wheneverでタスク手動実行に失敗する。

 前提・実現したいこと

railsアプリケーションでwheneverで日時タスクを実行したいです。
コントローラのメソッドを追記し、そのメソッドを実行する、
もしくはタスクファイルをlib/tasks/直下に作成し、クラス、メソッドを作成し、それを実行する形で実装したいと思っております。

動作確認として、タスクを手動実行したところ、エラーが表示され、エラー内容としてはクラスがうまく読み込めていない旨のメッセージが表示されているのですが、つづりは合っており、対応に困っています。
何かご存知のことがございましたら、ご教示頂けると助かります。

 発生している問題・エラーメッセージ

[root@localhost Myapp]# bundle exec rails runner items_controller.mail_notice
Running via Spring preloader in process 3927
/usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/railties-4.2.10/lib/rails/commands/runner.rb:62:in `<top (required)>': undefined local variable or method `items_controller' for main:Object (NameError)
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/railties-4.2.10/lib/rails/commands/runner.rb:62:in `eval'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/railties-4.2.10/lib/rails/commands/runner.rb:62:in `<top (required)>'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:274:in `require'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:274:in `block in require'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:240:in `load_dependency'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:274:in `require'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/railties-4.2.10/lib/rails/commands/commands_tasks.rb:123:in `require_command!'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/railties-4.2.10/lib/rails/commands/commands_tasks.rb:90:in `runner'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/railties-4.2.10/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/railties-4.2.10/lib/rails/commands.rb:17:in `<top (required)>'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:274:in `require'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:274:in `block in require'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:240:in `load_dependency'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:274:in `require'
        from /Myapp/bin/rails:9:in `<top (required)>'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:268:in `load'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:268:in `block in load'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:240:in `load_dependency'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/activesupport-4.2.10/lib/active_support/dependencies.rb:268:in `load'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:59:in `require'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:59:in `require'
        from -e:1:in `<main>'
[root@localhost Myapp]# bundle exec rails runner Tasks::Mailnotice.execute
Running via Spring preloader in process 4174
/usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/railties-4.2.10/lib/rails/commands/runner.rb:62:in `<top (required)>': uninitialized constant Tasks::Mailnotice (NameError)
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/railties-4.2.10/lib/rails/commands/runner.rb:62:in `eval'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/railties-4.2.10/lib/rails/commands/runner.rb:62:in `<top (required)>'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/railties-4.2.10/lib/rails/commands/commands_tasks.rb:123:in `require_command!'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/railties-4.2.10/lib/rails/commands/commands_tasks.rb:90:in `runner'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/railties-4.2.10/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/gems/2.3.0/gems/railties-4.2.10/lib/rails/commands.rb:17:in `<top (required)>'
        from /Myapp/bin/rails:9:in `<top (required)>'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:59:in `require'
        from /usr/local/rbenv/versions/2.3.7/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:59:in `require'
        from -e:1:in `<main>'

 該当のソースコード

/config/schedule.rb

# Use this file to easily define all of your cron jobs.
#
# It's helpful, but not entirely necessary to understand cron before proceeding.
# http://en.wikipedia.org/wiki/Cron

# Example:
#
# set :output, "/path/to/my/cron_log.log"
#
# every 2.hours do
#   command "/usr/bin/some_great_command"
#   runner "MyModel.some_method"
#   rake "some:great:rake:task"
# end
#
# every 4.days do
#   runner "AnotherModel.prune_old_records"
# end

# Learn more: http://github.com/javan/whenever

# ログ出力先ファイルを指定
 set :output, 'log/crontab.log'
# ジョブ実行環境を指定
# set :environment, :production
# set :environment, :production


# [例] 1分に1回
 every 1.minute do

 # bash コマンドの実行例
 command "echo 'hello, whenever world!'"

 # コントローラのメソッドを呼び出し
 runner "items_controller.mail_notice"

 # タスクを呼び出し
 runner "Tasks::Mailnotice.execute"
end

/lib/mail_notice.rb

class Tasks::mail_notice
  def self.execute
    SampleMailer.send_when_limit.deliver
  end
end

更新、動作確認の出力

[root@localhost Myapp]# bundle exec whenever --update-crontab
[write] crontab file updated
[root@localhost Myapp]# crontab -l
# Begin Whenever generated tasks for: /Myapp/config/schedule.rb at: 2018-05-29 13:25:56 +0900
* * * * * /bin/bash -l -c 'echo '\''hello, whenever world!'\'' >> log/crontab.log 2>&1'

* * * * * /bin/bash -l -c 'cd /Myapp && bundle exec bin/rails runner -e production '\''items_controller.mail_notice'\'' >> log/crontab.log 2>&1'

* * * * * /bin/bash -l -c 'cd /Myapp && bundle exec bin/rails runner -e production '\''Tasks::Mailnotice.execute'\'' >> log/crontab.log 2>&1'

# End Whenever generated tasks for: /Myapp/config/schedule.rb at: 2018-05-29 13:25:56 +0900

app/controllers/items_controller.rb

class ItemsController < ApplicationController

 before_action :authenticate_user


  def index


    # データを降順で表示する
     @items = GyomuDatum.all.order(created_at: 'desc')


    # 期限が迫っているデータを検索する

    # 1ヶ月前
    from  = Time.now.at_beginning_of_day
    to    = (from + 1.month)
    @items_1month = GyomuDatum.where(end_date: from...to)



  end

  def show
  end

  def new
    @item = GyomuDatum.new
  end

  def create
    # render plain: params[:GyomuDatum].inspect
    # save
    # @item = Item.new(params[:GyomuDatum])
    # @item = GyomuDatum.new(params.require(:GyomuDatum).permit(:manage_id, :category_id, :publish_corporation, :ip_address, :target_server, :start_date, :end_date, :comment))
     @item = GyomuDatum.new(item_params)
    # @item.save
    # redirect
    # redirect_to items_path

    if @item.save
      # redirect
      redirect_to items_path
    else
      # render plain: @item.errors.inspect
      render 'new'
    end
  end


  def edit
    @item = GyomuDatum.find(params[:id])
  end

  def update
   @item = GyomuDatum.find(params[:id])
#   pp @item
#   pp item_params

    if @item.update(item_params)
      redirect_to items_path
     else
      render 'edit'
    end
  end

 def destroy
   @item = GyomuDatum.find(params[:id])
   @item.destroy
   redirect_to items_path
 end



# cron用メール送信メソッド
 def mail_notice

 # メール送信実行
   SampleMailer.send_when_limit.deliver

 end


  private
    def item_params
      permits = [
        :manage_id,
        :category_id,
        :publish_corporation,
        :ip_address,
        :target_server,
        :start_date,
        :end_date, 
        :comment
      ]
      params.require(:gyomu_datum).permit(permits)
    end


end

 試したこと

 補足情報（FW/ツールのバージョンなど）

【環境情報】
・Apache
Server version: Apache/2.4.6 (CentOS)

・Rails
Rails 4.2.10

・OSバージョン
CentOS Linux release 7.4.1708 (Core)

・Mysql
mysql  Ver 14.14 Distrib 5.7.22, for Linux (x86_64) using  EditLine wrapper

・Ruby
ruby 2.3.7p456 (2018-03-28 revision 63024) [x86_64-linux]