So far, black light trap operators have reported very low numbers of corn earworm moths in their traps. Additional information: blacklight-table-09-doc
Category Archives: Insect
Thrips update for cotton, peanuts and soybean
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
First results from our corn earworm AVT pyrethroid monitoting program
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 in cotton, peanut and soybean
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.
Brown stink bug eggs being killed by tiny wasps
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
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
Insect Blacklight Trap Counts form the Eastern Shore – Week Ending May 29
After once again battling bird nests in our blacklight trap and a lot of rainfall for most of May in Painter, we have finally gotten some usable information. This week’s trap catch included 0 European corn borer moths, 12 Corn earworm moths, and 205 green stink bugs. It is early for corn earworm moths, so a catch of 12 moths is interesting and should be monitored closely in future weeks. A catch of 205 green stink bugs per week in May is both high and early for that pest. This is another insect that should be monitored closely for in the coming weeks on the Eastern Shore.
Pest concerns on corn this year on the Eastern Shore
The above-normal rainfall that we’ve had on the Eastern Shore has brought some pest problems to corn growers in Virginia.
Periods of cool wet weather after planting resulted in slow germination in many fields, which left seeds and seedlings more vulnerable to soil insect pests such as seedcorn maggot, white grubs, and wireworms. The longer the seed remains in the ground the greater the chance of it being discovered by the aforementioned soil pests. At this point, most corn has been planted and there isn’t anything a grower can do postplanting for these soil pests. The majority of corn was probably treated with an insecticide seed treatment such as Poncho or Cruiser, which undoubtedly helped improve stand in many fields this year.
Another problem that the spring rainfall brought was slugs in no-till fields. This is an age old problem, and the solution has not changed in decades. Dry weather will eliminate the slug problem. However, if seedlings are small (less than 3 leaves), and the slug infestation is heavy, economic damage can occur from this pest. Below is the recommendations taken from the Virginia Cooperative Extension Pest management Guide for Field Crops http://www.ext.vt.edu/pubs/pmg/fc/InsectsCorn.pdf
Slug, Snail Sampling/Decision Making
Slugs can become serious pests in no-till fields during spring periods of cool, wet weather. Fields with heavy layers of manure, crop refuse, or thick weed cover are at higher risk from slugs. Because slugs feed at night and hide during the day in the mulch and surface trash near the seedlings, they often are not suspected of being the cause of the shredded leaves on the young corn seedlings. Yet slugs can be found during the day by turning over clods of dirt and surface trash near the seedlings. It is suggested that samples be taken from the area around 5 plants in 10 locations of the field to determine the average number of slugs associated with each plant. Populations of 5 or more slugs around each plant at the spike through the 3rd-leaf stage may be economic, especially if injury is heavy, plant growth is slow, and cool, wet conditions prevail. During dry, warm weather, 10 or more slugs per plant may be tolerated. Also, corn seedlings that have reached the 3rd-leaf stage of growth generally are able to outgrow feeding damage by slugs.
Cultural practices which may help reduce slug populations include reduction in the use of manure, shift to conventional tillage practices for at least one season, and minimum tillage to reduce the amount of surface trash.
There is basically one registered product for control of slugs, and it works well – Metaldehyde (product = Deadline M-Ps, or Deadline Bullets)applied at 10.0-40.0 lb per acre. For best results, apply product in evening. Especially beneficial if applied following rain or watering. It should be noted that most corn-producing states are suggesting an application rate of 12 to 15 lb/A, if banded over or along side the row after the plants have emerged. Recent Delaware field trials indicate good results against slugs using 10 lb Deadline M-Ps/A broadcast with a cyclone spreader. Spreader must be calibrated to deliver at least 5 pellets/sq ft. Slugs generally stop feeding in 2-3 hours and die within 2-3 days.
Another potential spring pest problem in corn is armyworm infestations on seedlings or early-whorl stage plants. Armyworm is a common early season pest that can cause occasional losses in corn and should be monitored for in the spring. Infestations usually first develop in fields of small grains or in other grass cover crops. In conventional tillage systems, partially-grown larvae can migrate into corn fields from grassy waterways or wheat fields. Armyworms chew irregular holes on the edges of corn leaves. Damage is usually first noticeable around the field margins adjacent to these areas. The name armyworm derives from its behavior of migrating in large numbers into fields similar to invading armies. In no-till or reduced tillage systems, infestation may cover the entire field. In these systems, eggs may be laid on grasses within the field prior to planting and herbicides may force armyworms to feed on corn as the weeds or cover crop dies. Cool, wet, spring weather usually favors armyworm development. Armyworms overwinter as partially grown larvae in grasses or small grain fields. When warm spring temperatures return, armyworm feeding resumes. Armyworms may move onto corn during this period. Moths also begin flying in spring and deposit new eggs. Eggs are small, greenish-white, globular, and laid in clusters of 25 or more on the leaves of grasses.
True Armyworm Sampling/Decision Making (taken from the VCE Pest Management Guide Pub. No. 456-016).
No-till fields planted into a small grain cover crop, pastures, or weedy fields all have a high risk for armyworm infestation. Survey field edges where margins border small grains or large grassy areas and watch for damaged plants. If armyworm damage is seen, examine 20 plants at each of 5 locations within the field and record the percentage of damaged plants, the average size, and the severity of injury.
Armyworms usually migrate from small grains starting in late May. Spot treatments may be warranted if infestations are confined to small areas. Control for armyworms is recommended if 35 percent or more of the plants are infested and 50 percent or more defoliation is seen on the damaged plants, provided that larvae average less than 0.75 inch long. Worms greater than 1.25 inches in length usually have completed their feeding. A number of insecticide products provide effective control of true armyworm including: most pyrethroids such as Baythroid, permethrin, Asana XL, Mustang Max, Warrior/Karate, Hero, as well as other insecticides such as Lorsban, Lannate, Sevin, Pencap-M, and Bt products.
Thrips update revised to ‘high risk to cotton’
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¬ 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
Valent announces new supplental label for Danitol Insecticide on fruit and vegetables
Click on More for the new Danitol Supplemental Label, which contains the new uses that were recently approved by the EPA. Danitol is now labeled for use on stone fruit, olive, tree nuts, and tropical and sub-tropical fruit. Danitol is also labeled for use on caneberries (under the berries section). Last, additional pests were added to the fruiting vegetables, grape, pea, and pome fruit labels and they are included on this label. All of your states have been notified of this new Supplemental Label and it is ready to be used by growers on these new crops. Additional information: danitolsupplementallabel2009-pdf