ants on apple tree ????????????????

You've got an aphid infestation - ants will manage them like we do cattle because they want the honeydew they excrete. Spray with a pesticide for the aphids, don't use a systemic one as its a fruit plant, and keep treating it. Or washing up liquid in water, though I've no idea of the ratios.

Thanks Bamboo, Will these horrible aphids go on any othere plants, as acouple of my tomatoe an strawberry plants have died over the past couple of week .

Yes of course they will - they're hungry! Some plants are more prone than others, though, and it's usually blackfly rather than greenfly that infest food plants, though you can get both. Try growing English marigolds next year - blackfly love those and will choose them above your tomatoes!
By the way, browning leaves, especially if it starts at the edges and works in, and is crispy, could very well mean drought - watering not good enough.

If you don't want to use pesticides, put a grease band or something else round the trunk will which trap or stick the ants.