Applied Agroecology: Leveling up IPM

Management of insect pests requires a comprehensive evaluation of the pest’s interactions within the argoecosystem.

Put simply: pest management can interact with production systems in complex ways. Sometimes, these interactions are to our benefit and we observe a meaningful synergism of tactics, but more often than not we might be exacerbating pest problems on the farm.

► IPM programming with multiple targets

In my research at Cornell University with Brian Nault, I studied onion thrips (Thrips tabaci) and the impact of integrated pest management (IPM) programs on not only the insect pest, but the greater production system. Onion thrips is considered both a direct and indirect pest of onion. As a direct pest, onion thrips feed on onion leaves and reduce bulb size, and as an indirect pest onion thrips transmit or exacerbate establishment of onion plant pathogens (ask any onion grower and they will know this intimately). Onion thrips can transmit iris yellow spot virus, and worsen the severity of purple blotch (Alternaria porri), and bacterial center rot (Pantoea spp). As such, successful IPM programs that control onion thrips can reduce feeding damage by onion thrips and (hopefully) decrease the severity of associated onion plant diseases. These IPM programs combined 1) fertilizer use (nitrogen and phosphorus), 2) insecticide use and 3) onion cultivar with the aim of improving onion thrips control without comprising marketable yield.

Interestingly, we found that IPM programs in onion production require careful evaluation. Our results showed that an integrated pest management tactic (thrips-resistant onion cultivar ‘Avalon’) was effective in reducing densities of onion thrips, but highly susceptible to bacterial rot pathogens (see figure below). Additionally, an integrated pest management tactic, reducing rates of nitrogen, did not consistently reduce insect densities in our system. Instead, we found that nitrogen fertilizer did not impact marketable yield, and in one year it decreased the incidence of bacterial rot. In short, our results highlight the importance of holistically evaluating IPM programs, so growers can observe maximum benefits.