Does it really make a difference? While black plastic mulch is the overwhelming choice of growers, there are many color options that can impact crop yield and quality that are worthy of consideration. Many of the recommendations in the article that follows are from work done at the Penn State Rock Springs Research Farm in the 1990’s and 2000’s. During that time extensive testing was conducted on the effect of mulch color in various vegetable crops. Some generalities that can be made regarding color are: 1) silver repels aphids, 2) blue attracts thrips – blue sticky cards are best for thrips scouting so are often used in greenhouse tomato production and 3) yellow attracts insects-growers can purchase wide rolls of yellow sticky tape for insect and mite trapping in general indoor production. There appears to be some reduction in disease pressure with crops grown on specific colors.
Tomato – This crop appears to respond more to red mulch compared too black with an average 15% increase in marketable fruit yield over a 3-year period. There appears to be a reduction in the incidence of early blight in plants grown on red mulch compared to plants grown on black mulch. When environmental conditions for plant growth are ideal, tomato response to red mulch is minimal.
Pepper – This crop appears to respond more to silver mulch compared to black with an average 20% increase in marketable fruit yield and fruit size over a 3 year period. Lowest yield of marketable pepper were harvested from plants grown on either white or light blue mulch at this location. Pepper plants grown on green IRT had similar marketable fruit yields compared to plants grown on black. The response to silver is likely to be at least partially due to keeping aphids at bay.
Eggplant – This crop appears to respond more to red mulch compared to black with an average 12$% increase in marketable fruit yield over a 2 year period. Greatest response of eggplant to red mulch observed when plants were grown under stress conditions (temperature and water). There may be varietal response of eggplant to the use of dark plastic mulch.
Cantaloupe – This crop appears to respond more to green IRT or dark blue mulch compared to black with an average 35% increase in marketable fruit yield over a 3 year period. Lowest yield of marketable cantaloupe were harvested from plants grown on either white or black mulch at this location.
Cucumber – This crop appears to respond more to green IRT or dark blue mulch compared to black with an average 35% increase in marketable fruit yield over a 3 year period. There was a difference in yield response between an open-pollinated and hybrid variety. Lowest yield of marketable cucumber were harvested from plants grown on yellow mulch at this location.
Summer Squash – This crop appears to respond more to dark blue mulch compared to black with an average 20% increase in marketable fruit yield over a 2 year period. Lowest yield of marketable zucchini squash was harvested from plants grown on yellow mulch at this location.
Onion – This crop appears to respond more to several different mulch colors including red, metalized silver, and black compared to no plastic mulch with an average 24% increase in marketable bulb yield over 8 varieties. There was a significant difference in yield response between specific onion varieties and mulch color. This trial evaluated red onions, but other onion types should respond similar to the red onion varieties grown in this mulch trial.
Potato – This crop appears to respond more to several different mulch colors including red, metalized silver and black compared to no plastic mulch with an average 24% increase in marketable tuber yield. While there was no significant difference in yield response between the mulch colors, potatoes grown on the metalized silver had the highest marketable tuber yields, coolest soil temperature and least number of Colorado potato beetle adults. There was a significant difference in yield response between specific potato varieties and mulch color.
By way of summarizing all of this information, black plastic mulch is still the universal color. However the use of red mulch benefited tomatoes, silver mulch works best on peppers, and dark blue had a significant impact on cucumbers. Working around silver mulch on bright sunny days requires dark sunglasses. Black mulch can directly improve crop earliness in early plantings, while white can help to keep crop roots cooler for summer plantings. Much of the information contained in this article is excerpted from research done by Michael Orzolek and William Lamont, Penn State Department of Plant Science.
- Steve Bogash, Vegetable Crop Advisor