Cooperative ExtensionUniversity of California800 South Victoria AvenueVentura, California 93009(805) 654-2924

How to Cure Shade Tree Problems

Shade trees require care all year, however, fall is a season that brings withit many maintenance tasks. The University of California Cooperative Extension,in cooperation with land grant based experiment stations at Berkeley, Davis andRiverside have conducted research in tree related topics for many years.Coming out of this program of applied and basic research are many usefulrecommendations about tree pruning, fertilization and pest control.

Shade trees like all other plants require certain elements for normal growth.Some of these elements like carbon. Oxygen and hydrogen are supplied by airand water. However elements such as nitrogen, potassium, and phosphorous (andseveral others) are supplied in the soil to the roots. Studies at the U. ofCalifornia, Davis have shown that nitrogen is the element required most oftenby shade and fruit trees in most parts of California; the other elements areusually available in sufficient quantities in the soil. Authorities in shadetree research feel that fall is the best time to apply nitrogen fertilizer.Nitrogen applied in the fall may be taken up by the tree and stored untilspring when it is utilized by grov/ing roots and expanding buds or shoots.

Pruning recommendations in California are extremely variable. This is partlydue climatic variation throughout the state but also to the many tree speciesin California. In southern California many trees can be pruned at any time ofyear without apparent problems. However, fungi which cause heart-rot in shadetrees are sporulating now, so one recommendation has been to avoid pruning inthe fall if possible. This is also not a good time to prune conifers such asMonterey pine because of the possible attraction of pine bark beetles and redturpentine beetle to the pruning v/ounds. The best time to prune pines is inthe coldest winter months when beetles are not flying.

Pest control requirements change all year long depending upon the tree speciesand the pest. Now may be the best time to have trees sprayed for peppertreepsyllid, a new pest of California pepper. Although research has shown Ortheneto be one of the best spray materials, homeowners can not lawfully apply thematerial under the current product registrations. Commercial application ofOrthene (which is lawful) to California pepper has shown about sixty days ofcontrol of peppertree psyllid.

Fall is a good time to reduce watering frequency. As the days become shorterand cooler, trees require less water. This does not mean that trees need nowater. Many tree owners assume that because a tree is "established", it needsonly annual rainfall. Annual rains may be enough to maintain some trees themin an acceptable condition but this year we are in a drought, so many trees are

showing signs of stress, V/ater stress (either too much or too little) can pre¬dispose trees to attack from destructive insects or disease organisms. If yourtrees are watered by an automatic irrigation system, be sure to adjust the timeclock to reflect changes in temperature or rainfall.

OVER

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October 21j, 1987

f /l/iAt ADVISORS SAY

FARfl ADVISORS SAY

10/21/87Page 2

Most frequently trees are neglected or ignored until some problem occurs.When problems do occur, treatments are often applied too late. The bestcure for many tree disorders is to provide good tree care before problemsstart.

Jim Downer

Farm Advisor