Entomology: Lessons from the Garden

Multivotines vs. Univoltines: Adapting to Climate Change

I have just returned from a horticultural conference in Boston. One of the more interesting workshops was given by Michael Raupp, Ph.D, Professor at University of Maryland on climate change and plant pests. Thankfully, at least in this area, we are no longer talking about, “is the climate changing?” But what are the implications of climate change, and how does it affect families in western Massachusetts?

For insects, climate change is much more serious than just a bad hair day. There are many environmental factors that influence insects, but the primary one is temperature. As the environment gets warmer, some are winners and others are losers. Within the realm of insect pests – a major concern for farmers and gardeners of any scale – there are clear winners and losers due to the ways in which each species reproduces. The winner in the climate change war are multivotine insects, species who are able to reproduce multiple generations each year. On the losing side are univoltines , whose reproductive cycle makes it impossible to produce more than a single generation in a year.

Multivoltines have historically been hard to control as their ability to adapt to environmental conditions and pesticides is legendary – pesky aphids are a prime example of such a species. Because they have so many generations per year, adaptation of the species happens very quickly – hence an insect with the ability to persist, even as the conditions in its environment change. Univoltines such as the gypsy moth, on the other hand, reproduce slowly and, therefore, evolve slowly as well – making populations more susceptible to climate change-related damage.

Ladybug&Aphids_on_Milkweed_9587a

While it’s impossible to see aphid and gypsy moth populations for yourself during the winter, it’s still possible to learn about this phenomenon as a family while the ground is covered with snow. Instead of aphids and moths, think about dandelions and apple trees. During the summer, dandelions pop up everywhere and go to seed fairly quickly. The seeds, blown by the wind, grow more and more generations of dandelions before the warm weather ends. Apple trees, on the other hand, take years and years to begin producing apples. Instead of reproducing quickly, multiple generations of apple trees can take a century or more to exist. Which of these species do you think might be more easily affected by a climate in which the temperature continues to rise? The one that takes longer to reproduce, of course. And which one is generally considered to be more desirable and valuable? The slow, slow apple, of course.

Apple Blossoms in May

Challenge kids to think of other examples of species that fit this speed and adaptability vs. value to humans dichotomy – there are lots of possible choices to examine…

As someone who has been sustainably managing landscapes for almost 2 decades I can tell you that I have seen this class of insects on the rise. Might this be one more canary in the coal mine? Time will tell. What entomologists do not know is whether or not the insects which normally keep them in check will grow rapidly with them. In my own vegetable gardens, orchard, and greenhouse I have seen over the last decade more and harder-to-control pest outbreaks. Organic sprays that have traditionally worked well for me seem to be losing their potency, requiring me to up-the-ante.

We are in the midst of a great experiment.

We as a society need to empower ourselves with the knowledge and tools that give us the ability to take back our food system.

We shall find out whether we are as adaptive as the multivotines or destined to be the univoltines.


ABOUT THE AUTHOR

Jim McSweeney

Jim is a certified arborist, certified horticulturist, licensed pesticide applicator (needed for the application of organic pesticides in MA) & a professional landscape designer with over 15 years experience. He is also the owner of Hilltown Tree & Garden LLC. Jim is on the faculty at the New England Wildflower Society, teaching courses on a diverse range of topics. He lives and works in Zone 5 (Chesterfield, MA) with his family. Once a month here on Hilltown Families you will find timely gardening tips, from a pro in the field, that can be easily used by both avid and novice gardeners, specific to Western MA.

[Photo credit: (cc) JKehoe_Photos/Ladybug & Aphid; Skunkworks Photogrpahic/Apple Tree & Dandelions]

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