Which companion plants affect the performance of green peach aphid on host plants? Testing of 12 candidate plants under laboratory conditions
Entomologia Experimentalis et Applicata
Want to deter aphids? Plant some rosemary throughout the garden, African and French marigolds work well too. A group of French researchers designed an experiment that tested how effective 12 different companion plants were at deterring aphids from infesting a garden. The researchers set up two rows of pepper plants inside 13 individual growing chambers (there were 12 companion plants treatments and one control treatment with no companion plant), and then placed adult female aphids on each plant. Then, the various companion plants were set in between the two rows of pepper plants and allowed to grow alongside each other. Each day, the scientists would count the number of adult females remaining on the pepper plants, and also the number of neonate nymphs (baby aphids) that were produced by the adult female.
During the 12 day experiment, the scientists found that the aphids were more likely to flee from the pepper plants that were near companion plants. The control pepper plants did not lose any aphids, as the bugs were happy in their companion-plant-free environment. They also found that rosemary, lavender, geranium, African marigold, and French marigold significantly decreased the numbers of aphids being reproduced on the pepper leaves. In the end, rosemary outperformed the other companion plants in both deterring aphids, and lowering their reproduction numbers. The scientists attribute this effect to the VOC, or volatile organic compounds, produced by the plants. The VOCs signal to the aphids that the vegetation in a certain area near companion plants is not suitable for rearing young, so encourages the bugs to search on for more reproduction friendly fields. It looks like a flat of rosemary will be on the planting list for this spring.
Effects of compost tea treatments on productivity of lettuce and kohlrabi systems under organic cropping management
Italian Journal of Agronomy 2014
In the sunny Mediterranean climate of Italy a group of agricultural researchers looked into the effects of compost tea on two different leafy green crops, lettuce and kohlrabi. The experiment used compost tea made from a thermophilic compost combination of artichoke, fennel, escarole residue, and wood chips. The scholarly gardeners foliar sprayed the kholrabi and soil-drenched the lettuce. What they found was, compost tea works. As compared to the untreated control, foliar sprayed lettuce increased total production by 6% (measured in harvested weight), and more importantly, increased the marketable heads of lettuce by 24%. The soil drenched kohlrabi increased its total production by a whopping 26%, and its marketable product by 32%. That's a lot of kohlrabi. Grazie to the scientists for their diligent work.
Dialing In The Compost Tea Recipe: A look at Brew Times, Water Temps, Dilution Rates, and Food Sources
The Improving physico-chemical and microbiological quality of compost tea using different treatments during extraction
African Journal of Microbiology Research 2015
A group of Jordanian scientists wanted to determine what conditions produce more microbes in an aerated compost tea. Four microbial groups were assessed: Total Bacteria, Nitrogen Fixing Bacteria, Actinomycetes, and Fungi. The researchers tested four different brew conditions: Water Temperature, Brew Time, Compost-to-Water ratios, and Food Sources. A basic compost and molasses recipe was used for all the experiments, with additional food sources added for the last experiment.
The water temperatures tested were 68F, 82F, 99F, and 113F. The bacteria grew best at the lower temperatures (68-82F), while fungus and actinomycetes grew better at the the warmer temperatures. Regarding brew time checked at 12, 24, 48, & 72 hours, all microbe populations increased as brew time lengthened. The amount of compost used per gallon of water was found to correlate directly with microbial counts, ie. the more compost, the more microbes. The researcher indicate that a 1:20 ratio (weight to volume) is most efficient, meaning that for every 20 gallons of water only 1 pound of compost is needed.
Lastly, and most interestingly, food sources were looked at. The four microbial food source inputs were: (1)Molasses, (2)Ammonium Nitrate, (3)Potassium Phosphate, and (4) a combination of those three. The results showed that (1)Molasses does contribute to a boost in all groups, though the (4)combination of food sources led to an even greater boost in total numbers and diversity. The treatment with only Potassium Phosphate drastically increased Nitrogen fixing bacteria, while it significantly lowered the total fungi counts. The highest amount of nitrogen fixers were found in the Potassium Phosphate treatment, which showed the lowest populations for the other three groups of microbes.
