- Author: Cris L. Johnson
The latest issue has recently been posted on our website and features articles on:
Simazine degradation in California citrus orchards. This article focuses on research performed in response to concerns about the effectiveness of simazine as a means of weed control. Here you can read about the experiments performed to test degradation levels and recommendations made regarding use of this herbicide for weed control.
Lime-induced iron chlorosis. Iron deficiencies in many fruit trees can be escalated where soils and irrigation water contain lime which can in turn impede soil drainage. Iron oxides serve as a common source of nutrition for the trees and the deficiency of it can cause dieback and other disorders. This article explores the causes and possible treatments for this condition.
Avocado trunk cankers. UCCE Ventura citrus, avocado and subtropicals advisor, Dr. Ben Faber, contributed this article on the various types and causes for tree cankers. Wounds to the tree, low rainfall, fungi and moisture can promote this disorder.
Asphyxiation. Dr. Faber also explores the problem of asphyxiation that occur in parts or all of the tree. This condition can seriously harm the tree and Dr. Faber discusses some methods of treatment and prevention.
Tree wraps. This article presents information about some of the benefits and considerations in installing wraps on young trees.
Stem and leaf blight. Dr. Faber also wrote this item on blight that he has observed lately on local trees and how insufficient water can contribute to the condition.
Read the full articles from this newsletter or check out other issues of Topics in Subtropics here.
The Asian citrus psyllid (ACP) has now been found in eight California counties. Quarantines are in place. The psyllid by itself is not much of a problem; it is its ability to spread the fatal disease that has the potential to devastate both the California citrus industry and backyard citrus throughout the state.
Huanglongbing (HLB) is the name of the disease ACP can carry. Citrus and closely related plants are at risk. The disease is transmitted between plants by the psyllid. The psyllids transmit the disease to healthy plants and trees. After feeding on an infected plant, the ACP will transmit HLB to every other plant it feeds on.
While much outreach has focused on citrus trees, it is important to remember there are other plants that can host both ACP and HLB. This list from the University of Florida provides both the common and Latin plant name for many known hosts. Hosts include: curry leaf, ornamental orange-jasmine, and all the varieties of citrus, including kumquat, mandarin, grapefruit, orange and all of their hybrids.
Please remember to check your citrus and closely related plants regularly for signs of ACP or HLB. General information about this pest disease complex can be found on this section of the CDFA website. For local updates, the Ventura County ACP Task Force is a great source of information.
Caused by the bacterium Erwinia amylovora, fire blight is a common and frequently destructive disease of pome fruit trees and related plants.
Symptoms commonly appear in spring. The first sign is usually a watery, light tan ooze that leaks from cankers. After being exposed to the air, the ooze darkens and leaves streaking on branches or trunks. Other signs of infection are petal fall, flower stem wilt, and the blackening and shriveling of flowers, shoots, and/or young fruit.
As the disease progresses, the pathogen spreads into the wood. The infected wood tissue can become sunken and cracks often develop in the bark around the infected areas.
Ideal conditions for infection, disease development and spread of the pathogen are rainy or humid weather with daytime temperatures from 75 (degree sign) F to 85 (degree sign) F.
Home Gardeners can learn more about fire blight in UC IPM’s Pests in the Gardens and Landscapes: Fire Blight publication. Subjects include: identification and damage; life cycle; and management.
Commercial growers can find fire blight information by crop on UC IPM’s Agricultural pest page.
Looking to add citrus trees to your home garden? UC ANR’s new downloadable publication Tried and True or Something New? Selected Citrus Varieties for the Home Gardner has many color photos and general information on a wide variety of citrus trees.
Further resources for selection and care of home garden citrus trees can be found at UC’s The California Backyard Orchard website.
Do you know that California apple producers grow more varieties than any other state west of the Rocky Mountains? In addition to those grown in commercial orchards, apples can be grown at home in many areas of California.
UC ANR’s free publication, Apples: Safe methods to store, preserve, and enjoy provides practical information and advice to get the most out of this delicious and nutritious fruit.
- Growing apples in the home garden
- Selecting apples from the home garden or pick-your-own site
- Selecting apples at the grocery store
- Storing fresh apples
- Safety tips for handling
- Methods for preserving