From Illusions, the Adventures of a Reluctant Messiah, Chapter 10 (excerpt from the freely-available online book):

The afternoon was quiet... an occasional passenger now and then. Time between I practiced vaporizing clouds.

I have been a flight instructor, and I know that students always make easy things hard; I do know better, yet there was I a student again, frowning fiercely at my cumulus targets. I needed more teaching, for once, than practice. Shimoda was stretched out under the Fleet’s wing, pretending to be asleep. I kicked him softly on the arm, and he opened his eyes.

“I can’t do it,” I said.

“Yes you can,” he said, and closed his eyes again.

“Don, I’ve tried! Just when I think something’s happening, the cloud strikes back and goes poufing up bigger than ever.”

He sighed and sat up. “Pick me a cloud. An easy one, please.”

I chose the biggest meanest cloud in the sky, three thousand feet tall, bursting up white smoke from hell. “The one over the silo, yonder,” I said. “The one that’s going black now.”

He looked at me in silence. “Why is it you hate me?”

“It’s because I like you, Don, that I ask these things.” I smiled. “You need challenge. If you’d rather I picked something smaller ...”

He sighed again and turned back to the sky. “I’ll try. Now, which one?”

I looked, and the cloud, the monster with its million tons of rain, was gone; just an ungainly blue-sky hole where it had been.

“Yike,” I said quietly.

“A job worth doing...” he quoted. “No, much as I would like to accept the praise which you heap upon me, I must in all honesty tell you this: it’s easy.”

He pointed to a little puff of a cloud overhead. “There. Your turn. Ready? Go.”

I looked at the wisp of a thing, and it looked back at me. I thought it gone, thought an empty place where it was, poured visions of heat-rays up at it, asked it to reappear somewhere else, and slowly slowly, in one minute, in five, in seven, the cloud at last was gone. Other clouds got bigger, mine went away.

“You’re not very fast, are you?” he said.

“That was my first time! I’m just-beginning! Up against the impossible... well, the improbable, and all you can think to say is I’m not very fast. That was brilliant and you know it!”

“Amazing. You were so attached to it, and still it disappeared for you.”

“Attached! I was whocking that cloud with everything I had! Fireballs, laser beams, vacuum cleaner a block high...”

“Negative attachments, Richard. If you really want to remove a cloud from your life, you do not make a big production out of it, you just relax and remove it from your thinking. That’s all there is to it.”

It is my belief and experience that anything in my perceived reality is permeable, mutable, relative and transient, therefore . . yes, reality creations can and are discreated. Our abilities to participate in this is rather limited at this stage of evolution of consciousness as humans. Nevertheless, all cultures at all times have created art/science/magic/religions/technology based on this premise, that we can and do create and discreate out of our own realities. An interestesting aspect of this is called the perinneal wisdom, or the mystery teaching, or the Hidden Agendas, or shamanic wisdom, etc. This business of creating/discreating reality is BIG, therefore there are many taboos and control and value issues around who, what, and when we get to practice these capacities and for whose benefit. The question and answers are multi-dimensional, and since they are, then we cannot apply the logic of linear thinking to come to any final "solution" or right answer. This issue will always be in process, according to our times and the levels of perception from which they arise. Norma P

It is my understanding that what we actually create is our experience. Our focus, our attention, our beliefs, our emotions are tools for attracting the necessary elements for a particular experience. But the vibrational alignment of who we are Being and of our Intention, are the most powerful source in attracting the desired experience. And our perception and attitude affects how we experience our experience.

As far as discreating physical objects, well, here are some observations. I am relatively certain that the trees in the park down the street are there whether or not I have ever been to the park to observe them.I pretty certain that the world was round even when nearly everyone alive thought it was flat. But thinking that it was flat, affected how they experienced the world and the decisions they made (don't go too far in one direction because you will fall off the edge.)

Then there is the issue of perception. Our brain filters out a large percetage of the input we receive from our physical senses, based on our beliefs, intentions, attention, etc. South American Indians were unable to see the Spanish ships just off the coast because they did not exist in their frame of reference.

Beyond that, our physical senses only pick up a narrow range of the wavelengths that we interpret as sound and vision. Our sense of smell is pitiful and we lack some senses that other creature possess. Just because we couldn't observe the magnetic field until we had specialized instruments, didn't mean it wasn't there. And even when we were unaware of its existence, it still protected us from the suns harmful rays.

Here's the dilemna about discreating another physical form - plants, animals and even rocks have a level of consciousness. I don't believe that we have the power or the right to annihilate consciousness. Even a plant responds to attention and care. That is consciousness connecting with consciousness.

Physical form is the result of consciousness, not the other way around. Consciousness is the source of creation. So perhaps all forms of consciousness have creative abilities on some level, even if in some physical forms, it is mainly subconscious or instinctual.

As far as parallel Universes, perhaps we are already moving between Universes with every decision, choice or observation that we make. We are just not yet evolved in our consciousness to recognize it.

Since everything already exists in the sea of probabilities, then perhaps we can learn to attract particular situations, opportunities, etc., into our field of conscious awareness.

But since we are all creators, with similar abilities of perception, and we have free will, then we are likely to be aware of our fellow human's creations to some extent. We are all in this together, like it or not.

