ISSN 1392-3196 / e-ISSN 2335-8947
Zemdirbyste-Agriculture, vol. 101, No. 4 (2014), p. 431–436
Cold tolerance of Colorado potato beetle (Leptinotarsa decemlineata Say) adults and eggs
Külli HIIESAAR, Reet KARISE, Ingrid H. WILLIAMS, Anne LUIK, Luule METSPALU, Katrin JÕGAR, Viacheslav EREMEEV, Angela PLOOMI, Eha KRUUS, Marika MÄND
The cold tolerance of different seasonal groups (pre-diapause, diapauses and post-diapause) of Colorado potato beetle (Leptinotarsa decemlineata Say) was assessed by exposing them either to a constant temperature of –3°C for 48 to 624 h, or to –3, −4, −5, −6 or −7 °C for a constant 24 h. Cold survival was affected by the length of exposure, by the temperature rates and by seasonality. The least cold-tolerant were pre-diapause beetles in August with a mean lethal temperature (Ltemp50) of −4.4°C for 24 h exposure and with a lethal time (Ltime50) of 106.8 h at −3°C. Cold tolerance was significantly higher in the diapause group in January and in the post-diapause group in March; it did not differ significantly between these groups of beetle for 24 h exposure, the lethal temperature being −5.8°C for both groups. Seasonality had a greater influence on survival of these groups after longer exposure to constant mild sub-zero temperature (−3°C); in diapause group, all the beetles survived 624 h exposure, but in post-diapause group the survival limit decreased to 216 h and lethal time was 153.9 h. Colorado potato beetle eggs tolerated 24 h exposure to sub-zero temperatures from −3°C to −5°C or longer exposure at −3°C for 72 h without a reduction in hatchability. The mean lethal time for 50% mortality of eggs was 76.5 h and mean lethal temperature was −5.8°C. Thus, we conclude that night frosts common in northern regions do not damage Colorado potato beetle adults or eggs to the extent that might threaten the survival of the population.
Key words: cold tolerance, exposure temperatures, exposure time hatchability, seasonality.
Full text: 101_4_str55.pdf