Flea beetle is a jumping beetle of the Chrysomelidae or the leaf beetle family. There are numerous species of flea beetles around the globe and proved to be a cerebral pain amongst the farmers and agriculturists.
The flea beetles attack numerous plants and vegetations, but they are attracted towards vegetable crops. Their ability to jump like fleas is what ended up naming them flea beetles.
The flea beetles have a shiny small body with larger legs. Like any other beetles, flea beetles are active during the spring and summer. They infest crops during the summer and lay eggs on the base of the plant stems. The adult flea beetles feed on foliage like the leaves, producing small ‘shotholes’ whereas; the larvae feed on the roots of the plants.
Many species of the flea beetles attack different parts of flowers, fruits, and vegetables. However, the adult flea beetles are more likely to attack young transplants. Identifying a flea beetle infestation is very easy. If you find a leaf shot with holes, then it is an indication that you should work on conserving your crops.
This has made them the common pests on the vegetable crops. However, these beetles occasionally infest on flowers, trees, and ornamental shrubs.
The most common flea beetle that raids most home gardens and crops is Crucifer Flea Beetle. In most part of Asia and Americas, flea beetles are the most common economic pests.
Table of Contents
- List of Invasive Flea Beetle Species and their Characteristics:
- Flea Beetle Life Cycle
- Identification of Flea Beetles
- What are the Indications of Flea Beetle Infestation?
- Minimizing Flea Beetle infestation
List of Invasive Flea Beetle Species and their Characteristics:
Flea Beetle Species: Cruciferae or Cabbage Flea Beetle
Generations Per Year: 2 to 3
Characteristics: Attacks a wide host of plants, primarily cabbage and other plants of the Cruciferae family. It is the most damaging species in the world.
Flea Beetle Species: Palestriped Flea Beetle
Generations Per Year: 1 to 2
Characteristics: Attacks almost every plant type (has widest host range) including beans, squash, corn, lettuce, sunflowers, potatoes, and weeds.
Flea Beetle Species: Potato Flea Beetle
Generations Per Year: 1
Characteristics: Attacks mostly potato crops. But they are also known for tomato infestation along with other nightshade family plants.
Flea Beetle Species: Tobacco Flea Beetles
Generations Per Year: 1
Characteristics: They are found in warmer areas. They infest on Eggplant and some nightshade plants.
Flea Beetle Species: Tuber Flea Beetle
Generations Per Year: 2
Characteristics: Primarily attack potatoes crops. Their larvae cause tuber injuries in plants.
Flea Beetle Species: Horseradish Flea Beetle
Generations Per Year: 1 to 2
Characteristics: Infest on horseradish and other mustard plant species.
Flea Beetle Species: Apple Flea Beetle
Generations Per Year: 2 to 3
Characteristics: Their larvae feed on the grape, crabapple, Epilobium,
zauschneria, and other plants. However, the main damage is caused by the adult
Flea Beetle Species: Sumac Flea Beetle
Generations Per Year: 2
Characteristics: Sumac, Currants, and Skunkbrush are occasionally damaged by
Flea Beetle Species: Willow Flea Beetle
Generations Per Year: 1 to 2
Characteristics: Infest on Willow
Flea Beetle Life Cycle
Flea beetles normally have 1-2 generations per year, although some species appear thrice during the growing season. During the springtime, the overwintered adults feed on seedlings of plants. However, in the fall, it is the adult offspring of the overwintering adults who are seen feeding on seed pods, stem, and leaves.
The flea beetles prefer overwintering near the cruciferous plants, leaf litter, poplar groves, shelterbelts, debris, and grass. They prefer colonizing in high density, that is; within the leaf litter or stem, you can easily find 150-250 flea beetles/m2.
The flea beetles become active during April and May when the first extended period of summer starts. It can take a little longer if the temperature is still on the colder side.
On the other hand, the emergence also depends on the species of the flea beetle. That is; the palestriped flea beetles emerge 2-4 weeks earlier than those of crucifer flea beetles. In general, the peak emergence time occurs when the ground temperature reaches 12-15°C.