We may not be able to discreate everything that it not to our liking, but we do create our perception, our attitude, our response, and our understanding of how we experience any creation. Resisting, denying or avoiding what is, only serves to energize and perpetuate it, and then we spend more time and energy avoiding, denying and resisting.

A window with a screen, does not resist the wind. The screen allows the wind to blow through and it is no worse for wear once the wind has exhausted itself. A window fitted with a glass pane may resist the wind for a time. But eventually it will shatter, and remain broken long after the wind has died down.

Here's the explanation a master teacher gave when one of his students asked him if he would cease to experience negative emotions once he reached enlightenment.

"Smoke still rises, just doesn't stick to the walls."

I assume we working from the basic premise that we created these things/situations in the first place by paying attention to things that we don't want? Taking your attention from situations we don't want can, in my experience on occasion, make them go away, simply by focusing on something else that I have wanted. Some situations just stop. Belief is the key to all of this.

However, when it comes to making physical objects go away or vanish, that is another matter, (no pun intended - or, wait, maybe it was!). Energy = all matter - yes and physical matter is created, and then deteriorates and becomes energy again. The rate of deterioration depends on the matter. In fact I seem to remember a table of half lives from chemistry at school many years ago - yes, here it is ... http://www.periodictable.com/Properties/A/HalfLife.html

How this relates to Quantum I don't know. Quantum theory, as I understand it, means that whatever we observe with expectation IS. If we remove our observation, does it cease to be? By extension, I'm guessing that our belief that we can make things cease to exist is on a par along with not believing we can grow new limbs or teeth if we lose them. In other words, we don't believe we can do it, or that things just go away, but if we did ...?

Interesting question, and one I shal ponder on for a while!

We can't remove them from existence, we can only remove them from our experience. there are many ways to that, the easiest would be - as stated in another answer - by stop giving attention. the trick here is that - at the same time - our awareness of their existence must be active. in other words, when our conscious is not giving attention, our subconscious must give full attention. you need to practice this to be able to use it at will, without any problems. once you master it, in most cases you will get instant results.

I believe the less anyone focus thoughts upon something the less it is here in your reality. Now it may be here in the physical but it want be relating to you in anyway pertaining to your reality.

You must put it out of your mind and forget about it. There use to be an old saying "out of site out of mind" you will think less on it if you don't see. Than finally you want think on it at all. My goodness the mean of that saying just come to me.

So, I am thinking if we don't think on something especially negative things that we can send it back to the cosmos of super consciousness to be turn into another thought form or whatever.

Yes, there is always and opposite to everything.

I have a "colorful" background. I have done many rituals for people (cast spells) all across the world. Distance and time really wasn't a barrier. I accomplished all of these creations and Dis-Creations just with my thinking. A ritual or spell is just using my thought / intent with connection to a particular goal (adding some strong energy as well)... to affect a change. For all practical purposes in my experience I have been able to dis-create and create for myself and others (some things are harder than others!) But I feel that we probably all have varying views on what dis-creation really means. I may have a more "lose" interpretation of it than most. But I believe, the opposite or dis-creation of a thing; is already living within that very creation. There it is...a dormant potential :)

This is how I define dis-creation: The disc-creation of a thing (physical or non-physical) is really the creation of it's vibrational opposite or compliment. lol We cannot destroy anything, only recycle it or transmute it or convert it into a more subtle or more dense form.

When you want to dis-create your habit of cigarette smoking, what you are actually doing is creating a stronger (thoughtform) of a "neutralizing vibration. Just trying to ignore it or take your mind off it with a nicotine patch is not going to be enough. That is just physical. You have to dis-create the bad habit or create a non-physical neutralizing antidote ? Depending on how perfect your tuning into the proper vibration...will determine if you quit for good, or relapse. But remember the potential was always there...layingt dormant until the right food (energy) hit it... such as your enthusiasm and determination. If I need do dis-create poverty, then what I am really doing is feeding a seed of prosperity, growing it and expanding it until "it" takes over.

I am focusing on bad habits and such, but this extends to less subtle (more physical) things as well. Depending on the practitioner's skill level :)

So to answer your question, I think that it really all depends solely on how you look at creation and dis-creation. From a purely intellectual sense I don't think you can dis-create anything. But from a more practical living here on earth sense (lol) ; I think we as humans have the ability to strongly influence our environment (physical and non-physical). But I feel that we can't help ourselves because we are creators...made in the image of The Supreme Creator.

Since we are being created constantly billions of times a second as 3 points of light, THEN, the opposite of reality creation would be to stop those quarks from spinning. I would have to talk to my own soul that is creating me about that. And I have, but still I am here. I seem to be here. No rock dropping on my head today. So..... it looks like I either turn myself into light, meaning this dense energy body I am disappears OR, I keep on saying there is no such thing as what is called physical. Looks like this is my mission. That physical word has got to go. It is to blame for every atrocity on this earth. If people believed/knew that they are eternal energy and light, would they "kill" someone? NO !!!!! Of course not. If people believed that they don't die, then would they "kill" themselves? NO ! If people knew we are all ONE energy and light, would there be cartels and wars and prisons and other tortures? NO, NO, NO ! What is reality? The desire to create with such intense vibrational focus that the electrical energy field soul is hidden within those quarks and atoms.