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

Voliam   Xpress

lambda-cyhalothrin + chlorantraniliprole

6.0-9.0 fl oz

14 days

7 days

27 fl oz

3

5

Radiant   SC

spinetoram

4.5-8.0 fl oz

7 days

7 days

16 fl oz

2

5

Blackhawk

spinosad

1.7-3.3 oz

3 days

7 days

14.4 oz

4

6

Agri-Mek   0.15 EC

abamectin

8.0-16.0 fl oz

14 days

7 days

32 fl oz

2

15

Rimon2

novaluron

6.0-12.0 fl oz

14 days

7 days

24 fl oz

2

28

Coragen

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

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