Category Archives: Plants

Pathogen-Reducing Compost

January 14, 2020

Benefits of compost are widely known: 1) enhances water holding capacity, soil structure, organic matter, drainage, and nutrient holding capacity of soil, 2) provides a source of beneficial microbes, 3) decreases both inputs (to your garden) and outputs (from your garden), a plus for sustainability, and, 4) reduces fertilizer and pesticide use.

However, did you know that well-made compost has the ability to reduce pathogens and enhance plant growth?

An extensive research study of 120 bioassays, involving 18 composts and seven pathogens, found positive disease suppression in 54 percent of the treatment combinations, a disease stimulating effect only rarely (3%), and no effect in 43 percent of the treatment combinations (Termorshuizen et al., 2006).

Other studies have shown that “backyard” compost is superior to the commercial product, possibly due largely to richer and varied starting materials, plus a more relaxed thermophillic phase (wherein temperatures are sanitizing but lower than those recorded in commercial composts). Backyard composting presented higher counts of bacteria, actinomycetes, and fungi. It also shows higher percentages of isolates producing extracellular enzymes which allow the breakdown of tough substrates, including polyethylene!

Although the studies show the efficacy of compost, no one has come up with the perfect recipe or management strategy to combat a particular soil pathogen. This is because the soil microbial community is so dynamic and complex. Quality control tools are also lacking.

Still, we know from research that microbial organisms in compost are able to reduce pathogens my means of: direct antagonism (antibiotic production and direct parasitism), predation, competition for resources, enzyme production, and, induced resistance in plants – through signaling networks and hormones.

Sun, Jan 19, 2-4. work party
Sat, Feb 1, 10-12, Work Party
Sat, Feb 1, 1-3, PRUNING CLASS
Sun, Feb 16, 2-4, Work Party
Sat, Mar 7, 10-12, work party

Note, compost is more effective as a pathogen prevention method than when used as a management strategy for some existing soil or plant pathogen. Elaine Ingham, veteran soil scientist, points out that compost and soil should be colonized with a sizeable and diverse body of microbes. “There are only so many seats at the table. If the good guys are already there, the bad guys are turned away.”

Image Credit: Zosia Rostomian & Jill Banfield, Creative Services, Berkeley Lab

Who are these microbial actors who play such a beneficial role in a garden? It’s bacteria, fungi, protozoa, and nematodes, none of which can be seen with the naked eye. There are millions of microbes in a gram of compost and hundreds of thousands different species. In fact, it’s the diversity of players that makes good compost a pathogen suppressor.

Commercial composts can differ widely in their suppressive effects and can vary as to which pathogens are diminished. However, commercial composts can meet the objective of adding organic matter to the soil. In contrast, the special compost that you can produce with backyard composting, using correct temperature, moisture, aeration and curing processes, will yield a compost that you can use sparingly as an inoculum throughout your garden. It will jump-start good soil biology and maintain nutrient cycling, creating an environment fostering pathogen-suppressive soil.

Next up – A template on making a thermal compost.
Also, watch the FreewayEstates.org calendar for a hands-on thermal composting class, coming in early May, 2020

Ruth

References:

Hadar & Papadopoulou, 2012 – Suppressive Composts: Microbial Ecology Links Between Abiotic Environments and Healthy Plants DOI: 10.1146/annurev-phyto-081211-172914

Vaz Moreira et al., 2008 – Diversity of Bacterial Isolates from Commercial and Homemade Composts. DOI: 10.1007/s00248-007-9314-2

Welgarz et al., 2018 – Microbial diversity and nitrogen-metabolizing gene abundance in backyard food waste composting systems DOI: 10.1111/jam.13945

Fayolle , L., 2006 –  Eradication of Plasmodiophora brassicae during composting of wastes
https://bsppjournals.onlinelibrary.wiley.com/doi/full/10.1111/

Cangelos, G, 2014, Dead or Alive: Molecular Assessment of Microbial Viability
https://aem.asm.org/content/80/19/5884 DOI: 10.1128/AEM.01763-14

How to Guard Against Leaf Miners

November 16, 2019

Joan here. I have been volunteering at FECO since the beginning of time. Recently, in my writing class, the instructor charged us to write a set of instructions for how to do something. Here goes!

