A few weeks ago I was lucky enough to attend North Carolina State’s Tomato Field Day, at the Mountain Horticultural Crops Research and Extension Center in Mills River, NC. Every summer crowds flock from all over the Southeast to learn what’s new in the world of tomatoes. Since it’s not always convenient for you to drop what you’re doing to make a road trip to North Carolina, I’ll highlight something I learned from the field day.
Stink Bug Control by Dr. Jim Walgenbach
The brown marmorated stink bug (BMSB) was introduced into the United States from Asia. The insect pest was first found in Pennsylvania and is suspected to have made its way to the US in packing material. BMSB was first reported in 2009 in Hillsborough County, FL and since been found in additional Florida counties. It has a wide host range including fruits, vegetables, and ornamentals.
Fifth instar nymph of the brown marmorated stink bug on raspberry in Allentown, Pennsylvania. Photo Credit: Gary Bernon, USDA-APHIS
BMSB has a typical stink bug body shape and size with a mottled brown coloring. The key identification feature is alternating dark and light bands on the last two antennal segments.
Trissolcus japonicus adults. Female to the left; male to the right. Photo Credit: FDACS – DPI
Biological Control with Natural Enemies
Dr. Walgenbach’s team is currently researching the impact of suppressing BMSB populations by native predators such as: katydids; jumping spiders; earwigs; and lady beetles. Current observations indicate only a minor effect from these predators on BMSB.
BMSB egg masses parasitized by T. japonicus. Photo Credit: Matt Lollar, University of Florida/IFAS Extension.
Trissolcus japonicus Assessment
A regional effort has been implemented to monitor the introduction, spread, and efficacy of the Asian parasitoid Trissolcus japonicus. Trissolcus japonicus is a tiny wasp that parasitizes the eggs of various stink bug species. It was first collected from China and brought back to quarantine facilities in the US for evaluation, as a potential biological control agent. Host-specific tests have indicated that T. japonicus prefers to parasitize BMSB eggs over eggs of other stink bug species. It is suspected that release permits for the wasp will be available from the USDA in the near future.
Reporting in Florida
The brown marmorated stink bug overwinters in homes to keep warm. If stink bugs are found in yuor home, they may be the BMSB and should be reported to the Florida Department of Agriculture and Consumer Services Division of Plant Industry. Specimens should be collected for identification.
To follow the research of Dr. Walgenbach and his colleagues, please visit NC State’s Entomology webpage.
By Nicholas Dufault and Wael Elwakil
Fungicide resistance or reduced efficacy is a concern when managing peanut diseases, especially the foliar diseases early and late leaf spot. Managing these concerns requires an integrated approach with constant monitoring of the product’s efficacy and application programs to avoid resistance selection. Two common resistance management strategies are alternating (or rotating) and mixing fungicide product modes of action (MOA). It has been indicated that MOA mixtures are a more sustainable strategy for resistance management than alternating, but they may be costlier as they tend to increase the spray program’s number of fungicides. So, it is important to understand the value of these two strategies especially when using products that have a moderate to high risk for resistance selection.
A recent study explored the value of these strategies using the fungicide products azoxystrobin (Abound 2.08), pyraclostrobin (Headline 250 SC) and tebuconazole (TebuStar 3.6L). All these products are off patent and considered medium to high risk for leaf spot resistance or reduced sensitivity. The study consisted of various spray programs that had five applications of chlorothalonil (Chloronil 720) at 30, 44, 72, 100 and 114 days after planting (DAP). The at-risk products were then applied at approximately 58 and 86 DAP either alone (alternation program) or in combination with chlorothalonil (mixture program). The study was conducted at two locations in Marianna and Citra, FL during the 2017 season. The mixture programs generally had higher yields than the alternation programs (4 times out of 6), however, only one of these yields was significantly different (Fig 1). Both strategies provide significant yield savings compared to the untreated control plots (data not shown).