What do we learn from this? If you want microbial diversity, use diverse food sources, and if you want only nitrogen fixers, feed the tea with potassium and phosphate sources. Lastly, the researchers used inorganic food sources (Ammonium Nitrate, and Potassium Phosphate) in this experiment, we hope that the next time around they look at how organic sources of Nitrogen, Potassium, and Phosphorus affect microbial counts. Thanks to all the researchers out there doing the nitty-gritty work so we can grow happier, healthier gardens.
Antifungal effects of compost tea microorganisms on tomato pathogens
Biological Control 2015
It is becoming well documented that Compost Tea has fungicidal properties, and that those properties come by way of the microbes in the tea. Canadian agricultural scientists wanted to see which microbes were the most effective in control of two different tomato diseases, Botrytis and Alternaria. To do this, the research team identified 4 different bacteria known for having anti-fungal effects in a sheep manure compost tea (Advenella incenata, Aminobacter aminovorans, Bacillus subtilis, and Brevibacterium linens). The scientists were able to isolate the microbes, and then they ran several experiments with them.
In one experiment, the scientists simply grew the microbes on petri-dishes, and then placed actively growing fungal pathogens on the same dishes. They then looked to see how much the fungal hyphae were able to grow. They saw that the bacteria Brevibacterium linens and Bacillus subtilis were able to prevent fungal hyphae from growing at a rate three times that of the control. In another experiment, the scientists took tomatoes, poked holes in them, and inserted either Botrytis or Alternaria spores, and then immediately following washed the wound with a solution containing B. linens and B. subtilis, individually and combined. The results showed that the combination of B. linens and B. subtilis worked significantly better than using the two microbes individually. They also tested spore fungal spore germination, which was also reduced better by the combination of the two beneficial bacteria. This leads one to conclude that biological diversity in a rich compost tea is reason for the improved fungicidal effects.
Maize growth responses to soil microbes and soil properties after fertilization with different green manures
Applied Microbiology and Technology 2016
Are you cover cropping over the winter? According to a group of researchers in China, the type of cover crop is going to influence both your microbial diversity and your yield. Four types of green manure (a cover crop that gets tilled into the soil) were used in the experiment, Common Vetch, Milk Vetch, Vicia Villosa, and Radish. A soil plot with no cover crop was used as the control. The cover crops were seeded in the fall (October), tilled under the following May, corn was seeded right after, and then the corn was grown through the summer and harvested the following September. Upon harvest, the researchers collected soil from each of the treatments, then analyzed it for microbial content. They also collected ears of corn from the treatments and assessed yield characteristics.
The researchers found that Milk Vetch significantly outperformed the control and radish groups in yield, plant height, and cob weight. If fact, corn yield was increased by 31.3% as compared to the control. The Vicia and Common Vetch had slightly higher yields than the Radish and control group. The Radishes did not increase yield (explained by the fact the other treatments were legumes, which fix nitrogen, radish does not). On the microbial end of things, there were variations in types of microbes present in the different treatments. Several groups of bacteria were identified, though the most interesting finding was that the Milk Vetch showed a significantly higher amount of Acidobacteria, while the control had a higher amount of Proteobacteria. Acidobacteria are known to have disease fighting qualities which could have contributed to the increased growth. The Proteobacteria group contains disease causing organisms, as well as microbes that could potentially compete with crops for nitrogen.
The scientists also found that soil pH was lowered by the cover crops as compared to the control group. There was also an increase in the soil's organic matter content in all treatments. The Milk Vetch soil had significantly higher available Nitrogen and Phosphorus than both the control and Radish treatment. These factors would contribute to increased yield. The other treatments did show increases, though the results were varied and not always significant. This study teaches us that specific cover crops have influence on crop yields due to their influence on microbial and physical soil characteristics.
