Should I prune it or is there something else I can try?
The tree is stressed. Has there been a drought situation or site disturbance? Instead of watering every two days, which encourages shallow root development, water once a week during dry periods.
Here are some articles that should help pinpoint the stress to your tree. You can prune out the dead limbs except for the central leader. Also consider a call to your local cooperative extension agent for help.
https://www.gardeningknowhow.com/ornamental/trees/ginkgo/ginkgo-tree-care.htm
https://extension.tennessee.edu/publications/Documents/SP686.pdf
http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Rendition-3345/unknown
I need to know before I attack with a chain saw?
Be sparing. Gingko have adapted to be slow growing, and don't heal well from intentional damage. They are very strong trees, and don't get heavily damaged in nature very often.
You should only go about this while it is dormant. This will be when sap content is low, and will give the tree its best chance to heal over while in Winter.
This article will give you more information on the general care of Gingko Trees: https://www.gardeningknowhow.com/ornamental/trees/ginkgo/ginkgo-tree-care.htm
Does anyone knows what are these grey colour substance on the ginkgo tree?
That is one of many Scale insects. You will have to remove what you can, manually, then spray with an insecticide.
Since they seal themselves to the plant, insecticide alone will not suffice.
Here are some articles for more information:
https://www.gardeningknowhow.com/plant-problems/pests/insects/control-plant-scale.htm
https://www.gardeningknowhow.com/plant-problems/pests/insects/what-is-armored-scale.htm
https://www.gardeningknowhow.com/plant-problems/pests/insects/what-is-soft-scale.htm
Why would that be and is there anything wrong with the tree and can it be salvaged.
It is hard to say from the photo, but the first step will be to test the soil for nutritional deficiencies and pH swings. Once test results are optimal, then you can begin diagnosing issues that are not related to deficiencies.
Here are some articles that will help:
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/soil-ph-plants.htm
https://www.gardeningknowhow.com/ornamental/trees/ginkgo/feeding-ginkgo-trees.htm
https://www.gardeningknowhow.com/ornamental/trees/ginkgo/ginkgo-water-requirements.htm
https://www.gardeningknowhow.com/ornamental/trees/ginkgo/how-to-prune-a-ginkgo.htm
The tree is about 6years old and 15 ft tall. This year is has only few leaves that are big and numerous leaves that are tiny and curled out. What could be the problem. And how can it be helped.
Our 30 year old ginkgo tree has some roots protruding above ground. Can we cut these off so our lawn mower won't?
It is not recommended. Cutting or shaving tree roots can affect the stability of the tree plus leave it open to insect and disease invasion.
Here is more:
https://www.gardeningknowhow.com/ornamental/trees/tgen/shaving-down-tree-roots.htm
https://www.gardeningknowhow.com/ornamental/trees/tgen/problem-tree-roots.htm
Hello, How do I distinguish between male and that other sex, Ginkgo? Do you know where I can source two types of seed, Actaea Racemosa and Epimedium Grandiflorum. For me, in the jungles of Africa, it is difficult to get any seed types, except 7 year old Lettuce seed, which does not germinate. So, I will appreciate positive answers, please.
Here's an article with information about how to determine the sex of a gingko tree:
https://www.gardeningknowhow.com/ornamental/trees/ginkgo/ginkgo-male-vs-female.htm
Our best suggestion for sourcing seeds from your location is to search online gardening retailers. We are only a garden information site and do not make specific product or vendor recommendations.