Abstract:
Sugarcane White Leaf Disease (WLD) is one of the most devastative phytoplasma disease which
cause heavy losses to the sugar cane industry in Sri Lanka. Leaf hopper, Deltocephalus menoni
(Hemiptera: Cicadellidae) is the locally identified vector of WLD. Disease transmission proficiency
of the vector is a key factor to consider in disease management. Therefore, this study was
conducted to (a) find out the ability of males, females, and nymphs of D. menoni in transmitting
the WLD and (b) determine the level of persistency of D. menoni in WLD phytoplasma (WLDP)
transmission. To determine the percentage WLD transmission by virulified D. menoni males,
females, and nymphs were introduced to one-month-old healthy potted plants in insect proof field
cages for a one-week period. Test plants were maintained until WLD symptom development. In
estimating the WLD transmission pattern of D. menoni, virulified one-day-old adult females were
introduced to the healthy sugarcane plants allowing them to feed on healthy plant for 24h period.
Then they were recollected and introduced to another set of healthy sugarcane plants. Above
procedure was repeated in 24h frequency for 13 days. Test plants were maintained in insect proof
field cages for three-month period. Presence of WLDP in the tested plants was confirmed by PCR
with phytoplasma specific SPP1/SPP2 primers. Under local conditions, female and male adults,
2nd and 4th instar nymphs were capable of transmitting the WLDP to the healthy plants in a rate
of 55.5, 44.5, 22.2 and 33.3%, respectively. Transmission efficiency of females is comparatively
high. Adult female of D. menoni was capable to transmit the disease from just after acquisition of
the WLDP up to maximum of 11 days. Results imply that D. menoni is incapable to propagate the
WLDP within its body and circulative transmission dose not occurred within the insect. D. menoni
is an efficient vector in secondary transmission of the WLD and it is a semi-persistent vector. Due
to semi-persistent nature of the vector, the management practices are vital to prevent rapid
spread of this disease in sugarcane plantations.
