Filter row with one specific string value in R

I have a dataframe in R as below:

Fruits
Apple:1
Apple:4
Bananna    
Papaya    
Orange, Apple:2

I want to filter rows with string Apple as

Apple:1
Apple:4 

I tried using dplyr package.

df <- dplyr::filter(df, grepl('Apple', Fruits))

But it filters rows with string Apple as:

Apple:1
Apple: 4     
Orange, Apple:2

How to remove rows with multiple strings and filter rows with one specific string (in this case Apple)?

To only filter out Apple, you can use the regex anchor ^ to specify the start of a string, followed by "Apple:" and any digits. Finally close the search pattern with $, which specifies the end of a string, where the above pattern could happen more than once. The search will return FALSE if you have any other characters in between the string.

library(dplyr)

df %>% filter(grepl("^(Apple:\\d+(, )?){1,}$", Fruits))

   Fruits
1 Apple:1
2 Apple:4

EDIT:

Assuming, based on comments made by OP, that strings should be filtered where the only fruit mentioned is Apple and assuming further that the list of non-Apple fruit is manageable, you could do this:

df %>% 
  filter(str_detect(Fruits, '^(?!.*Banana|Orange).*Apple'))
                   Fruits
1 Apple, Apple:2, Apple:7

Here, we use negative look-ahead (?!.*Banana|Orange) to assert that Banana or Orange must not be present in the string together with Apple

Data:

df <- data.frame(
  Fruits = c("Orange, Apple:2", 
             "Apple, Apple:2, Apple:7", 
             "Apple:2, Banana:10"))