This article was published originally on 3/21/2012
Iowa State’s Plant and Insect Diagnostic Clinic has received several questions recently about the use of imidacloprid on apple trees and other edible fruits and vegetables. Imidacloprid is a systemic insecticide that has been available for many years under different trade names and concentrations. Systemic insecticides are taken up by the roots or other parts of the plant and then move internally through the plant tissues and kill insects eating those tissues. In contrast, non-systemic insecticides remain on the plant surface and kill insects by contact or ingestion of treated foliage.
Imidacloprid has been available to commercial growers for use on edible crops for over a decade. Homeowners, however, have not had any systemic insecticide available for insect control on fruits and vegetables until recently. A new product called Bayer Advanced Fruit, Citrus & Vegetable Insect Control is now available for the general public. It contains 0.235% imidacloprid. This product can only be applied to the soil.
In order to help you make decisions about using imidacloprid on edible food crops, we have compiled a list of the questions we are being asked. Remember, always read and follow label instructions when using any pesticide.
Does imidacloprid get into the fruits and flowers of plant?
Good question and not one that is easy to answer. Yes, it does get into the reproductive parts, but not in high enough concentrations to control pests. This is why if you use imidacloprid on your roses to control Japanese beetles it does not protect the flowers. Imidacloprid works best on pests that feed on leaves, stems, roots, or woody parts of the plant.
There is concern about how much imidacloprid gets into the nectar and pollen of plants and how this might affect pollinating insects. It is something to be aware of and why some labels say to not apply until after bloom. Imidacloprid is toxic to bees according to the imidacloprid fact sheet at Oregon State University’s National Pesticide Information Center. For this reason we favor an IPM-based pest management approach that reduces non-target effects by limiting insecticide applications to situations where other options are not available and using insecticides in a responsible manner.
What plants are listed on the label of Bayer Advanced Fruit, Citrus & Vegetable Insect Control?
There is a long list so check the label. Some examples plants likely to be grown in Iowa include:
- Pome fruit such as apples and pear
- Stone fruit such as apricot cherry, peach and plum
- Strawberry, blueberry, raspberry, blackberry
- Tree nuts such as walnut, chestnut, hickory
- Many cucurbits including cucumber, pumpkin, muskmelon, squash, zucchini
- Eggplants, peppers, tomatoes and some leafy vegetables
- Many herbs
What insect pests are controlled by Bayer Advanced Fruit, Citrus & Vegetable Insect Control?
It depends on the crop being treated so check the label but in general it is labeled to control: aphids, leafhoppers, whiteflies, mealybugs, spittlebugs, cucumber beetles, some thrips, Colorado potato beetles, and flea beetles.
What apple pests present in Iowa are listed on the Bayer Advanced Fruit, Citrus & Vegetable Insect Control label?
It controls aphids (including woolly apple aphid) and leafhoppers, both of which are generally not a problem for homeowners growing apples in Iowa.
Are apple maggot and codling moth listed as target insects for Bayer Advanced Fruit, Citrus & Vegetable Insect Control?
No, these fruit-infesting pests are not on the label and it will not provide control. The imidacloprid will not be present in the fruit in high enough concentrations to control these pests.
Will Bayer Advanced Fruit, Citrus & Vegetable Insect Control prevent Japanese beetle damage?
This product controls Japanese beetles on only bushberry plants (e.g., blueberry, current, elderberry, huckleberry, Juneberry, Ligonberry, Salal). It will not control Japanese beetles on other plants.
So, why can I use imidacloprid on other plants to control Japanese beetles?
Other products have a much higher rate of the active ingredient imidacloprid (1-3%) AND it is labeled for use on ornamental trees and shrubs, not plants with edible parts.
A different product, Bayer Advanced 12-month Tree & Shrub Insect Control Super Concentrate with 2.94% imidacloprid, controls Japanese beetles and lists apple trees on the label. Why can’t I use this?
This is confusing but in general any pesticide being used on any fruit, vegetable or other plant with edible parts will have information on pre-harvest intervals (the number of days from treatment until the plants can be harvested). This information is absent on the Bayer Advanced 12-month Tree and Shrub Insect Control label. We advise you not use this product for apple trees.
Further, we advise that if homeowners want to use a product with imidacloprid as the active ingredient that they use one specifically labeled for edible food crops. The product label will contain specific instructions on application, pre-harvest intervals, and special instructions on limiting harm to pollinators.
In Iowa what crop/pests will Bayer Advanced Fruit, Citrus & Vegetable Insect Control be most useful for?
Cucumber beetles that vector bacterial wilt on cucurbits. Other potential uses in Iowa are for managing whiteflies on tomatoes, flea beetles on tomato and eggplant, and leafhoppers on beans and peas.
When can I eat the fruit and vegetables treated with Bayer Advanced Fruit, Citrus & Vegetable Insect Control?
This varies with each type of plant being treated; the minimum is 7 days and the maximum is 45 days. It is very important to know this pre-harvest interval before treating your plants as you will not be able to harvest and consume the fruits and vegetables until after the required number of days have passed. The U.S. Environmental Protection Agency has specified this period based on manufacturer data and to protect the consumer from toxic effects.