Kudzu Bug moves closer to KY

Doug Johnson, Extension Entomologist

Title: First Report of Kudzu bug in Soybean [in Tennessee]


Author: Doug Johnson, Extension Entomologist

Figure 1. Kudzu bug adults on soybean

Dr. Scott Stewart, Extension Entomologist at the University of Tennessee’s research and education station in Jackson, TN has posted a blog concerning the first report of Kudzu bug on soybeans in Tennessee. I have included the entire text of his blog immediately below. Also, notice the link to the www.kudzubug.org web site. I offer my thanks to Mr. Cam Kenimer, the ANR agent in Fulton Co. KY, for bringing this to my attention.








“ First Report of Kudzu bug in Soybean

Author: Scott Stewart, IPM Extension Specialist

I’ve had the first report of a soybean field in Tennessee being treated for kudzu bug. The field is located in East Tennessee (Polk County).

The threshold recommendation below is quoted directly from a website dedicated solely to this pest (www.kudzubug.org). There is a lot of good information on this site. My counterparts in the Southeast have been working with this pest at a fevered pace for the past three seasons and generating a lot of good data. I would discourage any panic spraying. Kudzu bug infestations on soybean will almost certainly be isolated to a few fields in a very limited area. I do not expect problems in the larger soybean growing areas found in Middle and West Tennessee during 2012.

Threshold: “Kudzu bugs can be scouted using a 15-inch diameter sweep net. Kudzu bug populations can be extremely high, especially on field edges. We are suggesting a threshold of one immature kudzu bug per sweep. This suggested threshold is based on 2011 field trials where a single properly timed insecticide application preserved soybean yield. In the majority of trials we have conducted, nymphs usually appear at about the R-2 to R-3 growth stage. If adult numbers are extremely high (multiple adults per sweep) and soybeans are stressed, treatment should be considered; this is a judgment call but the idea is to avoid bug induced stress on soybeans that are also stressed for some other reason.”

Insecticide Selection: There is a limited list of insecticide that are well tested and specifically list kudzu bug on the label. Of these, Brigade 2E (bifenthrin), Hero (a premix including bifenthrin) and Endigo (a premix) appear to provide the best control. Some other pyrethroids such as Mustang Max, Declare and Karate appear to perform pretty well in limited testing, although Karate [sic same active ingredient as Warrior dwj] does not specifically list kudzu bugs on the label. Sevin, Orthene and Dimethoate also appear to perform reasonably well. These products should be used at or near the full labeled rate.

After looking at the data and talking with my counterparts, Brigade 2E or one of the other bifenthrin products at a rate of 6.0-6.4 oz/acre appears to be an obvious choice. It appears to provide the best bang for the buck. Not all insecticides will provide adequate control. The data I’ve seen suggests that Asana XL, Baythroid XL, Belay, Leverage 360, Lorsban are not good enough.”

To see the original text follow the link immediately below.

http://news.utcrops.com/2012/07/first-report-of-kudzu-bugs-in-soybean/

First, let me say that I concur completely with Dr. Stewart’s conclusions. In KY we should be even a bit further removed. Nevertheless, remember that this pest is not going to fly or walk to KY, but more likely to move on vehicles or in freight so its’ presence near the junction of I-75 and I-24 is important to us.

Figure 2. Location of Polk Co. TN

At present, this is certainly the closest Kudzu bug infestation on soybean to Kentucky. The county from which this is reported (Polk) is in the southeastern portion of TN and is bordered on the east by North Carolina and on the south by Georgia. Of particular interest with respect to eastern / central KY, soybean (also garden beans / peas) production, this county’s western border is only about 10 miles east of I-75. Additionally, Polk Co. TN is only one county removed from the junction of I-75 and I-24. The pest has already been collected from Kudzu in Marion Co. TN which is astride I-24. Interstate-24, of course, goes through the heart of soybean production in western Kentucky. Because of interstate access, this infestation should be of as much interest to Kentucky producers as it is to those in Tennessee.

There is no reason to panic at this point. As Dr. Stewart indicates for TN, we are quite unlikely to see any problem with this pest in Kentucky soybeans in 2012. I think we are much too far along. The story in 2013 may be a different.

Photo Credit Figure 1: Philip Roberts, Univ. GA., bugwood.org.
Photo Credit Figure 2: Wikipedia

Scouting Corn for Aspergillus Ear Rot

Paul Vincelli

University of Kentucky Extension Plant Pathologist

Aflatoxins are potent, naturally occurring toxins that sometimes develop in corn and certain other crops.  Aflatoxins are also among the most carcinogenic substances known.  There are well-defined limits on how much aflatoxin is allowable in corn, based on the intended end use.  For example, corn intended for human consumption must have less than 20 ppb (parts-per-billion!).  More information on aflatoxin can be found in the UK Extension publication, Aflatoxins in Corn, ID-59, at http://bulletin.ipm.illinois.edu/article.php?id=1244.

