How to manage the Colorado potato beetle’s summer generation
Colorado potato beetle summer generation adults are currently emerging in many parts of Michigan. Avoid building insecticide resistance with these guidelines.
Colorado potato beetles are notorious for developing insecticide resistance; therefore their management should follow appropriate guidelines to stop or slow this process. Our records show that between 1998 and 2011 the level of insecticide resistance to imidacloprid has grown exponentially in this insect in Michigan. The most common way to manage beetles currently in commercial potatoes is to apply neonicotinoid insecticides (imidacloprid or thiamethoxam) in-furrow, at planting. In most cases this treatment provides sufficient control for overwintered beetles and in some cases for summer populations as well.
If the summer generation of beetles needs to be managed, then foliar insecticides can be applied. In order to slow down resistance development of Colorado potato beetles, it is recommended that insecticide classes are rotated, meaning that insecticides with the same mode of action are not applied to Colorado potato beetles twice within a season. All of the insecticides in Table 1 below are non-neonicotinoid type, so they are good options for foliar beetle management if a neonicotinoid insecticide was applied at planting.
Colorado potato beetle summer generation adults emerge in large numbers after a rain (or irrigation) event that was preceded by a dry period. If you need to manage your summer generation adults, timing your application to when large masses of beetles emerge will prevent them from laying eggs on your crops and this will reduce larval damage later in the season.
The National Potato Council has prepared the following guidelines for Colorado potato beetle insecticide resistance management and has a factsheet with further details on neonicotinoid insecticides and resistance management.
Manage Colorado potato beetle insecticide resistance in the following way:
- If a neonicotinoid insecticide (Group 4A) was
applied at planting, either in furrow or as a seed treatment, do not use a
foliar neonicotinoid insecticide later in the season.
- Crop rotation with a minimum of a quarter of a mile
between successive plantings is especially important for management of Colorado
potato beetle.
- Apply insecticides only when necessary.
- Use scouting, sampling procedures and action
thresholds.
- Do not treat all potato fields on one farm or in
one localized area with products from the neonicotinoid class.
- Preserve natural controls by using selective
insecticides when possible (i.e., Rimon)
- Spot
treat when feasible (e.g., field edges). This can also be done by using a potato trap crop (untreated potatoes that are planted in field
margins earlier than the main crop) and therefore will harbor large numbers of
early emerging beetles that can be killed on the trap crop.
- Do not
apply insecticides below labeled or recommended rates. Applying sub-lethal
rates of any insecticide may result in poor product performance, insect damage
to the crop and an increased risk of resistance development.
Table 1. Foliar options for Colorado potato beetle management if a neonicotinoid insecticide (imidacloprid or thiamethoxam, Group 4A) was used at-planting.
Group |
Brand name |
Chemical name |
Rate (per acre) |
PHI |
Days between treatments |
Maximum use per season |
Maximum number of applications1 |
3 and 28 |
lambda-cyhalothrin + chlorantraniliprole |
6.0-9.0 fl oz |
14 days |
7 days |
27 fl oz |
3 | |
5 |
spinetoram |
4.5-8.0 fl oz |
7 days |
7 days |
16 fl oz |
2 | |
5 |
spinosad |
1.7-3.3 oz |
3 days |
7 days |
14.4 oz |
4 | |
6 |
abamectin |
8.0-16.0 fl oz |
14 days |
7 days |
32 fl oz |
2 | |
15 |
novaluron |
6.0-12.0 fl oz |
14 days |
7 days |
24 fl oz |
2 | |
28 |
chlorantraniliprole |
3.5-5.0 fl oz |
14 days |
5 days |
10 fl oz |
2 |
1 limit applications to a single
generation
2 only effective on larvae, time application when
small larvae are most abundant