Issue 2, April 7, 2017 • USDA-NIFA Extension IPM Grant
Take a look at some of the impressive black cutworm captures this past week, “Black Cutworm Adult Pheromone Trap Report,” with many intensive captures (9 or more moths captured over two consecutive nights). It is not unusual at this time of year to have very high catches mixed in with zeroes, one of the reasons we want many cooperators all over the state. Typically, we receive freezing temperatures following these early flushes. Since the black cutworm isn’t cold hardy, e.g., spending the winter in Southwestern States and Mexico, many likely perish during these cold spells. But since they will keep filtering in over the coming weeks, there are certain to be sufficient moths to lay eggs in the many winter annual weeds and cover crops. We use these trap counts only as a timing mechanism or presence/absence gauge, to help determine when to start looking for them. A record number of moths DOES NOT equate to a disaster in the making and vice versa for small numbers of moths. In the near future, we will publish color-coded maps with their anticipated development to help you to time your scouting trips. As a reminder, the cutworm threat will be greatest when they get large feeding on winter annual weeds and cover crops, and then get the opportunity to feed on seedling corn as it emerges. The best time for control, as with most insects, is when the cutworms are small.
Alfalfa weevil damage should be scouted for in southern Indiana counties. We are way ahead of what is “typical” in terms of heat unit development for this pest. A mild winter, including a warm finish in the months of February and March, was likely favorable for populations statewide. This is especially true for alfalfa stands of two or more years old. Look for the tiny holes in leaves of the upper canopy. Carefully unfold some leaves of the damaged tips and look for the greenish larvae with black heads.
A video to help identity and understand sampling for alfalfa weevil can be watched here:
|County/Cooperator||Wk 1||Wk 2||Wk 3||Wk 4||Wk 5||Wk 6||Wk 7||Wk 8||Wk 9||Wk 10||Wk 11||Wk 12|
|Dubois/SIPAC Ag Center||0||0||0|
|Jennings/SEPAC Ag Center||0||1||1|
|Knox/SWPAC Ag Center||0||13||26|
|LaPorte/Pinney Ag Center||0||0||3|
|Lawrence/Feldun Ag Center||4||108||216|
|Randolph/Davis Ag Center||0||29||41|
|Whitley/NEPAC Ag Center||0||34||90|
Wk 1 = 3/16/17 - 3/22/17; Wk 2 = 3/23/17 - 3/29/17; Wk 3 - 3/30/17 - 4/5/17
back to top
|Adams||Kaminsky/New Era Ag|
|Allen||Kneubuhler/G&K Concepts - Trap 1||0|
|Allen||Kneubuhler/G&K Concepts - Trap 2||9|
|Clay||Bower/Ceres Solutions - Clay City||0||0|
|Clay||Bower/Ceres Solutions - Bowling Green||0||0|
|Clay||Bower/Ceres Solutions - Brazil||0||0|
|Clinton||Emanuel/Boone Co. CES||8||9|
|Elkhart||Kauffman/Crop Tech Inc.||0||0|
|Fayette||Schelle/Falmouth Farm Supply Inc.||5||33*|
|Fulton||Jenkins/N. Central Coop - Talma||0||5|
|Fulton||Ranstead/NCC Coop - Rochester||0||0|
|Gibson||Schmitz/Gibson Co. CES|
|Hamilton||Truster/Reynolds Farm Equipment||0|
|Jasper||Overstreet/Jasper Purdue CES||2|
|Jay||Shrack/Ran-Del Agri Services||1||3|
|Jay||Temple/Jay County CES|
|Knox||Bower/Ceres Solutions - Freelandville||0||0|
|Knox||Bower/Ceres Solutions - Vincennes||0||0|
|Lake||Moyer/Dekalb Hybrids - Shelby||5||5|
|Lake||Moyer/Dekalb Hybrids - Schneider||2||5|
|Madison||Truster/Reynolds Farm Equipment||0|
|Marshall||Harrell/Harrell Ag Services||0|
|Marshall||Klotz/SR 10 & SR 331||0||0|
|Marshall||Miller/North Central Coop||0||0|
|Newton||Moyer/Dekalb Hybrids - Lake Village||2||6|
|Pulaski||Capouch/M&R Ag Services||0||0|
|Pulaski||Leman/North Central Coop||0|
|Rush||Schelle/Falmouth Farm Supply Inc.||6|
|Shelby||Fisher/Shelby County Co-op||2||3|
|Starke||Capouch/M&R Ag Services||0||0|
|Starke||Wickert/Wickert Consulting - California Twnshp||1|
|Starke||Wickert/Wickert Consulting - Railroad Twnshp||0|
|Sullivan||Bower/Ceres Solutions - Farmersburg||0||1|
|Sullivan||Bower/Ceres Solutions - Sullivan||6||21*|
|Tippecanoe||Kremer/Monsanto Research Farm||0||0|
|Wabash||Enyeart/North Central Coop|
