Since potatoes grow underground, the effects of tunneling worms, which cause holes will only be seen when it is harvested. However, the culprits can be stopped by a variety of easy methods.
Holes in potatoes are mainly caused by wireworms which are the larvae of click beetles. They tunnel into the potato tuber leaving a hole behind. Methods of control include crop rotation, traps, pesticides and predatory nematodes. Holes in potatoes can also be caused by hollow heart condition and white grubs.
Pest prevention can be done up front to ensure the potatoes are healthy when harvested.
However, if there are signs of wireworms in the soil we have outlined the things that you can do to help ensure that your potatoes are not attacked by tunneling worms further in this article.
What Causes Holes in Potatoes
Wireworms are the larvae (baby) of the flea or click beetles, meaning that it has yet to be fully developed into the adult as time passes.
The larvae are wire-like, having hard bodies that are slender, cylindrical, yellowish to brown in color, and about 0.75 inch long when full grown.
While adult click wireworms don’t attack potatoes, the larvae, known as wireworms, eat both potato seeds and developing tubers.
The potatoes are a source of nutrition to sustain their energy needs during their developmental stages.
The larvae spend a great deal of their life underground and most of their damage occurs in early spring when soil temperatures are cool.
This is because they move through the soil depending on temperature. As the soil warms up, they tend to go into deeper layers
One of the better pesticides used to control Wireworm that we have found is SEVIN. Its cost effective and ready-to-use, No Mixing Required!
White grubs are the larvae of several different beetles and are most widely known for the damage they do to turfgrass by feeding on the roots.
They have a pale body and reddish brown head; they are often found curled into a ‘C’ shape. Unlike wireworms, they burrow into potatoes leaving a large gaping hole in their wake.
The potatoes are left widely open to the elements allowing bacteria and fungus to fester in the open spaces similar to the holes caused in cucumbers. See what causes holes in cucumbers.
These spaces eventually turn black due to the onset of potato rot which can leave an unpleasant smell.
Hollow heart, sometimes called brown heart or sugar center, is a condition potatoes are faced with when there is an abrupt change in growing conditions.
Hollow heart occurs as a result of a rapid growth spurt after periods of drought. When the potato plant eventually gets watered the water is immediately sent to the area of the plant that is needed.
The plant then overcompensates for the loss of water by taking in too much. This results in an uncontrolled growth spike causing the internal parts of the potatoes to develop voids as the cell division rapidly increases.
These voids are initially filled with water which then dries out leaving a hollow space.
Table Summarizing the causes and control for holes in potatoes
|Causes of holes in Potatoes||Methods of Prevention and Control|
|Wireworms||Top layer cultivation|
Use beneficial insects
Planting resistant potato varieties
Cultivation Period when soil is warm
|White Grub||Neem oil, Carbaryl, pyrethrins|
|Flea beetles, |
Organic Pesticides: Neem oil or emulsion, Soapy insecticide
Inorganic Pesticides: Sevin® Insect Killer, Trifecta Crop Control
|Hollow Heart||Maintain Soil moisture|
Closer plant spacing
Controlling Pests that causes Holes in Potatoes
Wireworms or tuber flea beetles or “click’ beetle can be controlled by several methods including
- Top layer cultivation
- Crop rotation
- Wireworm traps
- Use beneficial insects
- Planting resistant potato varieties
- Cultivation when soil is warm
Top Layer Cultivation
This will include planting the crop within the top 6 to 8 inches of the soil.
As the crop is further at the top of the soil wireworms can easily be picked up by its natural predators like birds.
Furthermore , the sun will tend to heat the surface of the soil first. Wireworms are not tolerant to the heat and will tend to move further into the soil leaving the potatoes alone.
Rotating the crop will help prevent the occurrence of wireworms. For instance if the potatoes were planted in an area for too long the occurrence of pests will be greater as they know where to find food.
By switching things up, lets say, planting ground crops in areas where tomatoes or string beans were planted, there will be no wireworms in the soil when it is cultivated. Hence ensuring healthy and unaffected growth.
Crop rotation is a cost effective method that reduces the use of insecticide and their
Using wireworm traps or baiting is simple. Since tunneling worms like wireworms like the taste of the potatoes you can use potatoes themselves as traps.
Using potatoes or other vegetables to trap potato pests is a sacrificial method of control.
Simply cut a potato in half and stick it about 8 – 10 inches into the soil, here it will be easy for the wireworms to attack the sacrificial potato.
After a week or two the potato can be removed with the wireworms and fed to birds or chickens.
