[From the UC IPM blog Pests in the Urban Landscape]

Potato aphid adults and nymphs. (Jack Kelly Clark)

1. Aphids

These insects may be small, but they can quickly build up large populations. With many different species in California that feed on vegetables, flowers, fruit trees, and woody ornamentals, aphids are a common sight in landscapes and gardens. Year after year, aphids continue to hold the top spot. Learn more about aphids and their management in Pest Notes: Aphids. 

2. Fungus Gnats

fungus gnat. (University of Nebraska-Lincoln)

3. Thrips

Another tiny insect sometimes found on houseplants, thrips are slender insects about the size and shape of a dash printed in a newspaper. They suck out the cell contents, leaving a discolored speckling on leaves or stunting plant growth. For more about thrips monitoring and management, visit our Pest Notes: Thrips.

4. Mealybugs

If you've found soft, oval insects that are white in color with wax filaments on your indoor or outdoor plants, it is likely you have mealybugs. These wingless insects are often found in clustered colonies. In yards and gardens, handpicking, pruning, or high-pressure water sprays can reduce populations. For small infestations indoors, spot treatments may help reduce populations. For houseplants with severe infestations, consider disposing of the plant. Find additional information in Pest Notes: Mealybugs. 

5. Carpet Beetles

Adult varied carpet beetle. (Dong-Hwan Choe)

6. Peach Leaf Curl

Peach leaf curl can affect the blossoms, fruit, leaves, and shoots of peach and nectarine trees. The symptoms of the disease first appear in spring, when distorted red foliage emerges. However, focus management for nonresistant varieties in the late fall and early winter, after leaves drop. Read more about this disease in our Pest Notes: Peach Leaf Curl.

7. Clothes Moths

New to the top ten list this year were clothes moths. These pests tend to hide when disturbed, so you may not realize you have an infestation until after the moths have already damaged fabric, fur, or feathered items. Some clothes moths make webs while others are casemaking moths. Regularly monitoring and cleaning clothing and storage areas can help prevent or reduce infestations. Find more identification and management information from Pest Notes: Clothes Moths.

8. Springtails

Springtails. (Jack Kelly Clark)

9. Whiteflies

Whiteflies are not actual flies but are tiny insects that are often found on the underside of leaves, feeding on the phloem of many different plants. Certain species can cause significant loss in vegetable gardens; other species found in fruit trees are less damaging. Both adult and immature whiteflies also attack houseplants.  Management information can be found in Pest Notes: Whiteflies.

10. Scales

Scales are small, legless insects that look like tiny scabs on the stems, leaves, or fruit of plants. While some scale species can weaken a plant when abundant, other species do not appear to damage plants at all. Think you have a problem with these insects? Visit our Pest Notes: Scales for identification and management options.

Aphids

Oleander aphids on a milkweed stem. (Kathy Keatley Garvey)

According to UC Integrated Pest Management (UC IPM), aphids are small, soft pear-shaped bodied insects with long legs and antennae, with slender mouthparts used to pierce stems, leaves and other tender plant parts to suck out plant fluids. The site recommends first attempting to control aphids by washing them off with a gentle stream of water. I did this over several mornings and evenings, with my hose set on fine spray, washing both the top and underside of the leaves. After about a week, I still had quite a few aphids, so I sprayed an insecticidal soap, making sure I covered both the top and bottom of leaves. Aphids produce many offspring, so they required an additional treatment. 

Scale Insects

Black scale. (Jack Kelly Clark)

Soft scale is a sucking insect, appearing as tiny dots on the leaves or stems of a plant. They can grow up to ¼ inch long and have a smooth, cottony or waxy surface. They feed on the sap of the plant and excrete sticky honeydew, which can attract ants.  Mine were brownish-yellow with a waxy color, usually appearing on the underside of the leaves. 

I removed badly damaged leaves, checked undersides of the leaves for the scale and scraped off any scale I found using a wet Q-tip.  I also checked my other two plants and occasionally found a scale or two on them, scraping them off also.  I repotted the infested plant with potting mix. Over time I was able to completely get rid of the soft scale.

Whiteflies

Greenhouse whiteflies and nymphs. (Jack Kelly Clark)

 My Buggy Summer Summary

It has been an educational summer learning about these insect pests and dealing with their infestations. I'm gratified I've been able to manage them using less toxic pesticides that are less harmful to beneficial insects and the environment. You can learn more about less toxic pesticides such as insecticidal soaps and oils by visiting the UC IPM website or by watching this video. 

Denise is a UCCE Stanislaus County Master Gardener.

[From UC IPM's Pests in the Urban Landscape Blog]

Aphid adults and nymphs. (Credit: Jack Kelly Clark)

At some point, all of us encounter a pest in our home, garden, or landscape. But you're not alone! UC IPM publishes Pest Notes – a series of more than 150 papers reviewed by experts in the field – to provide science-based information about pests and their management.

These ten Pest Notes were the most frequently viewed online in 2019, with more than 330,000 total pageviews. While it's not a contest, we like to think these are the winners of 2019's most popular pests.

1. Aphids

These small, soft-bodied insects can multiply rapidly, especially in warm weather. Many species exist in California, feeding on vegetables,flowers, fruit trees, and woody ornamentals. Their sticky honeydew encourages growth of sooty mold, while their feeding can distort growth or transmit viruses from plant to plant. Managing ants and supporting natural enemies are two ways you can reduce aphid damage. Learn more about aphids and their manaent in the Pest Notes: Aphids.

 2. Thrips

Thrips are tiny, slender insects about the size and shape of a dash printed in a newspaper. Some are beneficial predators that feed on other insects and mites. But most feed on plants, sucking out the cell contents, leaving a discolored speckling on leaves or stunting plant growth. An integrated approach is recommended for management, incorporating good cultural practices, natural enemies, and least-toxic insecticides if needed. For more about thrips monitoring and management, visit our Pest Notes: Thrips.

