Q:

How to stop a toddler disturbing mother's eating

My wife often eats on kotatsu- low table. My 1year 8 months old will drop everything to disturb her eating- grabbing at the plates of food. He is not hungry and won't play with me. He will disturb her eating at normal table too. He rarely disturbs me. How do you manage this? 

A:

On Edit: If you do not have a relationship with your child except for a few minutes a day (This is not a judgment -- this happens when one parent works and the other is the primary caregiver.), then it is also natural that your child wants the more familiar (to him) parent. Try removing him to an activity he enjoys that can become a special time for just the two of you -- like perhaps his bath.
If you have not tried redirection, I suggest it. Prepare in advance. Have an activity ready and 'change the subject'. After a few days, your toddler may forget the game. If you need a further explanation, please let me know.
You can also be firm and say no. You do not need to raise your voice, but you can gently and firmly move him to another seat. I prefer redirection because he is playing, probably not trying to be naughty.
It is time to start allowing him to make some choices. Use choosing language and if he has been told "No.", you can then tell him that the consequence of this choice is to sit away from his mother.
I've decided to add information about redirection and choice to this answer.
The Redirection Technique
Redirection is a parental behaviour management technique that helps to prevent  injuries, and promotes desired behaviours. It furthers learning and exploration while reducing punishment and negativity.
In a 'nutshell', the parent changes the subject and redirects the child's attention to another activity when possible. When it is not possible, redirection is a positive way to interact and help the child accomplish or act in the desired way. There are no idle threats or extra words added. We do not add that "You could break your leg."  It is possible to talk about those worries at other times, but not in the moment.
LINK
Choice and 'Choosing' Language
As you child matures and has a few words and is able to point or grab for a wanted item, this is the time to allow them to make choices.
Choices are really important. They help to build respect, to invite cooperation, to develop problem-solving skills, and it
takes advantage  of a child's normal requirement for some control. 
I suggest the parent chooses two items that are acceptable to him or her and then allows a real choice to the child. The parent selects two shirts or two food items or two activities and then the child selects the one they prefer. You can add a third selection in time, but in the beginning -- keep it simple. Then use the Choosing Language. "Which shirt do you want, the red or the blue?" When the child selects by pointing or even a word you respond, "You chose the red shirt. Good for you." This teaches that their choice was good, that this shirt is the red one and it teaches them/reinforces the choosing words.
You expand the use of choices to other areas. "I am sorry that you chose to break your toy*." The consequence is that now that toy is broken and must be used that way (if it is safe) or they do not have it. This means the consequence is natural and you never need to be angry. *This is simply what happens when a toy is intentionally broken.
LINK Psychology Today

