Using Neem Oil to Kill Japanese Beetle Larvae

Neem oil is an excellent resource for killing an adult Japanese beetle. Japanese beetle larvae are hatched in the upper surface of the soil of a lawn and spend the first year of their life underground. To prevent their larvae you have to kill the adult beetles.

Step 1 – Make a Neem Oil Mixture

Neem oil is an extract from the neem tree and is very much like a detergent in the way it acts. You will need a gallon of water, an ounce of Neem oil and a teaspoon of mild liquid soap. Mix the soap and water and then add the Neem oil slowly while stirring constantly.

Step 2 – Fill a Spray Bottle

A hand spray bottle is ideal for applying the mixture to the plants. The best times to spray are early morning and early evening. Make sure all of the plant surfaces are covered. Saturate the soil under the plants as well.

Step 3 – Repeat as Required

The spray needs renewing once a week. You should also re-spray after rain. The spray will not kill the insects (unless you manage to spray them directly) but it will make the plants smell and taste unappetizing. If the insects do ingest the mixture it will start to attack the hard exoskeleton and the beetle will eventually die when it collapses. Insects that do not eat the leaves or stems of the plants will not be affected.

Step 4 – Prepare to Attack the Larvae

Now that you have made a significant reduction in beetle numbers you must turn to the larvae. Insecticides can be used against the larvae but they are not always safe or effective.

Step 5 – Biological Warfare

Milky Spore disease is caused by bacteria and can now be bought in a dry powder form. Milky Spore disease attacks and kills the larvae of the Japanese beetle.

Step 6 – Spread the Milky Spore Powder

Spread the powder carefully over your lawn and other suspect areas of your garden. The bacteria will be eaten by the larvae. The bacteria increase at a great rate inside the larvae and eventually kill it. As the dead larvae decompose, the bacteria are freed into the soil again and are ready to attack the next batch of larvae.

Step 7 – Self Perpetuating

The Milky Spore bacteria will reproduce and it will maintain a high level of protection against the larvae for many years.

A combined use of Neem oil and Milky Spore will help to keep the numbers of Japanese beetles down but it is not an instant killing solution so you will always need to resort to removing beetles by hand if you see them starting up in particular areas. The major problem is that Japanese beetles can fly long distances so there is always the risk of new beetles choosing your garden if you allow the Neem oil treatment to fall behind.