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...

Wet weather is favorable to mushrooms, which are sometimes called toadstools. Mushrooms are the visible reproductive (fruiting) structures of some types of fungi. Although the umbrella-shaped fruiting body is the most common and well known, mushrooms display a great variety of shapes, sizes, and colors. Some other fruiting bodies encountered in lawns include puffballs, stinkhorns, and bird's nests, descriptive names that reveal the diversity of forms among mushrooms. But regardless of shape, the purpose of all fruiting bodies is to house and then disseminate spores, the reproductive units of fungi.

Many people become concerned when mushrooms appear in their lawns; however, most mushroom-producing fungi in lawns are merely...

[From the April-May 2016 issue of the UC IPM Green Bulletin]

A downy mildew caused by the fungus Peronospora mesembryanthemi has recently been confirmed by the USDA-APHIS from a red apple ice plant (Aptenia cordifolia) sample collected in San Diego. Since this first finding in San Diego County in summer 2015, the disease has spread to Orange, San Bernardino, and Ventura counties and is now found in the Goleta area in Santa Barbara County.

Peronospora mesembryanthemi was first reported from South Africa and...

Fall is the best time to protect your backyard fruit and nut trees from winter and spring pests. By implementing good sanitation practices now, you can help eliminate future disease, vertebrate, and insect pests.

Did you know that fruits and nuts left on the ground and hanging in trees (called “mummies”) are an open invitation to pests? As the weather begins to turn cold, pests look for a safe place to overwinter and/or to lay eggs, and mummies are an ideal shelter for them. Fungi and bacteria present in mummies also remain in dormant and active states.

Keep your fruit trees healthy by removing and disposing of all mummies in and around trees, shrubs and vines.

Other practices to reduce pest problems...