- Author: Ben Faber
Keeping your eyes open in the field can result in some unusual finds. A recent observation that was sent in concerned an avocado fruit which didn't really have the shape of an avocado and certainly not the texture. It is a "woody avocado" as described by Professor Robert Hodgson of UCLA in 1935:
Hodgson, R. W. 1935. Avocado Fruit Abnormalities. California Avocado Association 1935 Yearbook 19: 108-109.
http://www.avocadosource.com/cas_yearbooks/cas_20_1935/cas_1935_pg_108-109.pdf
Dr. Art Schroeder at the same institution pursued it further, still with no clear cause for the condition:
Schroeder, C. A. 1953. Abnormal Fruit Types in the Avocado. California Avocado Society 1953-54 Yearbook. 38:121-124.
http://avocadosource.com/cas_yearbooks/cas_38_1953-54/cas_1953-54_pg_121-124.pdf
Mary Lu Arpaia and Reuben Hofshi revisited the issue of avocado fruit abnormalities in 2002:
Avocado Fruit Abnormalities and Defects Revisited
http://www.avocadosource.com/cas_yearbooks/cas_86_2002/cas_2002_pg_147-162.pdf
It is still not clear what causes this condition, other than it is not transmissible and does not occur very often.
- Author: Ben Faber
The first email has come in. Every winter when it rains, we get calls about these weird gelatinous blobs in orchards and garden beds. They can look like vomit, be yellow, green, red, or blue colors and they can actually move. A rich forest floor or an avocado orchard with its thick mulch or a lemon orchard with piles of chipped prunings or a yard with mulched beds make for a great environment for slime molds to start moving with rainy weather, or when there has been significant irrigation.
Slime mold is an informal name given to several kinds of unrelated organisms that can live freely as single cells, but aggregate together to form multicellular reproductive structures. Slime molds were formerly classified as fungi but are no longer considered part of that kingdom. Although not related to one another, they are still sometimes grouped for convenience within the kingdom of Protista.
More than 900 species of slime mold occur all over the world. Their common name refers to part of some of these organisms' life cycles where they can appear as gelatinous "slime". Most slime molds are smaller than a few centimeters, but some species may reach sizes of up to several square meters and masses of up to 30 grams.
Many slime molds, namely the "cellular" slime molds, actually do not spend most of their time in this state. As long as food is abundant, these slime molds exist as single-celled organisms. When food is in short supply, many of these single-celled organisms will congregate and start moving as a single body. In this state they are sensitive to airborne chemicals and can detect food sources. They can readily change the shape and function of parts and may form stalks that produce fruiting bodies, releasing countless spores, light enough to be carried on the wind or hitch a ride on passing animals.
They feed on microorganisms that live in any type of dead plant material. They contribute to the decomposition of dead vegetation, and feed on bacteria, yeasts, and fungi. For this reason, slime molds are usually found in soil, lawns and on the forest floor, commonly on logs. However, in tropical areas they are also common on flowers, fruits and leaves. In urban areas, they are found on mulch or even in the leaf litter in gutters, and also grow in air conditioners, especially when the drain is blocked. One of the most commonly encountered slime molds is the wonderfully described yellow "Dog Vomit" slime mold Fulgio septica, found both in nature in forests, as well as mulched orchards.
- Author: Ben Faber
Without a doubt the borers, PSHB and KSHB are going to hurt avocado production, but there are some California native and landscape trees that are also going to get hammered, like unto death. Much has been written about the borers in the press, from ag journals to environmental newsletters to newspapers, such as the New York Times, Los Angeles Times and more local papers like the Ventura Star and Riverside Press-Enterprise. Recent trap findings of PSHB in Ventura county brought a local gathering of community groups to discuss the situation and the need to get more information out to local residents of the major environmental disaster at our doorstep, It seems most homeowners are not aware of the problem or if so marginally so. Is it because it's viewed as just an avocado growers' problem? The CA Avocado Commission has lead in research and spending on this problem that will affect all citizens, not just growers and consumers of the fruit. Are we all just overwhelmed by the disasters that are occurring around us here and world-wide?
I'm not sure why the lack of general interest in this issue, but the only way to get control of these pests is to stop their movement, which is largely through humans moving contaminated wood. Slowing the spread will give time to develop control methods and measures that will allow our native woodlands to cope with this infestation. There are currently people looking for pathogens and parasites in the native range of these pests, in order to determine if those native control measure would fit into a California system. But this is going to take time and in the meantime the spread needs to be slowed. Talk to your neighbors, co-workers and friends. And have them talk to their neighbors, co-workers and friends. Get the word out about what we can all do to slow the spread.
Listed below are some of the common plants in which the borer can reproduce and spread its fungi that kill the tree. Many more trees have been identified to which the borer goes, but as yet it's not known whether the fungi spread in those trees.
