Seasonal occurrence of Characoma stictigrapta (Lepidoptera: Noctuidae) damage to pods of two cocoa varieties in Ibadan, Nigeria

The cocoa podhusk borer, Characoma stictigrapta is a serious perennial insect pest of cocoa in West and Central Africa. It is capable of causing significant yield losses if damage to pods and other plant tissues is left unabated.  The seasonal damage by the larvae of the pest on pods of two major variety of cocoa (Amelonado and Amazon) in Ibadan, Nigeria was investigated (2008-10). A total of 200 cocoa trees for each variety were sampled from the base to a height of 1.5 meters on a fortnightly basis for active damage symptoms of C. stictigrapta. Also, field investigations were conducted to establish any relationship between the burrowing activities of C. stictigrapta and the transmission of blackpod disease in cocoa. Monthly weather parameters (Temperature, Relative humidity and Rainfall) were also computed. More pods were damaged in the Amelonado cocoa (132.87) than in the Amazon variety (89.08). Damage peaked in November 2008 and 2010 and December in 2009 with 153, 138 and 115 damaged pods, respectively and least damage on pods was recorded in June 2008, 2009 and May 2010 with only 17, 15, and 19 damaged pods, respectively for Amelonado. The Amazon variety had pods throughout the cocoa growing season with highest pod damage in February 2008, November 2009 and September 2010 of 67, 52 and 50 damaged pods, respectively. The severe harmattan that came with a decline in relative humidity of 64.5%, 62% and 65% in December 2008, 2009 and 2010, respectively impacted negatively on the damage occurrence of the pest in the early quarter of the year in the Amelonado cocoa. There was also a decline in the pod damage on the Amelonado and Amazon varieties which coincided with the peak of the rainy season. Only 10% of the Amelonado pod variety damaged by C. stictigrapta was infected with Phytophthora podrot disease. The work therefore lends credence to the fact that varietal susceptibility as well as local environmental parameters does influence losses emanating from C. stictigraptainfestation and damage to cocoa pods. This also provides background information that will ultimately lead to the development of an appropriate control strategy for the pest in Nigeria.