Using a shader to oscillate plant

Hi everyone.

I'm new in Unity and I trying to develop my first mini video game for Android.

I imported the BananaPlant prefab and its texture and its shader (its name is Nature/Tree Soft Occlusion Leaves) provide from the Island Demo projet and I use them in my game.

Now, I try to make a shader to oscillate the BananaPlant in my game. But unfortunly, my shader doesn't work.

I know I have to use the initial shader to keep the texture and its renders and make a vertex program using the sine finction to oscillate the plants. But I have no idea the correct way to do this.

currently, my shader looks like that :

 Shader "Custom/MovePlants" {
 Properties {
 }
 SubShader {
 
     UsePass "Nature/Tree Soft Occlusion Leaves"
     Pass {
     
         CGPROGRAM
         #pragma vertex vert
         #pragma fragment frag
         #include "UnityCG.cginc"
 
         struct v2f {
             float4 pos : SV_POSITION;
             float3 color : COLOR0;
         };
 
         v2f vert (appdata_base v){
             v2f o;
             o.pos = mul (UNITY_MATRIX_MVP, v.vertex);
             v.vertex.y += sin(_Time * 2.2 + v.vertex.y);
             return o;
         }
         
         half4 frag (v2f i) : COLOR {
             return half4 (i.color, 1);
         }
             
         ENDCG
     }
 } 
 FallBack "Diffuse"

}

I using a fragment program because apparently I must a both of vertex and fragment program for a OpenGL ES 2.0 target but I really don't know what I can put in the body of this program.

Please Have anybody got a solution for my trouble ?

Thanks for your help.