Friday, July 7, 2017

Japanese Beetle Update - July/August 2017

Oh my, here we go again... the adult Japanese beetles have not only emerged, they've staked out their favorite plants and aren't leaving, just like relatives who don't follow the three-day stay rule. And to make matters worse, more relatives are showing up every day - eating and leaving plant destruction. There's just no more room at the inn guys and gals, time to take action!

My Japanese beetle removal action plan is in place. I use an alternating spray approach with a homemade cedar wood essential oil formula (**not research based), organic neem oil containing azadirachtin and mail ordered organic Btg called beetleJUS! 

The silver lace vines in our yard are just too tall to safely reach to flick to their soapy water death. So I am spraying the vines every few days in the hope that direct contact will take several out and repel their relatives for awhile. The plan is working.

Mixing up controls is recommended by local expert horticulturists and simply makes sense since there is not ONE perfect permanent elimination method, spray or granular for them. Unfortunately Japanese beetles are here to stay and we need to accept and just deal with them like any other pest insect.

Use care when using any spray (even ones listed as organic) and avoid contact with beneficial pollinators and insects. Spray very late in the day, bees stay up until the last light of the evening, so wait until they've left the area. And if using a home brew, test plant foliage on a few leaves to make sure it doesn't burn or adversely affect the plant. 


Controls:

Try to reduce adult numbers immediately by tossing into soapy water. The research confirms that removing adult beetles reduces their damage to plants and attractiveness to the plants. As volatile compounds are released from chewed plants the more attracted beetles are to those plants.

Scout for them early in the morning or late in the day when they are more sluggish and easy to flick. If squeamish, pay your children a nickle for each removed beetle, caution, if you live in central Denver where beetles have been a problem for several years, you may have to take out a loan for payment.

Mechanical Control: If you have a few rose shrubs or containers of plants that need protection for the weeks in the summer while Japanese beetles are in the garden you might consider using a mesh fabric or bridal veil (tulle) as shown in the Smart Pot containing basil. It is an expensive material to purchase from fabric stores. Replace every few years as needed.

Lawn Watering Cultural Control: JBs love moist turf conditions and if the lawn is mowed at low settings, then the table has been set for them! Try drying them out during their egg-laying months in June, July and August. They don't like dry lawns and if eggs and larvae are present, they may dry out as well. Yes, your lawn may suffer or go dormant, but it works. Be sure to deeply water trees that are growing in the lawn if you ease back on lawn watering. Resume regular watering and fertilization in late summer to fall to promote turf recovery.

Bridal Veil over Basil Growing in a Smart Pot
More Control Options for both Adult and Larval Stage (click on link):

From the Colorado Department of Agriculture - Best Management Strategies

From Colorado State University - Japanese Beetle Fact Sheet 5.601

From Department of Bioagricultural Sciences and Pest Management (CSU) - 
Japanese Beetle PowerPoint

Daniel Potter and David Held - University of Kentucky, Biology and Management of the Japanese Beetle 2002

United States Department of Agriculture -
Japanese beetle identification and life cycle 

Japanese Beetle traps for adults are not recommended, they attract more beetles not only to the trap, but to surrounding plants. Garden centers will gladly sell them to you but you're better off living next door to someone who puts up a trap - the beetles will go over there! 

No later than mid-August I will apply either *Chlorantraniliprole (trade names - Acelepryn or Scott's Grub-Ex) on the turf (where females lay eggs) to kill developing larvae that will be next year's generation of adult beetles. Or Btg, known as grubHALT!™, which is only available mail order at this time. Other, environmentally safe biological controls are available to the home owner, check the links above for more information. 

Timing is everything, get going by mid-summer if you wish to treat your turf for eggs/larvae this summer.

Keep in mind that large numbers of feeding JB larvae can hurt or kill grass turf. That hasn't happened in my yard and shouldn't as long as it is treated each summer.

*Fairly new registered insecticides that have a much lower potential hazard to pollinators than other insecticides used for Japanese beetle larvae control. 


**Betty's Cedar Oil Spray (not endorsed or researched by university or professional horticulturists)
Now Foods, Essential Oils, Cedarwood, 1 fl oz (30 ml)
Internet Photo
  • 1 teaspoon of cedar essential oil (sold at natural grocery stores, one ounce costs around five dollars and it will make several 32-ounce batches)
  • 3 tablespoons of soybean oil found at H Mart, an Asian market in Aurora, under $8.00 for a half gallon.
  • Add to at least 32-35 ounces of water in a spray bottle, shake well and start spraying the little brutes late in the day. 
  • Always spray late in the day (near dark) when pollinators are not in the area.
  • Always test plant foliage on a few leaves to make sure it doesn't burn or adversely affect the plant.
Cedar spray will kill adult Japanese beetles in a few hours if direct contact is made with the spray on the beetle. If plant foliage is fine after testing, then spraying often should be fine under the conditions outlined - late in the evening, after ALL pollinators are gone for the day. Aim for cloudy, cooler evenings if possible.

