As I sweated through another triple-digit day, this one thought buoyed my gardening spirit and made me feel a little less stressed:
Stink bugs hate high heat.
At least, that appears to be the case as Sacramento’s local population explosion of brown marmorated stink bugs has significantly slowed.
As a Sacramento gardener, this is huge. An Asian import, the dreaded BMSBs had hit midtown hard, devastating tomatoes and peaches. With no natural predators to control them locally and impervious to most pesticides, these little primeval monsters stick their tongues into juicy fruit and vegetables, then suck them dry.
At the Fremont Community Garden, several members abandoned growing fava beans and other stink bug favorites. The sight of deflated tomatoes, hanging on their vines like burst red balloons, became heart-breakingly familiar. Stung repeatedly by stink bugs, the garden’s pears and apples became inedible.
The abundance of stink bugs at Fremont Garden attracted University of California researchers, who have carefully monitored BMSB numbers since the bugs’ first local appearance in 2013. Not just a bane for backyard organic gardeners, the threat of these particularly voracious bad bugs is very real for the state’s agricultural industry. BMSBs eat apples, pears, cherries, peaches, plums, figs, melons, corn, beans, tomatoes, peppers, berries, wine grapes – almost anything with botanical fruit.
In 2014 and 2015, the BMSBs kept building their empire, producing baby bugs by the hundreds. After gorging themselves, they ventured into homes and offices, literally creating a great big stink wherever they went.
Then, came a breakthrough. When temperatures sky rocketed, stink bug numbers went down.
According to UC Cooperative Extension farm adviser Chuck Ingels, “2016 was heading toward being a far larger population than 2014 or 2015. But then in late July, there were seven days at or above 100 degrees F, including two days at 104, which was followed by a full month of near complete trap shutdown and the late summer bump was lower than 2014-15.
“This year, BMSB started off at historic lows (since 2013),” Ingels said. “Then, the June heat wave hit and the population that was there plummeted. Most of our trap counts for the last few weeks have been at or near zero, whereas there’s usually a peak in June.
“So, it seems to be proof that temperatures over 100 for extended periods reduces the population – probably especially eggs and nymphs,” Ingels said.
Ingels and UC Davis entomologists are further researching the connection between high heat and stink bugs. That includes lab experiments where BMSBs were exposed to extreme temperatures. One hour at 113 degrees killed all bugs, but mortality also was high over 104 degrees.
Besides helping Sacramento gardeners, this heat connection also could play a role in stopping stink bugs from entering North America or spreading elsewhere. Export containers could be heat treated before shipping, killing stink bugs and protecting crops.
That’s all good news for sweaty Sacramento gardeners like me. It may be hot, but our tomatoes will be fine.