- 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
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
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
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
The avocado is an amazing fruit. It grows on a tree and comes to maturity, reaches certain oil content and a stage at which it will ripen, but it does not ripen on the tree. It needs to be removed from the tree before it will soften. If the fruit is removed before it has reached maturity it will not soften, and will remain rubbery and inedible. One of the problems is that the fruit will hang on the tree for an extended period of time and it is hard to know when they are mature. Avocados are not like apricots where you have about 2 weeks to get the fruit off before it falls off. As the fruit stays on the tree in gradually develops more and more oil content and has a richer flavor.
If the fruit stays on the tree too long, the oil can develop and almost rancid flavor, however. So it is good to know when the best, acceptable flavor is. Avocado varieties fall into general seasonal periods when they are mature, such as Fuerte' and ‘Bacon” in winter, ‘Hass' in spring/summer, ‘Lamb-Hass' in summer/fall.
To assess maturity, take an unripe stage cut the fruit in half. Look at the seed coat. If the seed coat (the covering of the seed that separates it from the flesh) is white and thick, it is definitely not ready to pick. If it is whitish brown and getting thinner, then if you are desperate, you can try ripening the fruit and taste. If the seed coat is thin and brown, then usually this will mean that the fruit is ready to pick. If the seed has germinated already in the fruit then normally the fruit is over the hill. Some green skin varieties skin will begin to crack when the fruit are very mature on the tree. This will tell you when you have reached the end of the useful tree life of the fruit.
For ripening, pick the fruit and without any help, the fruit will typically be ripe in 7 to 10 days. If you want to speed things along a bit you can take 3 or 4 avocados and place them in a loosely closed paper bag with 2 – 3 Red or Golden Delicious apples or ripe kiwifruit. The purpose of the apples or kiwifruit is that these fruit produce a natural plant hormone, ethylene that will help stimulate the avocado to produce its own ethylene. Apples and kiwifruit are known to produce lots of ethylene. The Delicious apples are varieties that produce more ethylene than other apple varieties. You can keep them even after they are shriveled and they will be producing ethylene. Don't use a plastic bag unless you keep it opened since the fruit need to breathe during this process. Just keep the fruit on your kitchen counter or in a warm place. 68F is the ideal temperature. Lower and higher temperatures both actually slow the process.