Présentation avec posterinfo:eu-repo/semantics/publishedHexennial International Conference ‘Meeting on Mangrove ecology, functioning and Management – MMM3’, 2-6 juillet, Galle, Sri Lank

Dahdouh-Guebas, Farid

Kioko, E.N.

Koedam, Nico

M'rabu, E.

Dahdouh-Guebas, F.

Koedam, N.

Open Marine Archive

103 
 
Insect pest infestation on mangrove forests of Kenya: identification, threats 
and impacts 
 
E. M’rabu1, 2, 3, F. Dahdouh-Guebas2,3, E.N. Kioko4 & N. Koedam2 
 
1Kenya Marine and Fisheries Research Institute, P.O. Box 81651, Mombasa, Kenya. E-mail: 
elishamrabu@yahoo.com 
2Laboratory of General Botany and Nature Management, Mangrove Management Group, Vrije Universiteit 
Brussel, Pleinlaan 2, B-1050 Brussel, Belgium. 
3Laboratory of Systems Ecology and Resource Management, Département de Biologie des Organismes, 
Université Libre de Bruxelles -ULB, CP 169, Avenue Franklin D. Roosevelt 50, B-1050 Bruxelles, Belgium. 
4Inverterbrate zoology section, Zoology department. National Museums of Kenya, P.O. Box 78420-00500 
Nairobi, Kenya.     
 
Abstract 
 
Insect infestation in mangroves is one of the least investigated and thus least understood 
management problem faced by mangroves. In Kenya, the problem of insect pest infestation 
on Sonneratia alba (J. Smith) has persisted for long with very little efforts put into 
understanding its threat, impacts and management options. S. alba is pioneer species facing 
the open sea in many mangrove formations in Kenya and therefore assists the economic 
importance of mangroves. Consequently decimation of this species may lead to coastal 
erosion and strongly reduce the ability of carbon sequestration. Recently, a massive insect 
infestation event occurred in Pemba Tanzania where infested trees experienced massive 
defoliation such wide scale that it caused alarm to mangrove experts in the region. Despite 
the evident threat, there is scanty information on mangrove insect infestation in the region.  
This study reports the initial findings on the insect pest infestation on S. alba forests of 
Kenya: identification of the insect pest, threats and impacts caused by the infestation. Since 
pest detection, identification and impact evaluation are vital steps to meaningfully determine 
option targets in forest management. Our approach is to investigate (1) the insect(s) 
responsible for the infestation, (2) the infestation mechanism used by the insect(s), (3) the 
kind of damage it causes to trees (branch and tree level) and, (4) the trees’ response to 
infestation. Adult moths were captured using a trap that we devised in the field and larvae 
were reared from infected branches to adult stage for the purpose of identification. External 
inspection of infested branches was conducted in order to understand the insect(s) infestation 
mechanisms. Girdling experiments are also ongoing in order to understand damages caused 
to trees and the response of infested trees towards the infestation. We also designed a scoring 
criterion that we used to evaluate the status of health in the S. alba mangroves. Species 
identification of the insect is ongoing after we successfully trapped the elusive adult moth in 
Gazi Bay. Rearing of larvae from infested branches is on going with a good level of success. 
Scoring results indicate that S. alba zone had 55 % infestation level with no difference in 
infestation level between mono species forest plots and the mixed species forest plots.     
 
Keywords 
insect infestation, Sonneratia alba, mangrove management, Kenya 
  


Insect pest infestation on mangrove forests of Kenya: identification, threats and impacts

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