Identification of Diverse Mycoviruses through Metatranscriptomics Characterization of the Viromes of Five Major Fungal Plant Pathogens.
Journal of Virology, 2016
Fungal pathogens reduce total yields by an average of 10% annually, therefore new and effective ways of control are always of interest. A group of researchers from the Univeristy of Illinois evaluated the myco-viruses present in 5 common fungal plant pathogens. Myco-Viruses are simply viruses that infect fungi. The researchers were able to extract DNA and RNA from the fungal pathogens (which would have viral residual DNA/RNA fingerprints) and then compared what they found against a database of known viruses. They found DNA that matched a number of known viruses. Some of the viruses were encapsidated, meaning their DNA/RNA was packaged in a protein shell, allowing them to be transmitted outside the fungus. Because of their inherent hardiness, encapsidated myco-viruses have future potential for use as a fungicide. At this time, the researchers were not interested in their effectiveness in controlling fungal pathogens, rather they just wanted to identify the relations between known viruses and the newly found myco-viruses. Understanding lineage is the first step in developing a myco-virus for use in fighting fungal disease.
INM, it's the new buzz-acronym, and it stands for Integrated Nutrient Management. Similar to Integrated Pest Management, INM is a whole systems approach that looks to maximize soil fertility through the precise and coordinated use of fertilizer inputs. A conventional INM program uses both organic and inorganic fertilizers, along with bio-active inputs such as composts and worm castings and specific microbial inoculates. The goal of INM is to increase soil fertility and keep it sustained and sustainable.
Research is showing us that soils which are fertilized solely with synthetic chemicals become less productive over time. This decline has been attributed to secondary and micro-nutrient deficiencies, as well as a decline in microbial populations. Over-fertilization of soluble synthetic fertilizers can lead to leaching and environmental pollution. Integrated Nutrient Management works to solve these problems by encouraging a healthy and resilient soil microbiota.
As we are seeing in other articles posted to this blog, using Compost Tea is paramount when it comes to keeping plants disease free and abundantly productive. A farm or garden with a good INM program will have a compost tea brewer bubbling somewhere on site. That farm will also have years of healthy growth in its future.
Here are links to a few recent journal articles touting the benefits of a solid INM program:
Vermi-Compost Tea Production and Plant Growth Impacts
Biocycle Compost Research 2007
A team of Ohio State researchers undertook a series of experiments in order to assess a number of characteristics of vermicompost teas and their effects on plant growth. The most significant find was related to aerated versus non-aerated teas. They saw that Nitrate levels were higher in aerated teas. Nitrate is a form of Nitrogen that plants can more readily use. Also, microbial biomass and enzyme activity were greater in the aerated tea, indicating that the number of microbes and their metabolic activity levels were higher. In follow up experiment the brilliant Buckeyed scientists looked at how aeration affected plant growth. They ran trials on cucumber and tomato plants, some with aerated tea, some without non-aerated tea. The differences were drastic (click the Link Here to see pictures) and a significant effect was seen even at the lowest concentration tested, which was 1 gallon of tea in 20 gallons of water. Germination rate, leaf area, and plant height were all substantially increased through the use of aerated tea. It looks like if you're going to brew it, you should absolutely bubble it.
Mass spectrometric evidence for the occurrence of plant growth promoting cytokinins in vermicompost tea
Biology and Fertility of Soils 2014
A group of scientists in Singapore were interested in learning more about the growth promoting effects of vermicompost. In a very simple experiment they produced vermicompost using plant waste and chicken manure with two different types of worms, red wigglers and blue worms. They then collected the run-off (leachate, or tea as the researchers called it) from the vermicompost bin and then analyzed the liquid with a mass spectrometer, which allowed them to look at the chemical constituents of the vermicompost liquid. The spectrometer showed that there were significant levels of 3 different types of growth promoting hormones known as cytokinins. Cytokinins promote cell division, or essentially growth, in roots and shoots. The researchers speculate that the hormones are produced by the microbes in the vermicompost. Thanks again worms! Your unseen labors are thoroughly appreciated.