Debbie Arrington

Seeds: Expected stink bug invasion has gardeners on alert

Brown marmorated stink bug eggs are found on the back of a Chinese pistache leaf in midtown Sacramento. The pest lays its eggs in a distinctive pattern like little strings of pearls.
Brown marmorated stink bug eggs are found on the back of a Chinese pistache leaf in midtown Sacramento. The pest lays its eggs in a distinctive pattern like little strings of pearls.

Those tiny pearls meant problems.

As gardeners tended their plots at the Fremont Community Garden, they reached up the tall sunflower stalks, carefully turned each leaf over and looked for bug eggs.

They were looking for one pest in particular – the brown marmorated stink bug. It lays its shiny eggs, each no bigger than the head of a pin, in a distinctive pattern like minute strings of pearls. Sunflower leaves are a favorite nest.

Much to their disappointment, the gardeners found plenty of “pearls.” So much for a rest from this pest.

“Our trap counts in midtown are higher than the last two years,” confirmed Chuck Ingels, environmental horticulture adviser for the UC Cooperative Extension. “They’ll be back in force in late summer.”

Compared to the past two summers, it had seemed like the stink bugs were taking a break. To Sacramento gardeners who have battled these bugs, the lull felt like a return to normalcy. Tomatoes were ripening nicely, without dreaded attacks that left them looking like deflated red balloons hanging on the vine.

Brown marmorated stink bugs – or BMSB – suck the juice out of vegetables, fruit and flowers. That makes these Asian natives particularly destructive. First seen in Pennsylvania in 2001, BMSB have migrated to at least 40 more states, hitchhiking on trucks and cars to move to new feeding grounds.

Meanwhile, gardeners, farmers and horticulturists are still trying to learn more about this foul-smelling pest – and how to stop it. When squished, stink bugs live up to their name, emitting a sulfuric odor.

Considered a warm-weather threat, BMSB got an extremely early start this year with the first egg masses spotted by researchers April 18 in midtown Sacramento. That early start allowed stink bugs to produce two, maybe three generations in a single season instead of just one.

Ingels has been keeping careful track of BMSB since the first stinkers were sighted in midtown in 2013. (Learn more at StopBMSB.org.) He recently presented an update at Rutgers University in New Jersey to the national BMSB Working Group, a task force organized to combat this destructive pest.

“They were all quite surprised by the mid-April egg finds, which are by far the earliest in the country,” Ingels said.

Mature stink bugs hibernate over the winter, usually emerging with warm weather in late spring.

“I thought I’d surprise them early, so I put traps out Feb. 9 and checked a couple days later and there were already some in the traps,” Ingels said. “I caught many more in the following week or two and beyond.

“We started catching substantial numbers of nymphs (immature bugs) in the traps May 9, a full three weeks earlier than the previous two years,” he added.

Trapping takes some bugs out of circulation. So do trap plants such as sunflowers and horseradish, another favorite BMSB nesting place. Fortunately, at least for people, stink bugs move relatively slowly and can be easy to catch. The nymphs, or young stinkers, can’t fly. Bug hunters such as the Fremont gardeners squish them on sight or knock them into buckets of soapy water, where they die quickly.

“I think more BMSB will be coming shortly,” Ingels said. “The adults emerging now are from eggs laid in April and May by the overwintering adults. As the nymphs molt into adults, they’ll shortly start mating and the second-generation nymphs and adults will appear in August.”

The hotter the weather, the more stink bug sightings, Ingels predicted. “I’ve figured out that the best time for good photos is when it’s over 100 degrees in August. They love the heat, or, more accurately, they need to take in lots of liquid when it’s hot and dry.”

So in the weeks to come, expect to see more stinkers. Be ready to squish them.

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