Figure 1. Yield results from the various fungicide alternation and mixture programs at the two locations. Fungicide products consisted of azoxystrobin, pyraclostrobin, tebuconazole and chlorothalonil. All programs consisted of 5 applications of chlorothalonil with the products indicated on the x-axis applied alone or in combination with chlorothalonil at 58 and 56 days after planting. The yield was significantly greater for the mixture program compared to the alternation in the pyraclostrobin treatments for the Marianna location.
Identifying the pathogen population present is a key component when assessing these two strategies. Location populations varied with late leaf spot being the primary pathogen in Marianna, and early leaf spot in Citra (Fig. 2). It is also important to note that significant pressure was also present from late leaf spot and rust in Citra as well. This variation in pathogen population could be one possible reason for the inconsistencies observed between these strategies at each location. It does seem apparent that in situations where multiple pathogens are present that alternations are not as effective as mixtures.
Figure 2. Disease incidence percentages in the untreated control treatments for Citra and Marianna, FL. Early leaf spot, late leaf spot, and rust were rated separately on leaflet samples (48 leaflets/treatment). Disease incidence shown represents average seasonal incidence recorded in the locations during 2017.
Mixing fungicide MOA appears to be the optimal strategy for disease control, yield savings and managing fungicide resistance. However, alternating MOA is also a successful strategy, but its efficacy appears to be highly dependent on the pathogen populations present. Regardless of the strategy chosen, disease control and yield savings were improved with these strategies compared to the untreated plots. Both strategies will help sustain the efficacy of a fungicide product, and if cost is an issue then alternating modes of action in a program is better than repeated applications of a product alone. It should be noted that when using generic products like these, the average cost only varied by approximately $2.50 per acre. The cost of mixtures will depend largely on the mixing partners used, and with some planning these costs can be minimized.
Fungicide resistance management should be an important component of any peanut disease management program. More information about fungicide resistance and its management can be found in this UF/IFAS publication, Fungicide Resistance Action Committee’s (FRAC) Classification Scheme of Fungicides According to Mode of Action, or by contacting your local extension office.
Peanut farmers will have a new leaf spot fungicide option available soon from Syngenta called Miravis.
Syngenta has successfully completed the registration process with the Florida Department of Agriculture for a new fungicide for Florida peanut farmers called Miravis. Miravis is the brand name for Syngenta’s fungicide with the active ingredient Pydiflumetofen, which is a group seven fungicide product.
The following key information is provided on the Miravis label for use in peanut production:
Miravis is a broad-spectrum, preventative fungicide for use in the control of many important plant diseases. In peanuts these diseases include: Early leaf spot (Cercospora arachidicola), Late leaf spot (Cercosporidium personatum), Pepper spot (Leptosphaerulina crassiasca), and Web blotch (Phoma arachidicola) with supression of Sclerotina Blight (Sclerotina spp.) when applied prior to disease development at the recommended rate of 3.4 oz/acre. Miravis may be applied by ground, air, or chemigation, with a pre-harvest interval (PHI) of 14 days.
Dr. Bob Kemerait, University of Georgia Extension Plant Pathologist provided some highlights from his research of Miravis use in peanut:
By all accounts, Syngenta is ready to launch Miravis fungicide for peanut growers this season. There will be a very limited supply for the tri-state area (Georgia-Florida-Alabama) in 2018, perhaps enough to treat between 100 – 200 thousand acres.
Here are a few key points:
- Miravis is in the “SDHI” (succinate dehyrdogenase) class of chemistry, which also includes fungicides like Convoy (flutolanil), solatenol (a component of Elatus), fluopyram (Velum) and fluxapyroxad (a component of Priaxor). The SDHI class is quite variable and diverse.
- The mode of action of SDHI fungicides is to disrupt electron transport in the mitochondria of the fungus, thus depriving the pathogen of ATP and energy.
- The SDHI class is diverse, but not all things all the time. For example, flutolanil (Convoy) is excellent on white mold but does not touch peanut leaf spot diseases. MIRAVIS is excellent for control of leaf spot diseases, but does NOT control soilborne diseases like white mold or Rhizoctonia limb rot, or peanut rust.
