1800 x 1800 is not very effiicient in terms of VRAM. You should be working with power of two sized textures - 2, 4, 8, 16, 32, 64, 128 .... 1024, 2048.
Your 1800 square image will actually use 2048x2048 pixels in VRAM, with over 200 pixels wasted in each direction. If I was you, I'd shrink it down to 1024, then stretch it up to the size you need. The texture should end up filtered and smoothed when you stretch it, and in motion you probably won't notice the reduced resolution.
Bear I mind that I often think I know what I'm talking about only to be proven wrong by more knowledgable folks, so take this with a pinch of salt.