Boxwood Leaf Miner - Larvae Stage

Asked April 18, 2019, 5:49 PM EDT

Hello, I have boxwood leafminers within my boxwood petals. When I tear open the petal I am able to see they are in the larvae stage (maggots orange/yellow color) and "mining" away. I am curious to know what chemical will control these larvae before they turn into the adults. Below I have a few chemicals, would like to know what best controls at the larvae stage please; Imidacloprid, Spinosad, Dinotefuran, Abamectin, Bifenthrin, or Malathion. Please let me know what works best. Thank You!!

Oakland County Michigan

7 Responses

Hello,

This article lists the chemicals effective in controlling this pest-

https://www.canr.msu.edu/news/boxwood_leafminer_a_serious_pest_of_a_favorite_landscape_plant

Sprays are effective on emerging adults. Systemics, like imidacloprid, are effective on the mining larvae.

Thanks for using our service.

Hello Laura,

Thank you for this response - I’ve come across this article before sending my question in and am having issues with correct mixing rates for the product “imidacloprid” which is the product recommend for control of the leafminor larvae. The label for the product I am using “Merit 2F-imidacloprid 21.4%..” started 1.5oz per 100 gallon. I do not need to make 100 gallons. I need 1 gallon. According to my math - I’m order to make 1 gallon it would be 1.5oz/100gallon therefore 0.015oz per gallon. Can you please confirm this? I feel as though this is a very minimal dosage for a systemic foliar spray. Thanks in advance.

Hello,

This is a problem when trying to use professional strength products in a home setting. Professionals mix tankfuls of product and treat multiple customers or large commercial properties.

I read the Merit 2F label. It says for shrubs to apply

“0.1 to 0.2 fl ounces (3-6 mL) per foot of shrub height”.

They convert the ounces to milliliters for you on the label. Use 3-6 ml per foot height of shrub. You can buy eye droppers at the drug store that are marked in milliliters. Of course, only use that eyedropper for garden chemicals!

Mix the eye dropper amount in a gallon of water and apply to the shrub. You will want a gallon of water per shrub. For taller shrubs you will want more. A 3 foot tall shrub will need 3 gallons of mixture, with 9-18 mL mixed into the 3 gallons of water.

To be systemic the roots need to take up the mixture. Slowly pour the mixture around the base of the shrub so it soaks in and does not run off to other areas. Remove plastic or any other barrier that will stop the mixture from reaching the roots.

As always, Please read the label precautions and protect your skin , eyes, and the environment according to directions.

Thanks for checking back with us.

Laura

For the mixture rates your provided these are perfect - however this is for the systemic drench. Imidacloprid has 3 application types; one being the systemic drench which you mentioned, another being soil injection, and lastly a foliar translaminar spray also known as a local systemic foliar spray absorbed through the plants leaves/petals. I am looking for the mix rates for the last option - the foliar translaminar spray where the leaf petal of the boxwood will ingest the chemical targeting the larvae within the leaf. I’ve tried getting ahold of Bayer but they will not disclose any information hence I am not a “professional applicator.”

Please let me know - any feedback is appreciated. Thank you.

I am not a licensed pesticide applicator either. I will see if someone at MSU can help. Give me a couple days, as it may take some time. Thanks for your patience.

The label, under “application to ornamentals” does specify translaminar spray. Following the mixing directions for shrubs on page 4, the label specifies 45 mL per 100 gallons of water. You can mix .5 mL per gallon, by using an eyedropper marked in milliliters. Here is a link to the label should you need it-

https://www3.epa.gov/pesticides/chem_search/ppls/000432-01312-20040513.pdf

Always err on the short side, and follow label precautions and directions.

Have you considered becoming a licensed applicator? there is information here-

https://www.canr.msu.edu/news/michigan_pesticide_applicator_certification_part_1

If I hear anything more from other MSU Experts I will forward it on to you with an additional response to this question. Thank you.

Hello again,

A MSU Horticulture Educator reviewed your question and here is his response-

“I looked up the label and for leaf miner on woody ornamentals in the landscape it directs the use as a soil drench. We have to go with what the label says since the manufacturer has tested it for this purpose and found it to be most useful as a soil drench for leaf miner in ornamentals. The only time they went with it as a foliar treatment was for fruit and in that case they are preventing it from being taken into the plant internally since we eat the fruit.”

I hope this information is helpful.