Pesticide Use and IPM

I think many of you will find this statement interesting and very applicable for both conventional and organic producers of all crops.


Statement on “Least Toxic” & “Last Resort”

Recommendations and decisions to use “least toxic pesticides” and “pesticides as a last resort” have flourished in the last decade, but according to three scientific organizations – the Weed Science Society of America (WSSA), the American Phytopathological Society (APS) and the Plant-Insect Ecosystems Section of the Entomological Society of America (P-IE ESA) – these are not the correct approaches to the pesticide component of an Integrated Pest Management (IPM) program. The three organizations have joined to take an objective look at these two descriptions and prepared a position statement.

It is essential to practice integrated pest management (IPM), whether managing weeds, insect pests or plant disease - on the farm, on commercial sites, on public lands, or in or around the home. Key components of IPM include making the habitat unfavorable for pests, excluding pests where feasible, using proper sanitation practices, monitoring the infestation level, knowing the pest tolerance level for the specific situation and implementing the necessary management practices. Judicious use of pesticides is a critical component of many IPM programs.

Judicious (careful) use refers to various practices - following all label directions and making all appropriate stewardship decisions required in the particular situation. This includes applying a product registered for the target pest(s) after accurate pest identification, and consideration of the level of infestation and the potential for economic, health or other negative pest impacts. Careful use extends beyond pesticides to household chemicals, automobiles, medicines, alcoholic beverages, and countless other products that are part of our daily lives.

“Least toxic” implies there are pesticides available for every pest spectrum that are least toxic to everything else. This is not true. The toxicity of a pesticide depends on what is being evaluated and who or what may be affected. It is also important to remember that toxicity is not the same as risk, which is dependent on both toxicity and exposure. The risk associated with the use of pesticides and other chemicals is managed by establishing safe exposure levels based on the toxicity specific to each product. Assigning a “most” or “least” toxic rating does not equate to actual risk when the product is properly applied.

“Last resort” implies that pesticides will work as well when every non-chemical control technique is attempted first. However, delaying application of a pesticide can cause buildup of the pest(s) in crops, gardens, buildings and other sites, with negative impacts on yield, quality and/or health. In fact, delaying treatment can significantly increase the ecological and economic damage to crop and non-crop areas.

Using pesticides as the last line of defense can result in a more limited choice of pesticides, as well as reduced crop tolerance, the need for higher rates, and less effective control because of higher infestation levels and/or more tolerant pest stages. For example, seedling weeds and early-stage insect larvae and diseases are usually more easily controlled than later pest stages. Effective pesticide choices, when they are applied as a “last resort,” means fewer options to rotate pesticides, which is a critical step in preventing a pest from becoming resistant to a pesticide. “Last resort” pesticide strategies may also increase the need for multiple products and higher application rates to control the pest effectively. The term also suggests pesticides are always the worst choice, which is not true. First using non-chemical techniques that are ineffective or inefficient has the potential to add to the cost of pest management, intensify the pest problem or create new problems.

Finally, by branding pesticides as the “last resort” choice certainly does not stimulate a strong public interest in funding education on their proper use. Pesticides are widely used, but discretionary federal funding of the U.S. Pesticide Safety Education Program has been eliminated in 2011 and 2012.

This program is vital to educate pesticide users and dealers who must be certified to apply or sell pesticides, and to teach the public how to use pesticides safely. There is no benefit or scientific basis to simplistic messages like “use least toxic pesticides as a last resort” for the large number of pesticide users who apply pesticides according to the label and practice good stewardship. Nor are these messages beneficial for those who neither seek training nor adequately read the label believing instead that it is safe, practical, and effective to simply choose a product considered a “least toxic pesticide” and apply it only as a “last resort.” These messages hinder pesticide safety and stewardship education and practices that are in the best interest of the pesticide user, our food supply, public health and ecosystem preservation.

(WSSA/APS/P-IE ESA joint statement, 11/12/12).

How Does Bt Work?

Some of you may be interested in this information especially in light of the Bt resistance that has been identified: Researchers Identify Insect Resistant to Bt Pesticide.

Thanks to Gene McAvoy in Hendery County Florida for passing along this great info!

Bacillus thuringiensis, the active ingredient in the “Bt” insecticides, is a commonly occurring soil bacterium that was first discovered in 1901. Since their commercial introduction in the 1950’s, Bt products have become the most successful and widely used of the biopesticides.

