Geographic distribution and abundance of the Afrotropical subterranean scale insect Stictococcus vayssierei (Hemiptera: Stictococcidae), a pest of root and tuber crops in the Congo basin

Stictococcus vayssierei is a major pest of root and tuber crops in central Africa. However, data on its ecology are lacking. Here we provide an updated estimate of its distribution with the aim of facilitating the sustainable control of its populations. Surveys conducted in nine countries encompassing 13 ecological regions around the Congo basin showed that African root and tuber scale was present in Cameroon, Central African Republic, Congo, Democratic Republic of Congo, Equatorial Guinea, Gabon and Uganda. It was not found on the sites surveyed in Chad and Nigeria. The pest occurred in the forest and the forest-savannah mosaic as well as in the savannah where it was never recorded before. However, prevalence was higher in the forest (43.1%) where cassava was the most infested crop, compared to the savannah (9.2%) where aroids (cocoyam and taro) were the most infested crops. In the forest habitat, the pest was prevalent in all but two ecological regions: the Congolian swamp forests and the Southern Congolian forest-savanna mosaic. In the savannah habitat, it was restricted to the moist savannah highlands and absent from dry savannahs. The scale was not observed below 277 m asl. Where present, the scale was frequently (87.1% of the sites) attended by the ant Anoplolepis tenella. High densities (>1000 scales per plant) were recorded along the Cameroon–Gabon border. Good regulatory measures within and between countries are required to control the exchange of plant materials and limit its spread. The study provides information for niche modeling and risk mapping.

Stictococcus vayssierei. [Distribution map].

A new distribution map is provided for Stictococcus vayssierei Richard. Hemiptera: Stictococcidae. Hosts: cassava (Manihot esculenta), taro (Colocasia esculenta), yam (Dioscorea spp.). Information is given on the geographical distribution in Africa (Cameroon, Central African Republic, Congo, Congo Democratic Republic, Equatorial Guinea, Gabon, Uganda).

A study of some species of the genus Stictococcus Cockerell (Hemiptera: Sternorrhyncha: Coccoidea: Stictococcidae), and a discussion on Stictococcus vayssierei Richard, a species injurious to cassava in Equatorial Africa with adescription of a new species from Nigeria

The adult female of the scale insect Stictococcus vayssierei Richard is described and illustrated. The species feeds on the root system of cassava (Manihot esculenta) (Euphorbiaceae) in Equatorial Africa, affecting tuber formation of the plant. Although damage has been reported only recently, the species has probably remained unnoticed because of its subterranean habit. The distribution and host plants of this species are listed and the segmentation of the adult female of Stictococcus is discussed to help describe the characters in detail when specimens are prepared on microscope slides. Six other species of Stictococcus are described or discussed: S. formicarius Newstead, S. intermedius Newstead, S. pujoli Richard, S. sjostedti Cockerell & Cockerell, S. subterreus Williams, Matile-Ferrero & Miller sp. n., and S. formicarius var. tuberculata Laing which is here raised to specific rank as S. tuberculatus Laing.