I have a few roses that were infested by some worms or organisms. There are silk like tents coverings the buds. Can you tell me what the problem is and how I can deal with it?
P.s. our neighborhood is infested by Gypsy moths. Seems it is not Gypsy moths though.
Thank you for contacting the Toronto Master Gardeners concerning your roses.
Without a photo of the organism it is difficult to say with total accuracy what is harming your roses.
Do you see any tiny green caterpillars with white or black markings on the rose buds? Do you see any black sticky goo on the roses? If so then the pest in question is budworm. The University of California-Who’s eating the Petunia and Roses advises that the most effective control is done when the larvae are young. “A small infestation can be hand picked off the plants at dusk” and drop them into a container of soapy water. Make sure to wear gloves when carrying out this procedure as some of the caterpillars can posses irritating spines.
If the infestation is too big to pick off then BtK ( Bacillus thuringiensis) can be applied. This is product is only harmful to caterpillar insects. It is a bacteria that is naturally occurring in the soil which produces a toxin in the digestive tract of the caterpillar once it has been ingested. This product is available at local garden centers. Like all products make sure to read the instructions as to it’s dilution and application. For more information on BtK see The Truth about Btk
Do you see yellow green larvae on the underside of your rose leaves? If so then this is the larvae stage of Rose sawfly. The following information on this pest and how to treat it is from one of our archived posts:
“Rose sawflies (Arge ochropus). They appear in the early spring and lay their eggs on the underside of host leaves. The larvae appear several weeks later and feed on soft leaf tissue for about a month. They then drop into the soil to pupate and then appear as adult sawflies. There can be two generations each year. It is the larvae that are the problem for your rose. If the level of infestation is minor, the damage to leaves can be cosmetic and rarely harm the plant. However if there is a heavy infestation, the plant can be severely defoliated which will stress and weaken it, leaving it susceptible to disease and other insects.
Check the underside of the leaves on your plant carefully for eggs which might not have hatched yet, and also check for larvae anywhere on the leaves. Remove infested leaves and destroy the eggs and larvae. You can also use a forceful spray from your garden hose to knock off and kill the larvae.
It is still fairly early in the season so your rose might not be badly infested yet. Continue to check it throughout the growing season.
There is information and pictures of this rose sawfly at this website :
There is more information including how to treat rose sawfly at this website :
The spider webs could be caused by spider mites. Spider mites are not actually insects, these members of the Tetranychus genus form large colonies on the lower sides of leaves and drain juices from the plant, creating tiny, yellowed, stippled spots on the foliage, and they spin unsightly webs across the leaves and stems. Severely damaged leaves turn brown and fall from the plant. A forceful spray from your garden hose several times can control small populations. If chemical treatment is necessary, spider mites can be controlled with the application of insecticidal soap which is available from your local garden center. again, make sure to read instructions before applying. The University of California has an interesting article on Roses: Insects and Mites
Lastly, it is important to identify the pest before you begin to spray if you want to control the pest properly.
Good Luck with your roses.
May 26, 2021