- Because MIRAVIS is excellent on leaf spot diseases, but not used for soilborne disease control, Syngenta will promote use as a tank-mix with Elatus; thus providing strong, broad-spectrum disease control.
- Syngenta has collaborated with researchers and Extension from UGA, UF/IFAS, Auburn, Clemson, and other land-grant institutions to develop Miravis for use on peanuts. Because of this, we have significant experience with the product.
- Currently, a MIRAVIS/Elatus program from Syngenta is a 5-spray program. The MIRAVIS (3.4 fl oz/A) is mixed with ELATUS (9.5 fl oz if applied twice or 7.3 fl oz if applied three times in the season) at approximately 50 and 80 days after planting.
- The other two (3-Elatus program) or three (2-Elatus program) fungicide applications are something like chlorothalonil or Alto/chlorothalonil applied at 28, 104 and 120 days after planting.
- Fungicide resistance management is especially important for Miravis because of mode of action and reduced sprays (5 versus 7 in a “typical” program
- As of June 21st, there has been no word on cost yet.
- See the Miravis Label for more information.
Photo By: John D. Atkins
Temperature inversions form a kind of air layering or stratifying effect. It becomes visible when smoke or fog rises and then seems to abruptly hit an invisible ceiling. Credit Judy Biss
Farmers and ranchers must manage traditional business practices to be successful, but they also deal with the many challenges of ever changing weather. Rain, wind, and temperature are important and obvious aspects of weather that producers track on a daily basis, but there are other, not so obvious weather features that affect operational management as well. One of these is a phenomenon called “temperature inversions.”
What is a Temperature Inversion?
Most of the time, if you were to take the air temperature at measured intervals starting from the ground, moving straight up in to the air, the temperature would be warmer at ground level than it is at higher levels over your head. A temperature inversion is simply the reverse of this gradient – the temperature of air at ground level is cooler than the air above it. These inversions occur naturally and most often in the late evening to early morning hours when there is little to no wind. Temperature inversions form a kind of air layering or stratifying effect. If you have ever seen smoke rise and then seemingly, and abruptly, hit an invisible ceiling, you have probably witnessed a temperature inversion.
Why are Temperature inversions important?
Temperature inversions are important because the air layering effect they cause changes the anticipated dissipation of pesticide spray solutions used by agricultural producers. Inversions also affect the movement of smoke from prescribed fires used by land managers. Under a temperature inversion, spray solutions and smoke have the potential to move great distances offsite instead of dissipating and diluting under normal atmospheric conditions. To make a long story short, agricultural producers and land managers do not want their pesticide spray solutions or smoke to move offsite in such a way that could negatively affect non-targets areas. Minimizing pesticide drift is a critical and routine part of pesticide application procedures. There are a number of techniques pesticide applicators use to reduce pesticide drift. One of these techniques is being aware of atmospheric temperature inversions. This is especially important when using organo-auxin herbicides that have characteristics making them more volatile, and thus more affected by air currents. Additionally, in light of the new herbicide application rules for dicamba resistant cotton and soybean varieties, managing pesticide drift is a critical part of stewardship of these new herbicides.
Detecting and Managing Temperature Inversions
Properly managing pesticide drift and smoke from prescribed fire includes using a number of best management practices by trained applicators and managers. Being aware of temperature inversions is only one of the variables they incorporate into their management decisions every day. Some herbicide labels have sections dedicated to explaining the importance of not spraying in areas where temperature inversions exist, and list ways to detect the presence of an inversion. See for example, the herbicide Engenia® by BASF. This is one of the herbicides approved for use on the new dicamba resistant cotton and soybean varieties. Before herbicides approved for use on these new plant varieties can be used, the pesticide applicator must attend a specialized training on proper stewardship of these products.
The Engenia® Herbicide Resource Center provides a number of Technical Information Bulletins, one of which details Recognizing Temperature Inversions. Below is an excerpt from that bulletin.
