I know that many soil-based fruits and veggies are checked for bugs. I assume that it may be primarily due to bugs that crawl on the ground or on the tree that causes this problem.
Is hydroponic produce also typically checked for bugs? Or, is there little or no concern regarding hydroponics as they are grown in the air, and usually in greenhouses. Maybe there is no concern of bugs crawling around, for some reason? (Flies and gnats, etc. can still enter the greenhouse.)
Hyroponically grown produce is not grown in the air, but in a medium such as rockwool with liquid either run through it, or that it sits in. Typically, this is done indoors (e.g. in a greenhouse), however, there is exposure to the outside world. There may be less opportunity for infestation, however,the possibility exists. Insects can get in. Unless there is specific certification as "bug free" produce, I would check for bugs.
[DANF editing citation:]
In addition to romaine and other types of lettuce, one can grow herbs such as cilantro, dill, and parsley. Herbs are especially prone to infestation, are difficult to check, and are not widely available to the kosher consumer as ‘certified insect-free’. The kit is helpful in controlling infestation for these varieties.
Hydroponically-grown vegetables (lettuce, herbs, etc.) sold commercially without kosher certification should be thoroughly checked since they grow under conditions unknown to the consumer.
The Star-K discusses the situation here: https://www.star-k.org/articles/articles/1121/hydroponics/
