The developmental biology and adult longevity of Pezothrips kellyanus (Bagnall) (Thysanoptera: Thripidae) on lemon (Citrus limon L.) leaves was studied at five constant temperatures (15, 20, 25, 30, 32.5, and 357deg;C) under laboratory conditions. Developmental time and adult longevity were inversely related to temperature. The developmental time from egg to adult ranged from 10.1 d at 32.5°C to 40.3 d at 15°C. Adult thrips lived from 5.3 d at 35°C to 45.9 d at 15°C and females tended to live significantly longer than males at these two extreme temperatures. No significant differences were found in developmental times between male and female immature stages of P. kellyanus within each tested temperature regime. The highest larval to adult survival (80.6%) was found at 25°C and the lowest (50%) at 32.5°C. No larvae hatched from eggs incubated at 35°C. Both linear and nonlinear models adequately described the relationship between temperature and developmental rates for immature stages of P. kellyanus. Thus, thrips required 204.5 degree-days to complete development from egg to adult stage, above a minimum threshold of 10.2°C as estimated by linear regression. The temperature thresholds for all immature stages except for pupae of P. kellyanus, estimated by the linear model were similar to values that were estimated by the nonlinear model. The predicted upper lethal temperature was 33.12°C, with a minimum threshold for total development occurring at 10°C, as estimated by nonlinear model. The importance of the results in the management of this species through the prediction of its seasonal appearance and population levels are discussed.
The reproductive biology of a citrus pest Pezothrips kellyanus (Bagnall) was studied at four constant temperatures (15, 20, 25, and 30°C) on lemon leaf discs, under laboratory conditions. Lifetime fecundity of mated P. kellyanus was twofold higher at 20 and 25°C than at 15°C. Temperature had no significant effect on fecundity but daily oviposition rate increased as temperature increased. At 15°C, a female of P. kellyanus oviposited 1.13 offspring and at 30°C 5.35 offspring in average per day. Adult longevity was inversely related to temperature. Specifically, female longevity was longest at 15°C (53.90 d) and shortest at 30°C (13.64 d). Preoviposition, oviposition, and postoviposition periods decreased inversely to temperature. Sex ratio was strongly female biased (>60%) at 15 and 25°C. The net reproductive rate (Ro was highest at 15°C and lowest at 30°C. The intrinsic rate of natural increase (rm) as well as the finite rate of increase (λ) were related to temperature and were highest at 30°C. The mean generation time (T) and population doubling time (DT) were inversely related to temperature and were longest at the lowest studied temperature, 15°C. Almost all biological parameters (except preoviposition period) differed significantly between mated and unmated females when were tested at 25°C. The offspring sex ratio was significantly higher at mated than unmated females. Unmated females produced only a few female offspring confirming arrhenotoky in P. kellyanus.
The developmental time, fecundity, and longevity of Pezothrips kellyanus (Bagnall) (Thysanoptera: Thripidae) encaged on lemon, Citrus limon (L.) Burm.f., leaves supplied with different food sources (pollen, sucrose, and honey) were compared at 25°C. Only the addition of pollen offered a nutritional benefit for this thrips species. Pollen to the lemon leaf reduced total developmental time from egg to adult from 12.42 to 9.68 d, increased survival from 22.6 to 80.6%, and increased fecundity. When sugar was offered, only 10% of larvae survived. P. kellyanus larvae were unable to grow on lemon leaves as well as when honey was supplied to the leaves (recorded survival was 22.6 and 42.86%, respectively), and adult females were slightly able to reproduce (1.4 and 4.2 larvae per female, respectively). Pollen and honey supplements fed to adults double and triple adult longevity, respectively.
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