Got a little black lead or two on my kieffer pear here in NY. Been wet, Been wanting to spray for aphids for almost 2 weeks. Raining every day though.
Here's a list from cornell
https://blogs.cornell.edu/applevarietydatabase/disease-susceptibility-of-common-apples/
Fireblight isn't a big of a probem here in NY as in Texas. However, if you have regular access to your property it seems watering your trees during drought times helps alot. I put some 2.5 gal water jugs with a 1/8" hoe and rock in it, seems to water better than hosing it. Some like it, some hate it. But when it's dry, the tree needs water. When water is low, nutrients are low. I add a mild dose of miracle grow when things are particularly dry by me.
Freedom is a overall very resistant tree. Perhaps one of the most resistant overall on any variety. Grows up to zone 7. Might need more though.
Orange pippin, has a good tree selector catalog program. Went with high resistant to fireblght and zone 8, king david came up. Moderatly resistant added alot of varieties like sundance, triumph, freedom, enteprise, arkansas black. Zone rating doesn't always tell the story. For us northeast folk, the tree will grow, but apples might not make peak maturtiy / flavor. In your case in texas, got to keep an eye out for chill hours. There's a hormone that the tree uses to determine if winter is over. If you do not have enough cold days, certain trees may not flower at all, or well. Even though it says your ok in your zone.
Find the best fruit tree varieties for your garden - by pollination group, picking season, usage, disease resistance, origins, and many more attributes.
www.orangepippintrees.com
When I think I want a certain tree, I look up what cummins nursery has to say about it. Seems to have the most complete info about a variety.
I am doing pretty well with what I have at my zone 5 home. But, 2 trees I want you might be interested in NY 414-1 and Sundance. Sundance is talked out alot on here, disease resistant version of goldrush. Although goldrush issue I beleive is cedar apple rust, so goldrush might work for you. NY 414-1 is a cross between liberty and macoun. Family loves macouns, thats why I want it. Sundance / goldrush is well liked o this site. Bonkers might be a good one for you too, cross between red delicious and liberty. honeycrisp could be one for you too.
Fruit Trees, Scions, and Rootstocks for Apples, Pears, Cherries, Plums, Peaches, and Nectarines
www.cumminsnursery.com