The prevalence of drought conditions this growing season may result in aflatoxin contamination, at least sporadically.  Some agents have expressed interest in informally scouting for the problem in advance of harvest.  This is an excellent idea.  The problem is, it is very difficult to assess standing corn crops for aflatoxin contamination.  Some of the reasons for this include:

·       The mold associated with aflatoxin may not always be visible in contaminated grain.

·       The presence of the mold does not mean aflatoxin is present.

·       There are several green molds on corn, and they can be hard to tell apart.

·       Even when it occurs, aflatoxin is contamination is very sporadic for lots of reasons, so a grower may have very high levels in one field and low levels in another. 

Having now lowered expectations, I do think scouting is a good idea, especially this year.  It might help producers manage their risks a little more wisely. 

: Spider mites beginning to appear on soybeans, can corn be far behind?

Doug Johnson, Extension Entomologist

I warned of this pest some time back (See KPN No. 1308 June 26, 2012. I Hate Crying Wolf…). In fact, I am mildly surprised that it has taken this long for field scouts to come across the pest. Reports of spider mites have alerted us of their activity and samples sent to the Plant Diagnostic Lab have confirmed that it is the two-spotted spider mite causing the problems. At present the damage appears to be on a small scale and very localized in fields. Somewhat surprisingly some of the infestations were noted in irrigated fields.

For as long as we have drought stressed plants, and in particular LOW humidity, we are increasingly likely to be plagued by this pest. In soybeans, the most important time is during the reproductive stages of R1 (beginning bloom) - R5 (beginning seed) and it is even more likely in fields where a synthetic pyrethroid insecticide has been used. In our current corn production situation, it may very well be too late to worry about mites. In either case, one of the first and perhaps most important questions is: Am I likely to be able to make a crop? If you are or are planning to convert your corn to silage, then pay attention to the “days to harvest” restrictions on the product you choose to use.

To sample in soybeans, shake plants over a piece of white paper and look for tiny, black, moving specks. You will need a hand lens to determine if the specks are actually mites, but if they are crawling across the paper you probably know the answer. In corn, scouting is much more difficult and less is known about making a control decision. The mites are no harder to find, simply follow the instructions for soybean but use corn leaves. One simply wishes to determine if the infestation is only on the outer edges or occurs across the field. You will need to sample several areas of the field. Mites are notorious for being spotty in their distribution. They also have a very strong “edge effect” which would include waterways, etc., that may cross the field. If a treatable infestation is found, it may very well be controlled by a border application.

Scouting should start well before R1 (soybean) and in younger corn. Cooler temperatures and high humidity allow a natural fungus to control spider mites. Rainfall will help the plant tolerate the infestation but will not reduce the mite population. Application of synthetic pyrethroid insecticides and fungicides may worsen the infestation because these insecticides don’t work well on mites and the fungicide may hamper the natural occurring fungus that kills the mites.

In soybeans, if direct control is required, consider using an organophosphate insecticide like chlorpyrifos or dimethoate. If you must use a pyrethroid, consider bifenthrin. An application is warranted when most plants are infested with spider mites and leaf speckling and discoloration are apparent. Treating after R7 is not recommended

In corn, chlorpyrifos is not labeled for spider mites; dimethoate may not be applied during pollen shed. Bifenthrin may be used. See labels for rates and specific directions.

Information on insecticides is supplied for the readers convenience. Use of a trade name does not constitute a recommendation. These products are not ranked in preference or efficacy. Always read and follow the label.

Photo: Frank Peairs, Colorado State Univ., bugwood.org

Soybean Thrips on Soybean

Doug Johnson, Extension Entomologist


Several people have contacted me concerning the presence of thrips on soybeans. Thrips are a common pest of soybeans but rarely do they cause economic damage. Actually, given the drought stress that our production season has endured, I am surprised that this has not occurred earlier.

 Soybean thrips are very small slender insects. You will need a hand lens to see them. The immatures are yellow, while adults are black with yellow bands. These pests are common on flowers and weeds. They feed by rasping off the outer layer of the leaves and sucking the juices. This leaves a silvery appearance to the leaf surface. “Cupping” or other similar leaf distortion is often associated with thrips feeding. Another dead giveaway to their activity is the presence of black “tar spots” on the leaves. This is thrips excrement and the descriptive name is quite accurate. You will see lots of tar spots if there are many thrips around.

