Author Archives: Ames Herbert

Slugs in soybean: What to do.

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I have been getting a lot of calls this week about slugs in soybeans. They are a bigger problem this year in some areas because of the cooler, wetter spring/early summer. They are also typically worse in high-residue fields. Although we have had slug problems in both corn and soybean (even a few in cotton), we are not experts in management. We have been communicating with Dr. Ron Hammond at Ohio State University, who is an expert. I know Ron well. He and I have been serving on a soybean/insect regional project for many years and I have a lot of respect for him. Because of the more consistent pressure in his state, several years ago he took on the responsibility of doing slug management research.

Here are a few of the common questions that I have been getting, and some of Ron’s comments.

Question: I have lost my soybean stand and am considering replanting. Would tilling the field help get rid of the slugs?

Ron: “Tilling the field would probably help. However, if slug numbers are high, it might not get enough of them. But overall it should help. A good no-tiller will not do this however. As temps and soils warm and dry up, things will get better because seeds will germinate faster and plants will grow. Galen Dively (University of Maryland) normally suggests late plantings for this reason, as that is when the slug cycle tends to end. Just hope and pray for better weather. That’s what we do. Remember that the slugs are still there, just bigger and hungrier!”

Deadline (by AMVBAC) is the only registered product that will provide good, even excellent, control of slugs. It contains the active ingredient, metaldehyde. There are two mini-pellet formulations, M-Ps which are blue colored, and Bullets, which are tan colored. Most growers prefer the M-Ps as they are easier to see on the ground and make it easier to calibrate the applicator. If Deadline is applied when slugs are present, they will be attracted to it and will feed on it. But keep in mind the pellets do not stay active for more than a few days, and almost any amount of rain rinses out the active ingredient. A 10 lb/acre rate is sufficient, expensive, but effective. Consider treating the worst areas.

Question: What about Larvin? I have read that Larvin will kill slugs.

Ron: “Here is the scoop. Back in the 1980s, we had a grower-prepared bait for corn in Ohio that mixed cracked corn, beer, molasses, and mesurol for slug control. It was a state label. Never could get it for soybean. When soybean began being grown no-till, slugs then became a soybean problem. But we could not use the above bait. However, we found out that Larvin has molluscicidal properties, and got the exact same state label for soybean, but with Larvin rather than mesurol. Worked great. Remember that Larvin has a label on soybean as foliar, so has an EPA tolerance. Also remember that being a carbamate, Larvin has more impact on other things then does metaldehyde. Because of supposed bird kills, the company at the time pulled support of the label. So nobody has the ability to legally use it this way anymore. I checked into it for future use and was basically told, don’t bother…but yes, Larvin will kill slugs, is just NOT LEGAL.”

So what should you do? First consider delaying replanting until the weather straightens out. Delaying planting until it is warmer and drier could be the best approach. If you cannot delay planting, Deadline is the only legal and effective option.

Brown stink bug eggs being killed by tiny wasps

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For the past few weeks, we have been finding a lot of adult brown stink bugs in wheat fields. Most have been found on the edges of fields, next to a tree-line. These are overwintered adults that came into wheat fields after overwintering in nearby weeds. A couple of weeks ago, we began finding a lot of immature stink bugs, nymphs, indicating that a large clutch of egg masses hatched a few weeks ago. We are now seeing 3rd and 4th instar (nearly fully grown) nymphs. This is the first new generation of the summer. Adults from these nymphs will migrate into new host crops, like corn.
We have also noticed that many of the stink bug egg masses are parasitized (see attached image). A natural enemy of brown stink bugs is a tiny parasitic wasp called Telenomus podisi. Females use their ovipositor to lay eggs inside of stink bug eggs, and when the larvae hatch, they eat the developing stink bug embryos. This year, we have found that a very high percentage of stink bug eggs are parasitized which means that hundreds of stink bugs will never hatch. In past years, we conducted stink bug egg parasitoid surveys in Virginia. Results indicated that nearly 50% of all brown stink bug eggs and almost 90% of brown stink bug egg masses were parasitized. We are fortunate that these little natural enemies are working to reduce numbers of this troublesome pest.

