Inventaire rapide des principaux entomophages de la cochenille du manioc Phenacoccus manihoti (Homoptera : Pseudococcidae) en République du Congo

Dès l’année 1970, une baisse de production en tubercules de manioc de l’espèce Manihot esculenta Crantz (Euphorbiacée) a été constatée en Afrique. L’un des principaux ravageurs de cette plante est la cochenille farineuse du manioc. Au Congo, la lutte contre celui-ci s’est organisée dès 1982 par l’introduction d’un parasitoïde hyménoptère, Epidinocarcis lopezi. Mais cet insecte auxiliaire s’est très vite retrouvé à son tour la proie d’hyperparasites qui freinent ainsi son expansion et limitent son efficacité. La présente étude fait un inventaire des entomophages de la cochenille du manioc Phenacoccus manihoti. Elle s’est déroulée dans trois sites retenus dans la ville de Brazzaville : Kombé, jardin d’essai et Lycée Savorgnan de Brazza (LSB). La récolte des momies a été effectuée sur des feuilles infestées, les arthropodes ayant émergé ont été collectés et identifiés, les taux d’émergence et d’hyperparasitisme ont été déterminés. Les résultats obtenus montrent un taux d’hyperparasitisme élevé (60 et 66,66%) et une faible abondance d’E. lopezi comparé aux hyperparasites (22 hyperparasites pour 13 parasitoïdes). Un autre parasitoïde Acerophagus coccois Smith non encore décrit jusqu’ici au Congo a été découvert. Il pourrait avoir été introduit accidentellement avec les boutures importées et expérimentées dans le but d’améliorer les performances du manioc.Mots clés : Lutte biologique, Auxiliaire, Entomocénose, Momie, Brazzaville, Congo. English Title: Rapid inventory of the main entomophagous species of the cassava mealybug Phenacoccus manihoti (Homoptera: Pseudococcidae) in the Republic of Congo As early as 1970, a decrease in the production of cassava tubers of the species Manihot esculenta Crantz (Euphorbiaceae) was observed in Africa. One of the main pests of this plant is the cassava mealybug. In the Congo, the fight against it was organized in 1982 with the introduction of a hymenoptera parasitoid, Epidinocarcis lopezi. But this auxiliary insect very quickly found itself the prey of hyperparasites, which thus slowed down its expansion and limited effectiveness. The present study makes an inventory of the entomophages of the cassava mealybug Phenacoccus manihoti. It took place in three selected sites in the city of Brazzaville: Kombé, test garden and Lycée Savorgnan de Brazza (LSB). The mummies were harvested from infested leaves, emerging arthropods were collected and identified, rates of emergence and hyperparasitism were determined. The results obtained reached a high rate of hyperparasitism (60 and 66.66%) and a low abundance of E. lopezi compared to hyperparasites (22 hyperparasites for 13 parasitoids). Another parasitoid Acerophagus coccois Smith not yet described in Congo has been discovered. It could have been created accidentally with the imported cuttings and tested in corn to improve cassava performance.Keywords: Biological pest control, Auxiliary, Entomocenosis, mummy, Brazzaville, Congo.

Karakteristik Morfologi dan Kelimpahan Populasi Parasitoid (Hymenoptera) pada Hama Invasif Kutu Putih Ubi Kayu, Phenacoccus manihoti Matile-Fererro (Hemiptera: Pseudococcidae) di Bali

Morphological Characteristics and Populations Abundance of Parasitoid (Hymenoptera) on Invasive Pests Cassava Mealybug, Phenacoccus manihoti Matile-Fererro (Hemiptera: Pseudococcidae) in Bali. This study aims to know the morphological characteristics of parasitoid, population abundance and distribution patterns of parasitoid associated with P. manihoti on cassava crop in Bali. The study was conducted on all cassava crop in Bali with a field observation method that was determined by taking shoots of cassava plants attacked by cassava mealybug P. manihoti, then cassava mealybug P. manihoti were nurtured, then observation was carried out every day until parasitoid appeared and being identified. The results of the study showed that there were three dominant types of parsitoid that were found to be associated with invasive pest P. manihoti, namely Anagyrus lopezi, Acerophagus papayae and Blepyrus insularis. The abundance of parasitoid populations was dominated by parasitoid A. lopezi with a range of values 48.6–81.8%. Then followed by parasitoid A. papayae 7.7 - 37.1%, and B. insularis 3.4 - 14.3%. The distribution pattern of parasitoid varies in each species, parasitoid A. lopezi spreads in groups categories, Parasitoid A. papayae and B. insularis spread random-regulary on cassava crop throughout on each of the Regencies in Bali.

