Household remedies against Colorado potato beetles
Entire potato harvests can be destroyed by the Colorado beetle! We show you how to recognise an infestation, how to treat it effectively and how to prevent it.
Colorado beetles can become a real nuisance. It is therefore important to detect the pest at an early stage and to prevent it. However, if it is already too late for that, there are various ways of controlling the pest, ranging from household remedies and organic means to chemical sprays.
Pattern of damage: identifying Colorado beetles and their larvae
An infestation by the Colorado potato beetle is really easy to detect. It is crucial to pay attention to the feeding traces of potato bugs right from the sprouting of potato seedlings. Since the potato plant is rejected by many pests due to its toxic ingredients, potato beetles are often the obvious culprits whenever there are clear signs of eating. More precisely, it is the older larvae of the beetle that are responsible for the eaten leaves. If enough larvae are present, they can devour a potato plant down to its thick leaf veins. This usually results in a total loss of the harvest.
Besides identifying the adult beetle, you should also pay special attention to the larvae. The compact, red larvae can also be easily recognised by their black spots on the sides. If you are very observant, you may also be able to identify the small yellow eggs on the underside of the leaves – a magnifying glass can help of course. The eggs are usually arranged in a compact bunch.
Colorado potato bug: facts & information
The Colorado potato beetle (Leptinotarsa decemlineata) is a leaf beetle that originally comes from Colorado – hence the name “Colorado beetle”. The Colorado beetle was introduced to Europe at the end of the 19th century and soon enough it became a threatening pest. At the time there were no effective pesticides available and therefore people had no choice but to collect the beetles by hand from the potato fields. Entire hosts of people and especially children had to comb through the potato fields in order to secure the potato harvest, which was essential for their survival.
In order to control the potato bug effectively, it is important to have a thorough understanding of its development. In spring, when the first potatoes sprout, the potato beetles wake up and leave their winter quarters. After the insects have left the ground, they start to feed on the small potato shoots and lay their eggs on the underside of the potato leaves. However, the beetles’ feeding damage is very small and usually goes unnoticed. It is only after about two weeks, when the larvae hatch out of the eggs, that the actual problem begins. The larvae go through four stages of development before they develop into adult beetles.
In the first two larval stages, the larvae react very sensitively to plant protection measures and are not yet very hungry. However, once the third larvae stage is reached, the food feast starts, and even organic insecticides become less effective. For this reason, the larvae should always be controlled at an early stage of development. If the weather conditions are conducive to the beetles’ development, up to two more generations can plague the potato fields. They feel especially comfortable when the weather is dry. However, if effective control is achieved within the first generation, the number of Colorado potato beetles in the following generations will decrease and then become almost negligible.
Preventing a potato bug infestation
When the Colorado beetles come out of the soil in spring alongside the sprouting potatoes, nets or similar measures are of no use. Even a strict crop rotation in your garden does not bring much success against a potato beetle infestation. For that to happen, distances of about 500 m between the beds would have to be kept, which is very likely not possible in the vast majority of home gardens. But do not be discouraged: there are certainly ways and means to reduce the probability of a threatening Colorado potato beetle infestation. If you plant your potatoes into the ground pre-started, they will have a growth advantage over the Colorado potato beetles. The Colorado potato beetles and their larvae will do less damage to the potato plants and you may be able to avoid an actual treatment. In addition, and especially if you are often confronted with Colorado potato beetles, it is worth using early potato varieties. Again, the common Colorado potato beetle can no longer exploit its full damage potential. Furthermore, beneficial insects can help reduce the number of Colorado potato beetles. Therefore, make sure you have many insect-friendly hideaways, so that as many beneficial insects as possible can “work” for you in your garden. Useful predators include predatory bugs, ground beetles, lacewings, ladybirds and nematodes in the soil.
Getting rid of Colorado potato beetles
When treating the Colorado potato beetle, the time of control and choice of the right remedy are crucial. Since the adult Colorado potato beetles do not cause any damage worth mentioning, treating them is of secondary importance. In contrast, controlling the first larval generation in spring is vital. The first generation of larvae develops from the eggs laid by the adult potato bugs. They crawl out of the ground when the potatoes sprout in spring. If this larva generation is effectively controlled, there won’t be a large population of potato bugs throughout the year. In this case you will usually have some peace and quiet from the Colorado potato beetle and can relax and wait for the potato harvest to come.
- Combating potato beetles naturally with beneficial insects:
Currently, there are no beneficial insects on the marketplace that are able to control the Colorado potato beetle effectively. At this point, we would like to refer to the preventive measures mentioned above. With the potato beetle’s natural enemies present, the development of large populations of Colorado potato beetles becomes less probable. This means that you may be able to avoid using pesticides as a form of plant protection.
- Combating potato beetles naturally with household remedies:
The oldest and most cumbersome method of control is to collect the Colorado potato beetles yourself. However, for an effective treatment, the larvae as well as the adult beetles should be collected, and the egg clutches should also be crushed or wiped off. This may be a possible approach when you only have a few individual potato plants on a balcony or a terrace. However, if you are a proud owner of a large potato bed or even a field, collecting the larvae is an almost impossible task. It simply takes a lot of time. If you do choose to try this out anyways, we recommend that you start collecting the insects in the morning. Other household remedies, which are frequently mentioned in the context of Colorado potato beetles, are almost ineffective. These include:
- Rock flour
- Wood ashes
- Spray liquids from fern or mint
- Combating potato beetles naturally with organic means:
In theory, there are several effective means for controlling the Colorado potato beetle naturally and organically. Unfortunately, one very effective plant protection product is only approved for organic farming and not for private use. It is a bacterial protein which acts selectively on this pest and almost immediately stops it from attacking the plants. Soon after, the Colorado potato beetle dies. Though the extremely effective bacterial protein Bacillus th. Aizawa, normally used against caterpillars, is approved for every hobby gardener, the Bacillus th. tenebrionis, which is used against the Colorado potato beetle, is not obtainable. Therefore, the only organic resources that remain are neem preparations. For the neem preparation to work well, it must also be sprayed onto the underside of the leaves. But beware: the larvae of the Colorado beetle become more and more resistant to the natural sprays in the course of their development. Ideally, the crop protection product is therefore applied shortly post-egg hatching in spring. After repeatedly spraying the plants, the potato beetle-problem should soon be eliminated.
- Combating potato beetles with chemical sprays:
Among several chemical sprays, there is basically only one active ingredient that we can recommend with a clear conscience. This is due to the fact that the Colorado potato beetle is largely resistant to one of the most popular active ingredients, pyrethroids (the same applies to the similar natural active ingredient pyrethrum from the chrysanthemum). We strongly advise against treating the Colorado potato beetle with these two agents, as this further promotes their resistance. Only chemical pesticides containing the chemical compound azadirachtin A should be used for controlling the Colorado potato beetle. The substance is practically an improved form of neem oil.