Everyone who grows plants, whether rhododendron shrubs in the landscape or a bentgrass green, has one goal and that is to grow the healthiest plants possible. But as we all know, sometimes that is easier said than done. Many factors, such as weather conditions, cultural practices, or pest incidence may affect the quality of the plant in question. Proper diagnosis is critical in identifying the problem quickly and determining what corrective steps need to be taken. Not every problem can be answered in the field, but with the right information and a few helpful tools you can go a long way in narrowing the possibilities.
1. You should be familiar with the plants you are growing and what their cultural requirements are. Does the plant tolerate shade, is it winter hardy, does it handle traffic are all questions that you should consider. Also, knowing the common problems associated with the plants will help should there be a problem with plant health. Although some plants may have several possible pests that affect it, usually 1 or 2 are more common. Those 1 or 2 are the ones that you need to familiarize yourself with.
2. Learn how to look for symptoms and signs of problems. When you suspect that a plant may have a problem that needs to be addressed you need to know where and what to look for in order to correctly identify the problem. Some pests, such as chinch bugs, reside in the thatch layer and you need to get down on your hands and knees to find them. Other pests, such as the azalea lacebug are not visible unless you look at the underside of the leaves of the rhododendrons.
3. Keep a history of the site to track problems. Some problems, such as crabgrass invasion, white grub damage, and anthracnose may be an annual occurrence in a landscape. By maintaining good records you will know if you can expect to have a problem with a pest and what type of action needs to be taken. An occasional grub may not warrant treatment, however if you know that you get a heavy population every year you may want to make a preventative application of a suitable insecticide.
4. Some pests or the damage they cause can be difficult to see without the aid of a good diagnostic tool such as a magnifying glass. A magnifying glass (loupe) may help you see small insects or fungal spores more easily. This along with a white sheet of paper may be the easiest way to know if you have spidermites on your spruces. You simply shake a branch over a white sheet of paper. If there are spidermites on the branch they will fall on the sheet. The loupe will help further identify the spidermites to be sure which species you have.
5. Reference materials are helpful in confirming the identity of a particular pest. You can’t expect to remember every characteristic of every pest. Having a good reference nearby will help you locate the possible causal agent and research it to see if the problem you are seeing matches the description you read. A good reference will also give you information about the geographic location of the possible pest and the time of the year when it is likely to be a problem.
6. Not every problem can be answered in the field. In some cases it may be necessary to send a sample to a diagnostic laboratory for analysis. For example, what should you do if you apply a thiophanate methyl product for control of dollar spot and get poor results? You will need to double check to make sure that the application was made correctly. If that all checks out, then you should consider having the turf analyzed for dollar spot resistance, which can only be done in the laboratory. If resistance is identified then you know that you will need to apply a different active ingredient for control.
7. Be familiar with the remedies at your disposal. Although you do not need to memorize the pesticide label you should be familiar with the crop and pests listed on it. You may have a few products that list the same or similar pests. If you read closely you may find that a label indicates that it controls one pest, but only suppresses a similar pest. Some products work best as a preventative tool and others may be better suited for use in curing a problem. Make sure you know what you have so that you can achieve effective control if you have to act quickly.
© Cleary Chemical 2008