 3. Peach Leaf Curl

Peach leaf curl. (Credit: Jack Kelly Clark)

Peach leaf curl can affect the blossoms, fruit, leaves, and shoots of peach and nectarine trees. The symptoms of the disease first appear in spring, when distorted red foliage emerges. However, focus management for nonresistant varieties in the late fall and early winter, after leaves drop. Read more about this disease in our Pest Notes: Peach Leaf Curl.

 4. Scales

Scales are small, legless insects that look like tiny scabs on the stems, leaves, or fruit of plants. While some scale species can weaken a plant when abundant, other species do not appear to damage plants at all. Think you have a problem with these insects? Visit our Pest Notes: Scales for identification and management options.

 5. Fungus Gnats

This pest was surprising to find in this year's top 10. Fungus gnats are small flies that often infest soil and potting mixing, emerging from indoor houseplants and becoming a nuisance. The larvae, or immatures, can damage roots and stunt plant growth when present in large numbers. If you do see these flies flitting about, sticky traps may be effective in reducing the problem. However, the presence of gnats and decline of house plants are more commonly due to too much or too little water and improper soil conditions. More information on these frustrating flies can be found in our Pest Notes: Fungus Gnats.

 6. Mealybugs

If you've found soft, oval insects that are white in color with wax filaments on your plants, it is likely you have mealybugs. These wingless insects are often found in clustered colonies on indoor and outdoor plants. In yards and gardens, handpicking, pruning, or high-pressure water sprays can reduce populations. For small infestations indoors, spot treatments may help reduce populations. For houseplants with severe infestations, consider disposing of the plant. Find additional information in Pest Notes: Mealybugs.

 7. Opossum

Adult opposum in a tree. (Credit: R. O'Connell)

In residential areas, this not so mysterious marsupial will take up residence under porches, decks, garden sheds, attics, and basements. Opossums are nocturnal omnivores, foraging for fruits, nuts, plants, insects, snails, and even small mammals such as mice. In addition to being a nuisance in residential areas, they carry various diseases that can be transmitted to humans including tuberculosis, spotted fever, and typhus. The best control for opossums is to screen or block access to areas where they may den. You may also choose to hire a professional wildlife control operator to trap and dispense of any opossum visitors. Pest Notes: Opossum has more on the biology and management of these animals.

 8. Carpet Beetles

Carpet beetle adults are typically brought into the home on cut flowers or when they fly in through open doors, windows, or holes in screens. The immature beetles feed on animal products such as wool, silk, leather, fur, and hair. Regular cleaning of rugs, upholstered furniture and closets as well as eliminating accumulations of lint, hair, and other debris is an important preventive measure. Check out the Pest Notes: Carpet Beetles for more preventive and management methods of these pests.

 9. Ground Squirrels

Ground squirrels are troublesome rodents found throughout most of California. Their network of burrows can be extensive, damaging trees, lawns, and structures. Ground squirrels can also damage many food-bearing and ornamental plants in yards and gardens. For legal management methods, see our Pest Notes: Ground Squirrels.

 10. Whiteflies

Whiteflies are not actual flies but are tiny insects that are often found on the underside of leaves, feeding on the phloem of many different plants. Certain species can cause significant loss in vegetable gardens; other species found in fruit trees are less damaging. In home gardens, reflective mulch can repel whiteflies and yellow sticky traps can reduce numbers of high infestations. Additional management information can be found in Pest Notes: Whiteflies.

Aphids are a common garden pest in spring and are attracted to new, succulent plant growth. This year, heavy aphid infestations can already be found on roses and fruit trees.

Aphids often first show up along the edges of the garden. Many species infest the undersides of leaves first, so turn leaves over while looking for aphids. On some plant species, especially plum and apple trees, aphid feeding causes the leaves to curl. Once this happens, it's harder to obtain control because the curled leaves protect the pests from natural enemies or sprays.

Aphid infestation on a rose. (Pexels.com)

When you find aphids, check for evidence of natural enemies like lady beetles, lacewings,  syrphid fly larvae, and the mummified skins of parasitized aphids. Learn to recognize aphid “mummies,” as they indicate the presence of tiny parasitic wasps that lay eggs inside the aphids. The wasp larva hatches and feeds inside the aphid, killing it. The skin of dead aphids turns crusty and golden brown or black, a form called a mummy. Not long after, the adult wasp chews an exit hole and emerges from the aphid's body. During warm weather, parasitic wasps may have several generations and cause a rapid decline in aphid populations.

There are fungus diseases that infect aphids, especially when it's warm and humid. Entire populations of aphids may be killed when conditions are right. While aphids thrive under mild temperatures, populations of many species are reduced by hot summer weather conditions. If you have any of these natural controls at work, the aphid population may crash rapidly.

Aphid "mummies" and a parasitic wasp. (Jack Kelly Clark, UC IPM)

You may be able to control aphids in your trees by controlling ants. If large numbers of ants are seen climbing up and down tree trunks, it may mean an aphid infestation. Ants are attracted to the honeydew produced by the aphids.  If you plan to use pesticides for ant control, first seek out and treat the ants' nests in the ground near the tree. Or, place sticky barriers around the tree trunk to keep the ants from reaching the aphids. Unprotected by the ants, the aphids may then be attacked by natural enemies.

You can help prevent aphid infestations, especially in vegetables, by removing weeds where aphids may be building up. Also, check transplants for aphids and remove them before planting. If you notice a few curled leaves on your fruit trees, the best control may be to simply prune out and dispose of the infested shoots and leaves.