Influence of environmental factors on the population dynamics of <i>Diaeretiella rapae</i> (Hymenoptera: Braconidae) parasitizing <i>Brevicoryne brassicae</i> (Hemiptera: Aphididae) in cauliflower cultivars

Abstract

The experiment was conducted on five different cauliflower cultivars viz. Early London, PSBK-1, PSBK-25, Pusa Himjyoti and Snowball Super to study the influence of weather factors viz., temperature, relative humidity and rainfall on the population of cabbage aphid, Brevicoryne brassicae (Linnaeus) and its parasitoid, Diaeretiella rapae (MacIntosh) at Dr. Y. S. Parmar University of Horticulture and Forestry, Nauni, Solan, Himachal Pradesh during the year 2021-2022. The incidence of B. brassicae was first recorded on cv. Early London, Pusa Himjyoti and Snowball Super during 52nd Standard Meteorological Week (SMW) followed by PSBK-1 and PSBK-25 during 1st SMW while the parasitoid was first noticed in 8th SMW on cv. Early London followed by PSBK-1 (9th SMW), Snowball Super (10th SMW), PSBK- 25 and Pusa Himjyoti (11th SMW). The aphid population was maximum (177 aphids/plant) during 10th SMW whereas, the population of parasitoids was maximum (4.90 mummified aphids/plant) during 11th SMW on Early London. Among all the cultivars, the per cent parasitism by D. rapae was highest (17.31%) on Pusa Himjyoti during 13th SMW. The populations of cabbage aphid and its parasitoids exhibited positive correlation with the temperature and negative correlation with relative humidity and rainfall.