Wednesday, June 23, 2021


Gardening Corner: Popular Pandemic Pest Notes

Pest Notes are UC IPM publications written for people who want information about pests in homes, office buildings, schools, gardens, urban landscapes, and more. We have more than 170 peer-reviewed Pest Notes on topics ranging from ants to the Zoropsis spider, all available on our website,

We took a look at which titles were of greatest interest during the first five months of the COVID-19 pandemic when many Californians were staying home. These are the top ten most viewed Pest Notes from March to August 2020.

#8 Whiteflies

Whiteflies are tiny, sap-sucking insects that can become abundant in vegetable and ornamental plantings, especially during warm weather.

Signs of a whitefly infestation can include: Tiny nymphs on the underside of leaves; Sticky honeydew on leaves, fruit, or beneath plants, or a covering of black sooty mold; Yellowing, silvering, or drying leaves that have whitefly nymphs on them; Deposits of white wax (with certain whiteflies).

#7 Scales

Scales are immobile insects that suck plant juices from many types of trees, shrubs, and houseplants.

What does scale damage look like?

Damage resembles that of aphids and whiteflies. There is abundant sticky honeydew (excreted by soft scales and certain other species). Black sooty mold may be growing on the honeydew. Discolored, distorted, or dying leaves, twigs, or branches (especially with armored scales) may be present.

#6 Carpet Beetles

Carpet beetles can be found in homes, warehouses, museums, or anywhere else fabric, furs, and feathers are present.

How did carpet beetles get in my house? Carpet beetle adults are pollen feeders and are found on flowers with abundant pollen like crape myrtle, spiraea, and buckwheat; People often bring carpet beetles into their homes on cut flowers from the garden; Adults can fly in through open windows or doors without screens.

#5 Ground Squirrels

Ground squirrels may be cute and furry but they can injure many types of plants, harbor diseases harmful to humans, and damage landscapes with their burrowing.

Ground squirrels cause damage by, eating food-bearing and ornamental plants, gnawing on plastic sprinklers and irrigation lines, girdling young trees, and burrowing, which causes trip hazards and damages landscapes and structures.

#4 mealybugs

Mealybugs are small, soft, wax-covered insects that are common problems on houseplants and on outdoor plants in areas with mild winters.

What do mealybugs look like?

Most adult mealybugs are wingless females with oval, segmented bodies covered with wax. Males have wings but are rarely seen. Newly hatched mealybug immatures move around plants but soon settle down and produce a waxy covering. Different mealybug species can be distinguished by the length of the waxy filaments around their bodies. They may be confused with other insects that produce wax and honeydew like cottony cushion scale, woolly aphids, soft scales, and whiteflies. Mealybugs are sometimes hard to see. They often live in protected areas of plants such as in the crown of a plant, in branch crotches, or on stems near the soil.

Mealybugs suck sap, weakening plants. High populations can slow plant growth and cause leaf drop.

#3 Aphids

Almost every plant has one or more aphid species that occasionally feed on it, so it’s no wonder that so many people viewed this publication. Although aphids can curl leaves and produce sticky honeydew, they rarely kill plants, and can usually be washed off with water.

How can you reduce aphids? Prune infested leaves and stems; Knock aphid populations off plants by shaking the plant or spraying it with a strong stream of water; Protect seedlings with covers or aluminum foil mulches; Wait for hot weather; some aphids are heat-intolerant and will be gone by mid-summer.

#2 Fungus Gnats

Fungus gnats are small flies that infest soil, potting mix, other container media, and other sources of organic decomposition. Because adult fungus gnats are attracted to light, you first might notice these pests flying near windows indoors. If you spot fungus gnats flying around, check your plant pots. If the soil in the pots is overly moist, fungus gnat larvae could be feeding on the plant roots.

What can you do about fungus gnats?

Avoid overwatering and provide good drainage. Allow the surface of container soil to dry between waterings. Clean up standing water, and eliminate any plumbing or irrigation system leaks. Avoid using incompletely-composted organic matter in potting media unless it is pasteurized first, because it will often be infested with fungus gnats. Screen and caulk leaky windows and doors to help prevent pests like fungus gnats from coming indoors.

#1 Peach Leaf Curl

Our top viewed Pest Notes was peach leaf curl, a fungal disease that affects only peach and nectarine trees. Distorted, reddened foliage in spring is a distinctive symptom of peach leaf curl. Unfortunately, by the time you see symptoms, it’s too late to do anything this year. In order to manage this disease, treat trees with a fungicide in late fall and winter.

How do you effectively manage peach leaf curl? The fungal spores that cause the disease spend the winter on twigs and buds and germinate in the spring; For effective control, treat trees just after leaves have fallen, usually late November or December; Consider a second application in late winter before buds swell, especially in areas with high rainfall or during wet winters; Don’t apply fungicides during the growing season because they won’t be effective.

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