Note: A new pest,Liriomyza trifolii, on cotton in the Büyük Menderes Valley, Turkey
The study was conducted to evaluateLiriomyza trifolii (Burgess) in the cotton fields of the Büyük Menderes Valley, Turkey, from 1999 to 2000. Leaves were sampled weekly from the middle of June to the middle of August and kept in the laboratory to observe emerging leafminers. Leafminers were initially found on cotton leaves from 35 to 66 days after sowing. The numbers of larval mines varied from one to four per leaf. The largest number of infested leaves was observed in Aydın (Center), where 18.8% and 17.7% of the sampled leaves were infested in 1999 and 2000, respectively. We conclude thatL. trifolii is a potential pest in the cotton fields of Turkey and more research is needed.
Influence of seed treatment and abiotic factors on damage to Bt and non-Bt cotton genotypes by the serpentine leaf miner Liriomyza trifolii (Diptera: Agromyzidae)
In recent years, the serpentine leaf miner Liriomyza trifolii (Burgess) has become a major pest of cotton (Gossypium spp.) in India, with high levels of incidence observed at the seedling stage, particularly in transgenic Bt cotton. We monitored the severity of infestation and damage by L. trifolii to transgenic and non-transgenic genotypes of Gossypium arboreum L. and G. hirsutum L. between 2002 and 2007. Overall, significantly lower L. trifolii damage occurred in G. arboreum varieties than in G. hirsutum varieties and hybrids. Among the G. hirsutum genotypes, damage was significantly lower in varieties than in hybrids. However, no significant differences in damage were observed between Bt and non-Bt cotton hybrids. Abiotic factors had a major influence on the severity of damage; there was a significant and negative association of L. trifolii damage with open pan evaporation (E), maximum temperature, solar radiation and sunshine, and a significant and positive association with relative humidity and rainfall (RF). Multiple stepwise regression analysis indicated that 99% of the variation in L. trifolii damage was accounted for by RF, open pan E and relative humidity.
Effects of biological and operational factors on evolution of insecticide resistance in Liriomyza (Diptera: Agromyzidae)
Effects of biological and operational factors on rates of development of resistance to pyrethroid insecticides in Liriomyza leafminers were studied with a simulation model. Under the conditions examined, resistance evolved faster as fecundity increased, but a range of 5–50 eggs per female per day had relatively little effect. Immigration of susceptibles slowed resistance development, but variation from 0–0.01 adult immigrants per leaf per day did not greatly affect predictions. A refuge for 10%of the adults slowed resistance development. Reductions in spray frequency and dose substantially slowed resistance development. Model projections agree reasonably well with available data and may be useful for understanding and managing resistance in Lirlomyza .