Insecticidal activity of Bt derives from proteins that are produced and crystallize during bacterial sporulation (thus referred to as “Cry” toxins).

Most Bt products contain a mixture of Bt spores and toxin crystals. When a caterpillar ingests Bt, the crystals are dissolved in the alkaline gut environment. The insect’s own digestive enzymes convert the protein to an activated “delta endotoxin” which binds irreversibly to receptor molecules on the surface of cells lining the insect’s midgut, opening holes in the membrane that destroy the cellular lining of the digestive tract. The larva stops feeding (typically within hours) and may die quickly from septicemia as Bt and other spores in its food germinate, or may linger and die eventually of starvation.

Many different subspecies and strains of Bt have been described, producing different combinations of unique Cry toxins. Bt insecticides used for worm control are based on two of these subspecies which produce a few important Cry toxins.

Bt subspecies kurstaki (Btk) products such as Javelin®, Deliver®, and Dipel® contain primarily Cry1A and Cry2 toxins. These give broad spectrum activity against loopers, diamondback moth, imported cabbage worm, tomato fruitworm/corn earworm, tobacco budworm, hornworms, and other defoliating caterpillars common to vegetable production.

Xentari® and Agree® are based on Bt subspecies aizawai, which produces another toxin (Cry1C) effective against beet armyworm and other Spodoptera species, which are not very sensitive to Cry1A toxins.

Agree® contains a “hybrid” Bta, the offspring of a cross (transconjugation) between parent strains of Bta and Btk. As a result, Agree contains Cry1Ac (from Btk) in addition to Cry1C (from Bta). Other products such as Condor® represent unique combinations of Cry toxins resulting from transconjugation between different Btk strains.

Still other advanced Bt’s are products of genetic engineering to create unique Cry toxin combinations or higher levels of expression. CryMax® is such a recombinant Btk product, producing high levels of Cry1Ac in addition to Cry1C. Lepinox® is engineered for high expression of a combined Cry1Ac/Cry1F toxin particularly effective against fall armyworm (Spodoptera frugiperda), which is not highly susceptible to other Cry toxins.

All Bt products must be ingested by the target caterpillars in order to be effective, and small larvae in earlier stages of development are more susceptible than large, mature larva. This means that proper spray timing and technique are important to ensure that vulnerable plant tissues are uniformly covered by Bt spray deposits when young larvae are actively feeding. Worms that enter fruit or stems soon after egg hatch (such as squash vine borer, melon worm, and European corn borer) or are protected within mined or rolled leaves (such tomato pinworm) are susceptible to Bt if applied before they enter these protected environments.

Bt is not a systemic insecticide and tends to have shorter residual effect compared to many chemical insecticides (one of the reasons they present little risk to the environment, workers, and consumers). Reapplication may be required, especially during periods of rapid crop growth when new, untreated tissues may be exposed to infestation. Be sure to read the Bt product label for specific information regarding crops, target insects, and application instructions (such as rates, timing, and reapplication intervals).

Bt in IPM and Resistance Management

Bt insecticides are an ideal tool for the grower focused on IPM due to their selective control and low environmental risk. Bt also provides a unique mode of action (IRAC group 11) that can complement other insecticides in resistance management strategies. No evidence of cross-resistance has ever been detected between Bt and other insecticides; insects resistant to multiple classes of insecticides are still susceptible to Bt. Btk and Bta products also can be rotated to reduce risk of resistance to specific Bt’s.

At a recent symposium on “Insect Resistance in Vegetable Production” organized by the Entomological Society of America (Southeastern Branch), entomologists and IPM specialists (including Dr. Dakshina Seal of IFAS in Homestead) pointed to Bt products as the best rotational partners for delaying resistance to new insecticide chemistries such as the diamides.

Symposium participants listed the following benefits of Bt insecticides in a rotation program:

• High efficacy on a wide variety of worm pests

• Very low impact on beneficial insects.

• Avoidance of secondary pest problems.

• Not toxic to bees and predatory mites.

• No preharvest interval required after application.

• No restrictions on amount used.

• Resistance to Bt is slower to develop than resistance to chemical insecticides.

