<select onchange="SUGAR.email2.composeLayout.applyEmailTemplate('0',
this.options[this.selectedIndex].value);" id="email_template0" name="email_template0">

<option value="">-none-</option>
<option value="159a06ef-4d58-6eff-a969-52fdff05d328">Case Closure</option>
<option value="182641ab-44c0-719d-04b3-52fdffa2b2d2">Case Creation</option>
</select>

$(document).on('DOMNodeInserted', '#composeHeaderTable0', function(event) {
$("#email_template0 option[value='159a06ef-4d58-6eff-a969-52fdff05d328']").hide();
});

$(document).bind('DOMNodeInserted', '#composeHeaderTable0', function(event) {

$(document).on('DOMNodeInserted', '#composeHeaderTable0', function(event) {

$(document).bind('DOMNodeInserted', '#composeHeaderTable0', function(event) {
    if ($('#data_parent_type0').val() == 'Leads') {
    $("#email_template0 option[value='159a06ef-4d58-6eff-a969-52fdff05d328']").hide();
    }
});