Development and Age-Specific Mortality of Diamondback Moth on Brassica Host Plants: Pattern and Causes of Mortality Under Laboratory Conditions

The development and mortality of diamondback moth, Plutella xylostella (L.), were studied in laboratory at 25 +/- 1 degrees C, 65 +/- 5% RH, and a photoperiod of 16:8 (L:D) h on 10 canola cultivars: 'SLM046' 'Opera,' 'Okapi,' 'RGS(003)' 'Modena,' 'Sarigol,' 'Zarfam,' 'Licord,' 'Hayula(420),' and 'Talaye.' Larvae successfully survived on all host plants. The developmental time of immature stages ranged from 15.03 +/- 0.15 d on Hayula(420) to 16.65 +/- 0.29 d on Opera, with a larval period ranging from 7.67 to 8.91 d on these cultivars. Adult female longevity was longest on Hayula(420) without any supplemental food. Life table entropy values (H < 0.5) indicated Deevey's type I survivorship curve; however, the value of 0.541 on Hayula420 (H > 0.5) corresponded to type III. Major mortality parameters such as fraction of original cohort dying between successive days of age, death frequency (d(x)) of immature P. xylostella, average daily mortality ((mu) over bar), and central death rate (m,,) were evaluated on canola cultivars and indicated that the highest m(x) occurred on RGS(003), with relatively low potential of population growth, on fifth day of life when the pest is in early larval stages (L1 and L2). The early instars are the most susceptible stages and suffer the highest cause-specific mortality under laboratory conditions.