Shot hole borers are tiny insects the size of a sesame seed that don't look particularly harmful, but don't let their diminutive size fool you. Two of these borers are invasive—the polyphagous shot hole borer and the Kuroshio shot hole borer. They carry pathogens and are spreading them throughout southern California. Together, the borers and the fungi are a deadly combination that are killing many trees. Trees affected include avocado, sycamore, white alder, box elder, cottonwood, and willow.
The two shot hole borers are nearly identical in appearance, and both have a symbiotic relationship with several pathogenic fungi. The female borers lay eggs which introduces fungi into trees. The fungi grow and provide food for...
San Luis Obispo County has seen more than 20 detections of Asian citrus psyllid (ACP) since January 2018, according to Citrus Insider. The majority of these invasive insects have been found in the backyards of residential properties in the city of Nipomo.
If you haven't yet heard about this insect, Asian citrus psyllids can carry and spread the incurable citrus disease huanglongbing, also called HLB or citrus greening disease. Citrus trees infected with HLB develop mottled leaves and produce misshapen fruit that stays green and tastes bitter. There is currently no treatment for the disease, which usually kills trees within three to five years.
Due to these ACP finds, citrus growers in SLO County are on high alert,...
- Author: Janet Hartin
[From the Spring issue of the UC IPM Retail Nursery & Garden Center News]
Most disorders impacting landscape trees result from abiotic (non-living) disorders rather than attacks from biotic (living) pests like plant pathogens, insects, and vertebrates. Damage caused by abiotic and biotic disorders can appear similar, making diagnosis difficult at times. For example, discolored leaves on a Ficus nitida tree could be due to drought stress, a fungus, or a nutrient toxicity or...
/span>Winter is an ideal time to prune deciduous fruit and shade trees, since the trees are dormant and you can more easily see the tree canopy. In many cases, pruning can also help prevent or control certain insect and disease problems.
For help with pruning, visit the UC IPM web page called Pruning fruit and shade trees and shrubs.This page provides links to plant-specific pruning information for fruit trees, nut trees, landscape trees, and others. You can also find links to diseases and environmental disorders that commonly affect fruit and shade trees, as well as additional information on the topics of landscape management and videos on...
Mistletoe hung in doorways is a traditional holiday decoration, but when it's growing on trees in the landscape, this parasitic plant may not seem quite as charming.
There are two types of mistletoe: broadleaf and dwarf. Broadleaf mistletoe is evergreen and can be found growing on common trees such as flowering pear, ash, and birch, while dwarf mistletoe attacks firs, pines, and other conifers.
Mistletoe robs trees of both water and nutrients. If you see small amounts of mistletoe growing on healthy trees in your landscape, it's probably not a cause for concern. However, if a tree is heavily infested, individual branches may be weakened or killed, and trees affected by drought or disease may be stunted or even...