Thursday, October 13, 2016

Pictorial guide aids in Palmer amaranth and tall waterhemp identification

by Phyllis Bongard and Jeff Gunsolus

With the recent confirmation of Palmer amaranth in Minnesota, it is critical to identify this noxious weed, so it can be eradicated before it becomes widespread. A new pictorial guide compares key characteristics of Palmer amaranth and tall waterhemp at several growth stages throughout the growing season to aid in this identification.

The new guide, “Comparing Palmer Amaranth and Tall Waterhemp – Growth and Development” can be found at Detailed descriptions also accompany the photos. To access the notes, open the file in Adobe, click on “View,” scroll to “Comment,” then select “Annotations.”

Identification will be the key in reducing further infestation in Minnesota. For other articles on Palmer amaranth, see:

Tuesday, August 2, 2016

Free Waste Pesticide Collections

Collections available to eleven northwestern Minnesota counties

ST. PAUL, Minn. – The Minnesota Department of Agriculture (MDA) is hosting a series of free waste pesticide collections available to eleven northwestern Minnesota counties. Residents from Beltrami, Cass, Clay, Clearwater, Lake of the Woods, Kittson, Marshall, Pennington, Polk, Red Lake, and Roseau counties may attend any of the four collection sites in mid-August.

Friday, July 22, 2016

Part 5 ----> Just the facts: A review of the biology and economics behind insecticide recommendations

Biology helps determine the profitability of crop production on your farm – Ignoring biology is expensive

None of what we have presented here is new, or groundbreaking information. However, all of what we have presented here is based on science that has been vetted and implemented over thousands of acres for more than a decade. Economic injury levels take commodity prices, labor and control costs into account. Fortunately, the biological components of an EIL are not sensitive to commodity or input prices. The insects on your farm do not eat faster or more when crop prices are high or insecticide costs are low; nor is your crop more sensitive to insect damage (remember the damage boundary). Yield loss occurs at the same level of pest population, regardless of market prices of commodities. It makes no sense to treat if there is no reasonable likelihood of damage.

Science is best when it does not sit still. New research on pest and crop biology and on new management tools may change EIL’s and associated ET’s over time. However, since the adoption of the 250 aphid/plant economic threshold, additional research has only confirmed the results of the original multi-state biological and economic research.

While some may view an insecticide costing "only a couple of dollars" as inexpensive when compared to other production inputs, it is still an added cost for no added benefit. These inputs add up with each acre applied. Farmers often find the "free" application costs when insecticides are tank-mixed with herbicides or other pesticides have unintended negative consequences - poor control from poor timing or application techniques of one or more products. Using an ET, based on sound, peer-reviewed research will help you apply your crop input dollars where they are most likely to produce a positive return on your investment and minimize the chances of creating other problems for yourself.

Using fear or faulty economic logic is tried and true as a very effective sales tool. It’s always prudent to be a skeptical consumer and consider the messenger when you evaluate information - a conflict of interest can arise if a profit motive underpins recommendations made without facts behind them. Be very wary of ETs that are based on "feel," eyewitness accounts, or other anecdotes that are not supported by hard scientific data. ETs that are radically different from those recommended by agricultural research universities are another red flag.

Hopefully, this article has provided you with information that will help you sort through the information clutter on TV, radio, print media and especially the internet. A list of research references is included in the complete article ( for those who would like to read and learn of some of the research supporting our soybean aphid management guidelines and economic threshold recommendations. Contact Extension for the most up-to-date and state-specific recommendations.

This is the 5th and final installment in a series on soybean aphid management and insecticide recommendations.  Previous installments covered how recommendations are created, how aphids hurt yield, the economics and biology of aphid insecticide recommendations, costs associated with early treatment and how to know if you have a soybean aphid problem.  A link to the complete document is provided in this installment or at ( .

Thursday, July 21, 2016

Part 4 ----> Just the facts: A review of the biology and economics behind insecticide recommendations

Costs of treating soybean aphids too early

While some newer insecticides target a narrower range of insects, most insecticide applications are not specific. They will kill beneficial insects (lady beetles, parasitic wasps, etc.) as well as pests, later allowing soybean aphid populations to rebound in fields without those beneficial insects to slow them down. By using the ET, natural enemies will have a chance to suppress the aphid population and possibly prevent it from reaching economically damaging levels. After application, insecticide residues will kill insects for a short time, but insecticide activity invariably declines over time (generally, this is considered a good thing). With most insecticides registered for soybean aphid control (such as pyrethroids), soybean foliage emerging after treatment is not protected. Insecticides that are absorbed and translocated within soybean plants typically move upward only a leaf or two and eventually leave unprotected foliage, especially when applied early in the season. 

Applying treatments early can result in a false sense of security and a reduced reliance on scouting. If a re-infestation is not detected before reaching the EIL, yield may be reduced. If detected, the cost of additional insecticide applications are incurred. Early treatment can reduce or eliminate the cost efficiencies of a single, well timed threshold-based treatment. Finally, unnecessary insecticide applications do nothing positive for a short-term return on investment. Importantly, long-term returns can be reduced if insecticide resistance becomes fixed in the soybean aphid population. This has happened many, many times in the history of pest management. We know that managing pesticide resistant pests is seldom "cheap and easy" (for example, consider the problems with herbicide resistant weed control).

Wednesday, July 20, 2016

Part 3 ----> Just the facts: A review of the biology and economics behind insecticide recommendations

Economics of soybean aphid infestations: Math and biology matter

Figure 1. Relationship of insect population and crop yield
 (Modified from Pedigo et al. 1986).

The lowest level of aphid infestation that has been shown to cause yield loss in soybean is several thousand aphid-days. This value, referred to as the damage boundary, is a biological relationship between the insect, crop, and environment, and is independent of crop and input costs. Below the damage boundary, no damage can be measured. Therefore, management efforts directed at treating aphid levels well below the damage boundary cannot provide a return on investment.

The economic injury level (EIL) is the point at which the yield loss from insect damage is equal to the cost of a management action, such as an insecticide application. Insecticide applications made to pest populations that have not reached this point, and are unlikely to reach it, would not provide any return. To more readily apply this yield-loss relationship to field scouting and aphid management, a value in terms of aphids per plant was calculated as the threshold to apply an insecticide to threatening populations.