Through proper field scouting, correct identification of the worm pest, good timing of applications, correct selection of the Bt used, and judicious application of the Bt’s in rotation with new or older conventional chemistries, growers can gain effective control while reducing the risk of resistance and maintaining beneficial insect populations.

For more information contact Dr. Brett Highland, Certis USA, at bhighland@certisusa.com, or visit www.certisusa.com.

Fresh Market Vegetable and Tomato Field Day Tomorrow

Tomorrow, Thursday August 4 is the Annual Fresh Market Vegetable and Tomato Field Day at the Mountain Horticultural Crops Research Station in Mills River.

The annual tomato field day at the Mountain Horticultural Crops Research Station in Mills River! This is your opportunity to see new up and coming varieties and learn the latest about disease, insect, and weed control for staked tomato production and vegetables in western North Carolina. As always, the afternoon field day will be followed by a pig pickin' at Lake Julian.

The field day begins at noon and pesticide credits will be offered.

To view the complete program click here.

Tomato field day is sponsored by North Carolina State University, College of Agriculture and Life Sciences, NC Agricultural Research Service and NC Cooperative Extension Service, the North Carolina Department of Agriculture and Consumer Services, and the North Carolina Tomato Growers Association. For more information, contact Denny Thompson at 828.684.7197 or Jim Walgenbach at 828.684.3562.

New Pests: Spotted Wing Drosophila and Kudzu Bug

There are two new insect pests that growers need to be aware of, spotted wing drosophila and the kudzu bug.

Spotted wing drosophila (SWD) is an invasive fruit fly pest of soft-skinned fruit (strawberry, blueberry, blackberry, raspberry, etc.). SWD was first observed in California in 2008 and then identified in 2009. In 2010, Dr. Hannah Burrack of NC State began an intensive monitoring plan for SWD in the Southeast. SWD was captured in NC and SC late 2010. SWD gets its name because the males have two spots on the end of their wings (one on each). Female SWD do not have spotted wings, but do have a serrated oviposter. This serrated oviposter allows the female to lay eggs in sound fruit, unlike common fruit flies which prefer decaying fruit. Because of this, SWD has potential to be an economically limiting crop.

SWD trapping is well underway throughout NC, in fact SWD was captured in Henderson County in mid-June. Small fruits producers are encouraged to start a monitoring program. Dr. Burrack explains how to construct and monitor SWD traps and how to identify them.

For treatment considerations, visit Dr. Burrack's post What to watch for: When treating SWD.

To read more about SWD or to view images, please visit Dr. Burrack's SWD page on her NC Small Fruits, Specialty Crops and Tobacco IPM blog.

If you would like assistance with monitoring, please contact me at sue_colucci@ncsu.edu or your local extension office.

Kudzu bug (adult) on soybean leaf.

Multiple kudzu bugs (adults) on soybean stem.

The next pest is the kudzu bug. This pest prefers legume crops, especially soybeans, but has also been observed feeding on potatoes, cotton and wheat. The kudzu bug was confirmed in central Georgia in 2009 and then spread throughout the state and to neighboring states in 2010. This pest has been identified in many NC counties, including Buncombe and Henderson Counties on soybeans. This pest isn't thought to be a problem on most vegetables, but those who grow edamame soybeans or potatoes should be concerned. The kudzu bug is a stem and leaf feeder, so far there have been no reports of the kudzu bug feeding on blooms or pods.

Based on Georgia data the economic threshold is one bug per sweep with large nymphs present, or three bugs per plant with large nymphs present. This pest is very mobile and will re-invade after treatment, so capturing or observing nymphs is important. According to the latest edition of NC Pest News, killing this pest has been relatively easy with conventional insecticides except the neonicotinoids (kudzu bug seem to be attracted to areas that have been treated with neonicotinoids). For organic producers, PyGanic is recommended. Other options are options are azadirachtin (Azagard) or kaolin clay (Surround), but the efficacy of these products is unknown.

To read more about the pest, see more pictures and a map of kudzu bugs movement in the southeastern US, see the June 24th of NC Pest News.

Sustainable Insect Management Workshop

Yesterday I had the pleasure of attending the Sustainable/Organic Insect Management for Vegetable Growers Workshop in Clinton, SC. Our first stop was Parson Produce, a certified organic farm located at Bush River Farm.


