Effect of temperature on the life history of Liriomyza trifolii Burgess (Diptera: Agromyzidae)
Liromyza trifolii Burgess (Diptera: Agromyzidae) belongs to a group of phytophagous insects whose larvae feed inside the leaf of a wide variety of horticultural crops like snow peas (Pisum sativum L.), french beans (Phaseolus vulgaris L.), potatoes (Solanum tuberosum L.) and a variety of flowers. Studies were carried out at seven constant temperatures of 10, 15, 18, 20, 25, 30 and 350C to determine the effect of temperature on life history traits to determine the intrinsic rate of increase and to determine the potential geographic distribution range. The study entailed rearing of a pair of newly hatched L. trifolii fly in a cage under constant temperature, while providing for them with one potted Phaseolus vulgaris plant as a source of food and oviposition site. The plant was replaced after every 24 hours. Upon removal, potted plant was placed in a holding cage within the same temperature. Egg, larvae and pupae were observed and on reaching adult stage were paired to determine daily oviposition. Staining on leaves was done to count number of non-viable eggs. Data obtained from the study was analyzed using One-way Analysis of variance (ANOVA) to determine if there was significant difference in development at different temperature regimes. The data was later analyzed using Insect Life Cycle Model (ILCYM) to compare development rate, time, mortality, senescence and oviposition rate to determine influence of temperature on these development traits. Egg, larval and pupal development did not take place at 100C, development time was shortest at 350C (Egg 1.27 ± 0.00: larvae 2.43 ± 0.00 and pupa 6.82 ± 0.01 days), longest at 150C (Eggs11.4 ± 0.0014 days while larvae and pupa development did not take place), lowest mortality was at 250C (0.070, 0.449, 0.384 for egg, larvae and pupa respectively) and highest total oviposition was recorded at 270C at 60 eggs per female. Development rate was inversely proportional to temperature; male senescence was highest at 300C (0.56 1/days) while female senescence was highest at 350C (8.66 1/days). Analysis of Variance (ANOVA) showed a significant difference in development time at various temperature regimes (Egg F5, 2634=2806.84 p.value=0.00; Larvae F4,988=762.32 p.value=3.8E-300 and Pupa F4,448=2395.3948 p.value=8.5E-301). Development time of all life stages (egg, larvae and pupa) varied in temperature regimes tested. Data was further used to develop potential world distribution maps of L. trifolii for the year 2000 and 2050. The two maps indicated an increase in world temperatures as projected by Intergovernmental Panel on Climate Change by 3.2 to 4.00C would lead to colonization of new areas that previously were not affected by the fly.