Predatory nematodes are a biological means of control that can be used to reduce the occurrence of wireworms in the soil.
The nematodes feed on the bodies of the tunneling worms and wireworms, and can tremendously reduce the tunneling worm population in a short period of time.
Nematodes should be applied in the spring and fall seasons and their application should be done more than 2 times to ensure that there is a healthy population within the soil to control the tunneling worms.
Both organic and inorganic pesticides can be used to control worms that cause holes in potatoes. Pesticides should be applied before the cultivation period to prevent the onset of the tunnel worms.
Best results can be expected when the insecticide is placed directly in the soil where the potato is to be planted.
- Imidacloprid – insecticide that was made to mimic nicotine
- Thiamethoxam – is transported to all of its parts, including pollen, where it acts to deter insect feeding.
- Ethoprop – It affects the nervous system of wireworms rendering them inactive.
Cultivation when soil is warm
As mentioned previously, wire worms move through the soil depending on temperature and their activity is high when the surface is cooler.
For this reason it is recommended to wait till the soil warms up a bit before planting to reduce crop damage.
Controlling Pest that Cause Holes in Potato Leaves
- Flea beetles
An effective means of pest control is by using neem oil applied as a foliar spray on and around the plant. Apart from potatoes neem oil is also used for pest control in cucumbers for burrowing worms which also causes holes.
Liquid soap can also be used to emulsify neem oil. Dilute liquid soap is a common DIY garden spray used against aphids and other soft-bodied insects, disrupting their cell membranes – effectively killing them when sprayed in direct contact.
We use a potent neem oil formula from amazon for a great price, which works well on all our plants. You can find it by clicking here.
How to prevent Hollow Heart in Potatoes
Stress is the main cause of hollow heart in potatoes and applying methods for reducing plant stress will help prevent the problem altogether.
Closer Plant Spacing (prevent rapid growth spurts)
Giving the plants proper spacing will prevent the plant from actually competing with other plants for both water and nutrients.
When the potato plant competes for water and nutrients it can become stressed when it does not get what is required for healthy growth.
Subsequently this stress leads to hollowing of the internal which produces holes in the potatoes.
Prevent fluctuations in temperatures (Prevent drought stress)
By reducing temperature fluctuations which potatoes are exposed to will help prevent stress and the complications associated with it.
When growing potato plants, it is important to keep in mind that potatoes are cool weather vegetables. The best time when to plant potatoes is in early spring.
Maintain soil moisture (prevent drought)
Maintaining the soil moisture will reduce the occurrence of drought conditions which may arise from a lack of watering.
Soil moisture can be maintained by regulating the watering schedule ensuring that you are not applying more than what is needed.
If however, a day or two of watering is skipped you can still continue with the normal watering regime.
A handy tool that comes into use is a soil moisture meter which takes the doubt away from watering so you will know how much water the soil actually needs.
You can find a durable moisture meter which we use for a great price on amazon by clicking here.
When it comes to rain and the weather. Rainfall has to be monitored and depending on the frequency of rainfall you may not have to water the cucumber plants.
Therefore, watering is a give or take when it comes to crops outdoors and as mentioned a soil moisture meter can take the guesswork out of watering.
Are all Potato Variety Affected with Holes
It has been seen that potatoes with thick skins have a greater resistance to wire worms and other tunneling worm species.
However, scientists are working on more resistant varieties to help ensure the crop grows healthy without attack from wireworms. See article here.
Other Reasons for Holes in Potatoes
Potatoes can develop holes when kept in storage for too long. The average storage time for potatoes ensures that it is fit for consumption.
After that, the potatoes will start to develop holes in them. These holes are also caused by worms.
It may be a mystery how they get there in the first place but flies lay eggs during the storage of the potatoes which then develop into worms which then eat the potatoes.
It leaves a very strong smell of rot and starts to break down real easing stinky liquids. The only option after that is to discard the bad potatoes.
Potatoes can be kept in the refrigerator for some time. In the crisper to be exact.
The colder temperatures coupled with lower humidity will tend to prolong the shelf life of the potatoes.
Can you Eat Potatoes with Holes in them?
Potatoes with holes can be eaten when the affected areas have been removed.
Heat usually kills all bacteria above 212 degrees F. Therefore thoroughly cooking potatoes which previously had holes would ensure that any bacteria or fungus which accompanied the worms would be killed.
On the other hand, If the potatoes were affected by drought conditions and had suffered hollow heart, you can simply cut out the bad part and cook as per normal.
Bacteria and fungus in such cases will not be much of a concern.