Studies on Incidence of Insect Pests (Aphids) and Their Natural Enemies in Canola Brassica napus L. (Brassicaceae) Crop Ecosystem

It is important to identify insect pests, and their predators and parasites for pests’ management program in order to develop an effective biological control strategy in an economically and ecologically sound way. The monitoring, sampling and identification of insects fauna in canola Brassica napus L., field determined lady beetles (Coccinellidae: Coleoptera), green lacewing Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae), spider Tibellus oblongus (Walckenaer) (Araneae: Philodromidae) and syrphid fly Syrphus balteaus De Geer (Diptera: Syrphidae) as frequently found predators associated with aphid colonies. The most common parasite was Aphidius species (Hymenoptera: Aphidiidae) occurring in aphid populations. The relative abundance of different natural enemies in November and December was found minimum. All the natural enemies showed increasing trend from pods formation till prior to their maturation. During the months of January and February, the relative abundance of biological control agents was the highest, but their population started decreasing during March to onwards. Studies on relative abundance of natural enemies of aphid, revealed that populations of Coccinellid were highest followed by Aphidius, C. carnea and spider, while syrphid fly was with relatively less in profusion. Aphid Myzus persicae (Sulzer) (Hemiptera: Aphididae), was the major insect pest at the canola site and its incidence continued throughout the duration of the crop season. Obviously, meteorological conditions were more favorable for development of insect pests and natural enemies due to the combination of different abiotic factors.