When the temperature is cold, the flea beetles tend to hop or walk into adjacent crops and weeds. During that time, they feed on mustard and canola, or on weeds like flixweed, peppergrass, wild mustard, stinkweed, and lamb’s quarters. After that, they will move to new seedlings. And, when the temperature becomes favorable and the winds calm away, they fly and disperse throughout the fields for infestation.
Once they have commenced feeding, it is time for them to mate. They mate repeatedly. The female flea beetle starts laying eggs during May end and continues to do so for 30 straight days. One female flea beetle can lay up to 100 eggs. The flea beetles lay eggs in the soil so that the larvae can feed on the roots of the plants. Moreover, the soil has to be moist and warm for the eggs to hatch quickly.
It takes around 10-12 days for the eggs to hatch into larvae. The overwintering adults will die once the eggs are laid. The larvae, after hatching, feed on taproots and root hairs of the seedlings. Once the larval development is completed, the larvae pupate in small earthen cells.
The pupation period begins from mid-July and continues till October. It takes a total of about 7 weeks for a flea beetle egg to emerge as an adult beetle.
Identification of Flea Beetles
The adult flea beetles emerge from the ground after overwintering in early spring. They prefer woody and bushy areas for overwintering rather than grassy ones. The adult flea beetles are quite small as compared to the larvae. They range around 1/16 to 1/8 inches long. They have a small body with enlarged hind legs helping them to generate enough thrust while jumping.
The flea beetles have a shiny metallic colored body. Their body color includes blue, bronze, gray, brown, lack, and other metallic textured colors. Some of the flea beetle species have unique patterns on their body like strips.
The female flea beetle lays the egg on moist and warm soil near the base of a plant. The eggs are smooth, elongated, yellowish and oval in shape. The larvae have completely white bodies with a brown head and an anal plate.
Moulting takes place twice during the 30-day period, where it completes three larval stages. The larvae are generally around 3-4 mm long. The pupation takes place in the soil before they emerge out as adults.
What are the Indications of Flea Beetle Infestation?
The indications and damage symptoms of flea beetle infestation vary from species to species and the type of hosts attacked. Identifying flea beetle infestation is very easy. In general, they feed on grasses including corn. The appearance of narrow spots on the leaves is the indication that its tissue is removed. This is the first indication of the flea beetle infestation. The feeding scar runs parallel to the leaf veins or sometimes, zig-zag through the vein. This scar gives the leaf a jagged appearance.
However, these scars are confused for adult corn rootworm infestation. But the rootworm tends to eat out large portions whereas the flea beetles only eat in a proportionate amount.
The feeding of flea beetles on the leaves introduces bacterial wilt on them. Once the plant gets severely infected by the bacteria, it will ultimately die. On the other hand, lesions will be formed on the leaves as a late-season infection and it results in the crops drying down.
In case of plants and crops with broadleaves, the flea beetle infestation could be found out by looking at the plant leaves. The leaves have shotholes appearing all over it; then it indicates adult flea beetles are feeding on it. The beetles tend to chew down the tissue between the leaf veins. The damage appears as if someone has shot the leaves with a shotgun.
* Scouting techniques:
This is one of the preferred methods to identify flea beetle infestation. During the fall, scout the fields and observe the density of flea beetles. If the population is dense, then it means that your field is infested with flea beetles. Heavy infestation can cause damage to the stem and leaves of the plant which leads to crop delaying and crop thinning.
Most of the flea species attack a growing plant to an extent that it limits the plant’s ability to heal. Heavy attacks can wipe out the entire crop.
Seedling loss due to a severe plant disease is sometimes mistaken for flea beetle infestation. Dug out the damaged plants from the ground and inspect its stems, roots, and shoots to identify if it is a plant disease or flea beetle damage.
Minimizing Flea Beetle infestation
Flea beetles are the common pests, however; the injuries it causes are insignificant to the crop health. It is necessary to chop off 10-20% of the leaves from the established plants once you have got the slight indication of flea beetle infestation. Plants grown for ornamental purposes, edible greens, potatoes etc are prone to flea beetle infestation.
