NEWSLETTER ARTICLES
Franklin Laemmlen, Ph.D., County Director and Vegetables/Plant Pathology Advisor
From our Central Coast Agriculture Highlights newsletter -- April 2000 issue.
USE OF ANTITRANSPIRANTS ON PEPPER SEEDLINGS
Franklin Laemmlen
Conditioning and hardening transplants is critical for successful transplanting and the good survival of healthy transplants in the field. The use of antitranspirants (i.e., VaporGard or WiltPruf) and other transplant sprays (Frostgard) has been proposed to shorten conditioning time, reduce transplant shock, and increase plant survival.
To check this out, Dr. Marita Cantwell, Vegetable Specialist at UC Davis, ran some tests using untreated (UT) and Frostgard-treated (T) pepper seedlings. T and UT plants were exposed to several conditions of temperature and light, which could occur under present seedling handling practices. Her conclusions follow:
- Low to moderate temperatures (10-20°C [50-58°F]) are better for transplants than higher temperatures.
- Transplants stored in light were slightly greener than those stored in the dark for 2 days. Longer periods in the dark would result in further loss of chlorophyll and should be avoided.
- Frostgard treatment stimulated ethylene production by the plants and caused leaf yellowing and leaf drop, symptoms associated with ethylene. Frostgard damage was aggravated by exposure to light.
If you would like a complete copy of this report, please call me at 805.934.6240.
PESTICIDE-RELATED ILLNESS AND INJURY REPORT
Franklin Laemmlen
The Department of Pesticide Regulation (DPR) has just released the 1997 and 1998 report on pesticide-related illnesses and injuries. These are illnesses and injuries that have been investigated and documented by county agricultural commissioners, health officers, and physicians. State law requires that such illnesses/injuries must be reported to DPR and that an investigation has occurred, which confirms the source and cause of the illness/injury.
In 1997, 1,319 cases were reported. This is a 16.5% drop from 1996. In 1998, 998 cases were reported, a 25% drop from 1997. Of these 998 cases, 632 (63%) were found to be of non-agricultural origin, while 366 cases involved agricultural pesticides. In Santa Barbara County only 4 cases of illness/injury were reported and confirmed to be of pesticide origin, and only two of these were found to be of agricultural origin. In San Luis Obispo County the number was 6, of which only one was agriculture related. Congratulations to the agricultural communities of Santa Barbara and San Luis Obispo Counties for this excellent record.
These numbers indicate that plant protection products are being used safely, responsibly, and with concern for the environment and county residents.
Keep up the good work!
If you would like a copy of the complete statewide DPR report, call our office - 805.934.6240.
PLANT NUTRITIONAL DISORDERS: DEFICIENCY AND TOXICITY SYMPTOMS
Franklin Laemmlen
Plant nutrient deficiencies occur when the nutrient level is insufficient to meet plant demands to achieve normal growth. Nutrient toxicity occurs when plants grow in presence of excessive quantities of nutrients. This causes plant growth reduction or injury (salt burn). Visual nutritional disorders in plants are often not recognized when a mild plant nutrient deficiency occurs. However, a significant yield reduction may occur at this level of deficiency. This situation of “hidden hunger” can be detected only by plant and soil analysis. Nutritional deficiencies may be obvious when the expected yield is depressed. At this stage of plant growth, the yield reduction is usually irreversible regardless of the quantity of fertilizer added to correct the problem.
Plant nutrient disorder symptoms often vary with cultivars of a given species. Disorder symptoms are nutrient specific. These symptoms are recognized in different parts of the plant according to the translocation level (mobility) of the nutrient. Thus, it is important to distinguish among nutrients according to their mobility in the plant. The understanding of nutrient mobility in the plant is important for selecting the appropriate part of the plant for sampling.
Plant nutrient deficiency symptoms that are due to mobile nutrients generally appear in mature leaves because mobile nutrients have a tendency to move toward actively growing leaves, while nutrient deficiency symptoms that are due to immobile nutrients appear in younger leaves. Table 1 lists nutrients and their mobility level in the plant. The first column of Table 1 shows that nitrogen potassium, sodium, magnesium, and phosphorus are easily translocated from older leaves to younger leaves. Therefore, deficiency symptoms appear first in older leaves. Deficiency disorders due to immobile nutrients (ex. Ca, Ba, B) appear in younger leaves or stem tips.
Table 1. Mineral Nutrient Mobility in Plants
| Mobile | Intermediate | Immobile |
| Nitrogen (N) | Iron (Fe) | Lithium (Li) |
| Potassium (K) | Manganese (Mn) | Calcium (Ca) |
| Rubidium (Rb) | Zinc (Zn) | Strontium (Sr) |
| Sodium (Na) | Copper (Cu) | Barium (Ba) |
| Magnesium (Mg) | Molybdenum (Mo) | Sulfur (S) |
| Phosphorus (P) | Boron (B) | Iron (Fe) |
| Chlorine (Cl) |
When evaluating plant nutrient needs, both soil and plant tissue sampling is important. Soil sampling is most useful before planting to provide information on residual soil nutrients and providing an idea of what nutrients will need to be added. Plant tissue testing should follow periodically as the crop grows, so adjustments can be made to the developing crop to keep the nutrients available at optimum levels.
Plant tissue testing is used to make fertilizer adjustments during the growing season. This approach may work well for long-term growing season crops (mainly field crops). For short growing season crops, such as vegetables, it is more effective to have a soil test and make most of the fertilizer adjustments prior to planting. Should a plant test be performed, the following sampling rules should be observed.
- Sample the same portion of the plant at each growth stage.
- Take a large number of samples and make a composite sample.
- Collect separate samples from deficient growth plant areas and good growth plant area in separate bags.
- Obtain soil-free plant samples, and put samples in white paper bag. Brown bags usually are not N, B, S free, and samples spoil in a plastic bag.
- Write all the information for the sample on the paper bag.
- Dry samples before sending them to a laboratory for analysis.
- Ask commercial laboratories about the packing and shipping conditions, the sampling cost, and available soil calibration. Check more than one laboratory.
Plant samples for nutrient determination are collected as leaves samples, sap samples, and whole plant. Among these three methods, sap or petiole sampling is the fastest and least accurate way to make a determination. It can be done in the field. Leaf samples and whole plant samples require more time for drying, grinding, and laboratory extraction, but are usually more accurate. Usually it takes about one week to get the results from a commercial laboratory. Vegetable growers may need to have the results quicker to correct any deficiency. More modern and elaborate laboratory instrumentation currently available on the market may increase the accuracy of the analysis.
Plant parts sampled depend on the nutrient in question, and the plant species. Midrib and petiole samples are most often used for vegetable crops. However, check with your analytical laboratory to determine which tissues and sampling techniques will provide the best results.
Adapted from: Yuma County Newsletter, February 2000.
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