Known Suitable Reproductive Host Trees of PSHB:
2. Big leaf maple (Acer macrophyllum)*
3. Evergreen Maple (Acer paxii)
4. Trident maple (Acer buergerianum)
5.Japanese maple (Acer palmatum)
6. Castor bean (Ricinus communis)
7. California Sycamore (Platanus racemosa)*
8. Mexican sycamore (Platanus mexicana)
9. Red Willow (Salix laevigata)*
10. Avocado (Persea americana)
11. Mimosa (Albizia julibrissin)
12. English Oak (Quercus robur)
13. Coast live oak (Quercus agrifolia)*
14. London plane (Platanus x acerifolia)
15.Cottonwood (Populus fremontii)*
16. Black cottonwood (Populus trichocarpa)*
17. White Alder (Alnus rhambifolia)*
18.Titoki (Alectryon excelsus)
19. Engelmann Oak (Quercus engelmannii)*
20. Cork Oak (Quercus suber)
21. Valley oak (Quercus lobata)*
22. Coral tree (Erythrina corallodendon)
23. Blue palo verde (Cercidium floridum)*
24. Palo verde (Parkinsonia aculeata)
25. Moreton Bay Chestnut (Castanospermum australe)
26. Brea (Cercidium sonorae)
27. Mesquite (Prosopis articulata)*
28. Weeping willow (Salix babylonica)
29. Chinese holly (Ilex cornuta)
30. Camelia (Camellia semiserrata)
31. Acacia (Acacia spp.)
32. Liquidambar (Liquidambar styraciflua)
33. Red Flowering Gum (Eucalyptus ficifolia)
34. Japanese wisteria (Wisteria floribunda)
35. Goodding's black willow (Salix gooddingii)*
36. Tree of heaven (Alianthus altissima)
37. Kurrajong (Brachychiton populneus)
38. Black mission fig (Ficus carica)
Known Suitable Reproductive Host Trees of KSHB
1. Avocado (Persea americana)
2. California Sycamore (Platanus racemosa)*
3. Coast live oak (Quercus agrifolia)*
4. Cork oak (Quercus suber)
5. Draft coral tree (Erythrina humeana)
- Black Polar (Populus nigra)
7. Black locust (Robinia pseudoacacia)
8. Red Willow (Salix laevigata)*
- Arroyo willow (Salix lasolepis)*
- Cottonwood (Populus fremontii)*
11. Mimosa (Albizia julibrizin)
12. Castor bean (Ricinus communis)
13. Black Willow (Salix nigra)*
14. Strawberry Snowball Tree (Dombeye cacuminum)
*Native species to California
For other information sources of what these new borers can do to our wildscapes check out:
http://ucanr.edu/sites/socaloakpests/
- Author: Ben Faber
It is that time of year and we should be alert to threat of freezing weather and damage to trees. Last winter was one of the warmest on record, but there was still a sneak cold blast around the New Year that caused some problems in some areas. Wet winters tend to have lower frost threats, and even though wet is forecast for this winter, that rain is not forecast until late in January. That still leaves December and early January which historically when most of our damaging frosts occur. Fox Weather on the CA Avocado Commission is forecasting some cold weather coming up, so growers need to be prepared for the worst.
Here are some links to frost information, preparing for frost and managing frost damage to trees.
A Frost Primer
http://ceventura.ucanr.edu/Com_Ag/Subtropical/Publications/Frost/A_Frost_Primer_-_2002_/
Protecting Avocados from Frost
Rehabilitation of Freeze-Damaged Citrus and Avocado Trees
The forecast is for north winds, which often means cold, dry air and often with winds. Winds mean no inversion and no warm air that can be introduced at ground level to warm trees. If this occurs, running a wind machine can make the damage worse. Wind machines and orchard heaters work on the principle of mixing that warmer air higher up – 20-100 or so feet higher than ground level which has colder air. When temperatures drop, the air is dry (wet-bulb temp below 28 deg F) and there is no inversion, running a wind machine can just stir up cold air and cause worse conditions (freeze-drying). It's better to not run the machine. The only thing left to do is to run the microsprinklers during the day so that the water can absorb the day's heat. Then turn the water off before sunset so that evaporative cooling from the running water isn't accentuated. Then when temperatures drop near 32 at night and the dewpoint is much below that, it's time to start the water again and let it run until sunrise (when risk is less). Running water works even if the water freezes. This is due to the release of heat when water goes from liquid to frozen state. This 1-2 degrees can mean the difference between frost damage and no damage. Also, ice on fruit and leaves can insulate the fruit. As the ice melts at the surface of the plant, it releases heat, protecting the plants. If there is not sufficient water to run the whole orchard, it's best to pick out the irrigation blocks that are the coldest or the ones you definitely want to save and run the water there continuously. Running the water and turning it off during the night to irrigate another block can lead to colder temperatures in both blocks.
Keep warm this winter.
- Author: Ben Faber
Well it came again, the Citrus Tasting at Lindcove Research and Education Center in Lemon Grove near Exeter, close to Visalia and just down the road from Fresno and up from Tulare. They came, growers to see and taste new and old varieties. And then the next day, the general public with oooos and ahhhs to taste the range of flavors we call citrus. Big fruited pummelos and little fruited finger limes. Sweet, sour, not sweet, not sour, dull, and boing!. Growers came on Friday morning and the general public the following Saturday. It was crowded both days.
Citrus is wonderful, everyone knows, but it is also under dire threat of Huanglongbing and the potential destruction of this industry and the trees that are found in many backyards. So in a completely unscientific survey, I asked growers why they were there if their world was about to end. First of all, those who showed up were already optimistic about the future, so there was already a self-selection. But, growers felt like a solution would be found, science would find an answer. Driving across the Valley and through coastal counties like Ventura there are lots of new plantings......if there's water. But it's surprising how confident growers are about finding a solution. There are some hopeful signs out there like the new rootstock release from USDA of US-1516 which shows a lot of tolerance to the disease. Then there is the potential of disease tolerance in a citrus produced in Florida from a collaboration of Southern Gardens, USDA and a consortium of Universities. Yes, there is hope, but years are still needed to test and gear up for production for commercial applications.
So it was good to be around growers who have an enthusiasm for the future and looking for new planting varieites.
And they are both grapefruit, one is Melogold the one on right is Oro Blanco
Buddha's Hand citron
The Citrus Display at Lindcove Research and Extension Center, before the crowds
