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archives - greenhouse grower - july 2006
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The Twelve Most Common Mistakes In Using Pesticides
by C.C. Powell
Pesticides are probably our most important tool for combating weed, disease and insect problems on plants. Other health management practices are important, of course, but when the chips are down, most of us rely on a chemical to help us take care of the problem.
Growers often have trouble managing a problem, even with pesticides. The lack of success often relates to one or more of a few basic mistakes. Here is a list of the most common mistakes.
1. Wrong material used because of incorrect diagnosis.
We all know that there are many chemicals on the market today. They all have their uses. Most are specifically useful for a certain set of problems. Diagnose a problem as specifically as you can and you will avoid the mistake of choosing the wrong pesticide.
2. Material used incorrectly because of inadequate product knowledge.
Even after the correct product is chosen because of a correct diagnosis, there can still be problems with it and your decision. Most of these product "quirks" will be spelled out on labels or in trade journal articles. Consultants can assist you with maintaining good product knowledge.
3. Putting on the initial application too late.
Disease or insect pests react to the presence of crops in sensitive stages. They are most active when weather conditions are favorable for buildup. Know what to be on the lookout for. Know when plants are particularly sensitive to infestation. Know what the favorable environments are for the development of the pest or pathogen.
4. Improper tank mixes or improper mixing procedure.
Mixing pesticides often creates problems. We are dealing with complicated chemistry here. Read labels, try tank mixes out on a small scale and mix properly. Do not use more than one liquid or emulsifiable concentrate in a mixture. Mix each pesticide into a separate batch of water and then add to a half-full spray tank slowly, one at a time. Add spreader-sticker last.
5. Using pesticides that have been stored beyond their shelf life.
Even though you may be doing everything right so far, watch out for this common error. There are a few general rules - one is that you should never use a liquid product that is over two years old. Another is that you should never store liquid pesticides in freezing conditions.
6. Not paying attention to weather.
Plants go through periods when they are more prone to pesticide burn. Generally, this is when they are on the dry side or when the temperature is too warm. Secondly, a hot sunny exposure right after spraying will tend to dry spray droplets too quickly.
7. Improper rate of material applied per unit area of crop.
Labels usually tell us how much material to mix into the water (often given as "per 100 gallons"). They sometimes don't tell us how many plants to spray or drench with the 100 gallons. Of course, this will vary according to the type of plant and the stage of growth. If you are watching your coverage and using a standard high volume technique, you will generally be OK with rate problems because you are spraying to runoff.
8. Improper coverage of the target.
Pesticides work by getting to the target. This can be the pest or weed directly or to the plant surface or soil area that will soon be infected or infested by the pests or weeds.
9. Failing to apply follow-up applications if needed.
A single application of a pesticide to combat a pest rarely does the trick. There are some pests on some leaves that escape the spray. Furthermore, the chemical may be ineffective at killing spores, seeds or eggs. They soon germinate or hatch to cause further damage. Finally, the crop continues to grow. Protectant barriers are not present on new leaves or shoots. Rain and other factors wear away old pesticide barriers.
10. Not keeping thorough records.
Doesn't this seem like good, old common sense? Suppose something were to go wrong; the plant was damaged, the pest was not alleviated. If we are going to make a good management decision, then we need to change something. We need to know exactly what was done before to know what to change.
11. Incomplete cleanup and draining of sprayers.
Spray equipment is expensive and most pesticides are corrosive in one way or another. Safety to plants and people is at stake. Finally, the "residual" material left in the spray from a previous job may mean that a costly mistake will occur on the next crop.
12. Relying on the chemical alone to do the job.
This is a lesson from the "spray and pray" school. Health management is an integrated mindset. Attention to environmental control, sanitation and maintenance of plant vigor (control of plants stress) forms the basis of integrated plant health management.
About the author:
Dr. Chuck Powell is Plant Health Advisory Services is an educator and consultant, with more than 35 years of experience at The Ohio State University and in private consulting.
He can be reached at
phaspowell@aol.com
GG
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