According to the Territorial Seed Co. (which catalog also offers red plastic mulch--but no holes in theirs so I had to punch my own....), research by USDA and Clemson U. showed an increase in production of from 12-20% in early tomatoes compared to black mulch. Technically known as SRM-Red mulch. Strawberries apparently benefit also. I live in a very difficult area for tomatoes, beset by summer marine fog, and I have to say that the red mulch didn't do much for me--except to grow bumper crops of oxalis underneath. What does help (not surprisingly) is finding the warmest spot in my yard, using black plastic to warm the soil and carefully trimming off diseased leaves as soon as I spot them--oh, and choosing very "early" varieties.

I noticed this this year as well - normally I just use regular thick (4mm) black plastic as mulch, this year I did half my beds with regular, and half my beds with IRT, just to see what the difference is. So far for exactly this reason - I much prefer just the regular, thicker, black plastic mulch. We'll see as the summer goes on if it appears as if the IRT gives any benefits over the regular plastic, but so far the regular stuff is winning. As far as what to do about it... not sure, I just pull them as they come through, otherwise I'm letting them grow in the hopes that they will just cook as mid summer arrives. We'll see.

Last year I mulched with aged wood chips under a Sugar maple, under two concrete bird baths, and in a couple garden paths, to help keep the weeds under control. I used newspapers under the tree and pizza boxes in the other places. Then laid down 1-2 inches of wood chips aged about 3 years. (I got them for free from the town tree trimming). Many more weeds grew back under the tree through the newspapers than the cardboard. Here is what the mulch looks like under one of the bird baths where I used the pizza boxes - these were laid down kind of overlapping about a year ago and as you can see there aren't even any weeds growing through yet.

I always put down a layer of newspaper (and wet it) before I mulch - about 6 to 8 sheets - making sure to place it a few inches from the plants. This helps keep down the weeds growing through the mulch. The newspaper breaks down of course, so you have to do this every year (or perhaps twice, if you mulch in spring and in fall) before putting down new mulch. If your area is small enough, you could rake up the mulch and lay some paper down and remulch. Otherwise, as mxk says, use a rake or "claw" (just what the heck IS the name of that tool? :) I can't live without mine!) and cultivate lightly and the weeds should come out easily. Just yesterday I finally had some time to do some work in the vegetable garden. It's been very dry here, and I thought my newly planted cukes and tomatoes needed some mulch. I didn't get to shred as many leaves as I usually do last fall (my mulch of choice), and had nothing on hand, so I cut up old leaf bags, ones which the bottoms had rotted on anyway (I re-use these things till they literally fall apart), laid that down, and then mulched with shredded paper. Doesn't look too pretty, but one is so blinded by the sun boucing off the white mulch no one can look for long anyway, lol!