|Whitley||Walker, Richards/NEPAC1 - Main||10||28*|
|Whitley||Walker, Richards/NEPAC2 - Kyler||3||8|
* = Intensive Capture...this occurs when 9 or more moths are caught over a 2-night period
back to top
Results from 81 field scale trials around Indiana since 2008 suggest that maximum yield response to plant populations for 30-inch row corn grown under minimal to moderate stress conditions occurs at about 31,600 PLANTS per acre (ppa), equal to seeding rates of about 33,250 SEEDS per acre (spa). Corn grown under extremely challenging conditions (e.g., severe drought stress) may perform best at PLANT populations no higher than 22,800 ppa and perhaps as low as 21,000 ppa under truly severe growing conditions (e.g., actual drought, non-irrigated center pivot corners, non-irrigated sandy fields with minimal rainfall). Economic optimum populations are several thousand lower than the agronomic optimum.
For the full update, see the online summary at http://www.kingcorn.org/news/timeless/CornPopulations.pdf
Recently there has been increased interest in utilizing cover crops in our corn and soybean production systems. Concurrently, there has also been increased utilization of soil residual herbicides in our corn and soybean production systems to help manage herbicide resistant weeds such as marestail, pigweeds, and ragweeds. Soil residual herbicides can remain active in the soil for anywhere from weeks to months after application. The length of time a residual herbicide remains biologically active in the soil is influenced by soil type, soil pH, organic matter, rainfall, and temperature. Since these factors will vary from field to field, definitive time intervals of residual herbicide activity can be difficult to predict.
A significant challenge has arisen because use of residual herbicides in our corn and soybean production systems may interfere with establishment of fall seeded cover crops. An unfortunate coincidence is that many of the crops being used for cover crops were not evaluated for herbicide carryover when field research was being conducted for support of the EPA label of the respective herbicide. As a result, data are lacking regarding rotational intervals for establishment of many cover crop species.
Over the last couple of growing seasons we have established experiments designed to evaluate the impact of commonly used residual herbicides on the establishment of many cover crop species. In addition, our colleagues in adjacent states have conducted similar research and we feel like we have a better handle on this topic now than we did two or three years ago. As was mentioned above, predicting herbicide persistence is complicated because so many different factors can influence herbicide dissipation in the soil.
As a general rule, residual herbicides that have activity on grass weeds can interfere with the establishment of some grass cover crop species, especially the smaller seeded ryegrass species. Residual herbicides from group 2 (ALS), group 5 (triazine), group 14 (PPO), or group 27 (bleacher) can interfere with the establishment of some of the broad leaf cover crop species.
More specifically we have learned the following:
It is important to remember that herbicide application timing greatly influences the risk of carryover interfering with cover crop establishment. In general, herbicides applied at planting have a lower risk of interfering with cover crop establishment than herbicides applied postemergence later in the year. An example would be fomesafen, which can be applied both preemergence and postemergence in soybean. Fomesafen applied postemergence in late June is more likely to interfere with cover crop establishment than fomesafen applied at planting in April or May. We can use the knowledge we have about herbicide interactions with specific cover crops to assess risk of certain herbicide programs interfering with cover crop establishment. However, it is important to prioritize controlling weeds in your cash crop rather than dropping certain herbicides from your program to ensure successful cover crop establishment.
