Posts Tagged: phosphate
Snails, Slugs & Leaves with Holes
Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Client's Request: Hello. I'm looking for some help on what is eating leaves on my vegetable plants, and what may I do to help remediate. Below are some pictures.
![eggplant with eggplant with](http://ucanr.edu/blogs/ccmgblog/blogfiles/52101.png)
![basil leaf with basil leaf with](http://ucanr.edu/blogs/ccmgblog/blogfiles/52102.png)
MGCC Help Desk Response: Thank you for contacting the UC Master Gardener Program Help desk.
It is very hard to determine exactly what is causing holes in the leaves of your plants without direct observation. However, I think it may be slugs and/or snails, a common problem in spring. In order to determine if it is slugs or snails to implement an effective removal effort, you could look for slime on the leaves and slime on the ground around the plants. You could also go out at night with a flash light when they are active and check the leaves for snails and slugs.
The link following will take you to a UC Pest Management page on slugs and snails. It has some really nice videos (which are not long) on identifying whether or not slugs and snails are eating your plants. It also has a video on pest management of the slugs/snails (what to do about them). The pest note also has written information on management of snails and slugs. http://ipm.ucanr.edu/PMG/PESTNOTES/pn7427.html.
Managing snails and slugs can be done with trapping or hand picking and then snail and slug bait.
![brown snail brown snail](http://ucanr.edu/blogs/ccmgblog/blogfiles/52103.jpg)
![gray garden slug gray garden slug](http://ucanr.edu/blogs/ccmgblog/blogfiles/52104.jpg)
As you should always do when using pesticides, read the label on the snail bait box for use and cautions. The active ingredients that are in the snail/slug bait are in small print on the package. Metaldehyde and sodium ferric EDTA can be toxic to animals and harmful to the environment. Iron phosphate is safe for animals. The bait should be shaken around the plants.
It may also be cutworm. Management of this pest involves hand picking at night and protecting plants with cardboard collars, screens or protective cloth. The link following will take you to the UC Pest Management page on cutworms. http://ipm.ucanr.edu/PMG/GARDEN/VEGES/PESTS/cutworm.html
Finally, from my personal experience to reduce the snail/cutworm population, look for and destroy their daytime hiding places (e.g., wood debris, weeds, etc.). It's a lot easier than crawling around at night with a flashlight looking for them.
Please let us know if you have further questions.
Help Desk of the UC Master Gardener Program of Contra Costa County (DLD)
Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer our gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523, although we will be moving this spring. We will notify you if/when that occurs. We can also be reached via telephone: (925)646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog (//ucanr.edu/blogs/CCMGBlog/)
P a Simple Little P
It is such a simple little letter, P. It stands for the element phosphorus. It is often misspelled as phosphorous which is an adjective, but even in technical literature it is misspelled. But that's not the end. Phosphorus is an element that takes many forms called oxidation states. When it is in the form of phosphate or phosphoric acid, it is a fertilizer – H3PO4. But when it is in the form of H3PO3 or phosphonate or phosphonite or phosphite or phosphorous acid, it does not perform like a fertilizer. It acts more like a stimulant for a plant to fight off Phytophthora or Pythium. And it works well for avocado and citrus root rots, as well as citrus brown rot.
But a grower recently told me that there is no end of confusion about these two very different forms of P.
A recent article helps to clear up some of this confusion
http://www.spectrumanalytic.com/support/library/pdf/Phosphites_and_Phosphates_When_distributors_and_growers_alike_could_get_confused.pdf
and more if you are still interested
https://edis.ifas.ufl.edu/hs254
Sick avocado on the left and healthy on the right
root rot vs healthy
The Deal with Phosphite Fertilizers
Here is another interesting aspect of plant nutrition drawn from the October 23 Soil Fertility Short Course at UC Davis.
Phosphorous (P), an essential element for plants, does not occur alone in nature and rather it combines with oxygen and hydrogen. Bonded with four oxygen atoms P makes phosphate, and when bonded with three atoms of oxygen and one atom of hydrogen, P forms phosphite.
The fully oxidized phosphate (the one with four oxygen atoms) is the most stable form of P in the environment, and is preferentially taken up by microbes and plant roots. Then again, phosphate is adsorbed to soil particles more than phosphite, meaning it is less available. However, it does not necessarily follow that this enhanced availability of P via phosphite results in more uptake by plants, but even so, fertilizer formulations of phosphite plus calcium, magnesium or potassium have been formulated with the intent of taking advantage of this greater solubility in the soil.
Several studies examining a greater availability of P through phosphite have found that when phosphite is applied at an equivalent rate of P to phosphate fertilizer, it consistently underperformed when measured in terms of crop productivity, especially in the first year of cropping. In the way of explanation, the slower oxidation process of phosphite to the plant-root preferred phosphate, may be part of the equation of why the phosphite is not as effective as phosphate, in spite of having greater mobility.
In lay terms we can say, yes, phosphite might more available to plants in the soil, but they don’t want it as much as they want phosphate.
On the other hand, foliar applications of phosphite have shown that, while it can be converted to phosphate on the leaves by microbes living there, it is more readily absorbed into the foliage of some crop plants like citrus and avocados. Phosphite application (usually once at pre-bloom and perhaps a second time later in the season) to the foliage of avocados or oranges has resulted in more flowers, greater fruit yield and size, total soluble solids and anthocyanin concentrations.
For further reading, see the paper below, which among other things implies that the positive results experienced in oranges and avocados could be replicated in berries…
http://www.spectrumanalytic.com/support/library/pdf/Phosphite_Fertilizers_What%20are%20they.pdf
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