By managing alfalfa pests properly, growers can improve quality and yield while saving money. This guide will help scouts and growers learn to check for pests and decide whether treatment is economically justified. No pesticide recommendations are included. Refer to the latest issue of the North Carolina Agricultural Chemicals Manual or ask your county Extension agent for suggestions.

1 Integrated Pest Management

What is IPM?

What is integrated pest management (IPM), and how can it help me produce alfalfa? These are logical questions often asked by growers when IPM is discussed. Integrated pest management is a systematic way of controlling pests that combines tried and true pest control methods with new approaches. The purpose of IPM is to help growers produce crops more profitably by (1) using all proven methods of lowering pest levels (rather than relying solely on chemicals), (2) using pesticides according to need, and (3) helping growers consider all aspects of pesticide use.
    Pests can lower crop yield, quality, and profits. Profits may also be lost when money is spent unnecessarily to control pests. To avoid unnecessary expenses, pest levels must be determined in each field and the potential damage compared to the cost of control. The economic threshold is the point where the predicted cost of pest damage to a crop is higher than the cost of treatment for the pest.
    IPM is designed to help growers protect their crops at the lowest possible cost. A successful IPM program is composed of three elements:
1.  Regular and systematic checking or scouting of the crop for pests.
2.  Waiting until pest populations reach the economic threshold level before taking control measures.
3.  Making all pesticide use decisions on the basis of scouting results and economic thresholds (if available for the pest).
If a pest has no economic threshold or if chemical applications must be used preventively, then the pesticide used should be carefully matched to the pest and the situation, and all efforts made to time applications properly. Regular scouting for these pests should still be employed to evaluate control efforts.
 

Scouting

The purpose of field scouting is to detect the presence and concentration of pests. Scouting is not a casual or spontaneous procedure. Alfalfa must be checked regularly using methods described in this manual. The information gathered while scouting can be used to help make immediate pest control decisions. Scouting observations may also become part of a field history that can be used to make pest control decisions in the coming years.
    Accurate identification of pests is an important aspect of scouting. Lumping insects into a general category such as worms or identifying weeds only as grasses is not adequate. A good pest management plan depends on knowing precisely what insect, weed, or disease is present in a field. Accurate information allows a specific treatment plan to be devised instead of wasting money on a shotgun approach to pest control.
    Avoid die temptation to make pest control decisions for all fields based on information from only one or two fields. Pest levels can vary greatly from one field to another, even though the fields appear similar. Each field should be scouted closely according to the recommendations in this manual.
 

Economic Thresholds

It is logical to think that if pests are present they must be damaging the crop or interfering with its growth, thus causing a yield loss. In some cases, however, pests can be in the crop for weeks before it pays to control them. In other cases, no control will be necessary at all. For example, plants may simply outgrow a low level of insects. Treating for a pest that will not reduce die quality or yield of the crop is a waste of money, can cause unwanted residues on the crop, and can increase the possibility of off-site problems.

As described earlier, the economic threshold is the point where the potential loss due to crop damage by pests outweighs the cost of pesticide treatment. At this point, it pays to spend money on a pesticide treatment for that pest. When pests are found, however, it is sometimes difficult to decide when a pesticide treatment is justified. This is where thresholds can help.
Another point to consider is that nature itself has a way of working against an increase in pest levels (for example, through natural predators or diseases that attack pests). In other words, the presence of a pest in a field does not necessarily mean that the pest population will ever reach damaging levels. There is no point in spending money to control a pest that may never cause an economic loss. Helping a grower to determine if there will be enough pests to warrant treating the crop is one way IPM works to save money.
Keep in mind that although the thresholds given in this manual have worked very well, they were developed as guidelines for average conditions. In unusual situations, such as during periods of drought stress or when multiple pests are present, thresholds may have to be altered. Obtain experienced advice when such situations occur.
 

Pesticide Selection and Application

Once a pest exceeds the economic threshold, it is necessary to determine the best and least expensive way to prevent unacceptable losses. If treatment is needed, the pesticide and its rate and method of application must be customized to the pest. Making these decisions carefully is probably the surest way to save money. High pesticide rates are not needed if the correct pesticide is chosen and the method of application delivers the right amount of chemical to the pest. For pesticides to be applied properly and efficiently, die sprayer pressure and volume must be correct; the right nozzle type, arrangement, and number must be used; and the sprayer must be accurately calibrated. Pesticides may cause other pests, called secondary pests, to increase and require treatment. This treadmill effect, where one pesticide application causes another to be needed, must be avoided.
    Specific pesticide recommendations are not included in this guide. When deciding on a pesticide, talk to your county Extension Service agent and consult the North Carolina Agricultural Chemicals Manual before talking to your chemical supplier.
 

