Will Tomato Crops Require Climate Controlled Fields in the Near Future?
A new study reveals that a warming climate can do more damage to crops than previously forecasted. Here’s why that growing crops in a climate-controlled environment rather than outdoors might not be such a far-fetched idea in the future.
The Impact of Insects on Crops
Previous studies have reported that insects consume anywhere from 5 to 20% of our major grain crops such as wheat, corn and rice. To some, that may seem like an acceptable risk of loss that’s just a matter of doing business with regards to farming. However, newer studies have indicated that with increasing global temperatures, that acceptable risk of loss from insects could easily increase to unacceptable losses on the scale of an extra 10-25% loss per degree Celsius of warming above normal temperatures.
But wait. That estimate could become even higher according to the latest study that takes into account not just increased temps from global warming and a resultant increase in insect attacks, but also how some plants may be too stressed to cope with fighting a losing war on two fronts. Especially if that crop is like the ever-popular tomato.
Researchers from Michigan State University reported that currently estimated insect-caused crop losses might in actuality be on the low side, especially with plants like tomatoes that face a double-edged sword with respect to how they respond to rising environmental temperatures and insect attacks.
Tomatoes Can Ward Off Heat and Caterpillars, But Not at the Same Time
Tomatoes, it turns out, do not adapt well when facing both warmer temperatures and insects. When temperatures rise, the environment opens up to a wider range of pests. That warmer temperature also increases the metabolism of the insects, which in turn creates some very hungry pests that grow larger. Couple that with the tomato plant having to respond to the effects of the increased heat, and you have a scenario where the tomato plant cannot withstand this double-assault.
“We know that there are constraints that prevent plants from dealing with two stresses simultaneously,” said Gregg Howe, University Distinguished Professor at the MSU-DOE Plant Research Laboratory. “In this case, little is known about how plants cope with increased temperature and insect attack at the same time, so we wanted to try and fill that gap.”
Facing just one threat at a time, tomatoes can typically handle both increased temps and parasites like caterpillars. When temperatures are high, the tomato plant copes by raising its leaves higher above the hot soil and opening its stomata to facilitate cooling. When caterpillars attack by munching on a tomato plant’s leaves, the plant produces a phytohormone, called Jasmonate. Jasmonate signals the plant to quickly produce its own natural defense compounds to drive away the caterpillar munching on its leaves.
However, when a tomato plant faces both increased temps and hungrier caterpillars to fight off at the same time, the end result is that the tomato plant succumbs to the two-pronged attack and fails to thrive as it normally would.
Study Reveals Effects of a Two-Pronged Attack
In the study, Nathan Havko, a postdoctoral researcher in the Howe lab, was working with tomato plants grown in both normal temperature and relatively-hot temperature (38 degrees Celcius) growth chambers. When caterpillars were released into both chambers, he discovered that the caterpillars in the warmer chamber had grown larger and that the plant was doing poorly. The tomato plant in the normal temperature chamber was faring better, responding as a tomato plant normally does when attacked by a caterpillar.
Here’s a YouTube Animation of the Experiment
“I was shocked when I opened the doors to the growth chamber where the two sets of plants were growing at ‘normal’ and ‘high’ temperatures,” Howe said. “The caterpillars in the warmer space were much bigger; they had almost wiped the plant out.”
“When temperatures are higher, a wounded tomato plant cranks out even more JA (Jasmonate hormone), leading to a stronger defense response,” Havko said.
“Somehow, that does not deter the caterpillars. Moreover, we found that JA blocks the plant’s ability to cool itself down, it can’t lift its leaves or sweat.”
While the exact mechanisms resulting in the poorer growth of the tomato plant in the hotter chamber infested with caterpillars remains to be determined, the response of crops like tomato plants to simultaneous and multiple stressors, underscores the fact that crop yield estimates need to take into consideration that the effects of global warming on plant growth can be multifactorial.
“I think we have yet to appreciate the unexpected tradeoffs between defense responses and plant productivity, especially when other types of environmental stress are present,” Howe said. “Turning on the defense response may do more harm than good if the plants face high temperatures or other stresses.”
What is your opinion on Global Warming? Do you believe it may have a detrimental effect on plants and the foods we enjoy? Please comment below.
Timothy Boyer has a Ph.D. in Molecular and Cellular Biology from the University of Arizona. For 20+ years he has been employed as a freelance health and science writer. Today, with a background in farming and an avid home gardener, Timothy continues writing about science with a focus on the connection between plant biology and gardening for healthy living. For continual updates about plants and health, you can also follow Timothy on Twitter at TimBoyerWrites.
1. “Insect bites and warmer climate means double-trouble for plants” Igor Houwat and Gregg Howe, MSUTODAY Science & Technology, Jan. 20, 2020
2. “Insect herbivory antagonizes leaf cooling responses to elevated temperature in tomato”
Nathan E. Havko, Michael R. Das, Alan M. McClain, George Kapali, Thomas D. Sharkey, Gregg A. Howe
Proceedings of the National Academy of Sciences Jan 2020, 117 (4) 2211-2217; DOI:10.1073/pnas.1913885117
3. “Increase in crop losses to insect pests in a warming climate”; Curtis A. Deutsch
Et al., Science 31 Aug 2018: Vol. 361, Issue 6405, pp. 916-919 DOI: 10.1126/science.aat3466