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What Should You Do With Fruit and Vegetables After Pesticide Drift?

Posted: June 20, 2012

In this post, Dr. John Masiunas from the University of Illinois addresses the issue of what to do when vegetable or fruit crops are injured from pesticide drift.

A common question that we get after a garden, vegetable field, or orchard is damaged by pesticide drift is whether or not it is "safe" to harvest and consume the produce. This is a very difficult question to answer. Re-entry time and worker protection information on the pesticide label will provide guidance on when the garden, field, or orchard can be re-entered, but it provides no information about the residue that might be on or within the produce. To answer conclusively the question about whether or not it is "safe" to harvest and consume the produce requires knowledge of the pesticide involved, the amount of residues within the plant, the health effects of the pesticide, how the harvested part of the plant has changed, and laws regulating pesticides.

When herbicide drift damages your plants, it is an indication that the herbicide has entered the plant. To legally sell the produce, there has to have been an established tolerance for the particular herbicide causing the injury. Some herbicides such as glyphosate (active ingredient in Roundup, Touchdown and others) are used for spot or stale seedbed treatments in a wide range of fruit and vegetable crops. These herbicides have established tolerances (Table 1). Other herbicides do not have an established tolerance for most fruit and vegetable crops. If the concentration of the herbicide in you fruit or vegetable is above the established tolerance or there is no tolerance, then you have a tainted crop that is illegal to sell and is subject to seizure. The website to check for tolerances is: www.epa.gov/pesticides/food/viewtols.htm.

Table 1. Examples of some tolerances for herbicide residues in apple and tomato fruit.

Apple

Tomato

Herbicide

Tolerance (ppm)

Herbicide

Tolerance (ppm)

Casoran

0.50

Dacthal

1.0

2,4-D

5.0

Dual

0.1

Gramoxone

0.05

Poast

24

Karmex

1.0

Sandea

0.05

Liberty

0.05

Select

1.0

 

 

Sencor

0.1

Tolerances are not the only factor that should go into your decision on whether or not to sell or consume produce. The U.S. EPA tolerance levels are the best scientific information we have, but you or your customers may not trust that information completely, and if your customers have heard of the drift problem, selling affected produce may damage your farm's reputation. Concentrations detected by analyzing selected plant tissues, usually leaves, may have little relationship to the concentrations of herbicide occurring in the harvested portion of the plant, often the fruit. Because there are so many unknowns, I advise not consuming the fruit or vegetable when visible herbicide injury occurs to the plant. Herbicide drift can kill flowers and damage fruit and leaves. The damage makes the harvested fruit or vegetable unsightly and may affect storage life and taste. Instead of trying to use the fruit or leaves from damaged plants, I recommend that gardeners purchase locally grown produce at a farmers market or roadside stand.

If you are interested in harvesting some undamaged fruit or vegetables from a garden or field with areas having drift damage, get as much information as possible. What herbicide(s) drifted? Many herbicides that commonly cause drift injury are absorbed by the leaves and translocate to the growing points, fruit, and seed where they concentrate. Some herbicides such as 2,4-D degrade in plants, others such as glyphosate degrade only slightly in plant tissues. Over time the herbicide concentration in the plant may be diluted due to plant growth and herbicide loss in dead shoot and root tissue.

I feel that having the fruits or vegetables analyzed for herbicide residue is critical to making an informed decision in herbicide drift situations. Several private laboratories will analyze plant tissues for herbicide residues for a fee; that fee can be several hundred dollars per herbicide per sample. Talk to the applicator who caused the drift problem; they may be willing to pay for the analysis. Some manufacturers will analyze plant tissues for their products. The Illinois Department of Agriculture, as part of a pesticide misuse investigation, will collect plant samples and test for herbicide residues. For the Illinois Department of Agriculture to be involved you must file a formal written complaint alleging herbicide misapplication. Contact the Illinois Department of Agriculture as soon as possible after discovering herbicide injury. In Pennsylvania, pesticide misuse complaints are filed with the Pennsylvania Department of Agriculture’s Bureau of Plant Industry: http://www.agriculture.state.pa.us/portal/server.pt/gateway/PTARGS_0_2_24476_10297_0_43/AgWebsite/OrganizationDetail.aspx?name=Bureau-of-Plant-Industry&navid=34&parentnavid=0&orgid=22&.

In addition, whoever collects samples for residue analysis must collect them correctly and in a timely manner for it to be useful for you in the decision making process. If the harvested part is present, collect that tissue. If fruit are not present, then collect samples of recently formed leaves and the shoot tips. Translocated herbicides will concentrate in those tissues. Ask that fruit samples be collected later to help you in deciding whether or not to sell or consume the fruit. Make sure that samples are collected from the crop plants showing injury and as close as possible to the site of herbicide application.

What does information herbicide residue concentrations tell you? Sometimes it may not tell you much. Obviously the lower the herbicide concentration, the better, and a concentration below an established tolerance is better than one above, but there are no clear-cut answers. Low or no residues can mean a variety of things. The herbicide may be absent from the parts you wish to harvest and eat, or the herbicide concentration may be below the limits of detection for the equipment or procedure being used. Another possibility is that your sampling procedure was not careful enough to find fruit or vegetables with residues, and the herbicide may have degraded between the time of the drift and when you sampled (or during sampling, handling, shipping, or storage). Be conservative in how you interpret the residue information.

If herbicide residues are detected, the scientific literature suggests that for the concentrations likely to occur from drift and subsequent absorption into fruits and vegetables, acute poisoning effects are very unlikely. Questions about the possible chronic effects (including cancer, the endpoint that is always debated in questions about pesticide safety) from multiple exposures from repeated incidents of herbicide drift along with many other routes of exposure remain the subject of research.

John Masiunas, (217-244-4469, masiunas@uiuc.edu);

 Illinois Fruit and Vegetable News