Pests & Diseases

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Leaves with round holes in them and green fruit with red spots on them.

Wet Weather Tree Diseases

March 26, 2024
By Belinda Messenger-Sikes
After years of drought, we welcome rain in California. But we also recognize that rain can help spread a number of plant diseases. Rain and wind can splash bacteria and fungi from infected leaves, branches, and blossoms to uninfected parts of the tree.
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Several leaves on a branch are distorted and turning red while the others are green and healthy.

Peach Leaf Curl Control Period

March 13, 2024
By Lauren Fordyce
Spring is just around the corner and many types of fruit trees are starting to develop their leaves. If you are growing peaches or nectarines and are now seeing symptoms of peach leaf curl on new leaves, unfortunately it's too late to manage the disease.
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Two leafy green seedlings drooped over onto the soil.

Damping-off of Seedlings

January 24, 2024
By Lauren Fordyce
Springtime planting is almost here but don't rush to plant seeds until the soil has warmed up! Planting seeds too soon, when the soil is cold and wet, risks losing them to damping-off, a disease caused by fungi and oomycetes in the soil.
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A hand holding brown soil.

Healthy Soil Tips

December 5, 2023
By Lauren Fordyce
Healthy Soils Week (Dec. 4-8) is a week-long initiative by the California Department of Food and Agriculture (CDFA) to highlight the importance of soil health throughout California. Healthy soils can improve crop yields, sequester carbon, reduce erosion, and increase biodiversity.
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A close up of narrow, long green leaves of a peach tree. Some leaves have curled and are red and distored from peach leaf curl.
Pests in the Urban Landscape: Article

Peach leaf curl spray timing

November 14, 2023
By Lauren Fordyce
Peach leaf curl is a fungal disease that only affects peach and nectarine trees. The fungus causes distorted, reddened leaves to appear on the tree in the spring.
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A landscape photo of an oak tree with dying, leafless branches in a meadow of dry brown grass.

Sudden oak death: what is it?

September 11, 2023
By Lauren Fordyce
Sudden oak death (SOD) is a disease syndrome that has killed millions of native oak trees (Figure 1) along the west coast of the United States, from Big Sur in California up to Southern Oregon.
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Close up of a green sycamore tree leaf with irregular brown spots.

Defoliated Sycamore Trees?

September 7, 2023
By Belinda Messenger-Sikes
Have you been seeing a lot of defoliated sycamore trees recently? Sparse foliage and early leaf drop on sycamore trees might be due to anthracnose. The cool, wet spring in many parts of California provided the perfect conditions for this disease.
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Credit: Steve Garner, Flikr.
Pests in the Urban Landscape: Article

Wet Weather Dos and Don'ts

January 11, 2023
By Lauren Fordyce
An immense amount of rain has fallen across California in recent weeks. While rain is incredibly beneficial, in excess it can cause serious problems. The continued wet conditions opens the door for many pests, so see the list of dos and don'ts below for common wet weather pest prevention tips.
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