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Insects & Diseases

Updated: Jun 9

Most bugs are good; a few pests provide food for the “good guys.” However, sometimes the “bad guys” get out of hand and you might need to take action. Less-toxic insecticides, such as horticultural oils, insecticidal soaps and pyrethrins kill only those insects they contact, but are quite effective at reducing pest populations. Systemic insecticides are absorbed into the plant tissue and kill sucking insects such as aphids for a 3-week period. These products also contain a contact poison that kills chewing insects on contact. Since insecticides kill good as well as bad insects, they should be used only when absolutely necessary. With the decline in pollinator bee populations, we encourage our local rosarians to be very careful with which insecticides they use.


Pesticides are products containing chemicals or other agents designed to kill or disable pests. Herbicides destroy vegetation, miticides control mites, insecticides kill insects, and fungicides combat fungi. Some products combine a fungicide and an insecticide.


Organic Options

Neem Oil works both to kill insects on contact and prevent fungal diseases like black spot. We suggest spraying at dusk to avoid burning your plant leaves and avoid killing daytime pollinators.


Insecticidal Soap kills soft bodied insects like aphids on contact. This is safer for adult ladybugs and bees. We suggest spraying at dusk to avoid burning your plant leaves and avoid killing daytime pollinators.


Ladybugs can be purchased at local garden centers or online from companies like Nature's Good Guys. They will eat the local aphid population and lay eggs, and their larvae are vicious aphid hunters. Before releasing ladybugs, spray down all of your plants with water so they have something to drink. One of our members puts the ladybugs in a bug house with cotton rounds soaked with water first so they can drink, along with a small drop of honey for them to eat. This helps prevent them from flying away in search of food or water immediately. Generally, ladybugs will fly off after a few days, leaving eggs and larvae behind. Make sure they have water sources by spraying water on the leaves every day to prevent them flying off early.


Green Lacewings are great pest bug hunters. You generally receive them as eggs, often mixed with plant seed husks to make it easier to spread them because they are so small. They may also come attached to a little card you place right on your rose stem. You can place loose egg and seed husk mix in little bags next to the rose stems. Good bugs like ladybug larvae and green lacewing larvae will be killed by insecticides as well, so we suggest waiting until they've done their job to resume spraying.

Fungicides


Fungicides are preventative, not curative. A regular spray schedule is recommended for fungus protection. An all-purpose fungicide will prevent mildew, blackspot, and rust. Some are more effective with specific diseases, so Rosarians often rotate products in their spray program. Less toxic fungicide options include Green Light (neem oil), Safers Garden Fungicide (sulfur) and Concern ( copper soap fungicide). The next line of defense, if the less toxic options are not working, includes Spectraside Immunox Fungicide (myclobutanial), Garden Tech Daconil Fungicide (chlorothalonil), and Bayer Advanced Disease Control (tebuconazole).

Early morning spraying allows the foliage time to dry. Be sure to spray the underside of the foliage, where most insects live and spores germinate. After a spray material is mixed with water, use it within a couple of hours; it loses effectiveness if kept overnight or longer. Spraying should begin right after pruning time; fungi and insects have been dormant and protected during winter, and by pruning time are becoming active and vulnerable to pesticides.

Choose a sprayer that produces a fine mist. For a few plants, a pistol-grip sprayer will work. For more plants, choose a plastic pump sprayer; these range from ½ to 2 gallons in capacity.

The pesticide products on the market have undergone stringent testing and have been approved by the EPA. They are safe if you use common sense and follow directions. Read and follow all labeling directions. It is illegal to use a pesticide in a manner not in accordance with the label instructions.