Techniques for Evaluating Feeding Preferences of Lygus lineolaris in Midsouth Cotton
1Arkansas State University, University of Arkansas Agricultural Experiment Station, Jonesboro, AR, USA;
2University of Arkansas Northeast Research and Extension Center, Keiser, AR, USA
Correspondence: tteague@astate.edu
Field and laboratory studies to develop and improve methodology for screening promising cotton lines with host plant resistance to tarnished plant bug (Lygus lineolaris) were initiated in this Cotton Incorporated sponsored project in Arkansas in 2005. Field evaluation methods included measures of tarnished plant bug population densities, cotton square retention, and anther damage in squares and flowers. Results from standard field observations in small plot tests were compared with results from lab preference studies made using a laboratory feeding bioassay under development. In these initial studies, evaluations were made with cotton germplasm lines with distinct morphological traits including lines with and without extrafloral nectaries, with normal and Frego bracts, and lines with normal and early fruiting characteristics. Extrafloral nectaries provide feeding sites in pre-flower cotton for insects. Frego bract cotton types have bracts that are rolled and twisted leaving the floral bud (square) and fruit (boll) exposed. The early fruiting lines can have a lower first fruiting node compared to other lines. Earlier availability of squares can have a lower first fruiting node compared to other lines. Earlier availability of squares could affect adult Lygus feeding preferences in early season. A major goal in these first 2 years has been to develop laboratory screening techniques that could have practical utility in cotton breeding programs. One approach used small testing arenas where plant bug nymphs were presented squares from different cotton lines including small and large squares, and squares with and without bracts. Disposable plastic food containers lined with moistened florist water foam (bottom area of 100 cm2) and with the top fitted with netting were used for all tests. Three field collected nymphs (3 or 4th instar) were released in test containers with squares arranged on the water foam in either 2x2, 3x3 or 4x4 latin square designs. Nymphs were removed after 24 hrs; squares were held an additional 24 hrs and then dissected to evaluate anther damage. Nymphs preferred the Frego cotton type in the laboratory tests compared to two commercially available cultivars and a nectariless line from the breeding program. Differences in presence of bracts or square size were not significant factors in plant bug feeding preference. Results from laboratory assessments were comparable to measurements made for tarnished plant bug preferences in the field. The water foam arena test shows promise as a simple laboratory technique that allows rapid assessment of plant bug feeding preferences. Additional work will be needed to explore the utility of this technique to support on-going cotton breeding efforts in the Midsouth.
|
PREVIOUS Population dynamics of Lygus rugulipennis in agroecosystems of NW Italy |
NEXT Challenges of managing Lygus in strawberry plantations on the central coast of California |