What’s an Iris yellow spot virus epidemic without a host and a vector? Nothing. In order for an outbreak to hit peak levels, you need a lot of able-bodied thrips and lots of yummy host plant material. Sometimes you only have one or the other and this can drastically impact the disease challenges we face annually. In a 2 year study, we evaluated these two key components of the IYSV disease triangle (host and vector/virus), and monitored for viruliferous thrips in 4 different habitat types, 1) transplanted onions, 2) weedy areas, 3) cull piles, and 4) direct seeded onions.
Mean (± SE) estimated number of viruliferous adult onion thrips early, middle and late in the growing season (June, July and August, respectively) within four habitat types (onion cull piles, transplanted onion fields, weedy areas, and direct-seeded onion fields) that may contribute to IYSV epidemics near Elba, NY in 2014 and 2015. In both years, sampling was initiated when onions were 1-4 leaves, and concluded with onion harvest.
Abstract
Iris yellow spot virus (IYSV) is an economically significant tospovirus transmitted by onion thrips in onions. Limited information is available on habitats contributing to viruliferous onion thrips populations in onion ecosystems. In a two-year field study in New York, the abundance of dispersing onion thrips, including those determined to be viruliferous via reverse-transcriptase polymerase chain reaction (RT-PCR), was recorded in imported onion transplant fields, onion cull piles, weedy areas near onion fields and direct-seeded onion fields from early June until onion harvest (late August-early September). Results showed viruliferous thrips were encountered in all habitats, however transplanted onion sites accounted for 50% of the total estimated numbers of viruliferous thrips and had 9 to 11 times more viruliferous thrips early (June) to mid-season (July) compared to the other habitats. These results indicate that transplanted onion fields are the most important habitat for generating IYSV epidemics in all onion fields (transplanted and direct-seeded) in New York. Our findings suggest that onion growers should control onion thrips in transplanted fields early in the season to minimize risk of IYSV epidemics later in the season.