How to Identify if an Inversion Exists:
- Measure air temperature at 6–12 inches above the soil and at 8–10 feet above the soil. An inversion exists if measured air temperature at 8–10 feet above the soil is higher than the measured air temperature at 6–12 inches above the soil. Be sure the instrument is shaded and not influenced by solar heating.
- Morning dew
- Morning fog (indicates that an inversion existed prior to fog formation)
- Smoke or dust hanging in the air or moving laterally
- Overnight cloud cover is 25% or less
- Inversions can begin forming three to four hours before sunset and can persist until one to two hours after sunrise
This 3 minute video from the University of Minnesota Extension, provides great information on temperature inversions and how to detect them.
For additional resources on the topic of Temperature Inversions and Pesticide Drift Management, please see the following publications:
Last year, the Environmental Protection Agency (EPA) registered new dicamba herbicide product formulations for making applications to dicamba tolerant cotton and soybean crops. As a result, many states were overwhelmed with drift complaints regarding sensitive crops. This led to the 2018 EPA announcement requiring that anyone who wishes to apply dicamba to dicamba tolerant crops MUST participate in an auxin herbicide training before making applications in 2018.
[warning]This training is required of anyone applying newer dicamba products registered for use on dicamba tolerant cotton and soybeans.[/warning]
Product examples include XtendiMax, Engenia, and FeXapan. Applicators using older dicamba formulations in other crops (corn, forages, small grains, sorghum, and turf) can still apply dicamba products without having this training but thoseproducts CANNOT be used on the dicamba tolerant crops. If you have questions regarding the use of these products or if you need the training, call your local Extension Office before making any applications.
On March 16, Extension Offices from across the state hosted an online two-hour dicamba training, which was broadcasted live from Gainesville. This training was overseen by the Florida Department of Agriculture and Consumer Services (FDACS), who determined that the CEU form received from completion of this training would serve as the official documentation of attendance. If applicators desire to use the form for CEUs towards renewal of their pesticide license, they are required to keep an additional copy in their possession as proof of completing the dicamba training.
The training was recorded live and made available to all participating Extension Offices (see below). If you plan to make dicamba applications to dicamba tolerant cotton or soybean, you MUST complete this training before making any applications. The training is not required before planting dicamba genetics, but without the training dicamba cannot be sprayed on the crop. If you plan to spray the crop with dicamba, or want the weed control option later in the season, the training is mandatory.
[important]The recorded training has been made available to all participating Extension Offices. Applicators are required to watch it at the Extension Office, where it can be proctored by an agent who is a certified CEU provider and can issue/sign the CEU form. There are no exceptions, you must watch the training at an Extension Office. In the Panhandle, participating Extension Offices with access to the training include: Calhoun, Escambia, Gadsden, Holmes, Jefferson, Okaloosa, Santa Rosa, Walton, and Washington Counties. Contact information for the different offices can be found using the following link: Florida County Extension Offices.[/important]
Many fungicide products are examined each year for their efficacy. This is an example of one trial conducted at the NFREC in Marianna Florida.
Nicholas Dufault, UF/IFAS Crop Pathologist, and Patrick Troy, UF/IFAS Row Crop Regional Agent
As the 2018 peanut production season approaches, it is time for producers to start considering their fungicide programs. Chlorothalonil has been a staple fungicide in many peanut management programs, but shortages of this product are expected in 2018 as well as possible cost increases. Chlorothalonil is a critical broad-spectrum fungicide that has activity against early and late leaf spot as well as peanut rust. It is also an important tool for fungicide resistance management that can be mixed with high risk fungicide products (e.g. tebuconazole, azoxystrobin, etc.) to improve disease control. With short supply this year, growers may need to consider ways to stretch chlorothalonil use with alternative products that offer disease control at a reasonable price.
Tank Mix Options for Lower Rates
Tank mixing chlorothalonil with other fungicide products is one way to reduce the application rate from 1.5 pints/A or 1.4 lbs./A to 1.0 pint or 0.9 lbs. per acre for the flowable and dry flowable formulations, respectively. Some mixing products are:
- FRAC group 3 fungicides: tebuconazole (multiple generics, 7.2 fl oz/A), cyproconazole (Alto®; 5.5 fl oz/A), flutriafol (Topguard®; 7 to 14 fl oz/A) and tetraconazole (Eminent®, 6 to 13 fl oz/A).
