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 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.


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 Information Colorado - check out my dedicated JB website

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. 

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