Here we were greeted by Daniel Parson, a young and gregarious farmer who has been farming for 12 years. Daniel is a great presenter and has a Master's degree from Clemson University. Some of you may know Daniel from his presentations at SSAWG.

Daniel discussed his farm and showed us his farming equipment, which he stated is a piece of his pest management strategy. In true organic fashion, his production is a whole-farm system and pest management starts with productive soils, adequate not abundant nutrition, cover crops and good weed management.

Next, we moved to the field where Dr. Powell Smith (Extension entomologist and vegetable specialist from Clemson University) showed us some insect collection tools. These include sweep and butterfly nets, aspirators (used for catching small insects by sucking them into a container) and fabric sheets.

Below you can see Daniel's cover crop mixture of sorghum-sudangrass and buckwheat.

A great place to find insects!

Check out this field of pure buckwheat! A quick summer cover crop and insect attractor.

Insects, especially those that are predators to some plant-eating insects love the small buckwheat flower and will visit often for a source of food.


Daniel allows his buckwheat to go to seed and therefore re-seed the field.


Here is a group of workshop participants learning about the insects they collected in the buckwheat.


Next, we moved on to look at the broccoli to see what kind of insects we could find in this crop.


Here we saw some bad insects, but also some natural predators. We also learned about 'banker plants'. 'Banker plants' are plants that have some kind of problem and attract crop destroying insects and the predators that feed on them. Daniel has chosen to leave his 'banker plants' in order to keep the good insects in the planting. His 'banker plants' had lots of aphids (typically a sign of excess nitrogen). In addition to the aphids, they contained aphid predators. Below is a lady beetle larva feeding on the aphids.


Syrphid fly larvae were also present and feeding on the aphids(below). These insects are known as "aphid killers".


We also found harlequin bugs, a yearly problem on brassica crops. Below are nymphs of the piercing/sucking pest.


Exploring the eggplant crop we noticed a lot of flea beetle damage. Management for flea beetles is difficult. Some have found that row covers are effective for crops that do not require pollination. The covers cannot have open spaces for the beetles to enter. This control method is not effective if the flea beetle larvae are present in your soil. If they are, you will be trapping them in and may have a big problem on your hands.

Below you can see some flea beetle damage (the shot holes). The insect pictured below is an adult two-lined spittlebug, which is a plant-feeding insect.


Another plant-feeding pest that we found on the eggplant was a some kind of leaf-footed bug (below).


Thrips damage was also noted on the eggplant crop. Thrips are usually found in the flower of crops. These insects have rasping mouthparts. Damage on eggplant appears as green to brown streaking on the fruit. Sorry, I don't have a picture.

After all of our fun in the field, we enjoyed a delicious lunch prepared by the owners of Bush River Farm and Bed and Breakfast.

After lunch the group headed to Presbyterian College to learn some more about insect pest management and to do some more insect identification. Dr. Powell Smith discussed the different characteristics of identifying insects and the major plant-feeding and beneficial insect groups. The group discussed management options and the importance of attracting beneficial insects, as well as learning about the life cycle of an insect pest.


Overall, managing insects in vegetable crops organically is similar to a conventional IPM approach. Like discussed above, healthy soils, adequate nutrition and weed management will go along way. IPM includes cultural control methods (including proper selection of vegetable varieties for your area, avoiding insects by changing planting date, eliminating insect overwintering areas, attracting beneficial insects, planting trap crops, etc), using mechanical or physical control methods (tillage to disturb life cycle, row covers, hand picking or vacuuming) and finally the use of organically approved insecticides. Keep in mind that many insecticides will also kill or disturb your beneficial insects, that is why it is your last line of defense.

To learn more about attracting beneficial insects and biological control, visit NCSU's Biological Control Information Center or the Biological Control Resources page on GrowingSmallFarms.org.

Overall, the day was successful. We learned a lot about identifying insects, management options and even got to take a few specimen home with us. Below you can see our insect collection.


I took a wheel bug (a predator in the assassin bug family), a leaf-footed bug and larva, a squash bug and a running ground beetle (a voracious eater in the Carabidae that will feed on cutworms) home with me!

To learn more about insect identification, insect collection and insect control visit the following links:

ATTRA's Links to Insect Management
Growing Small Farms Links to Insect Management Web Resources
Collecting and Preserving Insects and Arachnids