Flea Beetles & Pill Bugs

Flea beetles on cabbage

The rains continue. Despite the wet and cool weather, a number of gardeners have mentioned to me the appearance of the usual population of flea beetles in their gardens.

Flea beetles comprise a large group of leaf beetles of the family Chrysomelidae.  Probably the most common flea beetles that backyard gardeners encounter belong to the Phyllotreta genus and show up on brassicas (cabbage, broccoli etc.)  and solanaceous plants (tomato, potato, eggplant etc.).

These varities of flea beetles are about the size of pin heads, typically black and have strong hind legs that they use to jump, like fleas, if disturbed.  First signs of their presence frequently will be damage to the surface of plant tissue or small pin holes through  leaves.  Adult flea beetles leave their eggs at the base of their preferred plants. When the eggs first hatch, the young initially feed on the roots and root hairs of plants; and then, as adults, they migrate up to the  foliage. There can be multiple generations during a growing season.  Larvae  over winter in plant debris left in gardens at the base of the plants they lived.  

A variety of organic technques can be employed to control, but not eliminate,   flea beetle populations. These include:

• adjusting planting times:  sow seed early  before flea beetle eggs hatch  or delay sowing to let eggs hatch before larvae have seedlings  to eat;

• tilling soils lightly in spring to disturb larvae; 

• using trap crops - first plant a crop attractive to flea beetles beside where you plan to plant you favorite crops,  e.g. dill  attracts flea beetles,  and the dill can then be tilled into the soil to disrupt a portion of the flea beetle population;

• interspersing companion plantings to  provide flea beetles with alternatives: e.g. dill, marigold and pac choi;

• mulching with straw or grass clippings can interfere with beetle egg deposit;

• keeping planting beds free of weeds such as wild mustards, a favorite meal for the beetles; 

• adding row covers - these offer some relief,  but soils need to be free of over wintering populations;

• placing sticky traps around plants also offers relief, but will also trap some beneficial insects;

• vacuuming may also reduce their numbers (check this  previous post).

There are also some biological methods to control flea beetles.  There is a common parasitic wasp, Microctonus vittatae, that specifically targets adult beetles. The wasps are a natural control, but not a quick solution.  At the subterranean level, there are also some nematodes that  devour flea beetle larvae as well as  a fungal pathogen, Beauvaria bassiana, that will infect the beetles.  Both of these should be present in healthy soil, but are available from commercial sources.  Finally, some pesticides, like neem,  that are approved for organic use  could be applied.

Pill Bugs

Pill bugs (Armadillicidam vulgare), alias: Rollie-Pollies, are not insects, but actually crustaceans and  members of the woodlice family.  Adults are usually between 1/4" and 1/2" in length, and black to grey in color.  Pill bugs do not lay eggs; females have a pouch that first carries the fertilized eggs and then serves as home to the hatchlings for up to their first two weeks of life. Pill bugs are eaten or preyed upon by birds, toads, spiders and some wasps.

In gardens A. vulgari can be both good and bad.  Pill bugs typically like damp or moist places and eat decaying plant debris - you will typically find them in your compost pile, under rocks and rotting wood. They are generally nocturnal  avoiding warmer daytime temperatures. However, if their population gets too large and there is a lack of decaying plant material in the soil, pill bugs will   eat living plants including many of our favoritge vegetables. Overly wet conditions, like this spring, also seems to engender their taste for  fresh garden salads.

In small gardens and greenhouses the following control strategies can be used:

•  placing plant collars around young plants; 

• removing of plant debris to reduce habitant; 

• reducing humdity levels and/or increasing air circulation (fans & dehumidifiers indoors; staking & pruning outside);

• vacuuming (place a cloth or cardboard sheet around a plant and shake);

• deploying sticky traps, or diatomaceous earth;

• traping  by placing wet, rolled newspapers in the garden at night (pill bugs will congregate   under the newspapers after first eating your eggplants;  and, of course, 

• applying neem or other pesticides. 

And remember:

"On every stem, on every leaf,... and at the root of everything that grew, was a professional specialist

 in the shape of  grub, caterpillar, aphis, or other expert, whose business it was 

to devour that particular part. - Oliver Wendell Holmes