Archives For pest alert

A gall, tumor, or burl is an abnormal growth on the leaves, stems, roots, buds, twigs, or crown of a plant. In most cases, the gall is unsightly but not damaging. In small plants, the vascular flow of water and food can be restricted, causing poor growth and making the plant more susceptible to other stresses. A large tree can be weakened by an infection over many years. Nematodes, mites, and insects cause 95 percent of galls. Bacteria and fungi cause the remaining five percent. In most cases, the gall-making organism can be identified by observing the structure of the gall and the species of the host plant.

Galls on a Flower

Galls on Rudbeckia laciniata ‘Herbstsonne’

Fungal galls are spread by ascospores in wind and water and can be found on many common trees including oak, maple, and common privet. Black knot affects many species of the genus Prunus—particularly cherries and plums.

Crown gall is a common problem caused by bacteria. The disease is spread by infested soil, transplants, or contaminated tools. The bacteria enters the plant through wounds caused by cultivation, pruning, or insects. Easy prevention methods are to plant only healthy stock (no suspicious bumps), to clean pruners between use on each plant with alcohol or a 10 percent bleach/water solution, and to take care not to injure plant stems. The bacteria stays active in the soil even after removal of infected plants, so place new, healthy stock elsewhere. Remove and destroy all infected plants. Galls caused by bacterial and fungus are more prevalent during wet years.

A gall can form in response to toxins injected during insect feeding or egg laying, or around a feeding larva. The hackberry leaf gall is caused by psyllids, which are tiny winged insects. Galls formed by insects usually do not affect the overall health of the tree unless they experience early defoliation over the course of many years. Parasites are an important control of this pest. Many oak galls are caused by gall flies and generally are not detrimental. A severe twig infection can, however, cause severe injury and even death. Spruce galls are often caused by several species of an aphid-like insect. If only a few galls are present, they can be cut off and destroyed before the insects emerge in midsummer.

Galls on a Flower
Galls on a Flower


Leaf galls on maple trees form because of feeding mites. Eriophyid mites produce a gall that resembles a felt patch and may occur on the upper or lower side of the leaf. The overall health of the tree should not be seriously affected.

Nematode feeding activity can injure roots and allow gall-forming bacteria into the plant. Nematodes can also form galls on carrots, camellia, fig, gardenia, okra, potato, roses, sweet potato, and tomato. Plants can be stunted, yellow, and wilted due to restrictions on the uptake of water and nutrients. Individual nematodes are invisible to the naked eye, but egg masses can be seen as pearly objects.  Roots can appear scabby, pimpled, rough, and have knots. Two important prevention methods are to rotate with nematode-resistant crops and to maintain rich organic soil.

Please contact Plant Information Service at (847) 835-0972 or at for additional information.

©2017 Chicago Botanic Garden and

Unwanted wiggler discovered!

About a month ago, one of our horticulturists called me out to look at a groundcover planting that was being heavily disturbed by worms. At first look, I thought nothing of it—maybe it was increased surface worm activity from all the rain. A couple of weeks later, they were still very active, and the groundcover was actually floating on worm castings! We rolled it up to expose many worms. When I picked up a worm, it flipped out of my hand and wriggled away quickly, snake-like—not like a typical worm.

Since this activity seemed strange, I asked our senior ecologist to have a look at the crazy-acting worms. Coincidentally, he identified them as “crazy worms” (Amynthas agrestis), an invasive worm on his watch-for list that has never been found in Illinois. Samples were sent to the University of Illinois for confirmation, and the Illinois Department of Agriculture and Illinois Department of Natural Resources were informed. Our find has been confirmed—along with another find in DuPage County—and a potential find in Wilmette is being investigated. The crazy worm has been in the United States for many years in many of the southeastern states (and in the Smoky Mountains). In 2013, it was found in Wisconsin. DuPage and our find are the first confirmed for Illinois.

PHOTO: Crazy Worm (Amynthas agrestis).

Crazy worm (Amynthas agrestis)

Why is this worm bad?

  • They out-compete and push out our common European earthworms.
  • They multiply very quickly.
  • They devour soil organic matter and drastically change soil structure. This has a huge impact on forest ecosystems as well as on residential and urban ornamental plantings.

How do I identify the crazy worm?

  • They are found near the soil surface.
  • When touched, they respond immediately with a crazy flipping and jumping reaction.
  • They have a fast, snake-like movement.
  • Unlike a common European worm, they have a milky white flat band (clitellum).
  • They are 4 to 8 inches long.
  • A worm may lose its tail when handled.

What should I do if I think I have found the crazy worm?

  • Report the find to the Illinois Department of Natural Resources or Illinois Department of Agriculture.
  • To learn more about the crazy worm, just do a Google search on Amynthas agrestis (crazy worm or jumping worm).

Currently there are no treatments recommended for management of the crazy worm. Education and slowing the spread is the current course of action. The crazy worm’s primary means of spread is through the movement of plants with soil.

The Garden is a member of the Sentinel Plant Network, a group that unites botanic gardens in monitoring and providing education on exotic, invasive plant pests and pathogens, and works in partnership with the National Plant Diagnostic Network (NPDN).

If you are a plant and bug person like me, please consider becoming a NPDN First Detector and help be on the lookout for these exotic, invasive plant pests and pathogens. The NPDN offers an online training course to become a First Detector at It’s free, and upon completion, you even get a printable certificate!

©2015 Chicago Botanic Garden and