With the wheat harvested, tomato growers will be on the alert for stink bugs. Stink bugs feed on a very wide range of plants, moving into tomato crops once fruit are present, as other food sources dry up or are harvested.
They are difficult to monitor, as they can hide deep in the crop canopy. According to Dr. Celeste Welty, a vegetable entomologist at Ohio State University, it is best to scout for them towards evening. Both nymphs and adults cause damage. In fact, researchers have found that when the nymphs are present, more damage seems to occur.
The photos below, from Ontario cropIPM, will help you identify stink bug nymphs and adults.
See Ontario cropIPM for the full stink bug photo gallery.
From mid-July and through August, Dr. Welty recommends examining the tomato fruit for damage (rather than searching for the insects, as you would do earlier in the season). Check 40 locations per field, inspecting 10 fruit at each location. Use a record sheet to keep track. If you don’t have the resources to monitor all your tomato fields this intensively, focus your most intensive scouting on fields near wheat or small grains as they are ripening and being harvested. Nearby hay fields being cut could also be of concern.
With this monitoring, you can determine the need to treat the field for stink bug and the need for follow-up treatment. Dr. Welty suggests a treatment threshold of 0.5 to 1% fruit damage. This means that of the 400 fruit inspected per field, you found two to four damaged fruit. Stink bug seem to prefer feeding on green fruit, although without a good monitoring program, the damage might not be noticed until fruit are ripe.
Commercial tomato growers can refer to OMAFRA’s Vegetable Crop Protection Guide for treatment options. Good coverage into the crop canopy is necessary.
An invasive stink bug species, the brown marmorated stink bug, is becoming established in Ontario, and is starting to be seen on farms – in traps and on wild hosts. Visit ontario.ca/stinkbug to learn more and if you suspect you are seeing this species, try to photograph or capture one or more, so identification can be confirmed, and notify OMAFRA at 1-877-424-1300.
Ontario cropIPM photo credits:
- Herb Pilcher, USDA Agricultural Research Service, Bugwood.org
- Megan Asche, BugGuide.net