Interspecific host discrimination and competition in Apoanagyrus (Epidinocarsis) lopezi and A.(E.)diversicornis, parasitoids of the cassava mealybug Phenacoccus manihoti

1995 ◽  
Vol 20 (4) ◽  
pp. 326-332 ◽  
Author(s):  
JANINE W. A. M. PIJLS ◽  
KEES D. HOFKER ◽  
MARTIN J. VAN STAALDUINEN ◽  
JACQUES J. M. VAN ALPHEN
1988 ◽  
Vol 120 (1) ◽  
pp. 63-71 ◽  
Author(s):  
Daniel J. Sullivan ◽  
Peter Neuenschwander

AbstractThe encyrtid wasp Epidinocarsis lopezi (De Santis) has been introduced into Africa as a biological control agent against the cassava mealybug Phenacoccus manihoti Matile-Ferrero. This host has a defense reaction against the immature parasitoid that involves encapsulation and melanization. Under laboratory conditions, 37.5% of once-stung cassava mealybugs had been parasitized, as indicated by eggs and larvae of the parasitoid in dissected hosts. Of these parasitized cassava mealybugs, 89.6% contained melanized particles (egg, partially melanized larva, internal host tissues, exoskeleton wound scars). Some of the parasitoid larvae were only partially melanized, and either freed themselves from the melanized capsule or else shed it at the next molt. By the 3rd day of their development only 12.5% were completely melanized. In cassava mealybugs with melanized host tissue but no living parasitoid, the survival of the host was not affected by the melanization. The mealybug itself sometimes shed black particles at the next molt and these were found attached to the cast skins. When superparasitized in the laboratory, 68.6% of twice-stung cassava mealybugs contained parasitoids. Mummies collected from a field experiment showed that melanization rates of mummies increased with increasing parasitization rates. Thus, melanization in the cassava mealybug was commonly triggered when E. lopezi oviposited, but this defense reaction was mostly ineffective, permitting the introduced parasitoid to be a successful biological control agent in Africa against the cassava mealybug, a major pest on this important food crop.


Since its accidental introduction into Africa, the cassava mealybug (CM) has spread to about 25 countries. The specific parasitoid Epidinocarsis lopezi , introduced from South America, its area of origin, into Nigeria in 1981, has since been released in more than 50 sites. By the end of 1986 it was established in 16 countries and more than 750 000 km 2 . In southwestern Nigeria, CM populations declined after two initial releases, and have since remained low. During the same period, populations of indigenous predators of CM , mainly coccinellids, have declined, as have indigenous hyperparasitoids on E. lopezi , because of scarcer hosts. Results from laboratory bionomic studies were incorporated into a simulation model. The model, field studies on population dynamics, and experiments excluding E. lopezi by physical or chemical means demonstrate its efficiency, despite its low reproductive potential.


1991 ◽  
Vol 81 (2) ◽  
pp. 127-132 ◽  
Author(s):  
U. Agricola ◽  
H.U. Fischer

AbstractIn 1988/89 the nature and degree of hyperparasitism in two newly introduced parasitoids of exotic mealybug plant pests were examined in Togo. Associated with Phenacoccus manihoti Matile-Ferrero (Hemiptera: Pseudococcidae) (cassava mealybug) five indigenous hymenopterous hyperparasitoids were found adapted to the primary parasitoid Epidinocarsis lopezi (De Santis): Chartocerus sp. A (Signiphoridae), Prochiloneurus insolitus (Alam), P. aegyptiacus (Mercet) (Encyrtidae), Tetrastichus sp. (Eulophidae), and Marietta leopardina Motschulsky (Aphelinidae). The rate of hyperparasitism varied considerably (20–90%). At one sampling site Chartocerus sp. A was most frequent (52%), at the other site P. insolitus was found to dominate (55%). The same hyperparasitoids were associated with Rastrococcus invadens Williams (Hemiptera: Pseudococcidae), but with an additional Chartocerus (sp. B). Hyperparasitism ranged from 56 to 86%, with Chartocerus sp. A being the most important species. Multiple parasitism was observed on several occasions. In spite of generally high hyperparasitism, no detrimental effect on the control efficiency of either primary parasitoid was noticed.


1987 ◽  
Vol 77 (2) ◽  
pp. 177-189 ◽  
Author(s):  
P. Neuenschwander ◽  
R. D. Hennessey ◽  
H. R. Herren

AbstractAbout 130 species of parasitoids and predators are reported, most of them for the first time, to be associated directly or indirectly with the cassava pest Phenacoccus manihoti Matile-Ferrero and its parasitoid, Epidinocarsis lopezi (De Santis), newly introduced into Africa as a biological control agent. About 20 species are common. The species are grouped in 11 guilds, which include the indigenous hyperparasitoids, which originally attacked parasitoids of other mealybugs, the predators with which E. lopezi competes for the same food source and their antagonists.


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