beetles in soil #144972 - Ask Extension


beetles in soil #144972

Asked August 03, 2013, 8:43 AM EDT

My rose bushes were beetle ridden. I sprayed with Ortho Rose and flower insect killer along with several beetle catchers hoping to rid the problem; however, both were only semi effective.  As I was weeding around the base of the bushes,   beetles were burrowed in the soil.   Please help as I have no clue what to do next to rid my soil of these pests, to literally get to the base of the problem. Thank you in advance.

Kent County Delaware

Expert Response

You really have a 2 part problem - getting rid of the adults and than getting rid of them in the soil.  For the adults: Step one is Neem oil applied to plants the beetles feed on every 1-2 weeks depending on the amount of rain. The neem oil seems to persuade the hordes they really do not want to eat the plant, but some still will.
Step two is a daily garden walk. Sometimes you can squish them, but if there are more than one or two, you can use a small bucket of soapy water and knock them into it. They do not escape, they just die. I prefer the bucket to finger squishing when there is more than one in an area   
Step 3 are the chemical pyrethrins used sparingly and only on those plants the beetles seem to be doing the most damage to. You will want to follow the package directions exactly when applying.

For the beetles in the soil, they are now in their reproductive stage and are laying their eggs in the soil.  You can pick out the adults and drop them in soapy water and/or you can wait until the grubs have hatched.  You will want to wait until late August or September and than decide which way you want to handle the grub problem..  
  • For a biological approach, water the ground, and apply parasitic nematodes to the soil when the Japanese beetle grubs are small. Each grub is about 1 inch (2.5 cm) in length and is oftentimes found in the curled position. The 2 types of nematodes that are most effective include Steinerema glaseri and Heterorhabditis bacteriophora. You need to mix the nematodes with water, and applied to the ground fairly quickly. Water after application.
  • You can chemically remove grubs by applying insecticides. Some may be applied before you notice a grub problem but have high Japanese beetle activity. Others are applied in the early fall once the eggs have hatched and grubs are present. Make sure you read the label on the insecticide before you purchase it and follow the package directions exactly.
  • There are 2 schools of thought with the JB traps.  Some say they are effective and others disagree..  With their pheromones they attract every beetle within a 1/4 mile radius.  If you wish to use them, than make sure you place them at the very edge of your property and far away from your roses.
  • I hope this helps.  Good luck

  • Suzan Swartz Replied August 05, 2013, 8:40 PM EDT

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