Assessing Transmission of Crop Diseases by Insect Vectors in a Landscape Context

Abstract

Theory indicates that landscape composition affects transmission of vector-borne crop diseases, but few empirical studies have investigated how landscape composition affects plant disease epidemiology. Since 2006, Bemisia tabaci (Gennadius) has vectored the cucurbit yellow stunting disorder virus (CYSDV) to cantaloupe and honeydew melons (Cucumis melo L.) in the southwestern United States and northern Mexico, causing significant reductions in yield of fall melons and increased use of insecticides. Here, we show that a landscape-based approach allowing simultaneous assessment of impacts of local (i.e., planting date) and regional (i.e., landscape composition) factors provides valuable insights on how to reduce crop disease risks. Specifically, we found that planting fall melon fields early in the growing season, eliminating plants germinating from seeds produced by spring melons after harvest, and planting fall melon fields away from cotton and spring melon fields may significantly reduce the incidence of CYSDV infection in fall melons. Because the largest scale of significance of the positive association between abundance of cotton and spring melon fields and CYSDV incidence was 1,750 and 3,000 m, respectively, reducing areas of cotton and spring melon fields within these distances from fall melon fields may decrease CYSDV incidence. Our results indicate that landscape-based studies will be fruitful to alleviate limitations imposed on crop production by vector-borne diseases.

Fine scale population genetic structure of Varroa destructor, an ectoparasitic mite of the honey bee (Apis mellifera)

“…Unfortunately, rates of inter-colony movement via robbing and drifting remain poorly characterized. Recent research suggests that robbing and drifting can result in a large amount of mite transfer especially in apiaries that contain a high density of colonies (Frey and Rosenkranz 2014). There remains, however, ambiguity in the published work linking bee drift to mite movement, with evidence that bees from heavily infested colonies do (Kralj and Fuchs 2006) or do not (Goodwin et al 2006) drift more often than their mite-free counterparts.…”

Crop‐dominated landscapes have higher vector‐borne plant virus prevalence

“…; Carrière et al . ). Our findings are some of the first to demonstrate that cropland cover can have a dramatic effect on local plant virus prevalence.…”

“…Finally, Carrière et al . () showed that the amount of the landscape containing reservoir host plants positively affected the prevalence of a whitefly‐transmitted virus in melons, and the authors found 1500 m to be the most predictive scale in this system.…”

“…Accordingly, Carrière et al . () found that increasing the amount of host plant in the landscape increased the abundance of the insect vector, and that vector abundance had a strong effect on virus prevalence. There are several viable hypotheses explaining the effect of the landscape on the vector community in this system, discussed below.…”

“…While increasing attention is being paid to landscape effects on plant pathogens (e.g., Plantegenest, Le May & Fabre ), to date there are relatively few landscape studies of plant viruses (but see Carrière et al . ). Yet, as the majority of plant viruses are insect‐transmitted (Power & Flecker ), the effect of landscape complexity on virus spread is likely to be strong.…”