Raw fruits and vegetables are approved for kosher use. However, since Kashrus precludes the ingestion of insects inspection of produce in which infestation is common, must occur prior to use. In plants that process large quantities of produce e.g. packaged salads commonly found in supermarkets, kosher certification is really a testament that the washing system employed rids the product of all pests.
Canned fruits and vegetables which are processed on equipment used exclusively for kosher productions, are acceptable and may easily be certified. Similarly, products derived from fruits and vegetables, e.g. purees and pastes, baby foods, juices, jams and jellies with the exception of grape, generally present little problem in getting certified.
One caveat would be agricultural products coming from the land Israel which have their own unique kosher requirements and are acceptable only with reputable supervision.