With the increased interest in the use of biological/softer chemistries and the recent commercialisation by Syngenta In the US the launch of New Daconil Action® based on Acibenzolar which stimulates the natural defence response of turfgrass, these appear to becoming more in vogue.
In fact there is increasing evidence that these do offer a viable alternative as stand alone or in use in conjunction with more traditional 'hard' chemistry.
Hopefully this article will help clarify how these work some major differences between options on the market and also how to use them to get optimal efficacy.
This article isn't solely about microbial/biological options but also discusses some softer chemistry that are being used worldwide.
First a quick maths lesson. CFU (Colony forming units is a measure of viable cells) and are listed on packaging. This refers to the number of viable spores the product contains. So for example 2 x 109 spores / gram (2 x 1 billion), 2 x 1010 is 2 x 10 billion) and 5.5x1010 (5.5 x 10 billion i.e. 2.5x as much).
Moving on. The table below shows some of the trial work carried out on turf diseases using biological options.
References are available upon request.
There are a number of these but the bottom line is most research appears to have been done on four strains QST 713, MBI 600, FZB 24 and GB03. If a product doesn't list one of these then you really have no idea what you are actually using and its efficacy has to be questioned.
The mode of action, is to basically exclude other organisms and exude an anti-fungal metabolite that will suppress or kill pathogens. The bacteria, is said to persist in the soil for some time with a reported shelf life of close to 2 years.
In the US there are two registered products on the market one called Rhapsody is 1.34% active and has a turf registration at 6-30L/Ha. The other is called Companion contains 0.03% active and the rate is 12-18L/Ha.
Over the last few years a considerable amount of confusion has arisen in relation to fertilisers and chemicals containing this. Many of us are familiar with MAP and DAP (mono and di- ammonium phosphate) and possibly even MKP (monopotassium phosphate) all of which provide phosphorous derived from phosphoric acid (H3PO4).
Phosphite is completely different in nature from phosphate having no real nutritional benefit (In the 1930's various phosphorous compounds were studied to look at their efficiency as fertilisers. The conclusion was that phosphite was a poor source of nutritional P) and being directly fungistatic i.e. it slows the growth of the disease pathogen and inhibits the formation of spores. This causes the release of stress metabolites (chemicals) by the disease which are recognized by the plant as signals or elicitors causing the plant to enhance its defence response.
In horticulture growers globally have discovered the following benefits of using these on treated crops:
a) Rapid uptake compared to conventional phosphates
b) Enhanced plant and root development
c) Improved plant health
d) Increased production of natural fungicides (phytoalexins) effectively providing organic disease control
e) Multiple sites of action effectively countering the development of resistance.
f) Low environmental toxicity effectively being safer than aspirin.
Reasearch did show however that phosphites were very efficient against the Oomycota (i.e species of phytopthera and Pythium). This market was pioneered by Bayer with Aliette® and fosetyl aluminium. When the patent for this expired in the USA several manufacturers created phosphite based fungicides by simple formualtions of phosphite with potassium, ammonium, sodium and aluminium. Plants can absorb these compounds through roots and leaves and once in the plant the phosphorous acid compounds are very stable.
2005 work determined if active ingredient and formulation of phosphonate fungicides potassium phosphite or fosetylAl (Aliette and Chipco Signature)] provide similar control of Pythium blight when applied at equivalent rates of phosphorous acid, the active compound for controlling this disease.
Results of this study showed that when phosphonate fungicides with different active ingredients and formulations [potassium phosphite (Alude® and the phosphorous acid/potassium hydroxide treatment) and fosetyl Al (Aliette® and Chipco Signature®)] were applied at the same rate of phosphorous acid, no differences in Pythium blight control occurred among these products.
When turfgrass is exposed to a stress (heat/cold/disease), the plant produces salicylic acid (the best description is like the human body produces white blood cells to fight infection). This boosting of a plant's immune system is known as Induced Systemic Resistance.
Research has found:
a) Exogenous application of SA improved plant tolerance to heat and specifically to creeping bentgrass and tall fescue seedlings.
b) Further research has shown that the application of SA improved heat tolerance of Kentucky bluegrass in a controlled environment.
d) Salt stress
Streptomyces lydicus strain WYEC108 and Streptomyces griseoviridis K61
This bacterial organism is used in US formulations called Actino-Iron® or Actinovate® with the mode of action being competition and antibiosis. This product has a well proven track record in the greenhouse industry.
Trichoderma harzianum Rifai strain KRL-AG2
Trichoderma strains are able to grow in a wide range of pH from 2.0 to 6.0 with maximal growth rates at 4.0, the optimum range being 4.6 to 6.8.
The issues here are efficacy and storage. Research has shown that storage temperature and longevity can play a major role in whether these products work or not. 2005 work showed that the optimal storage longevity and temperature was up to 90 days at 20-30°C. In other 2005 work it was found that storage was preferable at 4°C rather than 30°C, which makes claims re storage at room temperature somewhat questionable bearing in mind how hot it can get in Australia and no one has any idea how long product is stored on shelves for.
Obviously this list could be never ending and does not for example discuss compost teas or the use of cytokinins (the latter have been done to death!). However it hopefully does give a taste of alternative options that are out there. Please feel free to contact me if you would like to discuss further - email@example.com
References are available upon request
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