- Author: Lauren Fordyce
![Fuzzy-like white spots all over the green pad of a prickly pear cactus.](/blogs/blogcore/blogfiles/101738small.jpg)
It may be after Labor Day, but some of your plants may still be wearing white, breaking that long-standing fashion “rule”! While many of us don't adhere to this old rule for our wardrobes these days, you may care about white stuff on your plants this time of year.
There are several white colored pest insects and diseases that you could be noticing on your plants.
Scales
Several types of scale insects are white. Each has their own host preferences, or plants they feed on.
- Cochineal scales feed only on cacti, usually prickly pears. On the outside they are white and waxy but...
About: Powdery mildew is a group of fungal diseases that afflict a wide variety of plants. There are many species of fungi (e.g., Erysiphe spp., Sphaerotheca spp. Golovinomyces cichoracearum) that infect plants and cause the suite of symptoms we commonly call powdery mildew. Each species of fungus commonly attacks a limited group of closely related plants. A wide variety of plants are susceptible, including vegetables, fruits, ornamentals and even turfgrass.
The fungi collectively known as powdery mildew are unusual in that they don't require moisture to establish an infection and grow. Similarly, unlike most fungi, powdery mildew fungi do well in warm weather, and so are common at...
- Author: Alison Collin
I had a good patch of California Poppies (Eschscholzia californica) that had just finished flowering when I noticed the foliage on one of them was somewhat grayer in color than its neighbors. I did not think much of it at the time and put it down to being some sort of natural variant. As a Master Gardener I should be thoroughly ashamed of myself for not taking more notice!
The plant was suffering from powdery mildew, a fungal disease which, unlike most fungal infections, prefers dry weather. I have lived in the Owens Valley for ten years and so far have not seen much of this on my plants in previous years; even my variegated Euonymus which is renowned for its...
![Powdery mildew damage on tomato leaves. (Credit: Jack Kelly Clark)](/blogs/blogcore/blogfiles/69268small.jpg)
As you practice social distancing during COVID-19, you may find yourself spending more time in the garden. As we move into nice weather, we are sharing a few gardening tips for pest management.
Powdery Mildew
Check for signs of powdery mildew on fruit trees, landscape ornamentals, and vegetables. Symptoms can vary by plant species but common symptoms include white powdery spots developing on both sides of the leaf, leaves that turn yellow or brown and fall off, twisting and distortion of leaves and shoot. Prune out small infestations and remove infected material to reduce spread.
For more on this...
/h2>- Author: Anne E Schellman
Over the past few months, gardeners have asked the UCCE Master Gardeners for help with their grapes. They want to know:
- What's this white powdery substance on my grape plants?
- Why are my grapes so small?
- What's causing my grapes to split?
- What can I do to “save” my grape plants?
The culprit is a common grape disease called powdery mildew. This fungus leaves a telltale white powdery coating on plants. It also deforms leaves, shoots, and grapes. Young grapes can be stunted or scarred, and sometimes split open.
We've told gardeners that unfortunately, powdery mildew can't be eradicated. For now, gently hosing down plants weekly with water will help...