Parasitism of cassava mealybug by Anagyrus lopezi: Effects of varying host and parasitoid densities

Fanani MZ, Rauf A, Maryana N, Nurmansyah A, Hindayana D. 2020. Parasitism of cassava mealybug by Anagyrus lopezi: Effects of varying host and parasitoid densities. Biodiversitas 21: 4973-4980. The solitary endoparasitoid Anagyrus lopezi (De Santis) (Hymenoptera: Encyrtidae) was introduced into Indonesia in 2014 to control the cassava mealybug, Phenacoccus manihoti Matile-Ferrero (Hemiptera: Pseudococcidae). The objectives of this study were to understand the influence of host and parasitoid densities on functional response and mutual interference of the parasitoid, by altering either the host or parasitoid density while keeping the other constant. The effects of host and parasitoid densities on parasitism, superparasitism, progeny production, and sex ratio were also assessed. Logistic regression was used to determine the shape of the functional response. Nonlinear least-squares regression was used to estimate the attack rate (a) and handling time (Th). Nicholson’s model and linear regression were used to determine per capita searching efficiency and interference coefficient, respectively. The logistic regression results suggested a Holling type II functional response to changing host densities, with an estimated attack rate (a) and handling time (Th) were 0.037 h-1 and 1.19 h, respectively. The estimated maximum number of mealybugs parasitized over 24-h period was 20.2 mealybugs. The wasp-mealybug ratio and offspring production increased significantly from 1:2 to 1:100 and from 1.35 to 10.45, respectively. However, the per capita number of parasitization decreased significantly from 14.20 to 4.37, with the increase in parasitoid density from 1 to 8. Searching efficiency of the parasitoid decreased significantly with increasing parasitoid density, with a mutual interference constant (m) of -0.52.

INFLUENCE OF HOST STAGE ON OVIPOSITION, DEVELOPMENT, AND SEX RATIO OF Anagyrus lopezi (DE SANTIS) (HYMENOPTERA: ENCYRTIDAE), A PARASITOID OF THE CASSAVA MEALYBUG, Phenacoccus manihoti MATILE-FERRERO (HEMIPTERA: PSEUDOCOCCIDAE)

Influence of host stage on oviposition, development, and sex ratio of Anagyrus lopezi (De Santis) (Hymenoptera: Encyrtidae), a parasitoid of the cassava mealybug, Phenacoccus manihoti Matile-Ferrero (Hemiptera: Pseudococcidae). The parasitoid Anagyrus lopezi (De Santis) (Hymenoptera: Encyrtidae) was introduced from Thailand into Indonesia in early 2014 to control the invasive cassava mealybug, Phenacoccus manihoti Matile-Ferrero (Hemiptera: Pseudococcidae). Because of the need to produce large numbers of high-quality females, research was conducted in the laboratory to determine host stage preference for A. lopezi on different instars of P. manihoti. Individual female wasps were exposed to first, second, third instar nymphs, and pre-reproductive adult mealybugs. In the no-choice test, the frequency of parasitized hosts and the number of eggs laid per host was significantly higher in second and third instar nymphs as well as adult mealybugs compared to first instar nymphs. In the two-choice test, third instars nymphs and adult mealybugs were the most preferred host for oviposition. Immature development of parasitoids was faster and the ratio of female to male parasitoids was higher following oviposition in second and third instar nymphs and pre-reproductive adult hosts, compared to the first instar nymphs. Our findings indicate that the use of pre-reproductive adults as hosts in a mass-rearing program would be the most productive and fastest way to produce A. lopezi populations with a female-biased sex ratio. Field release of parasitoids should be conducted when the host’s third instar nymph is the most abundant because the period during which preferred and suitable host stages are available would be the longest.

The cassava mealybug, Phenacoccus manihoti Matile-Ferrero (Hemiptera: Coccomorpha: Pseudococcidae) arrives in India

Invasive species threaten the ecological and economic wellbeing of a country (Pimentel et al. 2001). In the last decade, several mealybugs and soft scale insects have been accidentally introduced to India, of which some have become serious pests (e.g., Phenacoccus solenopsis Tinsley, Paracoccus marginatus Williams & Granara de Willink, Phenacoccus madeirensis Green and Pseudococcus jackbeardsleyi Gimpel & Miller); others are widening their host ranges and spreading rapidly. Kilifia acuminata (Signoret) and Protopulvinaria longivalvata Green seem relatively harmless but Trijuba oculata (Brain) and Pulvinaria urbicola Cockerell cause economic damage (Joshi & Rameshkumar 2013; Joshi 2017).