Insect Ecology at Purdue - Ian Kaplan's Lab

Vector Ecology

Our research into insect vectors of plant pathogens focuses primarily on the Cucurbitaceae. This plant family contains many economically important crops and is highly vulnerable to a diversity of pathogens that are transmitted by insects.

First, we have been studying the landscape epidemiology of four cucurbit viruses (Cucumber mosaic virus (CMV); Papaya ringspot virus - Type W (PRSV-W); Watermelon mosaic virus (WMV); and Zucchini yellow mosaic virus (ZYMV)), all of which are aphid-vectored. Aphids are among the most severe crop pests worldwide and their damage is largely mediated by virus transmission, as opposed to direct injury from sap-feeding. The vast majority (ca. 76%) of aphid-vectored viruses are transmitted in a nonpersistent manner. This means that aphids acquire the pathogen near-instantaneously upon probing an infected plant, but the virus remains stylet-borne and thus transmissible to healthy plants for a relatively brief period of time (i.e., minutes to hours). Because of their nonpersistent mode of transmission, the majority of aphids in the Midwest can vector cucurbit viruses, albeit at varying levels of efficiency. This point is critical because only two species colonize and reproduce on the crop (green peach aphid, Myzus persicae and melon aphid, Aphis gossypii), the remainder are non-colonists. Thus, vector species considered transient or non-colonists nevertheless play a central role in the epidemiology of nonpersistent viruses.

Figure 1. Numerous aphid species in the Midwest act as non-persistent vectors of cucurbit viruses.

Additionally, we are investigating the ecology of cucumber beetles, which transmit Erwinia tracheiphila the causal agent of bacterial wilt that kills infected plants. Many organic vegetable growers rate this as the most devastating and difficult to manage pest on their farm. Fortunately, the chemical ecology of cucumber beetle attraction is somewhat well-documented, and we are exploring the interactions between factors that mediate beetle aggregation, e.g., induced plant volatiles, floral traits, aggregation pheromone, cucurbitacins. Also, we are testing various control methods such as high tunnel screening and grafting for non-chemical beetle management.

spotted cucumber beetles attacking watermelon

Figure 2. Spotted cucumber beetles mass attacking a wild watermelon (Citrullus colocynthis).