Problems With Japanese Holly Bushes


In the domestic garden, the Japanese holly bushes, also known as Ilex crenata, create a significant effect. It doesn’t matter if it’s going to be used as a screen, a hedge, or in mass plantings—Japanese holly is highly regarded thanks to the striking contrast between its delicate leaves and its robust constitution. However, despite their resilience, evergreens may still be affected by a variety of pests and diseases from time to time. Take care of issues as soon as they appear to avoid doing long-term harm.

Preventive Ilex Crenata Care

Shrubs that have been properly pruned and fertilised have a better chance of surviving and recovering from adversity, such as an infestation of insects or a disease. According to a North Carolina Extension Gardener, Japanese hollies achieve their optimal level of development when planted in regions of the landscape that get anything from full sun to moderate shade. Even though these shrubs are capable of developing well in the majority of soil conditions, they do best when planted in soil that is acidic, wet, and well-drained. Only those who reside in USDA hardiness zones 6 to 8 should bother planting Japanese hollies, since these are the only zones in which they will thrive.

Japanese Holly Diseases

The Japanese holly plants that are susceptible to black root rot disease have an infection caused by fungi. The fungal pathogen Thielaviopsis basicola is responsible for the illness known as black root rot, which is transmitted via the soil and may potentially live on dead plant material. Fungi propagate themselves by infecting the surrounding soil, while spores may travel via water. According to the research conducted by the University of Kentucky Cooperative Extension Service, disease is more likely to manifest itself in moist, chilly soil that has a temperature ranging from 55 to 65 degrees Fahrenheit.

Black root rot, as its name indicates, causes blackened regions of dead plant tissue on roots, as well as discoloured, wilting leaves, leaf drop, and slower or stunted growth in plants. Other symptoms include blackened patches of dying plant tissue on roots. Plants that are not handled will eventually perish.

Japanese Holly Problems With Pests

In spite of the fact that the Japanese holly is periodically plagued by sucking pests, these bugs seldom cause any significant harm to the plant. On the other hand, when Japanese hollies are infested by black vine weevils (Otiorhynchus sulcatus), this may lead to either aesthetic harm or the death of the plant. Black vine weevils are described as being grey to brown-black in colour, with snouted faces, and having short, stocky bodies that are around three-eighths of an inch in length, as stated by the Wisconsin Horticulture Division of Extension.

The larvae that are lighter in colour look like the letter C. Adults only chew on the leaves at the margins, creating distinctive notches in the leaf edges as they do so. A torn and worn look will develop on the leaf as a consequence of the feeding. However, the larvae feed on the roots that are buried under the soil, which may result in discoloured foliage, reduced development, and even mortality in extreme circumstances.

Solutions for Good Health

In order to prevent the spread of the disease known as black root rot on Japanese hollies, severely afflicted plants must be removed and disposed of. If the illness is not severe, a test of the soil may determine whether or not any changes to the environment are required to produce healthier plants. In addition, a fungicide drench that contains active components such as thiophanate methyl may be effectively used to achieve management of the problem.

Adult black vine weevils on Japanese hollies are removed by hand from the plants in order to maintain control over the pest population. In addition to watering, treating the soil with entomopathogenic nematodes such as Steinernema species and Heterorhabditis species may be helpful. This recommendation comes from Penn State Woody Ornamental Integrated Pest Management. Although chemical pesticides are not advised for use in larval management, it is possible to eliminate adults before they can reproduce by using preventative applications of a pesticide that contains the active component acephate.