(author: Amanda Koppel, Graduate Student, Department of Entomology, Virginia Tech, Advisor, Ames Herbert)
Additional information: parasitoids-008-jpg

Thrips numbers are up, ‘westerns’ are confirmed, and corn earworm moths are flying

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Several things have changed since last week’s advisory. Based on our sticky card samples and plant samples (cotton, peanut and soybean), thrips populations have increased a lot since last week. Interestingly, all five sticky card sample sites show the same trend (see the attached line graph), that numbers were very low last Thursday (probably the end of the second generation) and had much higher numbers this past Tuesday. We think this increase marks the beginning of the third and largest generation. Based on previous year’s data, this population will not peak for another 10-14 days.
Cotton treatments (Avicta, Aeris and Temik) are still holding for the most part but are beginning to show some damage. In our plots, there is not a lot of difference among the three except that the seed treatments may be showing just a little bit more damage. For example, in one test in a 5-plant sample, we counted an average of 7 adult and 55 immature thrips in the untreated control, 0.25 adults and 0.25 immatures in the 5 lb Temik treatment, and 4 adults and 4 immatures in the Aeris treatment. The ratings next week will really sort out the treatments, with the heavy and sustained thrips pressure that we expect will occur over the next few days. If seed treatments have not been sprayed, now would be the time to consider doing it, but only if damaged buds are visible, and plants have live thrips.
We have just confirmed western flower thrips in four cotton fields in North Carolina (in Hertford County near Winton). The samples came in yesterday. The fields had been planted with Avicta seed treatment with an additional 3.5 lb of Temik. In addition, they had been treated with 8 oz of Orthene 97 about a week prior to the discovery. In two of the fields, ‘westerns’ comprised close to 100 and 99% of the thrips complex. In the other two fields, they were about 50/50 with tobacco thrips. Each year we see a few fields with the ‘western’ thrips problem. Today, Jack Bacheler and Clyde Sorenson from NC State and me, with the aid of the crop consultant, Chad Harrell, put in a small plot test in the field with the worst damage and largest ‘western’ population. We applied different rates of Radiant SC, Tracer 4SC and Orthene 97. We will take samples next week to see which provide the best control.
As for peanuts, we are still not seeing visible evidence of thrips damage, any leaf crinkling. But based on the leaflet samples we took this week, it won’t be long. In all of the fields we sampled, there were adult thrips in the leaflets but no immatures. When those adults lay eggs and the immatures hatch and begin feeding, damage symptoms will start showing up. This is exactly the right time to apply foliar insecticide treatments to peanuts, if they have not already been protected with in-furrow insecticide treatments. Sprays now would prevent those immatures from developing. If peanuts did receive an in-furrow treatment, then we would recommend waiting a week to determine how well those treatments are holding.
Finally, we were surprised by the number of corn earworm moths that we collected in our local pheromone baited traps. Over the past two nights, we have collected about 200 moths. We have put them into what we call the AVT (adult vial test) to begin monitoring for pyrethroid resistance. Last year the AVT data gave us a good heads up on a potential resistance problem. We do not have vial test results yet, but will begin posting those as we get them.
Additional information: stickycards09-2-ppt

Thrips update revised to ‘high risk to cotton’

