Sunday, August 5, 2018

Keep an Eye Out for Summer Limb Drop

As the afternoons here get hotter and more humid it is the well irrigated trees that can become a threat. Summer limb drop affects trees like the Floss silk tree, The Italian stone pine, and other susceptible varieties. Here is a news interview I did on the subject several years ago after some children were injured by a falling pine tree :

Wednesday, August 1, 2018

Beating the Heat Lecture: How to Protect Your Plants in Record Temps


BEATING THE HEAT


·      July 6th -119 degrees F for over an hour here.
Many Plants Scorched.
In the following days trees, shrubs and woody plants start to defoliate.

The Physiology of Heat Damage
·         PWP -mostly a problem with herbaceous plants.
·         Chloroplast damage -sets off a chain reaction in the plant.
o   Increased production of protective proteins
o   Increased production of abscission hormones.
o   Increased production of damaging peroxides.
·         Leaf drop
·         Fruit drop
·         Flower drop
·         Twig drop
·         Leaf scorch
·         Trunk and branch scorch (citrus and avocados)
·         Limb drop in susceptible trees.
What to Do After
·         Mulch
·         Increase irrigation frequency (but do not overirrigate)
·         Do not fertilize
·         Do not overwater
What if More Heat is on the Way?
·         Anti-transpirants?
o   Work by either plugging up the stomata or causing it to close.
o   Can cause overheating, decrease transpiration.
o   Work best in frost situations
·         Misters
o   Are expensive
o   Can cause fungal infestations
o   Require installation and $
o   Cheap barrel misters may be the best bet.
·         Shade-cloth
o   Can injure plants if just ‘draped’ on.
o   Should be installed as a permanent structure.
o   Need to choose right % for the plant.
o   Do not prevent all heat damage.
·         Kaolin
o   Sprays on
o   Helps control some insects as well
o   Irrigation washes it off.
o   Looks terrible.
·         Modify Irrigation
o   Check Evapotranspiration Index
o   Water according to current ET number.
§  Make sure you do irrigation measurement before you do this.
o   Use coffee cups and turn irrigation on for 10 minutes, measure depth in inches.
·         Plant Choices
o   Plants with blue-green coating (glaucous) do well.
o   Plants from South Africa and Madagascar do well.
o   Plants form the Southwest, South and Central America (not all).
o   Many (not all) Australian plants.
o   Plants from temperate areas do not usually do well.
·         Landscape Choices
o   Remember to put heat and sun resistant plants near walls and walks.
o   Go with climate appropriate plants.
o   Build shade structures.
o   Consider a mist system (for you, not the plants).




Links:


Scorch, Sunburn, and Heat Stress
Plant tolerance to high temperature in a changing environment: scientific fundamentals and production of heat stress-tolerant crops
When it is too hot for photosynthesis: heat-induced instability of photosynthesis in relation to respiratory burst, cell permeability changes and H2O2 formation
Leaf scorch | The Morton Arboretum
Sunburnt plants 'myth' is debunked - Telegraph
leaf-scorch.pdf
Extension Service | Leaf Scorch
8445.pdf
Bacterial Scorch of Trees
Leaf scorch | The Morton Arboretum
Bacterial Leaf Scorch
Homemade Whitewash for Trees
Whitewashing an Avocado Tree
UC IPM: UC Management Guidelines for Sunburn on Avocado
Surround WP (25 Lb) - GrowOrganic.com
Reserach-Summary_Cochran-Dissertation-MBI.pdf
How to prune heat damaged foliage
Impacts of Kaolin and Pinoline foliar application on growth, yield and water use efficiency of tomato (Solanum lycopersicum L.) grown under water deficit: A comparative study
https://cimis.water.ca.gov/

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