Why does my custom Entry display a line across the bottom?

I have created a custom Entry control by inheriting from Entry. When I use this in a grid, I'm getting a line across the bottom as can be seen in the attached screen shot. How can I remove it?

The code is as follows:

CONTROL

    public class StandardEntry : Entry
    {
        public StandardEntry()
        {
            this.BackgroundColor = Color.Transparent;
            this.TextColor = Color.White;
            this.FontSize = 16;
            this.HeightRequest = 40;
            this.VerticalOptions = LayoutOptions.Center;
            UseValidation = false;
        }

        public bool UseValidation { get; set; }
    }

XAML

                <Grid Padding="50, 0" VerticalOptions="Center" Grid.Row="1" BackgroundColor="Maroon">
                    <Grid MinimumHeightRequest="150" VerticalOptions="Center">
                        <Grid.RowDefinitions>
                            <RowDefinition Height="0.25*"/>
                            <RowDefinition Height="0.25*"/>
                            <RowDefinition Height="0.25*"/>
                            <RowDefinition Height="0.25*"/>
                        </Grid.RowDefinitions>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="50"/>
                            <ColumnDefinition Width="200"/>
                            <ColumnDefinition Width="50"/>
                        </Grid.ColumnDefinitions>
                       <local:EmailEntryControl Grid.Column="1" x:Name="ctrlUser" BackgroundColor="Blue" />
                        <local:StandardEntry Grid.Row="1" Grid.Column="1" x:Name="Password" Placeholder="{local:Translate PasswordPlaceholder}" IsPassword="true"  BackgroundColor="Lime"/>
                        <Button x:Name="btnLogin" Grid.Row="2" Grid.Column="1" HeightRequest="37" BackgroundColor="#00a8ab" TextColor="White" Text="{local:Translate LoginButton}" BorderRadius="0" VerticalOptions="Center" Clicked="OnLogin"/>
                        <Button x:Name="btnForgotPassword" Grid.Row="3" Grid.Column="1" BackgroundColor="Transparent" Text="{local:Translate ForgotPasswordButton}" TextColor="#80868C" VerticalOptions="Start" Clicked="btnForgottenPassword_Clicked"/>
                    </Grid>
                </Grid>![](https://us.v-cdn.net/5019960/uploads/editor/1b/a2785eteomi1.png "")