Plant Lists:

The plants they favor or mostly avoid is compiled to the best of my knowledge from reliable university and government fact-based publications and websites. 

*Have seen on both like and dislike lists (please email me with your plant additions/comments).

Trees/Shrubs JB Favor
Trees/Shrubs JB Do Not Favor
Perennials JB Favor
Perennials JB Do Not Favor
American and English Elm
Arborvitae
Grape
Hellebore
Birch
Boxelder
Hollyhock
Iris
Black Walnut
Boxwood
Rose
Liatris
Hawthorn
Dogwood
Raspberry
Lily
Horse Chestnut
Euonymus (burning bush)
Virginia Creeper
Columbine
Norway Maple
Forsythia
Silver Lace Vines
Lily-of-the-Valley
Larch
Holly
Hibiscus
Coreopsis
Linden
Juniper
Common Mallow (weed)
Larkspur
London Planetree
Lilac (Common)
Evening Primrose
California Poppy
Malus spp. (crabapple, apple, etc.)
Magnolia
*Clematis
Foxglove
Mountain Ash
Mulberry
Peony
Coral Bells
Pin Oak
Northern Red Oak
Joe Pye Weed
Hosta
Pussywillow
Pine
St. John’s Wort
Impatiens
Prunus (flowering cherry, etc.)
Red and Silver Maples
Coneflowers


Beech
Redbud
Hops
Forget-me-knot
Rose of Sharon
Spruce

Pachysandra
Rose Shrubs
Sweet Gum

Poppy

Tulip tree

Moss Rose

Yew

Sedum



Yarrow



Milkweed and Butterfly Weed



Aster



Baptisia



White Mums



Dianthus



Bleeding Heart



Gallardia



Geum



Baby’s Breath



English Ivy



*Beebalm



Obedient Plant



Spiderwort



Veronica






Annuals/Vegetables/Herbs JB Favor
Annuals/Vegetables/Herbs JB Do Not Favor
Cannas
Begonias
Gladiolus
Caladiums
Sunflower
Dusty Miller
Morning Glory
Ageratum
Cardinal Flower
Lantana
Zinnia
Nasturtium
Anemone
Violet/Pansy
Dahlia
White Geranium
Sweet Potato Vine (seem to like darker varieties) in my garden
Snap Dragons
Asparagus
*Cosmos
Rhubarb
Ornamental Kale
Green Beans
Nicotiana
Soybeans
Ornamental Pepper
Sweet Corn
Petunia
Strawberries
Portulaca

Verbena

Garlic

Rue

Tansy

Catnip

Chives

Leeks

Onions

Tomatoes










6 comments:

  1. Just discovered them on my front rose bushes and thought to myself "I need to google how to get rid of them..." Instead I came to your blog page and voila, you've anticipated my problem. Going to get my soapy water right now!

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    Replies
    1. YES Christie, flicking them into soapy water will reduce overall numbers on your plants and next year's generation (dead beetles can't lay eggs in your lawn)!

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  2. I bought the ingredients for your solution and used it yesterday. I am not clear from your blog about the intent of using this solution. Is it to kill the beetles, or just to deter them from coming back? How often can we use this solution on a plant?

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  3. Hi Lynne - spraying this cedar solution directly on adult beetles will kill them, not immediately, but in a few hours or so. It may deter, but it's meant more to kill them on contact. Spraying late in the evening after pollinators have left the area is the best time.

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    Replies
    1. Thanks, Betty. Is it safe to spray the same area daily?

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  4. I spray the cedar twice a week on very still (no wind) evenings, and I try to choose a cooler, cloudy evening too (tonight, Monday will be very hot since it has been sunny ALL day). Since I've been spraying since they emerged, they seem to be manageable. I know more show up each day but since I will spray in a few days they don't get too out of control. As I mentioned in the blog, I change up sprays, next time I will use Btg (mail ordered from Gardens Alive) and at the end of the week I may use Bio-Neem which contains azadirachtin. Back to your question....if you ONLY use the cedar brew two - three times a week, I think you will kill many beetles and have peace of mind that you are doing something pro-active to kill them. I don't cedar spray the silver lace vines every night, BUT if your plants are not showing any ill effects from the cedar spray then they should be okay to spray often. But I can't stress enough - test an area of your foliage first, make sure your plants are fine after being sprayed (spray a small area, then wait a couple of days). Follow the formula, I don't veer from the ingredient proportions, remember this is NOT researched by anyone but me and a couple other gardeners I know who are trying it with success.

    Happy to answer any further questions - Betty

    ReplyDelete