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Forget everything I predicted last week. Most of it was wrong. I had a mentor early on in my career who very wisely said, “If you try to predict insects, they’ll make a liar out of you every time.” So true he was. Last week I suggested that we might have a relatively light thrips year; that based on the excellent soil moisture and warm growing conditions up to that point, cotton might grow so quickly as to not need extra foliar sprays. Two major things have changed. One, the weather took a dramatic turn to the cool side. Since May 11, we have had five nights in the 40s&not good cotton weather. We have continued to get rain, heavy in some spots, with up to 3 to 6 inches in single events. Most of our cotton is germinated, in the 1st to 2nd true leaf stage, but the cold weather has it ‘sitting still’. To make matters worse, thrips populations are increasing. As I said in last week’s email, we are using yellow sticky cards to monitor thrips populations in five locations across our cotton region. We check and replace the cards two times each week, on Mondays and Thursdays. The counts are up (see the attached line graph with sticky card data counts from the 5 locations), and based on what we know from sampling over the past few years, the peak has not occurred. When cotton is growing so slowly, plants are very vulnerable to thrips feeding. Thrips concentrate their feeding on the tiny seedling bud, or growing point. Just a few days of intensive feeding can have dramatic effects by stunting plants, greatly slowing maturity, or in really bad cases, will even kill the seedling. And in our experience, when plants are ‘sitting still’ it does not take many thrips per plant to cause significant damage.
So what should growers do? Scout fields and consider a foliar treatment if more than 10% of plants have noticeable damage to the bud. Damaged buds will be deformed and blackened. Bud damage indicates that whatever was applied at planting, seed or in-furrow treatment, is no longer doing the job. Fields that had heavy or continued rains will be at the highest risk as any planting time insecticides will most likely be washed out of the system. I have been asked about what to spray and how much. To date, our best foliar control has been obtained with acephate (e.g., Orthene). Pyrethroids do a good job, but never quite as good as acephate. Each year we do a lot of cotton thrips trials and we have yet to see an Orthene failure. But, it has happened on a few growers’ fields where western flower thrips have become the primary pest species. Orthene does an excellent job of controlling tobacco thrips, still our primary pest species, but does a poor job on western flower thrips. Pyrethroids are no better, even worse in some cases. To date, we have only seen ‘westerns’ as the primary pest species in a very few fields. The great majority are still infested with tobacco thrips, which means they can be protected with 4 to 6 oz of Orthene per acre. We recommend that broadcast sprays go out with enough volume to achieve good coverage of the seedlings. I tell folks that good coverage means seedlings should be completely wet after the sprayer passes over. Higher rates of Orthene are not needed for tobacco thrips, and higher rates are not more effective on ‘westerns’. Last year we found that the best product for controlling ‘westerns’ was Radiant SC (a Dow AgroSciences product). This would be a costly choice and only warranted if a good thrips sample and identification by a lab verified the problem. Let’s hope ‘westerns’ are not a big issue this year. Based on what we know today, we are still recommending the ‘old standards’. Additional information: stickycards-mar21-09-ppt

Thrips are slow to build and cotton is advancing

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This may be a year, the first in many, when cotton growers may not have to make as many, or any foliar insecticide applications for thrips. As of this week, we are just beginning to see movement of adult thrips into cotton. We have 3×5 inch yellow sticky cards placed into fields in 5 locations around our cotton growing area (one of those is just across the state line in Northampton County, NC). We are getting a few adult tobacco thrips, an occasional western flower thrips, and a lot of soybean thrips (which are not a serious problem in cotton). I think we are just at the beginning of the large third thrips generation that typically causes our problems. Thrips cause the biggest challenge to seedling cotton when it is cool and dry after emergence. Cool, dry conditions slow seedling growth exposing plants to thrips feeding for a longer period of time, and inhibit insecticide uptake creating the ‘perfect storm’. However this year, we have good soil moisture and a lot of cotton was planted in late April during the warm spell and is already pushing the 2-leaf stage. With one more rain and another week of warm weather, many fields will be out of danger, or at least at much lower risk to thrips damage. Once pants reach the 3-4 leaf stage, thrips feeding may cause some leaf crinkling, but the damage does not reduce yield. Thrips WILL invade cotton, and most likely in large numbers. But this year, if rains and warm weather continues, plants may be able to quickly outgrow the damage.

PS, we have been having some issues with this advisory, delivering multiple emails. The Southern Region IPM Center in Raleigh, NC hosts and services this advisory. They are doing what they can to clear up the problem. We are grateful to them for their continued support of our VA AG Pest Advisory.

Coragen is now labeled for cotton

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A new insecticide, Coragen, by DuPont, is now labeled for use on cotton (and several other crops). The active ingredient of Coragen is rynaxypyr, an insecticide in the new class, anthranilic diamides. Its main strength is against lepidopterous pests which means corn earworm (cotton bollworm), tobacco budworm, and fall and beat armyworms. We have done a fair amount of field testing against corn earworm and it works very well. Please see the product label for details.

Early Summer Row Crops and Vegetables Tour: Insects, Diseases, and Agronomics, TAREC

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We will be hosting the annual Early Summer Row Crops and Vegetables Tour: Insects, Diseases, and Agronomics at the Virginia Tech Tidewater Agricultural Research and Extension Center in Suffolk, VA on Thursday, June 4, 2009. The tour will begin at 9:00 am at the Hare Road research farm, and lunch will be provided. We plan to apply for Certified Crop Advisor Continuing Education Units for this meeting. More details will be provided as we get closer to the date. If you are interested in an equipment, company or agency display, please contact us. If you are a person with a disability and desire any assistive devices, services or other accommodations to participate in this activity, please contact the Tidewater Agricultural Research and Extension Center at 757-657-6450 (TDD number is 800-828-1120) during business hours of 8 a.m. and 4:30 p.m. to discuss accommodations five days prior to the event.