Posts Tagged: Sunburn
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Avocado Heat Advisory
Avocado Heat Advisory Temperatures are forecast to be in the triple digit range throughout much of the southern California avocado growing region beginning Sunday June 19 and extending into Tuesday June 21. The National Weather Service (NWS) is predicting maximum temperatures between 100 and 110 degrees with similar heat index readings away from the immediate coast for Ventura and Los Angeles Counties. In Riverside, San Diego and Orange Counties, NWS predictions are for 95 to 105 degrees in the valleys, and 105 to 113 degrees in the inland empire and high desert.
To ensure that California avocados maintain their superior quality it is imperative that growers manage their trees and harvest their fruit according to the best management practices as outlined below.
IRRIGATION Growers should be irrigating their trees now, in advance of the heat, to ensure that their trees are fully hydrated. An additional 50% of the budgeted amount of water is recommended to be applied the day before a heat wave. For extended heat waves, daily pulses of irrigation are recommended to maintain the trees' water status. A well-watered tree will tolerate the stress of a heat wave much better than a tree that is suffering from water stress. Signs of heat damage to trees include fruit drop, shoot damage, leaf burn and in severe cases leaf drop.
HARVESTING Every attempt should be made to harvest fruit when temperatures are below 90 °F, and no harvesting should take place when temperatures exceed 95 °F. Temperature in the shade should be monitored during harvesting and, when possible, harvesting crews should be moved to the coolest, least exposed areas of the grove.
Field bins should be placed under the trees while being filled to protect the harvested fruit from sunburn. Once filled, bins should be moved to a shade structure (open-sided roofed building), or covered with bin covers or light-colored tarps if they cannot be immediately transported to the packinghouse. Never leave filled bins exposed to the direct sun. The surface layer of fruit can easily heat up to more than 15 °F above ambient temperature when exposed to direct sun. Acute sunburn will only show on fruit after it is packed and is a major quality detractor.
To avoid water loss and decreased fruit quality do not hold fruit too long after harvest. Transport fruit to the packinghouse at least once per day, if not twice daily. Bins should not be left in the grove for more than 8 hours after harvest. Cover bins during transport to avoid sunburn and to reduce water loss.
Photos: Leaf sunburn, fruit sunburn
avocado leaf sunburn
avocado fruit sunburn
Japanese Maples Do Sunburn
Help for the Home Gardener from the
Contra Costa Master Gardeners' Help Desk
The client has several young Japanese Maples suffering from sun burned and sun scorched leaves. They are concerned about the welfare of the trees and how much to water them. They were told by the nursery to water one gallon every three days.
Master Gardener Response:
Sun Burned/Scorched Leaves: You did not mention what type of sun exposure your maples have so I will address that first. Most Japanese Maples will do well in a location with direct morning sun and shade in the afternoon. Hot afternoon summer sun exposure on many varieties of red Japanese Maples can result in sun burned leaves. I can personally attest to this. With the recent summer winds and hot sun, all of my Japanese Maples have sun burned leaves and some early leaf drop. This often occurs in late August through September but has so far never affected the overall health of my trees.
Leaf scorch can appear on any type of deciduous tree, shrub or plant. During prolonged periods of drought, windy weather or bright sunshine, Japanese Maples are particularly susceptible, especially young trees. In hot weather with dry soil, tree roots cannot absorb enough water to send to the leaves. Foliage may stay on the tree in mild instances, but premature leaf drop occurs in severe cases of leaf scorch.
Watering Japanese Maples: Your question regarding a proper watering schedule is challenging because of several factors including your soil type and whether this is a newly planted or an established tree. Generally speaking, watering of Japanese Maples should be done uniformly throughout the growing season and even more during summer heat. Japanese Maple trees have fairly shallow roots that can dry out easily. Your Japanese Maple requires a consistent amount of water. The amount of water will also depend on your soil type. A clay soil will retain more moisture than a sandy soil. Your nursery's recommendations on watering may fall short in during a drought season, and especially in light of our summer's high temperatures and windy days.
The University of Colorado web site referenced below is a great resource on caring for trees in a drought year. However, a Japanese Maple is a moisture loving tree and if it is newly planted, will require additional monitoring and water. A three inch layer of mulch is helpful to provide moist conditions as well as winter protection for the shallow root system. Mulch will also help cool the soil in summer. Some other good cultural practices for your tree's health include keeping lawn 2-3 feet away from the trunk and keeping mulch about 6 inches from the trunk.
Some Additional References Worth Reviewing on Japanese Maple Care:
General Information on Tree Care in Lawns from the Contra Costa Master Gardeners
http://ccmg.ucanr.edu/files/177645.pdf
Information on Japanese Maples; Master Gardener Newspaper Articles
http://ucce.ucdavis.edu/files/datastore/268-223.pdf
University of Colorado resource for addressing water needs in a drought situation
http://www.colostate.edu/Depts/CoopExt/4DMG/Trees/caring.htm
Missouri Botanical Gardens on leaf scorch:
http://bit.ly/1l1N4r8
Contra Costa Master Gardeners' Help Desk
Editor's Note: The CCMG Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. (map) We can also be reached via telephone: (925) 646-6586, email: ccmg@ucanr.edu, and we are on the web at http://ccmg.ucanr.edu/. "Ask a Master Gardener" help tables are also present at many Farmers Markets as well as at the CCMG's "Our Garden" programs (map). See the CCMG web page for details/locations.
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