I’m a “lumper” rather than a “splitter.” Give me lots of details on different crops, yields, pests, or weeds, and I’ll try to pull out some overarching idea to remember (I’m likely to forget the details). Luckily there are people who thrive on the details, as was made clear to me in a webinar given by Dr. Sanford Eigenbrode earlier this year, discussing climate change and insects in wheat systems.
Because I am a “lumper”, I’ll start with the overarching point I took away from the webinar: we (that is, entomologists like Dr. Eigenbrode, not me personally) know enough about the insect pests affecting wheat systems in the Pacific Northwest to know that different insects, the viruses they spread, and the parasitoids and predators that control them will respond differently to a changing climate. So while crop models suggest that wheat yields in our high latitudes will fare reasonably well as carbon dioxide concentrations increase and the climate warms, there is still a huge question mark related to whether insects and other pests will allow such yields to happen. Vigilance, and knowing what insects to pay particular attention to, can therefore make a big difference to wheat growers’ collective ability to respond and adapt to changes.
I won’t go into all the details of what is known—or not—about how myriad insects are likely to respond to a changing climate. Take the time to listen to Dr. Eigenbrode himself (the recording is available here), who does it more justice than I ever could. My intention in this blog is to highlight some ideas to think about, as a first step towards adapting to different pests as it gets warmer. My thanks to Dr. Eigenbrode who not only gave the webinar, but also provided these key ideas, making my job easy:
- Different pests—and their predators and parasitoids—will respond to climate change differently. Some will move, expanding into new areas or finding their current homes climatically intolerable. Some will develop quicker and go through more generations in a year. Some will now be able to do more—or less—damage to your crop. Some will change how they interact with the crops, or other insect species. And some will combine all of these changes.
- Researchers looking for patterns around the world (rigorous lumpers, if you like) are finding that the effects of climate change on pests can be positive or negative. This makes it much more difficult to determine the effect of climate change on pests than it is to assess climate change’s effect on the crop alone.
But what about pests affecting wheat in the Pacific Northwest? Here are some of Dr. Eigenbrode’s examples:
- Aphids – Research over 17 years found different responses to a warming period. Bird cherry-oat aphid flights occurred earlier, but their abundance was unchanged. Russian wheat aphid also flew earlier, but was also more abundant. That abundance could make a difference.
- Viruses – We don’t have hard data on this yet, but earlier aphid flights could affect the incidence of plant viruses that those aphids spread, like the barley yellow dwarf virus (BYDV, see photo above left). Research has found that the viral concentration can increase with increasing carbon dioxide and temperature.
Cereal leaf beetle – Lab studies and models suggest that the Pacific Northwest will become more suitable for this beetle as it warms. Climate change could also undermine the ability of an introduced parasitoid to control the beetle. If both these changes occur, cereal leaf beetle issues could become more severe.
- Hessian fly – In our region, resistant wheat varieties are the primary basis for managing Hessian flies, so projected climate change may not affect it. More data are needed, however, to ensure there are no other not-yet-considered pathways that could allow this fly to impact wheat yields.
- Orange wheat blossom midge – Models indicate this pest could invade more of Canada’s wheat production areas as the climate warms, but effects in the Pacific Northwest should be negligible.
- New pests – A new species of aphid, Metopolophium festucae cerealium (see photo), has become abundant throughout Washington and northern Idaho. Though we don’t know whether this invasion was facilitated by climate change, we do know that climate change can allow pests to become abundant where they were previously unable to thrive.
Although many details are still uncertain, there is evidence that different pests in the Pacific Northwest will respond differently to climate change. Those pests that become more severe may require more aggressive interventions. On the other hand, some pests may become less of an issue, so we can reduce inputs for their management. Since we can’t predict which will be the next heavy-weight-champion pest, there is a need for vigilance. Keeping an eye on how pests are changing is what will allow us to focus pest management efforts so they continue to effectively keep pests at bay, allowing our crops to thrive.