The threat from the Colorado potato beetle on potato plantations is increasing. Combating this pest is not easy, which is further complicated by the increasing resistance of the beetle to the active substances of insecticides.
Insecticides for combating the beetle: what’s on the register?
Currently, 93 insecticides are registered to combat the Colorado potato beetle in potato cultivation. Most of them, as many as 21, contain acetamiprid (e.g. Carnadine 200 SL, Los Ovados 200 SE, Mospilan 20 SP, Roslix 200 SL). We can find several dozen insecticides with active substances: deltamethrin (e.g. Decis Mega 50 EW, Delmetros 100 SC), cypermethrin (e.g. Cyperkill Max 500 EC, Sherpa 100 EW), lambda-cyhalothrin (e.g. Karate Zeon 050 CS, Topgun 050 CS ) and chlorantraniliprole (e.g. Coragen 200 SC, Voliam). Several insecticides on the market contain cyanoraniliprole (e.g. Benevia 100 OD) or
tau-fluvalinate (np. Mavrik Vita 240 EW).
An interesting proposition are insecticides with the active substance spinosad, which is produced through fermentation by bacteria. Some preparations containing spinosad are included in the list of plant protection products also approved for use in organic farming (e.g. SpinTor 240 SC). Another example of a slightly “niche” active substance is azadirachtin, which is obtained from a plant – neem. Azadyrachtin interferes with the metabolism and reproductive processes of pests. As a result of its action, insects may either gradually die or significantly reduce their activity and feeding. Also in the case of this active substance, we can find preparations approved for organic farming (e.g. NeemAzal-T/S). Alternative proposals also include Spruzit Koncentrat Na Szkodniki EC, containing rapeseed oil and pyrethrins. Rapeseed oil affects pests mechanically, creating a coating on the pest’s body that prevents it from breathing. Pyrethrins of plant origin directly lead to the death of insects.
Colorado potato beetle laughing at insecticides?
In combating the Colorado potato beetle using commonly available insecticides, the biggest problem is the small selection of available active substances and the decreasing sensitivity of the pest to the preparations used. From the “Report on the implementation in 2018-2021 of the national action plan to reduce the risk related to the use of plant protection products for 2018-2022” published by the Ministry of Agriculture and Rural Development, we learn that the Colorado potato beetle in 2020 showed:
- sensitivity or low resistance to acetamiprid;
- different levels of resistance to other active substances, such as cypermethrin, deltamethrin, tau-fluvalinate, lambda-cyhalothrin or chlorantraniliprole.
Resistance to the active substances of the Colorado potato beetle may vary depending on the location in the country. However, we see that the problem of pests developing resistance is progressing dynamically. For example: in 2019, the tested populations of the beetle showed only sensitivity to acetamiprid – a year later, low resistance was found. With such an advanced problem of resistance of the Colorado potato beetle population to the most commonly used active substances of insecticides, it may turn out that the protective treatment performed will have little effectiveness. Until recently, the active substance phosmet was available and was quite effective against the beetle, but it was withdrawn in 2022. Currently, the best weapon in the fight against the beetle seems to be acetamiprid, although in this case there may be local populations with a higher degree of resistance. Moreover, frequent use of one substance exerts strong selection pressure, resulting in an increase in the pest’s resistance.
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