Investigating the Interaction between Crop Age and Timing of Cotton Leafroll Dwarf Virus Inoculation on Disease Severity and Yield Loss

Cotton leafroll dwarf virus (CLRDV) is an emerging plant virus in the U.S. cotton belt that was first identified in samples collected from Alabama in 2017. A field study was conducted at the E.V. Smith Research Center in Shorter, Alabama to investigate the effect of crop age at the time of CLRDV infection on disease severity and yield loss. In this field study, cages containing insect-proof netting were used to cover two-row plots to confine insects released into the plots, and exclude natural infestations of early-season insects. Cotton aphids were released into plots over three consecutive weeks beginning at the 2 true leaf stage. Viruliferous cotton aphids were released into plots by introducing a CLRDV-infected cotton plant into the cage; these plants had been infested with cotton aphids 2 weeks prior to release. There were also a set of plots in which no aphids were released into cages, and another that had been infested with non-viruliferous aphids that had been reared on healthy cotton prior to release into plots. Two weeks after aphid release, plots were sprayed with insecticide to kill aphids, and this was done separately for each of the three release dates. One week after the last set of plots were sprayed with insecticide all cages were removed. Data collected from this trial included a proportion of plants infested with aphids, average number of aphids on 10 plants per plot, presence of CLRDV symptoms, boll retention, virus incidence, and yield. Results from this study will be presented.

*This study may be best presented in the symposium co-chaired by Jenny Koebernick on CLRDV.