Hey there Matt in Hawaii.

I know that copper fungicides can be used on a variety of fruit trees prior to problems showing up as a preventative measure and that sometimes it can be used to prevent early blight in tomatoes. But for white mold, I think the typical advice is to completely remove the plant. But you don't say where the mold is showing up (stems? fruit? leaves?) I'm not sure if it really is white mold. It could be powdery mildew if it's on the leaves.

Anyway. I'm not sure how you're watering but if you're watering the whole plant and letting the leaves stay wet, then that will add to your woes. Try soaker hoses or watering only at the soil level. Also, it doesn't sound like air circulation is a problem, but if you have a lot of overgrowth that will hold moist air close to the plants, then a bit of pruning is a good thing.

You might want to try calling the University of Hawaii's Cooperative Extension office. They have a Master Gardener hotline in Oahu at (808) 453-6055. The Master Gardeners love questions like this and would be glad to help you out with appropriate advice for Hawaiian growing climates and conditions. More info is at: www.ctahr.hawaii.edu/ougc/master.asp.

Here in California, we've got some online information that *may* be applicable to growing tomatoes on Hawaii, but there are some notable differences in growing conditions between the two places.

Here's the University of California Integrated Pest Management website that's chock full o' handy info for growing in CA.

Pest notes on Powdery Mildew on Veggies: www.ipm.ucdavis.edu/PMG/PEST...7406.html

Tomato care: www.ipm.ucdavis.edu/PMG/GARD...mato.html

White mold: www.ipm.ucdavis.edu/PMG/GARD...mold.html

Okey doke. Hope that's somewhat helpful. Again, give those Master Gardeners a call. Hours are usually 9-12 Monday thru Friday.

Good luck!

Lara (your friendly California MG)