As we did in 2008, we have set up moth pheromone traps and blacklight traps on the Eastern Shore of Virginia to monitor important agricultural insect pests including corn earworm, beet armyworm, and stink bugs. For corn earworm, trap catches of 7 or more moths per week indicate the need for intensive scouting of crops for the pests. This insect can damage numerous crops in late summer including sweet corn, tomatoes, cotton, soybeans, green beans, lima beans, and others. For beet armyworm, pheromone bucket traps are the best monitoring tool. Although there is no effective action threshold for moth catch and damage, traps can be used to alert growers to the potential of infestations of this pest in an area. Beet armyworms prefer pigweed to most other crops and the larvae will often be detected in those weeds before attacking most crops. Blacklight traps can be used to monitor the relative intensity of stink bug flights as well. There is no effective threshold level, but again, growers can be alerted to activity.

The trap counts for week ending July 9 were as follows:
Blacklight trap – David Long (Cape Charles) = 8 corn earworm, 1 beet armyworm, 20 brown stink bugs, 0 green stink bugs.
Blacklight trap – Mark Colson (Eastville) = 36 corn earworm, 2 beet armyworm, 10 green stink bugs, 84 brown stink bugs.
Blacklight trap – Painter = 0 moths, 88 green stink bug, 43 brown stink bugs.

Corn earworm Pheromone Traps:
Keller = 0
Tasley = 0
Modesttown = 2
New Church = 0
Horntown = 2
Eastville = 11
Machipongo = 25
Painter = 0
Guilford = 0

Beet armyworm Pheromone traps:
Modestown = 0
Horntown = 0
Machipongo = 13
Painter = 0

Summary, corn earworm and beet armyworm catch was relatively low in all locations, but picking up in lower Northampton County. Brown stink bug catch is relatively high at both Eastville and Painter.

As you may recall, each year we assess the susceptibility of corn earworm to pyrethroids using the standard AVT (adult vial test) process. This involves collecting live moths using pheromone baited traps from multiple locations across the area. Moths are individually placed into vials pre-treated with cypermethrin (the standard used across the southeastern states) and assessed for mortality after 24 hours. If moths survive this 24 hour exposure, they are considered to be ‘resistant’. The percentage of those that survive provides some indication of what growers might expect to see when they apply pyrethroids to crops (soybean, cotton, peanuts). Although not a perfect system for determining actual resistance levels in the population, this procedure does provide valuable insight. For example, last year we had unusually large numbers of survivors. Whereas in previous years we had seen 5 to 10% survivors, in 2008, survivorship in late June exceeded 20%, and then increased to over 40% by August. Over the course of the summer, we received several calls about spray failures: cases where application of normal rates of commonly used pyrethroids did not provide adequate levels of corn earworm control.
So, what is the situation this year? Things do not look good. We started the season in early June with less than 10% survivors (see the attached line graphs, 2008 on the left side, 2009 on the right side) but are now at over 30% survivorship, even higher than at this time last year. Granted these data are based on a very small subsample of moths (744 moths to date), but all indications are that we may be in for some problems. Of course things could change as we progress through the season. We will continue to provide updates.
Additional information: mean-weekly-cew-moth-survival-jul-2-09l-ppt

Corn earworm moth captures ranged from <1 to 5 moths per night. Please see the attached table for more information. Additional information: blacklight-table-09-doc

So far, black light trap operators have reported very low numbers of corn earworm moths in their traps. Additional information: blacklight-table-09-doc

As of this week, thrips numbers have decreased in cotton, and plants have grown out of the thrips-susceptible window. We have had good rainfall, temperatures are good and most cotton is at the fifth leaf stage or beyond. We have terminated our cotton thrips sampling and ratings for the season. The attached line graph provides the sticky card data and shows the decline in adult catch across the region.
Peanuts are still at risk. As predicted last week, immature thrips numbers have increased in peanut. We are expecting pressure to continue for a least another week to 10 days. In our plots, Temik and Thimet are holding well. For example, in one field trial where we are comparing Temik 15G at 7 lb/acre, Thimet 20G at 5 lb/acres, and some experimental compounds, in the June 9 sample, there were 81 immature thrips/10 leaflets in the untreated plots, 8/10 leaflets in the Thimet treatment, and 7 in the Temik treatment. Untreated peanuts are reaching about a 5.0 on our 0 to 10 plant injury scale (where 0 = no damage and 10 = dead plants). A rating of 5.0 means that almost all leaves are crinkled from thrips feeding and most of the terminals show darkening/blackening. We generally expect yield reductions if ratings get much higher than 5.0, and we will definitely see injury exceed that by next week (given the high number of immatures). But again in our plots, both Temik and Thimet are holding well. We are seeing a big difference among the foliar applied insecticides in terms of thrips control and plant injury. In a nut shell, Orthene 97 and Radiant SC are providing good control as evidenced by the lower plant injury ratings. Karate Z is not performing well in either our cotton or peanut trials.
The thrips situation is very different in soybean. We have several trials across the state assessing both seed and foliar treatments. In soybean, our standard sample consists of 10 leaf trifoliates per plot. As of this week, we are getting averages of about 8 to 15 adults and 30 to 50 immatures per sample. The species break down is also different from what we are used to seeing in cotton and peanut. In those crops we normally see 90% + tobacco thrips. In soybeans, we are finding a mix of about 40% tobacco thrips, 50% soybean thrips and 10% other (eastern, onion, other odd balls). We are taking a lot of data this week and next to track the results of our treatments. Thus far, the seed treatments have a lot fewer thrips compared with untreated plots. Although we are finding a lot of thrips on soybean, we see very little actual plant damage. To date, we have never been able to show a yield response from controlling thrips in soybean. With a coordinated effort, this year we will be able to add several more thrips/soybean yield assessments to our data. We will post these results.
Additional information: stickycards09-ppt

To date we have tested about 450 corn earworm moths collected from two locations (Sugffolk and Southampton Counties). So far, results are prmising with only about 5% overall survivorship. Anything below about 20% is considered low risk in terms of potential field control problems. So we are starting at a good point.

Thrips populations are still increasing. But, in cotton, the treatments seem to be holding, and cotton is growing. The recent rains in many areas may allow cotton to grow through the problem. We are finding a lot of thrips in soybean, and we hear that many growers are treating for them. But even with the leaf ‘silvering’ and ‘crinkling’, we have never shown a yield advantage from treating soybeans for thrips. Treatments will certainly green them up, but is that worth the cost, with no added yield advantage? In peanuts, we are expecting damage to get quite a bit worse in the next week. We are still finding more adults than immatures in our peanut leaflet samples. These adults will beget a lot of immatures. Peanuts should be scouted next week at the latest.

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

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