Comparative Effectiveness of Fipronil and Other Insecticide Treatments against Cotton Leafworm and Role of Two Detoxification Enzymes
Hamdy K. Abou-Taleb, Ahmed A. Barrania and Manal A. Attia
Field studies were conducted in two different locations at El-Behira Governorate, in 2013 and 2014 cotton seasons to evaluate some insecticide treatments against cotton leafworm (CLW), Spodoptera littoralis (Boisd.). Glutathione S-transferase (GST) and esterases activities in the CLW larvae from the two locations were compared. Spinetoram (field rate (FR)) / lufenuron (0.5 FR) mixture achieved the highest %reduction of CLW larvae, followed by fipronil (FR) / lufenuron (0.5 FR) mixture which are followed by spinetoram (FR) and fipronil (FR). At AbouElmatameer, spinetoram / lufenuron mixture achived CLW %reduction of 90.3, 92.5, 91.5, 89.8 and 86.5% in 2013 and 90.8, 94.5, 90.3, 85.8 and 83.0% in 2014 season after 1-, 3-, 5-, 7- and 10-days of treatment, respectively. The same mixture reduced CLW larvae numbers by 91.3, 91.0, 89.0 85.8 and 83.3%, in 2013 and 91.0, 92.0, 91.0 90.3 and 88.3% in 2014 after 1-, 3-, 5-, 7- and 10-days of treatment, respectively, at Shobrakeate. On the other hand, cypermethrin and chlorpyrifos treatments achieved the least %reduction of CLW larvae. Mixing the 0.5 FR of lufenuron with the tested insecticides (chlorpyrifos, cypermethrin, fipronil and spinetoram) resulted in increasing their efficacy against CLW. Statistically, field performance of cypermethrin, chlorpyrifos and cypermethrin / lufenuron (0.5 FR) mixture were higher at Shobrakeate than at AbouElmatameer in both seasons 2013 and 2014, where other insecticide treatments were comparable. AbouElmatameer CLW strain showed significantly higher esterases and GST activities about 2- fold compared with that of Shobrakeate one in both seasons. From these results, fipronil and spinetoram can be good alternatives and can be used alone or in a combination with lufenuron to improve the CLW control and overcome the insecticide resistance.