About Basic Care

Pests and Pestilence

by Phil Ash

If you grow good roses in your garden, there is an equally good chance that your roses will be attacked by a goodly assortment of pests and a variety of forms of pestilence.

If you grow mediocre roses in your garden, there is almost a certain chance that your roses will be attacked by a goodly assortment of pests and a variety of forms of pestilence.

Well, that's the first clue for you! Growing good roses reduces the number and frequency of attacks by pests and pestilence. Mediocre or poorly grown roses by definition are more vulnerable, stressed, and less able to ward off attack. But, regardless of growing success, your roses will be attacked!

Pests mostly commonly tend to be insects in one of their stages of development, usually in either caterpillar or adult form. Damage is commonly in the form of holes or discoloration of the leaves, gouges to the bud or bloom, or some internal damage to petals. During daylight you can see large insects like grasshoppers, which munch large segments of leaf tissue, or the green fruit beetle working on leaf or bud.

Also quite visible on the fresh new plant growth are aphids. They're small waxy looking things, light brown or green or transparent colored, that leave a sticky residue behind. With their piercing mouthparts they suck the juices out of the plant tissue. As you notice leaf yellowing, look at the underside for signs of salt and pepper colored residue, webs, and truly ugly, tiny spider mites, which also suck out leaf juices. The cutter bees, who cut perfectly round holes in leaves, are more difficult to spot, but the damage is clearly visible.

Less visible by day are the several varieties and sizes of worms and earwigs, which populate and destroy both leaves and blooms at night. Take your flashlight and go out after dark and examine what's going on. The number and variety of pests may well surprise you! Thrips are the insects that grow up inside the bud and damage the petals by sucking out the substance of the petals discoloring the bloom or worse as it opens.

Don't reach for your sprayer! Insecticides tend to wipe out not only the bad guys but also the good guys, the beneficial birds and insects, as well. Instead, pick them off by hand (the squeamish may want to wear gloves), bag them securely in a plastic bag, and trash them. Or get the hose blasting again, and using a pistol grip nozzle blow the pests off with a water jet.

For spider mites use a watering wand and blast water up under the leaves. The roses will love the extra water, and after several days of doing this, there is a good chance the pests will get the message. No toxic chemicals are used. The beneficial insects and birds have a good chance to snack on your former problems. The one exception that will defy the water treatment is the thrips, deep inside the bloom. Thrips tend to like light-colored blooms best. Don't make a full recipe for a small number of thrips-susceptible blooms. Use a small hand sprayer with a half-pint of Orthene spray mix. Get up-wind, put on nitrile rubber gloves and with one hand holding the newly formed bud gently spray it. Repeat the treatment weekly until the bloom is cut and it should be free of thrips damage.

Pestilence usually includes rust, powdery mildew, blackspot, anthracnose, and downy mildew. These all have visual behaviors trying to call the problem to your attention. Leaves are discolored and/or fall off, stems get mottled colors, canes start dying back. If you can identify the early stage, the cure can be as simple as pulling affected leaves off, bagging them, and trashing them.

Typically, one plant will show specific disease symptoms before others are involved. If you will visit and look at your roses regularly, you will be able to initiate treatment early on all after seeing the problem starting on one. Start with leaf removal if that is feasible. If all the leaves on all your roses are involved, you are starting late. It helps to know specifically what the problem is. Splashing water on your plants may accelerate the spread of the problem as with rust or downy mildew.

If pulling leaves doesn't do the job, your attack plan may involve spraying something on the plant which will either kill the pestilence on contact or when absorbed into the plant's system will move through tissue overcoming the disease. Environmentally friendly, "organic" mixes typically call for a tablespoon each of baking soda, canola oil, vinegar, and liquid hand soap in a gallon of water. Organic does not necessarily mean safe to breathe or drink! Also organic, but clearly labeled Caution are sprays made from neem tree or jojoba tree oil. Chemical fungicides such as Fungicide require that you practice SAFE SPRAYING. Read the label and follow all of the required safety procedures.

Rose pests and pestilence can be overcome. Grow good roses. Know and use the effective, non-toxic methods to move them off your plants (and into your neighbor's yard, not yours?). The beauty of your roses will be all the thanks you need to make it all worthwhile!

This article was originally published in Rose Ramblings, Vol. LXXIV, No. 5, May, 2001. © 2001 San Diego Rose Society, Inc.

Keywords: Pests