I would agree with not using any systemics on any edible fruits/plants (Many of them are now being tied to honeybee colony collapse too. The bees IMO are just the canary in the coal mine). For most trees you need nothing to seal a pruning wound, the tree will take care of it. This assumes that healthy wood was removed, and done properly so that the growth area at the base of the limb was left intact. Look online for some diagrams of how to do this. If you must use something, the old black oil based tree wound compounds are still available. As for borers, there are quite a few options for killing them once they are in a tree, from running a wire up their hole, to injecting predatory nematodes or insecticides in the hole. General prevention is harder. One source claims that white interior latex mixed with spackle (sheet rock joint compound) to s spreadable mix, painted on the base of the tree works. Others claim fine gravel at the base of the tree will deter borers. And their are traps for the adult borers too.

I think they are fascinating trees--Poncirus. The first time I ever the tree was in Longwood Gardens in Pa.. They are hardy were I am but no one seems to grow them and I never see them being sold at garden centers. As I understand it, botanists classify them either as true Citrus or a very close relative. Their leaves remind me of the Kaffir lime (though the Ponciris has an additional third lobe). I As I said, I have mine containerized because I tread the thought of what I'd have to go through if I ever wanted it removed--those thorns are NASTY. Then again, I'd imagine they make for great security fences--and they're deer resistant I believe. Keep in mind though that the tree is deciduous.

This is what I found. My thoughts...if in doubt, DON'T USE IT! Butterflies often lay their eggs on plants, and when those eggs hatch the little caterpillars will stay and feed on the plant as they grow. Caterpillars can be controlled using a common organic insecticide known as Bacillus thuringiensis, or Bt. Bt is a naturally occurring bacteria that causes caterpillars to stop eating and die. There are several varieties of Bt that can be used, depending on the type of caterpillar you’re after, including one specific to Colorado potato beetle larvae and another for corn earworms. Bt is also effective against tomato hornworms, the little green worms that like broccoli and cabbage, and bagworms. Bt should be applied at 1-2 week intervals to kill succeeding generations of insects. Gardeners with butterfly gardens should avoid using Bt on their plants because it is harmful to butterfly caterpillars. However, Bt is completely harmless to pets and people. Diatomaceous earth is another natural insecticide that may be used on a variety of insects. Diatomaceous earth is a fine powder that feels like talc, but it is actually the fossilized skeletal remains of small aquatic critters called diatoms. It is completely harmless to people and pets, but when soft-bodied insects come in contact with it, the tiny sharp edges of the diatoms lacerate the insects, making them dehydrate and perish. Apply diatomaceous earth in the early morning or evening when the plants are wet with dew, which will make the powder stick to the surface of the leaves and doom the insects that walk through it. Diatomaceous earth can be used to control ants, aphids, beetle grubs, box-elder bugs, flea beetles, those nasty little earwigs and many more insects. It’s also safe to use on houseplants, and can even be sprinkled on the ground to control slugs. http://gardening-articles.com/controlling%20insects%20organically.htm Outdoor insects affected by Diatomaceous Earth include:- ants, caterpillars, cut worms, fleas, ticks, cockroaches, snails, slugs, spiders, termites, silver fish, lice, mites, flies, centipedes, earwigs, aphids, beetles, fruit flies, lemon tree borer, borers, thrips, pysllid etc.. http://www.greenurbanliving.co.nz/diatomaceous-earth-for-natural-insect-control/ And from the manufacturer: (look half way down where I bolded, italicized, and starred) While Red Lake Diatomaceous Earth works well to kill most crawling insects, there are a few species that DE is known to be especially effective against. These include: • Ants • Bedbugs • Fleas • Cockroaches • Silverfish • Flour Beetles • Darkling Beetles • Grain Beetles • Carpet Beetles • Colorado Potato Beetles • Caterpillars ******* • Earwigs • Centipedes • Millipedes • Sowbugs • Pillbugs • Spiders • Crickets • Slugs http://www.absorbentproductsltd.com/diatomaceous-earth-insect-list.html

Did your trees receive adequate water this year? Were any lawn fertilizers applied near the tree? Was the tree mulched to reduce water evaporation?