ABSTRACT
ABSTRACT Ceratothripoides claratris, the predominant thrips species on tomato in Thailand, was tested for vector competence and efficiency to transmit Capsicum chlorosis virus (CaCV) (isolate AIT) to tomato. The efficiency of adult-stage transmission was influenced by the larval stage at which virus was acquired. Adult C. claratris showed 69% transmission efficiency after acquiring the virus as freshly emerged (<1 h) first-instar larvae. However, when just molted (<1 h) second-instar larvae acquired the virus, the percentage of adult transmitters significantly decreased (48%). Transmission efficiency of up to 47% was detected with second-instar larvae of C. claratris which had acquired the virus as freshly emerged first-instar larvae. Transmission efficiency did not significantly differ between adult males and females, irrespective of the larval stage at which the virus was acquired. Highest transmission efficiency for CaCV was recorded in adult C. claratris derived from second-instar larvae collected from infected tomato plants in a greenhouse. Lowest transmission efficiency was observed in adults directly collected from infected tomato plants in the greenhouse. The spread of CaCV on tomato plants in greenhouses showed a close association with thrips infestations.
ABSTRACT
Ceratothripoides claratris (Shumsher) is a serious pest attacking tomatoes in Thailand. Temperature-dependent development of C. claratris was studied at seven constant temperatures, i.e. 22, 25, 27, 30, 34, 35 and 40 degrees C. Pre-adult survivorship was greatest (95%) at 25 and 30 degrees C and shortest at 22 degrees C. Egg-to-adult time decreased within the range of 20 to 30 degrees C and at 34 degrees C it started to increase. The lower thermal threshold for egg-to-adult development was estimated at 16 and 18 degrees C by linear regression and the modified Logan model, respectively. The optimum temperature for egg-to-adult development was estimated at 32-33 degrees C by the modified Logan model. The influence of temperature on reproduction and longevity of C. claratris was determined at 25, 30 and 35 and 40 degrees C. Both inseminated and virgin females failed to reproduce at 40 degrees C. Virgin females produced only male offspring, confirming arrhenotoky. The sex ratio of the offspring of fertilized females was strongly female-biased, except at 25 degrees C. Mean total fecundity per female and mean daily total fecundity per female were highest for both virgin and inseminated females at 30 degrees C. Female longevity was longest at 25 degrees C and shortest at 40 degrees C. Male longevity was longest at 30 degrees C and shortest at 40 degrees C. The net reproductive rate (R0) and intrinsic rate of natural increase (rm) was greatest at 30 degrees C while, mean generation time (G) and the doubling time (t) were highest at 25 degrees C. The finite rate of increase (lambda) was fairly constant (1.1-1.5 days) over the three temperatures tested. The pest potential of C. claratris for tropical Asia is discussed.