This summarizes our current knowledge on establishment of cover crops following the use of residual herbicides. The final two things to mention is that if you have questions about specific situations, one way to address the residual herbicide left in a field is to do a bioassay. Simply collect soil from the area you would like to seed the cover crop into and an area with a similar soil type, but no herbicide residue, and plant seed from the cover crop you would like to use. Observe growth for 3 weeks and if the plants look the same in the untreated and treated soil, you should be safe to plant to desired crop. Waiting 3 weeks to observe growth may push the planting of cover crops beyond the desired planting window, so careful planning is required to conduct a bioassay. One method is to collect soil at least 4 weeks ahead of your planned day of planting fall cover crops to allow enough time to observe the plants in your bioassay. Another consideration if you do not have time to do a bioassay is to plant a cover crop mixture. Cover crop establishment may be more reliable when mixtures of grass and broadleaf species are purchased and planted. Residual herbicides may interfere with establishment of some species in the mix, but have no effect on other species. The use of mixtures may allow one more protection from complete failure due to excessive residues in the soil. It would be important however to be sure that at least one or two of the species in the mixture is tolerant to the herbicides used in a specific field.
This article was originally published in November 2016. The information presented in this update is accurate as of March 31st 2017. Here are the key dicamba label changes since November:
As everyone has probably heard by now, there are federal labels for the use of 3 dicamba products, on dicamba-resistant (Xtend) soybeans. These products are Xtendimax (Monsanto), FeXapan (DuPont), and Engenia (BASF). Xtendimax and FeXapan are essentially the same product being sold by two different companies, and the labeling and eventually also the list of approved mixtures and nozzles should be the identical between these products . Engenia is a new formulation of dicamba. We cover some of the highlights from the Xtendimax label here. Table 1 lists the label differences between Xtendimax/FeXapan and Engenia.
If you plan on using dicamba in your Xtend soybean fields, it is important to monitor the associated websites for approved tank mixes and nozzles. At the time of this writing, 20 nozzles are approved for use with Xendimax. There are a handful of adjuvants and herbicides, including glyphosate, that are approved for tank-mixtures with Xtendimax. However, it is clearly marked on the website that several of these adjuvants and herbicides, including all approved glyphosate formulations, also require a specific drift reduction agent (DRA) in the tank as well. It is our understanding that any combination on this list can be mixed and matched according to the most restrictive label. Engenia currently has 6 nozzles approved for use, and also several adjuvants and herbicides. What is different from the Xtendimax label is that when applying an approved glyphosate product with Engenia, you do not need to add an approved DRA in the tank. Currently, there is only 1 approved nozzle, and no approved tank-mixes for FeXapan. These websites seem to be updated weekly, if not daily, so the situation is constantly evolving.
It is going to be imperative that everyone involved completely understands without confusion the application guidelines with regard to not injuring nearby sensitive crops, ornamentals, etc. The label places responsibility for this directly onto the person making the application, so applicators will need to figure out what type of system and alternative plans to have in place to keep up with their typically hectic application schedule and still meet label guidelines based on current weather and proximity to sensitive crops.
|Formulation||DGA salt + VaporGrip 2.9 lb./gal.||BAPMA salt 5 lb./gal.|
|Tank mixtures and nozzles||http://www.xtendimaxapplicationrequirements.com & http://www.fexapanapplicationrequirements.dupont.com||http://www.engeniatankmix.com|
|Wind speed||3-15 mph||0*-15 mph|
|Rain - do not apply if rain is expected within||24 Hours||4 Hours|
|Buffer||110 ft. for 22 oz., 220 ft. for 44 oz.||110 ft. for 12.8 oz.|
|*Only apply when wind is 0-3 mph after confirming no temperature inversion is present.|
back to top
If you would like to be alerted by e-mail when the current issue of the Pest&Crop is available on-line, please enter your e-mail address and click the submit button.
It is the policy of the Purdue University Cooperative Extension Service that all persons have equal opportunity and access to its educational programs, services, activities, and facilities without regard to race, religion, color, sex, age, national origin or ancestry, marital status, parental status, sexual orientation, disability or status as a veteran. Purdue University is an Affirmative Action institution. This material may be available in alternative formats.