General management guidelines for insect pests of vegetables
Location of fields in areas of low insect populations should be attempted. For example, most cotton production areas in the mid-south harbor significant populations of the cotton bollworm, also called the corn earworm. Snap bean production in these areas will likely be much more difficult than in non-cotton areas.
Removal of alternate host plants several weeks prior to the production season will reduce the likelihood of high insect populations at transplanting. This is particularly important with host specific insects, e.g., many insect pests of brassica crops. And not only do these alternate hosts include cultivated vegetables but also weeds.
Use of transplants free of insects should be the producer’s goal. Row covers, application of insecticides to nursery beds and location of nursery beds away from old production fields can prevent insect occurrence on transplants.
Use of vegetable cultivars that are resistant or tolerant to insects may be available. Often host plant resistance (HPR) is most effective with host specific insects.
Practices which promote rapid plant growth often will aid the vegetable plant to better tolerate low levels of insect damage. These include proper fertilization and irrigation and delaying planting until an optimal soil temperature is reached.
Scouting for insects throughout the production season can often detect low pest populations while management is still practical. This is especially important with whiteflies as large whitefly populations are very difficult to manage.
Use of “soft” insecticides that are less toxic to beneficial organisms will preserve the beneficials that may provide sufficient suppression of the pest insect. These insecticides are often most useful early in the production season. In some cases, however, the beneficial insect, e.g., lady beetle pupae on spinach, may be as or more harmful than the pest if the vegetable is produced for the canning industry.
Use of surfactants often increases insecticide effectiveness particularly with small insects like aphids, thrips and whiteflies.
Sanitation, including destruction of crops immediately following the last harvest, will likely reduce damage in subsequent plantings.
Crop rotation not only can be used to improve plant production but can often reduce the impact of insect pests on later plantings.
Plowing that exposes soil insects to beneficials and to the harmful effects of the environment can prove beneficial in vegetable production.
Newer insecticides are often more effective and less hazardous than older traditional insecticides. However, insects have short life cycles and many insect species have numerous generations each year. Thus, insects have great potential for development of resistance to both new and older insecticides. Insecticide use may offer numerous benefits but insecticides should be used wisely and cautiously.
Proper sprayer calibration and correct mixing of insecticides not only reduces costs but may prolong the useful life of insecticides. Several mixing formulas are available and if used correctly will provide the correct amount of pesticide to add to a spray tank. However, these formulas have generally been developed for large agronomic sprayers and may not always be applicable to vegetable production. The following is an alternative to the formulas.
Sprayer calibration
The purpose of spraying is to place the correct number of spray molecules (volume) on a specific area (area), i.e.,
Volume
______
Area
Volume is determined by collecting the total amount of water the sprayer discharges during a specific time period, e.g., 30 sec. The sprayer should be set at the same speed it will be used to apply the insecticide. If several nozzles are present, spray can be collected from representative nozzles, averaged and multiplied by the total number of nozzles.
Area is determined by measuring the spray width and the length the sprayer travels in an equal amount of time that the volume was collected, e.g., 30 sec. By converting the volume to gallons (128 oz. per gal) and the area to acres (43,560 sq. ft. per acre) and then dividing, the sprayer will be calibrated to gallons per acre (gpa).
Calibration example: A vegetable sprayer has 12 nozzles each of which delivers 5 oz. in 30 sec. The spray width is 12 ft. and the sprayer travels 105 ft. in 30 sec. Total spray volume in 30 sec. is 60 oz. (12 nozzles x 5 oz. per nozzle). Total area of spray is 1260 sq. ft. (105 ft. x 12 ft.).
Volume 60 oz. 60 oz. x (1 gal/128 oz.)
______ ® _____ ® ______________________ = 16.2 gpa
Area 1260 sq. ft. 1260 sq. ft. x (1 acre/43560 sq. ft.)
Insecticide mixing
Using the above sprayer calibration of 16.2 gpa and the recommended insecticide rate of 3.8 oz. imidacloprid per acre. The proper mix would be 3.8 oz. insecticide in 16.2 gal. Because 16.2 gal. is impractical to measure, the insecticide amount should be proportioned to the volume that the sprayer holds, e.g., 100 gal.
3.8 oz. x
________ = ______
16.2 gal 100 gal
In this case x = 23.5. Thus 23.5 oz. of the formulated insecticide should be added to the 100 gal tank.
Insecticide safety
The labels of many of the restricted use insecticide state that applicators are required to wear complete protective dress that includes respirator, spray suit, rubber gloves and rubber boots. Unfortunately, use of protective dress is not always practiced.
Regardless of the availability of full protective clothing, additional precautions will aid in reducing exposure to insecticides.
- Rubber gloves – Use is very important because the most common route of applicator exposure is through the hands.
- Maintain sprayer without leaks
- Spray down wind and start on down wind side of field
- Wash body and clothing after spraying
- Allow time for residue to dry and dissipate before reentering field – Check reentry times on insecticide label.
- Do not store pesticides in feed/drink containers
- Do not permit children to spray or have access to pesticides
- Read and follow pesticide labels
|
