As to bees - I'm sorry if you've been at this for X years and here's little old me in my only 3rd year of beekeeping getting smart with you, but I don't know that so I'll just go ahead and say it, maybe it's for the good.
- By the time oilseed rape which is usually the first crop to flower in zone 6a gets started, the overwintering bees should already have started developing. For those early stages hazel and pussy willow are great. They cover February and early March. In our locale they are considered essential. But possibly this is also influenced by the fact that we only keep Carniolans since Slovenia is where this strain comes from. Carniolans are known for extreme swings in cluster size - very small and low consumption in the winter and explosive development in the spring.
- Apart from usually not being there in the earliest spring, farm forage is also not particulary varied - there are not that many plants in a given year on the
local menu. A wide variety, especially of pollen sources, is a good thing.
Moving on - if a tree is listed as hardy, in my experience this usually relates to surviving a freezing winter. A tree with known good tolerance to various blues would be called "robust" or "healty". If the cultivar is actuall resistant / immune, not only tolerant, to certain problems, that would be listed explicitly, being an excellent thing.
However, also remember the saying that the difference between theory and practice is that in theory there's no difference, whereas in practice there is. For example, one of our apple trees is the cultivar Nela, an older release from the Czech breeding program [
http://www.ueb.cas.cz/en/content/station-apple-breeding-disease-resistance ] which concentrates on bringing together field resistance to apple scab and improved taste. You might have heard of Topaz - in Slovenia it's the standard of scab-resistant, market quality apples. Well, one of the previous generations is Nela. In our orchard it's been great until a really wet year came along. It has had scab that year and it's been so-so ever since. And that's not an early childhood problem - it's an 8 year tree grafted on a seedling.
One apple cultivar that comes from the USA (or Canada?) seems to do particularly well here - Enterprise. The leaves stay in super shape, they are almost plastic. Sadly, its taste is not as super as its resistance to disease. It's a good apple and fit for fresh consumption after 3 weeks or so after picking. But if the taste were of the same standard as leaf health it would be out of this world. Also, Goldrush (Coop 38 ). William's Pride is also good; the leaves can look spotty but it doesn't get critical. It's somewhat given to watercore. I'm told more potassium would prevent it. Again, I'm hobbled here by the fact that the US and continental Europe have a largely different set of cultivars. Try this as a starting point -
http://msue.anr.msu.edu/news/a_review_of_apple_scab_resistant_varieties_for_commercial_growers and
http://www.orangepippintrees.co.uk/ for descriptions of many many cultivars including disease behavior.
In our orchard we have 3 lines of disease-tolerant/resistant apples:
- the American line: Enterprise, Goldrush, William's pride
- the Czech line: Nela, Rajka, Topaz, Ametyst
- the "old traditional Slovenian" line which means old German / Austro-Hungarian: Kronprinz Rudolf, Winterrambour, Rote Sternrenette, Batulenapfel, Prinz Albrecht, Purpurroter Cousinot
All of them are doing well except Nela as described; all are eating apples but are also fine for cooking / cider / vinegar. Preferrence is a matter of taste. For me, William's pride, Goldrush, Topaz, Kronprinz Rudolf and Prinz Albrecht are the standouts. I like apples in which both the sugar and the acid are strongly represented.
I don't know about cedar apple rust since, I believe, we don't have that around here. (Doesn't mean we're in apple growing heaven... Especially on flat low lying land where cold air likes to accumulate if it decides to have one last go in late spring.)
Fireblight is primarily a pear thing. Presumably Harrow Sweet is immune. We have the cultivar but not the disease - anywhere in the orchard - so I can't talk about experience. There's an insect that causes damage which eventually starts looking very much like fireblight, causing many false alarms.
Nut trees - you're in 6a so look for late blooming walnut cultivars. Some new French ones are excellent (Fernor for example).
In peaches, apart from selecting a curl-resistant and tasty cultivar (in my limited experience nothing is 100% immune *and* tasty but it's possible to get tasty + almost-truly-resistant, such as for example Benedicte), try to go for the ones that come true from seed. Peach trees are, in the poetic words found once upon a time on Gardenweb, "just not that excited about life" and might need replacing often. In Europe there are many local historical cultivars that have all these properties - resistance, taste and coming true from seed. I think I read once that of the US cultivars, Amsden comes true? Try it out and let me know since it's also started to be available over here recent.
Actually, you can take that as a general remark: if possible get a fruit tree that grows on its own roots. It's a bonus for vigor and health. It's a super sized bonus with peaches and apricots but it's a plus with all trees.
This completes my brain dump for now
BTW, what I know of New Jersey is that it exists. So I've been relying on your being in zone 6a as the main guiding point. Hopefully I haven't spend many words on things that totally don't apply to your situation. And as you go on developing your land and accumulating experience, remember, it's good to be good, but it's great to be lucky.