You could also do it with your SQL statement,
Code:
Using con As New OleDbConnection(My.Settings.waterConnectionString), da As New OleDbDataAdapter("Select crop, count(*) as cnt from groups group by crop", con),
dt As New DataTable
da.Fill(dt)
For Each row As DataRow In dt.Rows
Dim str As String = row("crop").ToString & " " & row("cnt").ToString
MessageBox.Show(str)
Next
End Using
I tested this on a table called "groups" and a field called "crop". You will need to use your own table and field names.