Pests In July

Written By: Chad Kuwana, Master Gardener Volunteer Trainee

Black vine weevil
Credit: University of California Agriculture & Natural Resources

Check back in with your azaleas and rhododendrons this summer!

At this point of the year, summer is in full swing and daily high temperatures are consistently in the upper eighties and nineties. The beautiful spring weather that brought about stunning blooms in your garden is just a memory as you try to beat the heat with some freshly picked berries.

While some spring blooms may be holding on, most azalea and rhododendron bushes have lost their flowers and your attention has likely shifted to other parts of your garden like your fruits and vegetables. However, as you water your plants, you might notice notched edges on the leaves or fuzzy white spots on the branches of your azaleas or rhododendrons. These are signs that black vine weevils or scale might be present on your plants.

Black Vine Weevils – Otiorhynchus sulcatus

Description

Black vine weevils are a type of beetle (Curculionidae) about ½ inch (12.7 mm) long. They cannot fly and are mostly black with small patches of white. The larvae are also about ½ inch (1.27 cm) long but are white with a brown head. Adult black vine weevils eat foliage and are most active at night. You will notice notches in leaves from where they were feeding. Larvae, however, feed on the roots of your azalea or rhododendron, so they can cause more severe damage to your plant as it can lead to diseases like Phytophthora root rot.

Damage from the black vine weevil.
Credit: University of California Agriculture & Natural Resources

Life Cycle

The reason you might be noticing evidence of their presence in July and early August is because of their life cycle. Black vine weevils usually emerge between May and June after overwintering in their larvae stage. Upon emerging they need anywhere between 21 and 28 days of feeding before they are ready to lay eggs and begin a new generation. Thus, peak adult populations are seen in the summer. Once they are ready to lay their eggs, black vine weevils can lay as many as 500 eggs over a two to three-week period.

Control

Assuming you don’t have cultivars that are less susceptible to weevils in your garden, there are a few things you can do. 

If you’ve caught it early and the weevil population isn’t overwhelming, you can get rid of the weevils by hand. Once it’s dark (remember they are active at night), you can shake and beat the leaves over a sheet that will collect the fallen weevils and then dispose of them.

Another option is to use corrugated cardboard as a wrap around the trunk (also overnight). This wrap will serve as a trap so that when they seek shelter during the day, you can collect and dispose of them. Instead of a cardboard wrap, you can use a sticky material that will trap the weevils as they crawl up and down the trunk.

Lastly, you can also use parasitic nematodes to help control the infestation at the larval stage.

Azalea (rhododendron) Bark Scale – Eriococcus azaleae

Credit: Michigan State University Extension

Description

Azalea bark scale are small insects about .13 inches (3.3 mm) long. They are red in color but are most recognizable by the fuzzy white sacs on twigs and branches. These egg sacs or ovisacs are important to remove during the summer so they do not hatch. When they hatch in September, the young scale will start to feed on the azalea or rhododendron by penetrating the bark and sucking out sap and will excrete a substance called honeydew. This honeydew will invite sooty mold and fungi to grow and cause your plant to look darkened, yellow, and/or sickly.

Credit: Michigan State University Extension

Life Cycle

The azalea bark scale lay their eggs in early April to hatch in May. During the summer, the young scale will feed and mature to produce the fuzzy white sacs in June and July. This is when you might notice the sticky substance on branches called honeydew and sooty mold covering the leaves. You might also start to see more fuzzy white sacs on the twigs and branches.

Control

Starting with the fuzzy white sacs, you can brush them off with your fingernail or toothbrush. If an area is heavily infested, pruning is the best method for removal. Keep in mind also that fertilizing with too much nitrogen will support the population growth of scale.

Wrapping Up

Hopefully, this post can help you get familiar with these two pests that might be hurting your azaleas and/or rhododendrons. Please reference the resources below for more detailed and extensive information on monitoring and controlling these pests in your garden. It’s easy to forget all the details that go into keeping up your garden so make sure to check in with the OSU Extension Monthly Garden Calendar to help you stay on top of key garden chores throughout the year.

References

Before Reaching for Pesticides, Get to Know Beneficials – The Good Guys!

By Judi Di Bord, Master Gardener Volunteer

Did you know there is an alternative to controlling pests in your garden by using a pesticide?  Attracting beneficial insects, like lady beetles, green lacewings, praying mantis and dragonflies can help control insects that feed on your plants.  Beneficials don’t just help control pests. Some beneficials are also important pollinators! 

Ladybug (Coccinella septempunctata) on an Common Yarrow's umbel (Achillea millefolium)
Ladybug (Coccinella septempunctata) on an Common Yarrow’s umbel (Achillea millefolium). By Hélène Rival on Wikimedia Commons.

How can you attract beneficials to your garden?  One way is to purchase them at a local garden center and release them into your garden.  You can also attract them to your garden by growing plants to provide an enticing habitat for them.  If you are able to dedicate some space to growing these habitat plants, the rest of your garden can reap the rewards.

