Looking over the search history on my blog it seems you have some questions! One that I encountered was from someone worried about their tomatoes. I love tomatoes so I am more than happy to assist.
The Question: “bugwitch, found these little black beetle-like bugs on my tomatoes. are they harmful to my tomatoes?”
Without a picture I can’t confirm, but my best guess based on my experience with my own tomatoes is you’re seeing Brown Marmorated Stink Bugs (BMSB) (Halyomorpha halys: Pentatomidae: Hemiptera) on them. Though they are brown as adults (hence their name) the nymphs can be black to blackish-brown with other accent colors. It really varies depending upon their nymphal stage (instar). BMSB’s are a pest of increasing concern. They have been found feeding on numerous types of fruits and vegetable crops such as apples, apricots, corn, grapes, nectarines and peaches, soybeans, and of course tomatoes, among others. As agriculture is a hugely important element of our health of our economy as well as our citizens, keeping these critters under control is becoming a huge deal.
Brown Marmorated Stink Bug 4th Instar nymph Rutgers University
BMSB 1rst instar nymphs and eggs Recently emerged. UC Davis
Thankfully, the damage caused by their feeding doesn’t kill the plant or make the fruit unusable; but it does make it less visually appealing. Pitting and scarring of the surface caused by their piercing/sucking mouthparts makes for a less attractive fruit. Because most consumers want a pristine items from the store, these affected items are not usable for direct sale. If it is a crop that can be turned into a secondary product this allows the farmer to recover some of their investment. But, this means a decrease in expected annual income. This isn’t a big deal for your small home garden, but when you have 40 acres of apples and can only recover half of your usual income due to pitted fruit, you’re not going to be a happy farmer.
BMSB’s on tomato
BMSB external damage to tomato.
BMSB damage to apple Mouthparts pierce through apple surface and damage tissues below making fruit unsellable.
These critters are also well known pests of homes. With the changing season you’ll be sure to see them entering your home to find a nice space to hunker down for the winter. Here in Ohio they will be coming inside within the next month or so (October-November). However, you probably won’t see them in large numbers indoors until early Spring. Some stragglers will likely come out in mid-Winter as you heat/cool your home.
There are currently no really effective chemical methods for control. I meet people who are terrified to squish these critters. Why? “They’re STINK bugs! They’ll make everything smell horrible!”
No. Yes, they do have a “stink” gland but the chemical produced isn’t necessarily horribly smelling to us, but it is irritating to potential predators. The excreted chemical is quite similar to that which is produced in cilantro! To some, this may smell bad; to others, it’s just ‘eh.’
Not great for your tomatoes, will put little spots on it from their feeding, but you can eat them just fine.
Treatment? Not many options. Squish. There are also a number of researchers working on them. Maybe collect some and bring them to them. If you’re worried about them getting into your home, be sure to seal up every crack and crevice you can. Windows, screens, foundation, door jams, etc.
Ohio State Fact Sheet (Downloads)