Permethrin is one insecticide that can be used on 4 lined plant bugs.  Others include insecticidal soap and pyrethrins that must contact the insect to kill them and do not have any residual activity.  Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.
Be sure that the vegetable you wish to treat is listed on the label of the pesticide you intend to use. Also be sure to observe the number of days between pesticide application and when you can harvest your crop.
More info on permethrin and 4 lined plant bugs in the attached links:
http://npic.orst.edu/factsheets/PermGen.html
https://extension.umn.edu/yard-and-garden-insects/four-lined-plant-bugs
https://www.canr.msu.edu/news/four_lined_plant_bugs_attractive_with_a_big_appetite
https://hort.extension.wisc.edu/files/2014/11/Four-Lined-Plant-Bug.pdf