applyplugin: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/applyplugin - from package: ladspa

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/applyplugin - from package: ladspa-sdk

You may install the required package with command apt-get install {package}

Error in other languages:
applyplugin: bevel nie gevind nie
applyplugin: comandă negăsită
applyplugin: comando não encontrado
applyplugin: commande introuvable
applyplugin: command not found
applyplugin: käsku ei ole
applyplugin: không tìm thấy lệnh
applyplugin: komanda nerasta
applyplugin: Kommando nicht gefunden.
applyplugin: kommandot finns inte
applyplugin: komut yok
applyplugin: nie znaleziono polecenia
applyplugin: níor aimsíodh an t-ordú
applyplugin: no se encontró la orden
applyplugin: no s'ha trobat l'ordre
applyplugin: opdracht niet gevonden
applyplugin: parancs nem található
applyplugin: perintah tidak ditemukan
applyplugin: príkaz nenájdený
applyplugin: příkaz nenalezen
applyplugin: команда не найдена
applyplugin: командата не е открита
applyplugin: 命令找不到
applyplugin: コマンドが見つかりません