Ilex vs The Japanese Beetle

Some woodies seem to attract the Japanese Beetle (Popillia japonica) like a tween to Justin Beiber, whereas others don’t seem to exist to them. Why is that? Some scientists have experimented as to just what makes a Japanese Beetle want to eat a plant… or not.

Things that seem to attract them are:jap beetles

  • Lightly pubescent leaves
  • Red or burgundy leaves
  • Light colored roses

They seem to dislike:

  • Heavy pubescent leaves
  • Waxy, or glossy leaves
  • Darker colored roses

The following information should not be taken to the bank, but used as a guide to choose better (or try to) planting options. The following plants seem to have a neon sign hanging in their branches saying, “EAT ME”:

  • Acer palmatum – Japanese maple
  • Acer platanoides – Norway maple
  • Betula populifolia – Gray birch
  • Clethra alnifolia Summersweet – clethra
  • Castanea dentate – American chestnut
  • Aesculus hippocastanum – Horsechestnut
  • Juglans nigra – Black walnut
  • Sassafras albidum – Common sassafras
  • Lagerstroemia – Crapemyrtle
  • Malus baccata-  ‘Liset’ ‘Royalty’
  • Platanus × acerifolia – London planetree
  • Prunus × cistena Purpleleaf – sandcherry
  • Prunus sargentii – Sargent cherry
  • Prunus serotina – Black cherry
  • Prunus serrulata ‘Mt. Fuji’ – Mt. Fuji Oriental cherry
  • Prunus subhirtella ‘Autumnalis Rosea’
  • Prunus × incamp ‘Okame’  – Okame cherry
  • Rosa spp. and hybrids Roses
  • Sorbus Americana – American mountain ash
  • Ulmus Americana – American elm
  • Ulmus procera – English elm
  • Tilia cordata – ‘Greenspire’ and ‘Olympic’

Control on a larger specimen is very difficult. It is better to take a few of the control options and work a plan out for the season. If one type of control doesn’t seem to work switch gears, and try another. You may need an application of a systemic insecticide like imidacloprid by a licensed arborist.

Pheromone beetle traps are a misconception. Yes, the bag gets full, but the beetles aren’t great fliers, and most of them will not find the trap. This trap now becomes an attractant for them to your area.

Try these IPM (Integrated pest management) options & if one doesn’t work, move on to another:

  • Make sure the plant is in great health.
  • In the morning, place a sheet under tree and shake the beetles off.
  • Use a hose end sprayer to apply Neem (an organic pesticide) to branches it reaches when you see the beetles.
  • The two nematodes that are most effective against Japanese beetle grubs are Steinernema glaseri and Heterorhabditis bacteriophora. The latter is commercially available.
  • Apply Milky Spore to your lawn area only if you’ve seen grub activity in your lawn during the spring. Many experts do question it’s effectiveness, though.
  • Make your yard attractive to birds that might eat them.
  • Attract the solitary fly (Istocheta aldrichii) and the parasitic wasp (Tiphia vernalis) that lays its eggs inside the adult beetles (fly) or the grubs (wasp). Adult wasps feed almost exclusively on the honeydew of aphids associated with the leaves of maple, cherry, and elm trees and peonies.

© Ilex Farrell – Midwestern Plant Girl

5 thoughts on “Ilex vs The Japanese Beetle

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