- Author: Ed Perry
Symptoms of Blossom-End Rot
The first symptom is usually the appearance of a small spot at or near the blossom scar of green fruits. As the spot enlarges, the affected tissues dry out and become light brown to dark brown. The area then develops into a well defined sunken spot, with the tissues collapsed and leathery. The spot can grow large enough to cover the entire bottom half of the fruit. The skin remains unbroken because it is the tissues beneath that have dried out and collapsed. The disorder not only affects tomatoes, but can also occur on peppers and squash. While the fruit looks unappetizing, you can still eat it - just cut out the affected part.
Causes of Blossom-End Rot
Tips for Preventing Blossom-End Rot
There are several things you can do to prevent the calcium deficiency, and blossom end rot. First, water deeply, and on a regular schedule, especially during hot weather. Use a soil-covering mulch around your plants to conserve moisture, especially if your soil is sandy. If you are growing tomatoes in containers filled with a porous potting soil, you may need to water the plants every day during hot periods. When cultivation is necessary, it should not be too near
the plants nor too deep, so that valuable water absorbing roots remain uninjured and viable. The best way of preventing the disorder is to maintain adequate and uniform soil moisture in the root zone throughout the growing season.
More Questions about Vegetables?
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References
UC IPM http://ipm.ucanr.edu/PMG/GARDEN/VEGES/ENVIRON/blossomendrot.html
Ed Perry is the emeritus Environmental Horticultural Advisor for University of California Cooperative Extension (UCCE) in Stanislaus County where he worked for over 30 years.
/h3>/h3>/h3>/h3>/h3>- Author: Alireza Pourreza
Kearney Research and Extension Center, University of California Cooperative Extension
California is the major producer of fresh market citrus in the U.S., a $2 billion industry that is threatened by a devastating disease called citrus Huanglongbing (HLB). Unfortunately, there is no cure for this disease and if a tree gets infected, it will die in a few years. In Florida, HLB was first seen in 2005, but after a few years the entire state of Florida got infected. Today, about 60% of Florida citrus has gone, mostly because there was no efficient HLB monitoring practice. HLB diagnosis using laboratory-based methods required manual sampling and they were time and effort consuming. An efficient HLB management requires high spatial and temporal resolution monitoring and eradication of infected trees. Therefore, a diagnosis sensor is needed for detecting HLB infected canopies before the development of symptoms. For high resolution monitoring, the sensor should also be able to conduct rapid and inexpensive inspection with high accuracy.
Starch accumulation in HLB infected leaves is an early indication of the disease. Starch has an optical characteristic of rotating the polarization plane of light. We employed this characteristic of starch to develop an early detection methodology in which the sensing system was very sensitive to the rotation in polarization plane of light. The sensor has a customized illumination system including 10 high-power and narrow band LEDs at 591 nm and a polarizing film. The sensor also has a monochrome camera equipped with a linear polarizing filter that is set in a perpendicular direction to the polarizing film of the illumination system.
Starch accumulation in an HLB infected leaf generates blotchy mottle in an asymmetrical yellowing pattern. Deficiency of certain nutrients such as Mg and Zn causes symptoms similar to HLB.
The sensor was mounted on a gator vehicle and was tested in a citrus grove in Florida. The polarized images acquired from healthy, HLB, and Zn deficient canopies were further analyzed for diagnosis purpose.
HLB samples were accurately identified from healthy and Zn deficient samples. Also, the sensor was able to detect HLB within Zn deficient samples.
The polarized imaging methodology was adopted in two separate studies at the University of Florida to investigate the earliest time HLB can be diagnosed by polarized imaging technique after infection. In one study, two-year old Valencia orange plants were inoculated using disk-graft method.
Time-lapse polarized images of leaves from inoculated citrus plants were acquired on a weekly basis. HLB symptoms (as starch accumulation) started to become visible in the polarized images five weeks after inoculation, while the plants were still in asymptomatic stage.
