One of the avenues of research being pursued in the Szendrei lab involves integrated pest management of the asparagus miner (Ophiomyia simplex (Loew), Diptera: Agromyzidae). The asparagus miner is a putative vector for pathogenic species of Fusarium fungi (see Figure 1), which are the causative agents for “early decline syndrome” in asparagus fields. Fusarium can decrease the life span of an asparagus field by 5-8 years. Newly planted asparagus fields are especially vulnerable to asparagus miner attack, and the immature stages are challenging to control because of its hidden inside the stem of the plant. While there has been much research looking into controlling the fungi, very little has been devoted to the asparagus miner.
Our lab is looking at various ways to effectively monitor and manage asparagus miner populations as part of an integrated pest management program. We have three main pillars to this research. First, we are developing a degree-day model to accurately predict important phenological events in the life cycle of the asparagus miner (see Figure 2).
This involves elucidating the lower developmental threshold for the asparagus miner, and incorporating it into a model that can help guide grower’s decisions about the timing of pesticide applications. The model will allow growers to access real-time weather conditions using the MSU Enviro-weather network in the state (see Figure 3) and determine if they are at a point when the asparagus miner is vulnerable. In the end, this will save growers money and time by reducing the overall number of pesticide applications, as well as spare the nontarget ecological costs associated with insecticide usage. Concurrently, the lab is also investigating more targeted, systemic pesticides which may be able to control the immature stages of the asparagus miner. Field trials with these chemicals are ongoing, and once effective chemistries are found, they may also be used in conjunction with the degree-day model to manage miners.
Secondly, we are in the process of identifying naturally occurring arthropod parasitoid species of the miner, as well as examining their abundance over time. So far, six species of parasitoids have been identified: three pteromalids, one braconid, one eupelmid and one eulophid (see Figure 4). We have also been examining their life spans when reared on different diets, both artificial and natural, and how this varies relative to the life span of the asparagus miner. More recently, we have been offering various native and exotic flowers to the asparagus miner and the parasitoids to understand how this affects their life span. It is our hope that one or two species of flowers can be chosen that can be incorporated into the asparagus ecosystem to increase the abundance, life span and efficacy of parasitoids. The ultimate aim is a system that will be able to suppress asparagus miner populations with little external inputs.
Lastly, we are exploring the chemical ecology of the asparagus miner/asparagus system. Specifically, we are interested in host plant finding and location by the asparagus miner, and parasitoid detection of the asparagus miner. To address these topics and related ones, we utilize gas chromatography coupled with mass spectrometry (GC-MS) to elucidating the bioactive compounds involved in host-plant location. We have done a survey of asparagus headspace in the lab using greenhouse-reared plants, and have identified many compounds emitted from the plant based on health status (e.g. healthy, herbivore-damaged, or mechanically-damaged). From this survey, we have incorporated several compounds present in high abundance in the headspace in a field baiting experiment to screen the compounds for a potential attractant or repellent for the asparagus miner. Once identified and their biological activity corroborated, these compounds can be used in monitoring and management of the asparagus miner. In coming years, we plan on collecting asparagus headspace in situ to evaluate how asparagus miner-damaged bouquets may differ from healthy plants.
(Rob Morrison’s Ph.D. thesis focused on this project. Article written by R. M.)
Check out our extension articles about asparagus miner here.
This work is funded by Agriculture and Food Research Initiative Competitive Grant#2012-67011-19672 from the USDA National Institute of Food and Agriculture, Project GREEEN and C.S. Mott Predoctoral Fellowship in Sustainable Agriculture.