POPULATION-DENSITY, DEVELOPMENT AND BEHAVIOR OF DIOPSIS-LONGICORNIS AND D-APICALIS (DIPTERA, DIOPSIDAE) ON RICE IN THE REPUBLIC-OF-GUINEA

The behaviour and pest status of the rice stem borers Diopsis longicor nis Macquart and D. apicalis Dalman were investigated in the Republic of Guinee, particularly during the dry season. The variables were dire ct seeded and transplanted rice, and three (1988, 1989) and four (1987 ) planting dates. Transplanted rice was damaged nearly three times mor e than direct seeded rice in the dry season, but no significant differ ence was detected during the wet season. As previously observed in oth er West African countries, D. apicalis only occasionally damages rice in Guinee. Contrary to findings elsewhere, D. longicornis was not an i mportant pest of Guinean rice, infesting only 5% and 3% of stems over the three dry and the two wet seasons, respectively. However, year rou nd rice production could promote build up of the diopsid population if dry season planting is not sufficiently delayed (45 days) after the l ast rains of the wet season.