Reasons and Prevention of Withering of Old Rose bushes in Summer and Autumn
The following is an introduction to the reasons and prevention methods for the withering of old rose bushes in summer and autumn, let's take a look together!
Rose enthusiasts who enjoy growing climbing roses or rose trees often encounter the phenomenon of rose branches inexplicably turning yellow and withering at the end of summer and beginning of autumn. In severe cases, the entire rose plant may wither. What exactly causes this, and how can it be prevented?
Reasons and Prevention of Withering of Old Rose bushes in Summer and Autumn
Although yellowing and withering of rose branches are usually noticed at the end of summer and beginning of autumn, the damage has already occurred. The main culprit behind the yellowing and withering of strong branches or the entire plant is often boring insects, mainly the larvae of the scarab beetle and the longicorn beetle.
The adult scarab beetles and longicorn beetles lay eggs in May. After the eggs hatch, the larvae of the scarab beetles bore into the main roots of the plants, while the larvae of the longicorn beetles bore into the main stems. Either type of borer is fatal to roses.
The damage caused by the larvae begins from the moment the eggs hatch. As the larvae grow and their food intake increases, the intensity of plant damage also increases. Therefore, roses often do not show obvious abnormalities in summer, but by the time autumn arrives, the yellowing and withering of branches become evident.
For borers, enthusiasts should detect and treat them early, or use pesticides preventively, especially for roses that have been buried with raw fertilizer. It is recommended to apply insecticides with systemic properties around the root system at the beginning of summer to prevent problems.
1 -- Characteristics and Treatment Methods of Longicorn Beetle Larvae --
In summer, one should observe frequently, especially the longicorn beetle larvae, which are relatively easy to detect. The larvae mainly bore into the main stems of roses, and during the boring process, they produce excrement. Therefore, if sawdust-like material is seen around the rose roots, it is a sign of the presence of longicorn beetle larvae.
At this point, one should carefully observe the branches to find the boreholes. If boreholes are found, a cotton ball soaked in concentrated insecticide can be used to plug the boreholes tightly. This will prevent the larvae from breathing, causing them to bite the cotton ball.
If there is no insecticide, a thin iron wire with a small hook at the tip can be used to reach inside the borehole to try to hook and pull out the longicorn beetle larvae, or simply stab them to death.
Reasons and Prevention of Withering of Old Rose bushes in Summer and Autumn
2 -- Characteristics and Treatment Methods of Scarab Beetle Larvae --
Compared to longicorn beetle larvae, scarab beetle larvae are more secretive and harder to detect because they are in the soil, boring into the main roots of roses, with no visible excrement on the soil surface.
However, careful observation can still reveal some abnormalities. For example, if the growth of roses weakens significantly, or strong branches suddenly stop growing, the plant may become unstable, indicating the presence of scarab beetle larvae. If there is an area around the rose roots that remains moist for a long time, it can be assumed that scarab beetle larvae are active.
If scarab beetle larvae are suspected, the soil around the root surface can be dug up to check for signs of boring on the main roots. If boring marks are found, the larvae inside the main roots must be located and destroyed.
If the growth of roses weakens significantly and scarab beetle larvae are suspected but not found, insecticides can be directly applied, such as using phoxim or lambda-cyhalothrin to灌根 (irrigate the roots), or shallowly burying insecticide granules.
For roses with main roots bored by scarab beetle larvae, in addition to controlling the pests, Green Enthusiast Network suggests applying rooting hormone to the branches near the main roots, then covering them with soil to promote the rapid growth of new roots and restore the plant's health.
The above information on the reasons and prevention of withering of old rose bushes in summer and autumn, and the likely cause of weak growth in climbing roses in summer, is hoped to be helpful to you!