Not all stink bugs are bad and few do crop damage, but the Brown Marmorated Stink Bug (Halyomorpha halys) has been found in Napa, and this one is a different story.
The Brown Marmorated Stink Bug (BMSB) was accidentally imported to the United States in the late 1990s. Since then it has hitchhiked and spread across the country, leaving a wake of vegetal destruction.
Unlike most stink bugs, BMSB has proven to be a devastating pest to agriculture crops, with research reporting that many backyard gardeners in the Mid-Atlantic states lost all their susceptible crops.
“All their susceptible crops” packs quite a wallop. The list of over 160 known hosts includes peaches, nectarines, apricots, plums, soybeans, tomatoes, corn, apples, pears, legumes, grapes, pecans, cucumbers, pole and bush beans, peppers, raspberries.… you see the problem. As distressing and long as the list is, expect new crops to be added as stink bugs discover their taste for them.
The BMSB does damage by sucking moisture from fruits, vegetables, trees and shrubs. It does not like leafy greens, root crops, onions or grasses, but otherwise, it likes what we like. These gadabouts can take one nip out of each fruit they pass. Unfortunately, just a little damage makes most fruits or vegetables unmarketable or inedible.
BMSB nymphs and adults pierce fruits and vegetables with sucking stylets, causing fruit to appear sunken, misshapen or discolored. The broken skin increases susceptibility to secondary pathogens. And attacks at the early fruiting stage can cause plants to abort their crop altogether.
Local problems can become regional problems quickly if these stink bugs are not controlled when found. MSB multiply quickly and can fly up to 70 miles a day.
Adults measure about ?-inch long. They are marbled brown and distinguished from other stink bugs by tiny yet distinct differences, such as white stripes on their antennae. A stink bug in your garden, a neighborhood child and a magnifying glass could become a teachable moment this summer and fall. If you find a bug you think may be a BMSB, put it in a jar and bring it down to the Agricultural Extension office at 1710 Soscol Avenue in Napa.
All stink bugs are fast and can see you coming. They go through five different stages of development, and knowing how they look at each one can help you find and destroy them.
After sheltering through the winter, adult stink bugs mate and lay barrel-shaped eggs in clusters in the spring. These are reasonably easy to see if you are looking. Detecting and destroying eggs and small nymphs at this stage is probably the easiest and most effective control. Wipe or spray eggs off.
Helping you at this stage are predators you might consider pests, such as earwigs. They eat stink bug eggs and help break down other components of your soil, too. Other natural predators of BMSB eggs include Asian lady beetles, pirate bugs, jumping spiders and spined soldier bugs. At the nymph stage, assassin bugs, praying mantis and lacewings join in. The “Stop BMSB” website is a terrific resource that shows all stages of the pest's development, what damage on different crops looks like and everything else you need to know about BMSB.
Fall is when you are most likely to see stink bugs congregating on outside walls, coming out of cracks around windows or doors or emerging from loose bark on trees. If you see them on structures, check University of California's Integrated Pest Management Pest Notes (http://ipm.ucanr.edu/PMG/PESTNOTES/pn74169.html0 for information on how to control them.
Properties near woodlands are often susceptible since BMSB naturally disperse from forests and wildlands. The bugs are often attracted to lights. If they congregate on your porch, move the light or set a trap to catch and destroy.
To trap stink bugs, fill a dish tub or bucket with water and detergent. Place it in a dark place or room and shine a flashlight into it. Bugs will be attracted to the water, and you can pour them out in the morning.
Some insecticides effectively kill BMSBs, but unfortunately, they kill the beneficial bugs in your garden, too. For that reason, the University of California recommends managing them other ways.
Hand-picking them is effective, if you can catch them. But then you need to squash them. Ew.
Probably the best way to deal with stink bugs is to avoid being attractive to them in the first place. Eliminate places for them to overwinter on your grounds, clean summer beds, pick up debris and cut back weedy corners and overgrown shrubs.
Do you want to become a UC Master Gardener of Napa County volunteer?
To obtain an application you must attend an information meetings. For dates, location and times, or to learn more about the program and volunteer commitment, see the U.C. Master Gardener of Napa County website.
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U.C.Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.