- Author: Anne E Schellman
Why Not Move Firewood?
By bringing wood from home, you can unknowingly spread invasive pests and diseases that can harm trees. This includes dry, aged, and seasoned wood. Once you arrive at your destination, pests can emerge from the firewood and spread to the trees and forests where you camp. Invasive and hard-to-control pests kill several million native trees every year, causing environmental and economic problems.
Did you Know?
New infestations of tree-killing insects and diseases are often found in campgrounds and parks as a result of campers moving firewood!
This trip, tell your friends and family why you aren't bringing firewood. For more information about firewood pests and resources for finding good firewood, visit the Don't Move Firewood web site. To learn about many of the invasive wood-boring pests and associated diseases and problems, visit the UC IPM web site.
First posted on August 30, 2021
Anne Schellman has been the Coordinator for the Stanislaus County Master Gardeners since 2018.
/h4>/h4>[From the Summer issue of the UC IPM Retail Nursery & Garden Center News]
When you use firewood in the great outdoors, be aware that moving firewood can transport tree-killing insects and diseases. Find out more at the following resources:
- “Don't Move Firewood,” a campaign created by the Nature Conservancy, is an informational site aimed at the general public. You can also print posters, brochures, and other handouts.
- The California Firewood Task Force website offers California-specific information about invasive species and firewood.
- UC IPM Invasive and Exotic Pests webpages contain links to relevant information on current invasive pests in California.
- The California Oak Mortality Task Force website focuses on sudden oak death, a disease affecting many woody plants
- Author: Jeannette E. Warnert
Holtz has been pioneer in ag burn alternatives throughout his 26-year-career with UCCE, and going back still further on his family almond farm near Modesto. Beginning in the early 1990s, Holtz and his father experimented with chipping almond prunings instead of burning them, long before air quality regulations required wide implementation of the practice.
When Holtz heard a four-acre stone fruit orchard was slated for removal at the UC Kearney Agricultural Research and Extension Center in Parlier seven years ago, he took the opportunity to study the impact of grinding up and incorporating the whole trees before planting a new orchard.
“When an orchard is pushed out, there is about 100 tons per acre of organic matter that is taken out of the system,” Holtz said. “My previous research showed positive results from organic matter. Our San Joaquin Valley soils are typically critically low in organic matter. Why remove it if it is good for the soil?”
A local company was contracted to grind up and incorporate the trees using an Iron Wolf, essentially a 50-ton rototiller, in selected research plots. (See video below.) At first, Holtz was concerned that the Iron Wolf left “firewood-sized” chucks of wood in the plots, pieces much larger than he had studied before in his wood chipping research. But the worry turned out to be unfounded.
In comparison plots, trees were pushed together and burned. The ashes later were spread out on the soil. All the plots were fertilized at the normal rate.
Over the years, Holtz has compared laboratory analyses of the nutrients available to the trees in the soil and nutrients in the leaves. Initially, the burn treatments had more nutrients available. The second year, nutrient availability was about equal. Leaf analyses in the third year began to show a higher level of nutrients in the leaves of trees growing in the area where old trees had been ground up and incorporated. In the fifth and sixth years, Holtz didn't see any differences in growth, but data suggests slightly higher yields where the trees were ground up.
“A lot of growers feared if we added that much carbon to the soil, the microbes breaking down the organic matter would tie up nitrogen and the trees would be stunted,” Holtz said. “But the research results suggest that the trees will do just as well or better in the presence of the additional organic matter.”
One potential barrier to grinding up old trees is the cost. Holtz said the Iron Wolf treatment cost $800 per acre and it is not readily available in the San Joaquin Valley. Burning is nearly cost-free for the farmer, but contributes to air pollution and is highly regulated.
Another option for almond farmers preparing to remove an orchard and replant is employing a large tub grinder, which leaves much finer particles of wood than the Iron Wolf, is more readily available but more expensive. Holtz said he hopes that growers in the future will receive incentives to grind up their orchards and incorporate the wood chips into their soils before they plant a second- or third-generation orchard.