Responsible Use of Pesticides

Pesticides have become an important tool in producing crops. But like any tool, they can by overused and misused.   New rules concerning registration of pesticides, public concern, cost, environmental contamination, water resource degradation, and a host of other issues require that all growers reexamine their pesticide use. Responsible use of pesticides will help ensure that growers continue to have access to these tools.
 

Pesticides and Water Quality

Pesticides have been found in groundwater in many states, including North Carolina. There is good evidence that this situation can be avoided if a few precautions are taken when loading and using pesticides.
    One of the most likely locations for off-site movement of pesticides is at the loading station. This location is often near a residence and close to the wellhead because it is convenient. However, during the season small amounts of pesticide are spilled. These amounts, after a number of growing seasons, begin to accumulate in the soil. The natural chemical and biological systems that normally neutralize pesticides are overwhelmed. Rain moves these chemicals down through the soil.  If there is enough pesticide and enough rain, groundwater may be permanently contaminated. This situation is even worse if the well is shallow (less than 50 feet), improperly cased, or the casing is cracked.
    This situation is easily avoided. Mixing and loading stations should be a minimum of 150 feet from a wellhead. A concrete pad should be constructed so that spilled pesticides can be collected for proper disposal.
    Many farms are in close proximity to surface water, including rivers, streams, and lakes. These resources are valuable and should be protected from pesticide contamination. There are two primary ways that pesticides move off site: by spray drift and runoff with rain water.
    Spray drift is difficult to control because wind can carry a pesticide a great distance before depositing it. Alfalfa spraying is especially susceptible to this problem since high pressure is often used. Obviously this situation can be avoided by spraying when it is calm. But often the wind continues to blow even when pesticide applications are necessary. This is a difficult situation and there are no sure solutions. Consider spraying fields that are not close to water or that have a hedgerow or some other buffer. Try to spray the fields next to water resources early or late in the day when the wind is calmest. Reduce spray pressure to the lowest amount possible. This will decrease the number of small droplets that are easily moved by the wind. A conscientious effort by growers to reduce drift will greatly reduce the chance of water pollution.
    Pesticide runoff with rainwater may be the primary way pesticides move off site. As little as 0.1 inch of rain can wash pesticides off plants. This can cause two problems. First, it removes pesticides from the target plant, which is no longer protected. Also, the pesticide may contaminate nearby water. The easiest solution to these problems is not to use a pesticide just before rain is expected. However, this strategy presents two more problems.
    First, summer thunderstorms are hard to predict. However, many growers are familiar with the patterns of rainfall on their farm and are pretty good at figuring out where it is going to rain, if it rains. Use this knowledge to avoid spraying just before a rain.
    Second, some pesticides, such as preemergence herbicides, require rainfall to be effective. Of course, too much rain will reduce the effectiveness of these materials. Avoid application just before anticipated rains of I inch or more. Doing so will allow the pesticide to be incorporated and will lessen the likelihood of off-site movement.
 

Pesticides and Wildlife

Wildlife is an important and valued resource for all citizens and should be protected as much as possible. Wildlife can be affected directly and indirectly by pesticides. When an organism is directly exposed to a pesticide - for example, when a bird eats a granule of pesticide - the direct effects of such exposure include death, weakening, or behavior change. An organism is indirectly affected by a pesticide when its habitat or food source is removed. This can happen when herbicides kill plants that are vital to an organism's habitat or when an animal eats prey that has consumed a pesticide. Using the least toxic material possible will also help minimize the toxic effects of pesticide use on wildlife. Look at the LD50 on the label of any pesticide that is being considered. Generally die more toxic the material (die lower the LD50) the more likely it is to affect wildlife. If there is a choice among pesticides, choose the one with the highest LD50. Reducing drift and off-site movement of pesticides will also lower the possibility of affecting nontarget species and help preserve our rich wildlife heritage.
 

Pesticides and Food Safety

There are concerns that residues in alfalfa may affect animal health or be passed on to consumers in animal products. Scientific evidence does not support this contention. However, this perception is enough to deter consumers. The best way to avoid potential problems is to minimize pesticide use and use pesticides properly (at the correct rate and timing). This will assure potential buyers that agricultural products are the safest possible.