Common insects and associated pests attacking bedding plants, perennials

There have been several calls on the information line in the last couple of weeks complaining about insect problems. Following are some common pests and solutions:

Bedding plants and perennials provide the homeowner and landscaper with a multitude of colors and textures. Unfortunately, numerous insects, mites and other invertebrates (i.e. slugs, sowbugs and millipedes) consider these same plants as food. 

In order for you to manage the activity and damage caused by these pests, you must understand “pest management” and learn how to identify each pest. There are numerous “bugs” in a healthy garden and most do no damage. A common mistake is to spray anything that moves. 

Each plant has a number of pests that may attack the flowers, foliage, stems or roots. Some of these pests will only attack a certain kind of plant. Other pests are generalists and can feed on a variety of plants. This fact sheet will attempt to help you identify the common “generalists” and suggest methods of keeping them under control. 

Pest management 

We now use the term “pest management” because we know from experience that there is no way to totally rid the garden of unwanted pests. We can merely attempt to keep pest numbers low to minimize their damage. This is management. 

When we use pest management there are two important principles to remember: 1) The mere presence of a pest is no reason to attempt control. 2) Reliance on a single control technique will eventually fail. 

Perhaps the old farmer’s saying of “plant five seeds–one for the weather, one for the crow, one for bug, and two to grow!” should be considered in our gardens today. Pests will always cause some damage to our flowers but is the amount of damage unacceptable? We know that complete reliance on pesticides will eventually fail. In order to manage pests and their damage, we need to use cultural (and mechanical) control (i.e. resistant plants, traps, crushing and sanitation) and biological control (i.e. predators, parasites and diseases) with chemical control. 

Diagnosis of a problem 

To manage pests, you must become a pest detective. To do this, you must learn some of the terms used to describe pest damage to plants. Generally, pests have either chewing or sucking mouthparts. 

Pests with chewing mouthparts eat portions of the plant. They may defoliate the plant by eating all the leaves. They may only eat portions of leaves, resulting in skeletonized foliage (the leaf tissues between the veins are eaten), notched foliage (only the edge of the leaf is eaten), shot holed foliage (tiny holes in the leaves), or shredded foliage (most of the leaf eaten except for the major veins). Other chewing pests feed inside leaves (leaf miners), or bore into stems and roots (borers). 

Pests with sucking mouthparts usually cause the plant to discolor or twist and curl. The plant may discolor from tiny yellow speckles (spider mites), larger darkened spots (plant bugs), or coatings of black sooty mold growing on honeydew deposits (from aphids, whiteflies and scale). Many plants react to the saliva and damage of sucking pests by causing the foliage to curl or the young stems to twist. 

Locating an actual specimen of the pest makes diagnosis easier. Many pests stay on the plant at all times and a close inspection is all that is necessary. Others run or fly when disturbed and you may need to sneak up on the plant to avoid scaring the pests. Carefully approach the plant low to the ground and try to observe the plant’s upper and lower leaf surfaces without casting a shadow. Many pests come out at night and you will have to look for these with a flashlight. 

If you have located a suspected pest and you cannot identify it, try to capture a specimen and take it to your county’s Extension office. Most pests can be placed in a dry jar or plastic bag. A dry tissue or paper towel placed inside the jar or bag will keep the specimen dry. Be sure to keep this container out of direct sunlight and get to the office as soon as possible. 

Snails and slugs 

Snails and their “shell-less” cousins, the slugs, are common residents in the garden. Most of these feed on decaying organic matter but many can chew the foliage of living plants. Snails and slugs prefer the dark 

and usually do their damage at night, leaving ragged leaves. Use a flashlight at night to detect these pests or look for the slime trails on damaged plant foliage in the early morning. 

These pests require high humidity or moisture and usually reach pest status during wet years or during the rainy periods of the spring and fall. Control is best achieved by making the garden less suitable for snails and slugs. Remove excess mulch in order to allow the soil to dry slightly, clean up any fresh plant debris and open the plant canopy so that sunlight can reach the ground. 

Snails and slugs are attracted to the yeasty odor of beer and several traps are available that use this odor. The larvae of fireflies, ground beetles and parasitic flies feed on snails and slugs. If habitat modification, traps or natural predators do not reduce snails and slugs, pesticide-laced slug and snail baits can be use. 

This publication contains pesticide recommendations that are subject to change at any time. These recommendations are provided only as a guide. It is always the pesticide applicator’s responsibility, by law, to read and follow all current label directions for the specific pesticide being used. Due to constantly changing labels and product registration, some of the recommendations given in this writing may no longer be legal by the time you read them. If any information in these recommendations disagrees with the label, the recommendation must be disregarded. No endorsement is intended for products mentioned, nor is criticism meant for products not mentioned. The author, North Carolina State University and North Carolina State University Extension, assume no liability resulting from the use of these recommendations. 

Thanks to David J. Shetlar.

Send your gardening questions or comments to: Brunswick County Master Gardener Column, P.O. Box 109, Bolivia, NC 28422, or call 253-2610. Enclose a self-addressed stamped envelope if requesting information or a reply. Answers may be printed in this column.