“I'm trying to find growers who would be interested in trying this approach to conduct on-farm research,” Holtz said.
In the video below, the Iron Wolf grinds up whole trees and incorporates the organic matter into the soil:
An initiative to enhance competitive and sustainable food systems is part of the UC Division of Agriculture and Natural Resources Strategic Vision 2025.
- Author: Lorin Lilikoi Lima
Pests and diseases such as the Goldspotted Oak Borer, Emerald Ash Borer, and Sudden Oak Death can travel on firewood long distances, endangering previously unexposed areas, and potentially causing catastrophic die offs of trees and plants with little or no natural resistance to the intruder. As pests and diseases are often not easily identified on firewood, it is best to assume all wood is a potential risk. Choosing to buy and burn local wood is an easy solution, assuring you aren’t part of the problem. By keeping wood within its area of origin, you can be sure you are keeping any pests and pathogens already present in the area local as well.
The health of your forests, campgrounds, and your own backyards depends on you. For more information, go to the Don’t Move Firewood website at http://www.dontmovefirewood.org/.
Photo Source: Lorin Lima, UC Cooperative Extension - San Diego
- Author: Richard Smith, Vegetable Crop and Weed Science Farm Advisor
In recent weeks a number of samples have come into our office of lettuce plants that have the following symptoms: stunting, yellowing outer leaves and occasionally with wilting during the afternoon (Photo 1). The symptoms superficially resemble Lettuce Dieback caused by Tomato Bushy Stunt Virus, but Steve Koike has not detected this virus in these plants. Affected plants also typically have roots that are no longer than 1.5 to 2.0 inches long (Photo 2). Upon careful examination of the root tissue, it can be seen that the roots once extended further, but were burned off at this point in the soil. The death of the tip of the root was not caused by a disease. In nearly all cases that I have seen so far, this problem occurs on heavier clay loam to clay type soils.
Based on the uniformity of the depth of the point of death of the tap root, it appeared that this problem was associated with an application of fertilizer. Given that fertilizer is a salt, it is capable of damaging young root tissue. These symptoms are distinct from ammonium toxicity which damages lettuce root tissue by the toxic action of the ammonium on root tissue (see Blog entry April 26 by Steve Koike). Ammonium toxicity causes distinct symptoms on affected roots; however, these symptoms are distinct and appear to be caused simply by salt burn of fertilizer. (Photo 3).
To confirm this hypothesis, last summer I worked with a cooperating grower to recreate these symptoms on lettuce. I used a pipette to inject fertilizer 0.5, 1.0 and 2.0 inches from the base of lettuce plants, and 1.5 inches deep in the soil; all applications were applied at the thinning stage. We observed that there were higher levels of plants with the tap root burned off in the plots where the fertilizer was applied 0.5 inch from the plant than farther from the plant. These results are not surprising, but the question is why do these symptoms occur at all? Tractor applied fertilizer is spaced 2-3 inches from the plant to avoid fertilizer burn. One possible explanation on how the fertilizer may reach the lettuce roots has to do with soil type. As I mentioned the problem seems to occur on heavier soils; these soils are more prone cracking which can permit liquid fertilizers to flow a short distance towards the seedline during the application. If the material flows close enough to the taproot of the young plant, then it can burn the tap root at the level of injection in the soil. This explanation may explain why the problem occurs at more or less a uniform depth in the soil and why affected plants are scattered in the field (e.g. scattered plants or 2-3 affected plants next to healthy plants) (Photo 4).
Photo 1: Typical symptoms of plants with fertilizer burn on the roots
Photo 2. Plant with the tap root burned of 1.5-2.0 inches down in the soil
Photo 3. Close up of the burned of tap root (note that the remainder of the root tissue is healthy)
Photo 4. Pattern of the problem in the field