Ea. Heinrichs et al., SEASONAL OCCURRENCE OF RICE YELLOW MOTTLE VIRUS IN LOWLAND RICE IN COTE-DIVOIRE, International journal of pest management, 43(4), 1997, pp. 291-297
Monthly plantings of the rice variety Bouake 189 were made under lowla
nd irrigated conditions, to obtain information on the phenological and
seasonal occurrence of pests and diseases on the West African Rice De
velopment Association (WARDA) research farm near Bouake, Cote d'lvoire
. Regular sampling of insect pests and observations on rice yellow mot
tle virus (RYMV) disease infection throughout the year provided inform
ation on the occurrence of RYMV and potential insect vectors. RYMV inc
idence and grain yields varied depending on planting date, and for a g
iven planting date, varied from one year to another. There was no evid
ence that RYMV incidence increases in successive seasons under continu
ous cropping. There was no significant correlation between RYMV incide
nce and either rainfall or wind speed. Leaf feeding damage by the beet
le vector of RYMV, Trichispa sericea Guerin-Meneville (Coleoptera: Chr
ysomelidae), and percentage RYMV infected plants were severe in the Ju
ly and August plantings in 1993, but whereas T. sericea was not observ
ed thereafter, RYMV spread continued. The white leafhoppers Cofana spe
ctra (Distant) and C. unimaculata (Signoret) (Hemiptera: Cicadellidae)
, the green leafhoppers Nephotettix spp. (Hemiptera: Cicadellidae), th
e spittle bug Locris rubra F. (Hemiptera: Cercopidae), the diopsids Di
opsis longicomis Macquart and D. apicalis Dalman (Diptera: Diopsidae),
and the grasshopper Oxy hyla Stal (Orthoptera: Acridadae) were the mo
st abundant of the insect pests and had distinct population peaks with
in a year. However, population abundances were not correlated with RYM
V incidence. The variability of RYMV in time and space and the potenti
al role of weeds as alternative hosts for RYMV are discussed.