted on 20 randomly selected hills and consisted of counting the total number of tillers and galls per hill. These hills were identified on one of the two diagonals of each treatment. At the rice maturation stage, 20 randomly selected hills were harvested and the grains from each hill were weighed and recorded. Yield loss was estimated for each treatment from these data. Results showed that the later the planting date, the higher the damage caused by O. oryzivora. The damage was low (>10%) during the vegetative phase but increased dramatically (<20%) during the reproductive phase of the rice plant, regardless of the planting date. Yield losses were correlated to the observed damage: In 2003, for the first planting date, 1% of galling was associated with 1% yield loss, while the same level of damage was associated with 1.3% yield loss for the second planting date.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1742758406454278

The effect of planting date on the African rice gall midge Orseolia oryzivora (Diptera: Cecidomyiidae) damage under irrigated conditions in Boulbi, central Burkina Faso

Stemborers are a major constraint to the production of rice in the Kou Valley, Burkina Faso. Biological control is a good alternative to the use of agrochemicals that are harmful to human and animal health, and the environment. A survey of natural enemies of stemborers was conducted during the 2014 rice-cropping season across three transplanting periods (P1, P2 and P3). Plant and insect samples were collected by mowing and trapping at weekly intervals until harvest, starting 21 days after transplanting, and examined microscopically. Immature stages of the parasitized stemborers were reared to maturity for a positive identification of the parasitoids. Three genera of stemborers were identified: Chilo (Lepidoptera: Pyralidae), Maliarpha (Lepidoptera: Pyralidae) and Sesamia (Lepidoptera: Noctuidae). The Chilo genus was the most important with an average percentage of 41.4% of the pre-imaginal population in P2 followed by Marliarpha (1.1%) and Sesamia (0%). A total of 15 hymenopteran parasitoid species that included nine genera and seven families were identified. All the parasitoids were associated with Chilo and only two of the species parasitized Maliarpha. The most frequent parasitoids encountered were Bracon testacerofatus, Goniozus indicus, Dolichogenidea oryzae and Bracon spp. A total of 28 predator species were recorded from 22 genera, 6 orders and 15 families. Leucauge sp., Agriocnemis sp., Lycosa pseudoannulata and Lycosa sp. were the most important predators with frequencies reaching 15% of the arthropods caught in some fields. These results will be employed to develop a sustainable system to manage rice stemborers.

Souleymane Nacro

Papers

Estimation of rice yield losses due to the African rice gall midge, Orseolia oryzivora Harris and Gagne

Population Dynamics, Host Plant Damage and Parasitism Associated with the African Rice Gall Midge in Southern Burkina Faso

Seasonal abundance of lepidopteran stemborers and diopsid flies in irrigated fields of cultivated (Oryza sativa) and wild rice (Oryza longistaminata) in western Burkina Faso.

The effect of planting date on the African rice gall midge Orseolia oryzivora (Diptera: Cecidomyiidae) damage under irrigated conditions in Boulbi, central Burkina Faso

Natural enemies associated with rice stemborers in the Kou Valley, Burkina Faso