* Cultural Control (Field Management):
Agronomic practices promoting rapid seedling growth plays a crucial role in lessening the effect of flea beetle damage on crops and plants. The growth and emergence can be improved by planting seeds having 95% or above germination rate in the pre-chill test.
On the other hand, the size of the seeds also matters when it comes to controlling the infestation. Seeds varying between 1.8-2.2 millimeters are more tolerant and vigorous to flea beetle attacks. The plants and crops grown from heavy and large seeds have less flea beetle damage as compared to plants grown from small and light seeds. Heavy and large seeds tend to grow with a better stand establishment, faster growth rate, higher seed yield, and higher shoot weights.
Flea beetles like any other beetles prefer warm and relatively bright environment. The farmers prefer direct seeding as it provides a microclimate for the plants which is less ideal for flea beetles to colonize. Tillage before seeding will open up the soil layers. Moreover, planting into or near a stubble can provide your plant a microclimate which is moist, cooler, and less ideal for flea beetles to infest. The cooler microclimate will reduce the flea beetle injury as the cooler climate slows down the activities of flea beetles. However, this can also slow down the growth of your crops. Thus, frequent crop scouting is recommended to ensure that the damage is not done over the limit.
The producers are recommended to follow early seeding practices as it maximizes the seed yield. Early seeding will ensure the plant reaches its maximum growth before the emergence of flea beetles. The reason behind early seeding is that the fully grown plants are more tolerable towards any damage or attack. It can easily recover from certain bug damages.
Increasing seeding rate is also responsible for combating flea beetle damages. More the crops less would be the feeding damage as the flea beetles will spread all over the field not focusing on a particular plant. Higher plant densities and seeding rates are believed to reduce and dilute the damage to individual plants.
Another great way to deal with flea beetle infestation is row spacing. The row spacing of 20-30 cm per plant reduces the flea beetle damage. The reason is still not explained but the producers say that the close spacing provides the plants with microclimate where the environment is much cooler. Moreover, it is believed that the flea beetles get confused with all the visual contrast between the soil and vegetation.
Crop rotation is yet another method to control flea beetle infestation. But this procedure is not appreciated by most of the producers as the adult flea beetles overwinter inside and outside the cropped fields and are capable of migrating to long distances. However, if we talk about brassicaceous vegetables, intercropping non-host plants has surely provided some promising results when it comes to flea beetle damage.
The producers also perform seed treatment blends where they blend a proportionate amount of insecticide-treated seeds with without insecticide-treated seeds and plant them on the fields.
* Biological Control and Natural Enemies:
Diseases, parasites, and predators play a crucial role in regulating flea beetle population. In the present scenario, the biological control agents are limited in numbers but there are several insects that feed on adult flea beetles.
Lacewings, field crickets, damsel bugs, big-eyed bugs, and flower beetles play acts as the important biological agents who help in regulating the flea beetle population.
Moreover, the braconid wasps parasitize the adult flea beetles but it only affects the 5% flea beetle population. Parasitism is a common biological weapon against the flea beetles but it works slowly and the flea beetles multiply in thousands.
However, it was documented that a braconid wasp species from Europe were able to parasitize 50% of the flea beetle population attacking the cruciferous vegetation.
Unfortunately, due to flea beetles reproduce in thousands in just short time-span, these biological weapons seem to be ineffective.
* Resistance Breeding:
No crop has shown resistance to flea beetles, but there are some studies that suggest the flea beetles only prefer certain plants and crucifer hosts.
It was found out that the yellow mustard seedlings have lower levels of flea beetle infestation as compared to other vegetations. This may be due to the fact that mustard is rich in high level of glucosinalbin which most of the beetles resist from consuming.
* Insecticide Control Options:
The crops and vegetations can be protected from the flea beetle infestation using insecticide treatment options. In-furrow and granular insecticides were once popular amongst the farmers and producers but eventually, its application was withdrawn due to its hazardous impact on the environment.