- FRAC group 11 fungicides: azoxystrobin (18.5 fl oz/A), pyraclostrobin (Headline®, see label for rates) and fluoxastrobin (Evito®, 5.7 fl oz/A).
- Some Premixed compounds (Custodia®, Absolute®, Elatus®, etc) that can also be mixed with chlorothalonil.
These are just a few examples of fungicides that can be mixed with chlorothalonil. A more complete list can be found in the 2017 Peanut Update and other mixing scenarios in the 2015 Auburn Extension guide (PP-765). Besides mixing with other products, it is also possible to use a reduced rate of chlorothalonil on its own. This should only be considered early in the season when disease pressure is low or absent, and/or in areas that have had minimal rainfall.
A few products that can substituted for chlorothalonil are:
- dodine (Elast®, 15 fl oz/A)
- mancozeb (multiple generics, 2.0 lb/A)
- thiophanate-methyl (Topsin®-M, 5 to 10 fl oz/A).
Both dodine and mancozeb are protectant products similar to chlorothalonil, and are generally recommended as mixing partners with products like tebuconazole and Topsin®-M. However, 2017 data from Auburn University showed that both of these products alone reduced late leaf spot defoliation, and saved yield when compared to the untreated control. Even so, yield savings tended to be greater when these products were mixed with other fungicides. When using thiophanate-methyl, resistance is a concern. So, no more than 2 applications of this fungicide are recommended, and consecutive applications need to be avoided.
The fungicide products Provost® Opti, Elatus®, Fontelis® and Priaxor® are chlorothalonil alternatives that can be applied alone and tend to provide soil borne disease control as well. It is important to consider cost and the disease of interest when considering these or any other fungicides.
If the goal is to possibly eliminate one or two chlorothalonil sprays, then it is recommended that special attention be given to the peanut variety’s resistance traits, preseason disease risk and the current or predicted frequency of rainfall. Research at the University of Florida has indicated that in years when total defoliation is less than 50% at harvest, similar yields can be achieved with spray programs consisting of 5 and 7 sprays (Fig. 1 below). However, both environment and variety were important factors driving these results. Thus, it is critical that as much information as possible about disease risk and presence be collected before making spray reduction decisions. Producers are advised to watch 10-day rain forecasts and appropriately shorten spray intervals in especially wet weather or increase them in dry weather.
Fig. 1. Yield results from the 2016 spray input by variety trial conducted at the Plant Science and Education Unit in Citra, FL. The cultivars in the trial were Georgia-06G (GA06G), TUFRunner 511 (TUF511), TUFRunner 297 (TUF297) and FloRun 0331 (FL0331). Spray application numbers varied from 0 (no sprays) to 4, 5 and 7 sprays within the season. Each spray program is represented by a different color according to the legend on the right. Fungicides used in the applications programs were chlorothalonil, tebuconazole and azoxystrobin. Chlorothalonil was applied in every spray of each program either by itself or as a mixture. All spray programs had one application of azoxystrobin at 90 days after planting (DAP). The 4 and 5 spray programs had two applications of tebuconazole at 60 and 115 DAP. The 7 spray program had three tebuconazole applications at 60, 75 and 105 DAP. Error bars represent the standard error of the mean.
There are many fungicide options available for peanut disease control, and it is not possible to go over all the combinations here. Producers are encouraged to work with University of Florida extension personnel and chemical dealers to develop an appropriate disease management strategy for their field and rotate FRAC chemistries. They are also encouraged to consult the 2018 version of Peanut Rx which will be available at the UGA peanut website, as a smart-phone app and through various program publications from a number of chemical companies. Developing disease management strategies can be difficult. However, while some fungicides can vary in their disease control performance, they all continue to provide quality tools for disease management.
Further information can be found at: