Henry Ofosuhene Sintim, Toru Tashiro, Naoki Motoyama
Abstract
A mixed cultivar (54) of sesame collected from ten Asian, three African and other regions were evaluated in the field for arthropod incidence for three consecutive years
between 2005 and 2007. Insects were recorded from as early as 6 days after transplanting to as late as the harvesting day (24 weeks). Arthropods recorded on the plants were
from the orders Orthoptera (Pyrgomorphidae), Lepidoptera (Noctuidae and Sphingidae), and Hemiptera (Aphididae, Miridae and Pentatomidae). Predators (Mantodea and Araneae) and
pollinating Hymenoptera (bees and wasps) were recorded as well. In a small plot experiment the sesame cultivars were ranked based on the relative incidence frequency and the
mean population of insect pests. Eight cultivars including a comparatively susceptible cultivar were selected and sampled for a further season to confirm the insect spectrum
after the first two years. Early maturing cultivars like 11Pusan are suspected to employ also evasive mechanisms in avoiding insect pests. In the third season when selected
cultivars were kept at the vegetative stage in tandem by debudding the early maturing cultivars during the entire sampling period, 11Pusan became a preferred host amongst
the selected cultivars for Myzus persicae and Psilogramma sp. The cultivar 56S. radiatum hosted only Atractomorpha lata in each of the three years irrespective of the number
of available cultivars. These results indicate that insect pests of field sesame select their hosts amongst available cultivars based on relative repellent attributes.
Although all the cultivars were susceptible to at least one insect, the incidence intensities were graded. Insect population counts on the sesame cultivars over time enabled
us to select the high insect aversion cultivars for further insect physiology tests.
Key words:
Sesamum sp., field arthropods, insect aversion