Leaf miner larvae were infesting the Swiss chard I was trying to grow in the FECO raised beds. They ruined the leaves, inserting themselves between skins of the leaf blades and laying their itty-bitty eggs on the backs.

“What to do?” I asked Sue Hartman, who had helped me plant the seeds in April. “Cover the

Sun Nov 16, 2-4, Work Party
Sat Dec 7, 10-12, Work Party
Sun Dec 15, 2-4, Work Party
Sat Jan 4, 10-12, Work Party
Sun Jan 19, 2-4, Work Party

Swiss chard with Reemay, a light cloth that lets air and water in,” she said, and showed me how to do it:

First, cut off all and destroy all the infected leaves. I lost about 1/3 of them.

Second, find five one-inch bamboo posts, four of the same length, and one slightly longer for the middle of the plot.

Then, so the posts don’t pierce the Reemay, duct-tape and secure eight-ounce yogurt cups upside down on each post.

Drive holes into the four corners of the plot, and one into the center of the plot to hold the poles.

Cut the Reemay generously and carefully lay it over the protected stakes.

Trim the Reemay where it gathers over the corners and apply two two-inch binder clips at each corner.

Set stones on the edges of the plot, so the Reemay won’t blow off. Presto: A leaf-miner-proof-plot!

Joan Davis

P.S. For more information on leaf miners, visit this website:
https://extension.umn.edu/yard-and-garden-insects/leafminers

Are Those Freckles?

October 18, 2019

Not Freckles. Dimples? Not dimples. Bitter pit. It’s a bothersome disorder, common in  Honeycrisp apples. In the cells of this apple, there is more air space and more pores than in normal apples. The pits are manifestations of clumps of dead cells. The scanned photo of an apple shows fewer veins in the calyx (bottom) of Honeycrisp, which is why bitter pit tends to show up near the bottom.

Lee Kalcsitis, WSU Assistant Professor, Tree Fruit Physiology, writes: Honeycrisp naturally have bigger cells than most apples. That seems to predispose them to structural degradation associated with bitter pit. And trees that have access to extra water allow those cells to grow even bigger, while limited water during the later stages of fruit growth can keep the fruit cells a little smaller and more stable.

Sun Oct 20, 2-4, Work Party
Sat Nov 2, 10-12, Work Party
Sun Nov 17, 2-4, Work Party
Sat Dec 7, 10-12, Work Party

Calcium binds up pectins which translates to the glue that holds the cells together. That glue helps to resist bitter pit but it breaks down as the apples mature. The glue breaks down faster in fruit with less calcium.

However, calcium is one of the most immobile nutrients. When leaves pull up water from the roots, calcium also travels up. Since the leaves transpire more water than fruit, they get the bulk of the calcium. (Cork spot in pears and tomato end rot have the same issue in that the calcium may be in the soil but it’s not necessarily in the fruit tissue where it is needed.)

The strategy for commercial growers is to withhold water, without stressing the tree, and apply calcium sprays. Still, results of these techniques are highly varied. Crop load is also an important factor because, if there are a small number of fruit, they will be large and more susceptible to bitter pit. On the other hand, too many apples can cause fewer blooms the following season.

My strategy: eat them when they are ripe! (Storage time increases the pitting.)

Ruth

additional resources:
Calcium Absorption during Fruit Development in ‘Honeycrisp’ Apple Measured Using 44Ca as a Stable Isotope Tracer. L Kalcsits, G van der Heijden, M Reid, K Mullin – HortScience, 2017

Advanced sensing techniques for analysis of elemental concentrations associated with bitter pit in apple. Zúñiga CE, Jarolmasjed S, Kalcsits LA, Sinhal R, Zhang C, Dhingra A, Sankaran S*. 2017. Postharvest Biology and Technology 128, 121-129.