Following are some recommendations from the Penn State Extension Service:

  • Carrot Family (Apiaceae)  Plants in the carrot family are especially attractive to small parasitic wasps and flies. Interplant them in your vegetable garden and flower beds. Plants in this family include: caraway (Carum carvi); coriander/cilantro (Coriandrum sativum); dill (Anethum graveolens); fennel (Foeniculum vulgare); Bishop’s flower (Ammi majus); Queen Anne’s Lace (Daucus carota); and toothpick ammi (Ammi visnaga).
  • Aster Family (Asteraceae)  Attractive to larger predators such as lady beetles and soldier beetles. Incorporate into the vegetable garden and flower beds. Plants in this family include: blanketflower (Gaillardia spp.); coneflower (Echinacea spp.); coreopsis (Coreopsis spp.); cosmos (Cosmos spp.); golden marguerite (Anthemis tinctoria); goldenrod (Solidago spp.); signet marigold (Tagetes tenuifolia); sunflower (Helianthus spp.); tansy (Tanacetum vulgare); and yarrow (Achillea spp.).
  • Legumes (Fabaceae)  Generally grown as cover crops and attractive to many beneficials. Plants in this family include: alfalfa (Medicago sativa); fava bean (Vicia fava); hairy vetch (Vicia villosa); and sweet clover (Melilotus spp.).
  • Mustard Family (Brassicaceae)  Attractive to beneficials that are parasites and predators of the insect pests of the mustard family (broccoli, Brussels sprouts, cabbage, cauliflower, kohlrabi, mustard greens). Be sure to plant these away from the garden rather than in the garden since these plants attract pests as well as beneficials. Some are common weeds, such as yellow rocket and wild mustard. Plants in this family include: basket-of-gold alyssum (Aurinia saxatilis); mustards (Brassica spp.); sweet alyssum (Lobularia maritima); yellow rocket (Barbarea vulgaris); and wild mustard (Brassica kaber).
  • Verbena Family (Verbenaceae)  Attractive to a variety of beneficial insects. Many plants in this family are favorite garden flowers. They include: lantana (Lantana camera); Buenos Aires verbena (Verbena bonariensis); hybrid verbena (Verbena x hybrida); and lilac vervain (Verbena rigida).

Beneficial insects also need a source of water. Shallow containers such as ceramic pot saucers with pebbles for the beneficials to rest on are best.

Suggested OSU Extension publications:

PNW550: Encouraging Beneficials in Your Garden

For kids:

EC1601: The Wildlife Garden: Dragonfly

EC1604: The Wildlife Garden: Lady Beetle

EC1605: The Wildlife Garden: Praying Mantis

Suggested websites:

National Pesticide Information Center, Beneficial Insects.

Penn State Extension, Attracting Beneficial Insects

Sick plants? Get the most out of Master Gardener Plant Clinic!

By Elizabeth Records, Master Gardener Program Assistant

Previously published in Growing.
 

Three gardeners standing at info booth.
Master Gardeners are here to help at Pop up Plant Clinics in a location near you.

It’s gardening season! Whether you’re a longtime gardener or are new to growing things, OSU Extension Master Gardener Volunteers are here to help you grow your best garden yet and deal with garden challenges.

Master Gardeners are volunteers who complete a specialized training program and work as a team to help find solutions to garden problems for people in our community. We are from all walks of life and have widely varied gardening interests and experiences. Together we bring lifetimes of collective garden knowledge to solving plant problems with research-based information. Here are some scenarios where Master Gardener volunteers can help:

Plant Identification

You are digging in the garden and find an unfamiliar plant that you did not put there. Will it produce lovely flowers or tasty food? Or will it prove to be an invasive weed that takes over your garden? Master Gardener volunteers can help you find out. Bring a sample of your plant including a full branch or stem with any leaves, flowers and fruits that may be present.

Insect issues

You find a mystery insect in the garden and wonder if it is going to harm your plants or be a helpful pollinator or a useful predator of insect pests. A dozen insects appear in your garage, and you don’t know if they are a simple nuisance or are likely to feed on you, your pets or your home. Master Gardeners can help identify insects and suggest how to manage them! Bring the insect in a sealed jar, or a high resolution photo of the insect on a pale colored background, next to a ruler or coin so we can tell the size.

Gardening guidance

Just starting your first veggie garden and wondering when to plant, or what varieties do well in your location? Want to make your garden more sustainable by using less water, attracting more pollinators or using fewer chemicals? Short on space but excited to grow fresh herbs or salads on your windowsill? Whatever your gardening goals, Master Gardeners can help you find research-based information to get the most from your garden.

Diagnosis and recommendations          

Your previously healthy plant suddenly wilts. Brown spots appear in your grass. A tree that produced lots of fruit in the past stops setting fruit. Master Gardener volunteers can help figure out what is going on and decide what to do next for best results. Bring samples and/or photos that show the problem and also the surrounding area.

Get the most out of plant clinic
  • Be ready to answer questions that will help Master Gardeners hone in on the source of your problem so we can provide the best advice possible. Master Gardeners might ask, “how long has this problem been going on?” and “Are all of the similar plants affected, or just one?” “What treatments have already been attempted to remedy this situation?”
  • Bring good samples – you can always call us for suggestions to bring the most helpful samples.
  • Master Gardeners cannot answer questions about State or Federally controlled plants, identify mushrooms, or offer medical advice. We are pleased to assist with all your other garden questions to the best of our ability.
  • Sometimes we may need input from other team members or horticulture faculty to resolve your question. Be ready to share an email or phone number if we need to do some extra research and follow up.
  • Have fun and enjoy your garden, even when things don’t go as you expected!
Plant Clinics near you!

Find us at your local office most weekdays from 9-12 and 1-4. Email or leave a phone message anytime.

Benton County

  • 4077 SW Research Way, Corvallis, OR97333
  • Call with your question: (541) 766-6750
  • Email your question and any photos to: bentonmg@oregonstate.edu

Linn County