Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Abstract Only
Publication Acceptance Date: 1/20/2013
Publication Date: 2/20/2014
Citation: Portilla, M., Snodgrass, G.L., Luttrell, R.G. 2014. Field evaluation on the lethal effect of Beauveria bassiana strains NI8 and GHA against the tarnished plant bug in cotton. National Cotton Council Beltwide Cotton Conference. Proceeding of Beltwide Cotton Conferences, January 7-10, 2013 San Antonio, Texas p.254.
Interpretive Summary: Two isolates of Beauveria bassiana (Balsamo) Vueillemin including the commercial strain GHA and the Mississippi Delta native NI8 strain were evaluated in the field for pathogenicity and infectivity against tarnished plant bug (TPB), Lygus lineolaris (Palisot de Beauvois). Thirty 2-d old TPB adults from a laboratory colony were placed in cages located on top and bottom parts of cotton plants in the field prior to spraying with B. bassiana. A total of 240 cage were used in 40 plots (20 plots per strain) (0.068 acre each) sprayed with four concentrations and a control with each B. bassiana strain (4 plots / concentration, 6 cages / plot, 2 cages/ cotton plant). Concentrations sprayed (spores / acre) were 4.0x1010, 4.0x1011, 4.0x1012, 4.0x1013 of B. bassiana strain NI8 and 4.1x1010, 4.1x1011, 4.1x1012, 4.1x1013 of B. bassiana commercial strain GHA. All sprays included 1.5 ml of Tween-80 per gallon of spray. Sprayed insects were collected from the cages and placed individually on Lygus solid diet and observed for ten days under laboratory conditions. Mortality and sporulation from Lygus collected on top and bottom parts of the plants were recorded daily. Differences of mortality and sporulation on day 3, 5 and 10 were significant among concentrations for both isolates and locations. Based on the LC50 (lethal concentration) and LS50 (lethal sporulation) estimates determined by probit analysis of the concentration-mortality (top and bottom) and concentration-sporulation (top and bottom) relationships 10 days after spray, B. bassiana native strain NI8 with a LC50 of 6.5x1012 and LS50 of 1.7x1013 (spores / acre) was more infectious to TPB than the commercial strain GHA with a LC50 of 4.74x1014 and LS50 of 2.27x1015 (spores / acre). Overall, these results indicated that B. bassiana strain NI8 was superior to the commercially-available isolate suggesting that a 50% reduction of adult populations of L. lineolaris may occur 10 days after spray using a spray concentration about 73 – fold lower than that of the commercial GHA strain.
Technical Abstract: The entomopathogenic fungus Beauveria bassiana Delta native strain NI8 have shown great potential for the management of tarnished plant bug adults when compared with the commercial strain GHA. Population of L lineolaris in cages was reduced by 50% 10 days after application of the NI8 native strain at a rate of 6.5 x1012 spores per acre, while 7 x 1013 spores per acre was the rate of GHA commercial strain required to obtain the same mortality. In this study several characteristics of two strains of B. bassiana were assessed and previously shown to be pathogenic to L. lineolaris in laboratory assays. Both fungal strains were efficacious and have promise as control agents for tarnished plant bug. However, NI8 was more infectious than GHA strain.