In another study, the polarized imaging methodology was employed to detect HLB in insect inoculated citrus seedlings while in asymptomatic stage. Citrus seedlings were exposed to intensive HLB-positive Asian Citrus Psyllid (ACP) feeding. Polarized images were acquired two times; once after one month after inoculation and again two months after inoculation. As well as HLB detection, the level of infection was obtained for different leaf samples. Polymerase chain reaction (PCR) tests were conducted to validate the HLB status and the level of infection in each leaf sample.
Currently, we focus on improving the accuracy and early detection performance of the polarized imaging sensor and developing a commercialized product for practical in-field diagnosis. This affordable tool can help the California citrus growers to protect their groves from HLB.
Photos, from top to bottom:
Sensor Prototype
Leaf Symptoms of HLB and Zn Deficiency
Time Lapse Images of HLB Infected Leaves Over Time
- Posted By: Mark Bolda
- Written by: Mark Bolda
It is at times perhaps tempting to take an uncomplicated view of nutrient deficiency in strawberry. The mantra goes a little bit like yellow leaves are nitrogen deficient, phosphorous deficiency is given by purple leaves, potassium shortages easily marked by scorched leaves and so on.
I don’t believe any of this is so simple and so attempt to challenge this facile thinking when I have the opportunity to do so.
The following situation was a good one. A smallish field of ‘Albion’ variety strawberry was not given supplemental fertilizer beyond a standard dose of preplant slow release 18-8-13 in the area of 500 lbs per acre. The result in late June was as seen below- severely chlorotic plants with a strong tendency towards purpling of the middle age to older leaves. Additionally, flower production had nearly ceased and fruit was sizing down substantially.
I tested the soil to 6 “down at six different points throughout the field, amalgamated them and got the following results:
Nutrient Sampled |
Concentration (PPM) |
Nitrate (NO3) |
4.1 |
Ammonium (NH4) |
3.5 |
Phosphorous |
58 |
Soil pH was a perfectly normal 6.4. As one can see from the numbers above, plant available nitrogen sources nitrate and ammonium were sort of low (usually want to be 10 ppm for either one), while phosphorous was a quite sufficient 58 ppm.
Tissue samples consisted of leaf blades. Four separate samples were taken from different sections of the field and each sample consisted of a dozen leaflets of middle age- meaning not the very old ones at the bottom of the plant nor the young tender leaves emerging from the center of the crown.
Nutrient Sampled |
Average Concentration |
Nitrogen (N) |
1.7 % |
Phosphorous (P) |
0.2025 % |
Potassium (K) |
1.38 % |
Calcium (Ca) |
1.475 % |
Magnesium (Mg) |
0.3675 % |
Sulfur (S) |
0.1325 % |
Copper (Cu) |
4.3 ppm |
Zinc (Zn) |
15 ppm |
Iron (Fe) |
212.5 ppm |
Manganese (Mn) |
805 ppm |
Boron (B) |
79.25 ppm |
Comparing the nitrogen results from the leaf blade with the 2.6-2.8% concentrations described as sufficient as from UC Publication 4098 and Dr. Tim Hartz’s work last year, we see that this vital nutrient is a full percentage point below what is deemed necessary for normal production. Phosphorous, while below the 0.36% field average taken by Dr. Hartz’s study last year, is still understood to be well above the 0.10 % baseline given by UC Publication 4098. All other nutrients, with the exception of zinc (15 ppm compared to a recommended 18-20 ppm), in this sample are well within sufficiency ranges.
Why then the pronounced purpling of the leaves if the phosphorous is not dramatically, if at all, insufficient in the tissue? There are in fact other possibilities. A lack of nitrogen, which is a component of some amino acids and other compounds, can result in a similar build up of excess carbohydrates as in phosphorous deficiency. Essentially, both deficiencies have the same result then that these carbohydrates can end up being used in anthocyanin synthesis resulting in accumulation of these flavonoid pigments. Some are red, others pink and some purple. This may be an explanation why strawberry leaves lacking in nitrogen but not ostensibly lacking in phosphorous are actually turning red to purple.
So, while undoubtedly light green to yellow leaves are still a good indication of nitrogen deficiency in strawberry, don't be fooled that the purple that often accompanies it is actually caused by something else like a lack of phosphorous.
Thank you to Soil Control Lab in Watsonville for processing and evaluating these samples.