Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2012
Publication Date: 1/7/2013
Citation: Sisterson, M.S., Stenger, D.C. 2013. Roguing with replacement in perennial crops: modeling conditions for successful disease management. Phytopathology. 103:117-128. Interpretive Summary: Removal of a diseased plant (roguing) and subsequent replacement with a healthy plant represents a simple cultural method of disease control practiced in long-lived perennial cropping systems. However, for roguing/replacement to be an effective method of disease suppression, a variety of conditions must be met. Computer modeling was performed in which spatially-explicit simulations examined the effectiveness of roguing/replacement in a long-lived perennial crop. Simulations indicate that both primary and secondary pathogen spread may be effectively halted if roguing/replacement is aggressively practiced by most growers on a regional scale, with lifetime crop yields increased substantially with replacement of a relatively small number of plants. However, if roguing/replacement is practiced by only a minority of growers and/or if there is considerable delay between infection and removal of infected plants, disease incidence may not be reduced and lifetime crop yields may actually be decreased despite replacement of a large number plants, particularly in crops with long maturation periods affected by a disease in which infection results in only modest yield reductions compared to uninfected plants.
Technical Abstract: Replacement of infected plants with healthy plants is commonly used to manage spread of insect-transmitted plant pathogens in perennial cropping systems. This strategy has two potential benefits. First, removing infected plants may slow pathogen spread by eliminating inoculum sources. Second, replacing infected plants with healthy plants may negate yield losses due to disease. The extent to which these benefits are realized depends on multiple factors. In this study, sensitivity-analyses of two spatially-explicit simulation models were used to evaluate how assumptions concerning implementation of a plant replacement program and pathogen spread interact to affect disease suppression. In conjunction, effects of assumptions concerning yield loss associated with disease and rates of plant growth on yields were simultaneously evaluated. The first model evaluated effects of plant replacement on pathogen spread and yield on a single farm, consisting of a perennial crop monoculture. The second model evaluated effects of plant replacement on pathogen spread and yield in a 100 farm crop growing region, with all farms maintaining a monoculture of the same perennial crop. Results indicated that efficient replacement of infected plants combined with a high degree of compliance among farms effectively slowed pathogen spread, resulting in replacement of few plants and high yields. In contrast, inefficient replacement of infected plants or limited compliance among farms failed to slow pathogen spread, resulting in replacement of large numbers of plants (on the minority of farms practicing replacement) with little yield benefit. Replacement of infected plants always increased yields relative to simulations without plant replacement provided that infected plants produced no useable yield. However, if infected plants produced useable yields, inefficient removal of infected plants resulted in lower yields relative to simulations without plant replacement for perennial crops with long maturation periods.