God created the universe and the laws it operates with. That does not mean God creates plagues.
For example, God created gravity. Is that a blessing or a curse? It is a blessing in one way. We don't float off into space. That's a good thing. However if you jump off a tall cliff, you could injure or even kill yourself. That can be called a curse. You might even say God killed you since He created the gravity that killed you.
Is drain cleaner a curse? It could be for a child if he drinks it. If he obeys his parents and doesn't drink it, he'll grow up and come to know how drain cleaner can do good things. Is electricity a curse? It could be for a child who disobeys his parents and decides to play with it. If he grows up, he will find electricity is useful.
Do not say that the devil created plagues. He can't create anything. The only power the devil has is when he can talk people into doing things. Remember Eve? Do not say that God created plagues or curses. He created the laws that can bring about plagues and curses, depending on what people do.
Deuteronomy 11:26 Behold, I set before you this day a blessing and a curse;
27 A blessing, if ye obey the commandments of the Lord your God, which I command you this day:
28 And a curse, if ye will not obey the commandments of the Lord your God, but turn aside out of the way which I command you this day, to go after other gods, which ye have not known.
try reading ur bible, book of exodus!!