Monitoring The Population Density Of The Diamondback Moth Plutelila Xylostella Using Growth Degree Days

Abstract

This study was conducted to develop monitoring programs for diamondback moth Plutelila xylostella in Basrah province.
Four cultivars of Cabbage (Karmizi, Hanar, Dalal and Hortus) were planted to determine the population density of the insect
during the growing season of 2020/2021. The highest density of larvae was recorded on Dalal cultivar, while the lowest
density was found on Hanar cultivar. The first appearance of the moth was recorded in Zubair region in the second week of
December with an average of 0.13 larvae/plant. The population of larvae increased reaching the peak (8.53 Larva/ plant ) in
the fourth week of February, then the density decreased to 5.21 larvae/ plant in the fourth week of March. The first
appearance of pupae was recorded in the second week of December (0.92 larvae /plant). The number of pupae increased
reaching the peak in the fourth week of February (6.83 larva /plant), then the density decreased to 4.9 larvae /plant in the
fourth week of March. In order to develop pest control programs using Growth Degree Days, laboratory experiments were
conducted to determine the appropriate temperature for the development of the insect from among the temperatures (20,
25, 30, 35° C). The longest incubation period of eggs (the highest average of development) was 4.33 days at 20° C, and
decreased to 3 days at 35° C. The development period of the larva was 12 days at 20° C, and decreased to 8 days at of 25°
C, then to 5 days at 30° C. However, all larvae were killed at 35° C. For the pupal stage, the developmental period reached 6
days at 20° C and decreased to 4 days at 25° C, then the pupal stage decreased to 4 days at 30° C. The appearance of DBM
was predicated by accumulative temperature (Degree days) modeling in Basrah province that was set at 18.6 DDs