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Attack of the hoplia beetles

Sacramento Digs Gardening
BY Debbie Arrington PUBLISHED MAY 4, 2020

What happened to this rose? Hoplia beetles attacked it. (Photos:

Debbie Arrington)

This pest loves to eat light-colored roses and other spring flowers

What’s eating your roses? If it’s early May in Sacramento, most likely you’ve been visited by hoplia beetles.

This pest loves light-colored roses, especially white, yellow, apricot or light pink. It chews round holes in the petals as it works its way to the tasty center. It likes the unopened buds, too. But it doesn’t eat rose leaves – just the flowers.

According to UC Cooperative Extension master gardeners, hoplia beetles also feed on the flowers of calla, citrus, irises, lilies, magnolia, olive, peonies, poppies and strawberries, and on the young leaves and fruit of almonds, grapes and peaches.

In other words, these beetles are hungry, destructive pests.

Members of the monkey beetle family, hoplias are common in our area from late March through May, depending on the weather. More than 300 species of hoplia are known. Our most common local hoplias are Hoplia callipyge . The adults are brown, oval and about 1/4 inch long.

The adult beetles can fly, which is how they made it to your roses. They over-winter in the larval or pupal stage underground in undisturbed areas, feeding on roots and decaying vegetation. They emerge from the soil as adult beetles with an appetite. After feeding for several weeks, they fly back to their nesting site to lay eggs.

This life cycle takes a full year, which is key to their control. They’re only a problem right now. By the end of May, they’ll have disappeared.

This hoplia was eating a rose Sunday in midtown Sacramento.

Because the beetle tunnels into the bloom, chemical pesticides are not effective – or necessary. The pesticide has to come in direct contact with the beetle to kill it. In addition, systemic insecticides aren’t effective because concentrations of the poison in the plant’s petals aren’t high enough to be effective.

When you see a rose or other flower with hoplias, cut off the whole bloom, drop it in a plastic bag, seal and dispose of it.

Or use the bucket method: Fill a 5-gallon bucket with soapy water. Then, shake flowers suspected of containing beetles over the bucket. The beetles will fall in and drown.

Hoplias are attracted to white, so try this trick: Fill white buckets (preferably 5-gallon) or other large containers with water; the important thing is that these containers are white. Add a few drops of detergent to the water to break surface tension. Place these beetle traps at several locations among your rose bushes. Thinking it's a giant white bloom, hoplias will fly into the white bucket and meet a watery death.

The other solution? Stick to red roses; hoplias don’t like red.

For more information on hoplia beetles, check out the UC Integrated Pest Management pest notes at: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7499.html

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GENERAL GARDENING

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Keywords:

UCCE master gardeners hoplia beetles gardening Sacramento integrated pest management insecticides pest damage pests roses spring flowers UC IPM

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Garden Checklist for week of May 5

Survey your garden after the May 4 rainstorm. Heavy rain and gusty winds can break the neck of large flowers such as roses. Also:

* Keep an eye on new transplants or seedlings; they could take a pounding from the rain.

* Watch out for powdery mildew. Warmth following moist conditions can cause this fungal disease to “bloom,” too. If you see a leaf that looks like it’s dusted with powdered sugar, snip it off.

* After the storm, start setting out tomato transplants, but wait on the peppers and eggplants (they want warmer nights). Pinch off any flowers on new transplants to make them concentrate on establishing roots instead of setting premature fruit.

* Trim dead flowers but not leaves from spring-flowering bulbs such as daffodils and tulips. Those leaves gather energy to create next year's flowers. Also, give the bulbs a fertilizer boost after bloom.

* Pinch chrysanthemums back to 12 inches for fall flowers. Cut old stems to the ground.

* Mulch around plants to conserve moisture and control weeds.

* From seed, plant beans, beets, cantaloupes, carrots, corn, cucumbers, melons, pumpkins, radishes and squash.

* Plant onion sets.

* In the flower garden, plant seeds for asters, cosmos, celosia, marigolds, salvia, sunflowers and zinnias. Transplant petunias, zinnias, geraniums and other summer bloomers.

* Plant perennials and dahlia tubers for summer bloom.

* Don’t wait; plant summer bulbs, such as gladiolus and tuberous begonias.

* Harvest cabbage, lettuce, peas and green onions.

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