I recentley found these small white things on my tomato plants. When I took a closer look I noticed that they were a small oval shaped worm with fuzzy white stuff all over them. I have never seen them move except when I scrape them off the plant. I have read several articles that have similiar descriptions to this insect but not any pictures that give me a posative id. I now have them on my orange tree and there are always ants crawling all over them.
Your photo is of mealybugs. They can be found on many different plants, tho I think the one on citrus is a different species than the one on tomatoes.
Mealybugs are covered with a white waxy coating.
Since they feed by sucking juices out of plants if you have a high infestation then they can damage your plants turning them yellow and causing the leaves to curl.
If they are only on a few leaves or branches, prune out those infested. Mealybugs are attracted to plants with high nitrogen levels and soft growth…so if you have fertilized heavily the plants are more prone to infestation.
For control you can try to hose them off. If that does not work then use a labeled insecticidal soap. It will break the waxy surface tension of the mealybug so it dries up and dies.
The ants are crawling on them to get to the ‘honey dew’…the droppings of the mealybug. The honey dew can also encourage sooty mold to form….leaving a blackish mold on the plant.