Enhancement role of Chrysoperla carnea stephens as a biocontrol agent for controlling insect in sugar beet fields

Chrysoperla carnea Stephens, as one of the important predators, has been relatively suppressed due to pesticides use on several crops, from which is the sugar beet. The population fluctuation of C. carnea exhibited four peaks of abundanc. The highest peak was detected on November, 24th and followed by three peaks towards the end of the season. The correlation between C. carnea population and temperature was negative, but in case of relative humidity was positive. However, both correlations were not significant. Experiments were carried out at the experimental farm of Sakha Agricultural Research Station to apply techrniques for enhancing populations of C. carnea at experimental plots. Spray of aqueous solution containing one kilogram of brewer's yeast and four liters of molasses per 100 liters of water increased the predatory population density in the experimental plot by 45.16%, which reflected reductions in the population densities of major insect pests by 4.12-64.08%. The most reduced populations were those of Bemisia tabaci nymphs (64.08%), Pegomia mixta eggs (29.33%) and Myzus persicae nymphs and adults (23.79%). In another experiment, release of C. carnea in sugar beet plots at the rate of 5 larvae/plant reduced the population densities of major insect pests by 3.51-35.97%. The most reduced populations, due to release, were those of aphid nymphs and adults (35.97%), B. tabaci nymph (35.22%) and Cassid a vittata larvae (33.18%). The current investigation results point out the possibility of enhancing the role of C. carnea against sugar beet insects, by release of the solution of brewer's yeast and molasses to improve the nutritional status of the predator. Also, the release of the predatory larvae can be helpful to increase the predatory population and reduces the occurring insect pests.