Alternative controls in the garden


By Patricia Hanbidge

Saskatoon School of Horticulture Principal

Many thanks to Joanne Messer from Tisdale for calling me up and asking for some alternative methods for troubles she is having with her roses — that conversation enticed me to write this column. This is a challenging summer for gardeners everywhere with monsoon rains, flooding, cool temperatures and sweltering heat.


Roses seem to attract a great variety of pest and disease problems. Sometimes these problems can easily be managed by just pruning off the infected parts or by physically removing the pest itself, but here are some hints to help you more sustainably have beautiful roses that are beautiful.

If you are having troubles with aphids, mites, scale or whiteflies on your roses, then here are some options to making those problems go away in a safe manner. A solution of a half-teaspoon of any type of dish soap with a teaspoon of cooking oil in one quart of water is a great spray for a variety of pests. To get good control, it is important to spray when the problem is small. Also, it is beneficial to spray off the plant with plain water approximately 30 minutes after applying, to ensure the plant does not desiccate as much.

This year powdery mildew is a big problem. I suspect that blackspot and rusts will also rear their ugly heads. Mixing a solution of one tablespoon baking soda with one teaspooon of cooking oil in one gallon of water will help immensely with these troubles. Spray your plant liberally with this spray and repeat as needed. It also helps if you remove any infected leaves and destroy them, while at the same time keeping the ground underneath the rose free of debris and weeds. If you are just having a problem with powdery mildew, spray the leaves each morning with cool water and allow the sun to dry things off. 

There have also been a number of calls to try to deal with slug problems. They cause so much damage when conditions are right. One of the best ways to control slugs is diatomaceous earth. It is the jagged skeletal remains of microscopic creatures that effectively lacerate soft-bodied pests like slugs, thus causing their demise. It is a powdery granular material that can be sprinkled around garden beds or individual plants and can even be mixed with water to make a foliar spray. Be careful when using this product as it can irritate your eyes and lungs. To ensure the best control, purchase the natural or agricultural grade.

Remember that slugs are most active at night, so adjusting when you water may be an effective fix. Avoid watering in the afternoon and evening and instead, water early in the day. If you water in the morning and we do not get rain, the soil surface will be dry by evening and the slug damage is greatly reduced. Slugs don’t like dry conditions so they move on to moister areas.

If you eat grapefruit, then another easy way to get rid of the slug population is to place your half grapefruit rinds upside down where the slugs like to be. They will congregate in masses in the rind; you can simply pick up the rind and toss it in the garbage each morning.

One last remedy is a bit gruesome, so beware readers! Mix up a 10 per cent solution of isopropyl alcohol and water in a spray bottle. Lay some boards down on the ground where slugs are a problem and leave them overnight. Slugs will congregate on the bottom of the boards overnight. In the morning simply flip over the boards and spray the slugs liberally with your alcohol solution — they will shrivel and die before your eyes.

Hanbidge is a horticulturist with Saskatoon School of Horticulture; she can be reached at 306-931-GROW(4769) or This email address is being protected from spambots. You need JavaScript enabled to view it. . If you would like to receive our monthly newsletter filled with tips, tricks and all the latest happenings, we need your consent; please email us if you would like to receive our newsletter. Like us on Facebook, follow us on Twitter @horticulturepat or visit