Seasonal Patterns of Aster Leafhopper (Hemiptera: Cicadellidae) Abundance and Aster Yellows Phytoplasma Infectivity in Wisconsin Carrot Fields

Abstract

In Wisconsin, vegetable crops are threatened annually by the aster yellows phytoplasma (AYp), which is obligately transmitted by the aster leafhopper. Using a multiyear, multilocation data set, seasonal patterns of leafhopper abundance and infectivity were modeled. A seasonal aster yellows index (AYI) was deduced from the model abundance and infectivity predictions to represent the expected seasonal risk of pathogen transmission by infectious aster leafhoppers. The primary goal of this study was to identify periods of time during the growing season when crop protection practices could be targeted to reduce the risk of AYp spread. Based on abundance and infectivity, the annual exposure of the carrot crop to infectious leafhoppers varied by 16- and 70-fold, respectively. Together, this corresponded to an estimated 1,000-fold difference in exposure to infectious leafhoppers. Within a season, exposure of the crop to infectious aster leafhoppers (Macrosteles quadrilineatus Forbes), varied threefold because of abundance and ninefold because of infectivity. Periods of above average aster leafhopper abundance occurred between 11 June and 2 August and above average infectivity occurred between 27 May and 13 July. A more comprehensive description of the temporal trends of aster leafhopper abundance and infectivity provides new information defining when the aster leafhopper moves into susceptible crop fields and when they transmit the pathogen to susceptible crops.

Identifying Leafhopper Targets for Controlling Aster Yellows in Carrots and Celery

“…Our leafhopper survey confirmed that M. quadrilineatus is the primary leafhopper vector of aster yellows phytoplasma in Michigan celery and carrot agroecosystems, which is consistent with findings from Ohio [ 12 ] and Wisconsin [ 78 ] carrot fields, and is the first study to confirm this in Midwestern celery fields. While other leafhopper species reside in and near these crops, we did not find strong evidence that they contribute to phytoplasma infections within these crops.…”

The complete mitochondrial genome ofMacrosteles quadrilineatus(Hemiptera: Cicadellidae)

“…One such species is the aster leafhopper, Macrosteles quadrilineatus, that is widespread throughout the North American continent. This species causes millions of dollars in agricultural and ornamental crop losses annually by vectoring the Aster Yellows phytoplasma that can infect hundreds of plant species (Hoy et al 1992;Frost et al 2011;Frost et al 2013). Macrosteles quadrilineatus relies on bacterial symbionts for the provisioning of essential amino acids that are limited in their phloem diets, which also helped the host exploit novel niches (Moran 2007).…”

A novel plant pathogen management tool for vector management

“…Time delays between the insect vector acquiring the pathogen and transmitting it (latency) may contribute to differences between the population abundances of infected and uninfected individuals 14–16 . Infections may occur at various spatial scales, both within a cropping system (as a patchwork of infected and uninfected plants) and across cropping systems due to differences in host suitability and management, creating a mixture of infected and uninfected insects due to differences in the infectivity status of their host plants 17–19 .…”