Thrips rarely cause economic damage. Nevertheless, yields may be reduced if plants are under moisture stress and thrips populations are high. If over 75% of leaflets are damaged and there are an average of 8 thrips for every leaflet sampled, treatment may be advised.

Following is a sampling and decision-making aid. Examine at least five locations in each field. At each location examine 10 individual plants. On each plant examine the fifth trifoliate below the the uppermost node. If the plants are not developed to R5, then examine the lowest trifoliate. Examine each leaflet using a hand lens. Count and record the number of damaged leaflets and the number of thrips on each leaflet. An insecticide application may be useful if:

1.) Plants are under drought stress

2.) 75% of all leaflets examined are damaged,

3.) on average each leaflet has 8 or more thrips present.

All three conditions should be met to consider an insecticidal application.

Insecticides for control of thrips are not found in our insecticide recommendations. However, many of our commonly used insecticides lists thrips control on their labels. These include but are not limited to products containing:

Acephate (Orthene & others), beta-cyfluthrin (Baythroid), bifenthrin (Brigade & others), lambda cyhalothrin (Warrior & others), carbaryl (Sevin & others), cypermethrin (Mustang & others), and many others.

Use of Trade name does not constitute a recommendation. These products are not ranked in preference or efficacy. The information is supplied for the readers convenience.

Photo Credit: Marlin E. Rice, Iowa State Univ.

Application of Fungicides to Corn/Soybeans Under Drought Conditions is a Bad Idea

I was just reading an article in AG Professional Magazine http://www.agprofessional.com/newsletters/agpro-weekly/articles/Dry-weather-crops-still-need-fungicides-162045795.html entitled "Dry Weather Crops Still Need Fungicide". The article was discussing  the "Plant Health" benefits of strobilurins when applied to corn or soybean under "dry" conditions. The article did not mention the use of fungicides on crops that have been severely compromised by extended drought conditions. Everyone knows that extended drought greatly lowers yield potentials (hence the ability to recover the cost of the fungicide and application are very limited) AND disease pressure of most fungal diseases that are controlled by strobilurin fungicides is very low.  Conversely charcoal rot can be very severe on both corn and soybean in drought years, but this disease is not controlled by any foliar fungicide.  I will simply conclude by restating my the blog title:  Application of Foliar Fungicides to Corn/Soybean Under Drought Conditions is a Bad Idea.

2012 Kentucky Corn and Soybean ACRE Payment Prospects By Cory Walters and Greg Halich

The possibility of payments from the USDA Average Crop Revenue Election (ACRE) program increases as Kentucky average corn and soybean yield prospects decline. Kentucky corn crop conditions as of July 8th are rated at 34% very poor, 38% poor, 23% fair, 5% good, and 0% excellent. Kentucky soybean crop condition as of July 8th is rated at 23% very poor, 39% poor, 30% fair, 8% good, and 0% excellent. The following short discussion provides a brief review of the ACRE program and an analysis of potential for payments as of mid-July 2012.

Kentucky yield prospects are dropping to unexpected levels. At this point it is unclear whether ACRE payments will occur and if so, the size of the payment. Currently it appears there is a good chance for corn ACRE payments in Kentucky for 2012/13 given the current crop conditions. Soybean ACRE payments appear less likely at this point, especially with the recent rainfall, but continuation in dryness with high temperatures would increase the possibility of soybean ACRE payments.

Continue reading at: http://www.ca.uky.edu/agecon/index.php?p=110 or use GOOGLE with the title and author names.

Nutrient Removal from Corn Silage Harvest

Edwin Ritchey, Extension Soil Scientist, University of Kentucky

Assumptions made: 

Nutrient removal at standard harvest moisture per ton of corn silage as reported in AGR-1, Table 5:

• Nitrogen = 7.5 lbs/ton
• P₂O₅ = 3.5 lbs/ton
• K₂O = 8 lbs/ton

Pounds of N, P2O5, and K2O removed in silage at various silage yields.
	Amount of Silage Removed per Acre
Nutrient	5 tons/A	10 tons/A	15 tons/A
Nitrogen	37.5	75	112.5
P2O5	17.5	35	52.5
K2O	40	80	120

Greatest removal will be for potash.  Make sure to soil sample if silage is not typically in your rotation, potash removal will be greater than for corn for grain.

Typically, we don’t account for nitrogen removal or carryover to other crops with the exception of wheat.  Usually, wheat following well-fertilized corn should have enough nitrogen for fall growth. With limited nitrogen uptake this year in the corn, nitrogen in the fall for wheat (or other fall-seeded crops) should be sufficient. Monitor wheat growth. If the wheat appears to be N limited, then apply more than 40 lbs N/A in the fall.