Most farmers and producers prefer treating their seeds with neonicotinoid insecticide for controlling the flea beetle infestation. This insecticide is known for triggering systemic activities in plants and ultimately inhibiting nervous conduction in flea beetles. It works in a way that the chemicals block the flea beetles’ nicotinoid acetylcholine receptor.
Another option is to coat the seeds with an insecticide and fungicides before planting it. It is a widespread practice and more than 90% of the canola crops are grown using this method.
Treating the seeds with fungicides and insecticides will ensure that it repels flea beetles the moment it starts to grow. The seed treatment available today for controlling the flea beetle infestation come with fungicides an insecticides either at higher or lower rate. The companies offering pretreated seeds provide maximum protection against flea beetle invasion. However, the recommended higher rates of application are expensive as compared to lower rates. But it can result in extending the protection against the flea beetles.
In case, if the field is invaded by the high population of flea beetles and the provided seed treatment is not doing the trick, it is recommended to use a foliar spray. The use of foliar insecticides will come handy when the damage starts. Note that limiting the insecticide concentration is necessary if the infestation is not spread throughout the field.
On the other hand, the producers who are combining foliar insecticides with herbicides should ensure that the damage at the threshold. Applying foliar insecticide before the damage reaches the economic threshold can result in the flea beetles developing a certain sense of resistance towards the insecticides. Also, it can have a negative impact on the natural enemies such as other beneficial insects.
* Organic Control and Preventative Measures:
- Transplant or plant susceptible crops to the fields and gardens as late as possible to reduce the possible flea beetle attack. You have to remember that as late as possible means plant only after the flea beetles are about to go into overwintering. Also, avoid planting seeds and practice growing large and healthy transplants as much as possible.
- Avail the benefits of trap crop method. The trap crop method will do no harm to the flea beetles but will surely take their mind off from your main crop. It works in a way that the trap crops you grow will be the favorites of these flea beetles. Grow these crops on all the corners of your field, keeping a certain distance from the crops that you want to protect. Radishes and giant mustards prove to be the best trap crops. To ensure maximum security, spray the crops that you want to protect with insecticides.
- Ensure that your garden or field is free of crop debris and weeds as these things prove to be a wonderful habitat for the flea beetles, due to the moist and warm environment it provides. Also, plowing the field on a regular basis will kill the overwinter flea beetles.
- The producers and farmers have also claimed to use handheld vacuums, even the household ones to suck out the flea beetles. This technique can certainly reduce the pest numbers.
- Another effective way to reduce flea beetle infestation is to use the mulching technique. It is one of the simplest techniques used by the producers and farmers for pest control. It is a process of covering the topsoil with a layer of grass, leaves, crop residues, twigs, etc. Mulching your field will make it difficult for the female flea beetles to find a place to lay eggs.
- You can use the help of flea beetles’ natural enemies like wasps, tachinid fly, soil-dwelling nematodes, and other insects that prey on flea beetles. You can use fennel, daisies, alyssum, cosmos, dill, etc to attract these insects to your field or garden.
- Practice planting vulnerable plants that can put up with shade as flea beetles prefer nesting where there are enough sunrays.
- Plant resistant verities of crops that include waxy and hairy leaves. Flea beetles will not attack such plants due to certain chemicals and attributes.
- Inter-planting is another method to avoid flea beetle attack. For example- Plant cabbages with radishes as the flea beetles will prefer radishes over cabbages.
- You can prepare yourself a homemade spray to be used against the flea beetles. Prepare a mixture of water, liquid soap, and rubbing alcohol. Put it in a spray bottle. Spray this mixture on susceptible plants. The farmers and producers are also known for using catnip tea sprays, pepper sprays, and garlic sprays on susceptible plants.
- Using sticky traps can reduce the population of flea beetles but it will deceive the beneficial insects (common enemies) as well.
Cultural control is the best way to control the population of flea beetles. The overwintering larvae can be killed during cultivating and hoeing.