Category Archives: Pest Group

Introducing – Insect trap counts for Virginia Beach

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Click more to find the pheromone trap counts and blacklight trap counts for corn earworm moths, beet armyworm moths and some other pests in Virginia Beach. In 2010 we initiated a monitoring program for these pests at the Hampton Roads AREC and on three commercial farms near Pungo, VA. These data will be posted weekly so that you can monitor the flights of these key insect pests of vegetables and field crops.

In summary corn earworm moths have been flying in the Pungo, VA area since June, but we’ve probably not seen the huge migratory flight that occurs each year around mid July. Beet armyworm moths have yet to appear in traps. Additional information: vabeach-pheromone-trapping-2010-xls

Cotton insect pest update

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Not much is happening in cotton right now in terms of insect pests. The hot, dry weather seems to have things on hold, for the most part. Spider mites are common on a lot of field edges but are not widespread. We are not seeing much evidence of square loss to plant bugs (in untreated fields) and square retention is in the 90% + range. A few stink bugs, mostly brown stink bugs, are beginning to show up and soon we will begin assessing bolls for stink bug damage using our newly released ‘Decision aid for stink bug thresholds in Southeast cotton’ which presents a dynamic internal stink bug damage percentage threshold (changes as the crop matures) that begins with 50% internal damage in the first week of bloom. We will post more details soon.

Corn earworm update

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It is too early to say a lot about corn earworm, but year in and year out, this critter causes us a lot of problems. Each year we conduct a large survey of field corn in late July to get a ‘read’ on the size of the population that could move to soybean, cotton, peanut and other host crops. Although we have not done the survey, some random checks of sweet corn and field corn show from 40% to 90% infested ears. This constitutes a possible threat. Earworms are worse in dry years as fewer are killed by rain (can drown pupae before they mature, can wash eggs from plants, can increase the incidence on fungal worm diseases, etc.). The other ‘shoe to drop’ is the issue with pyrethroid resistance. In the last two years (2008 and 2009) we found a large increase in the number of moths that survived in our pyrethroid vial testing program (from less than 5-10% survivors prior to 2008, to 20-40% survivors in 2008 and 2009). So far this year we have tested a total of 235 moths from May 27 to the present. The % survivorship has fluctuated, as is normal, starting at 13%, then to 12%, to 7%, to 25% in last week’s sample. Granted these results are from a small number of moths, but all indications are that we may need to address use of pyrethroids again this summer. We will keep posting the information.

General crop insect pest overview

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Because of this continuing hot, dry weather, we are not seeing a lot of insect activity in cotton, peanuts or soybeans. There are a few exceptions. Grasshoppers are doing some damage to soybeans in certain areas. Spider mites are starting to show up in most crops, but so far, the buildup is pretty gradual. Finally, there is some hope this Saturday for some decent amounts of rainfall for a lot of the area. If we miss that opportunity&& Potato leafhoppers are showing up in peanuts, but again, the buildup is gradual. We are just beginning to get a picture of how the 2010 corn earworm population is developing. We may be in for some problems (see the Corn earworm update), again, if the weather doesn’t turn around with more frequent rains. PS, if we could shoot about ½ million deer we would solve a lot of our ‘pest’ problems, at least for many of our soybean growers.

Grasshoppers in soybean

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Grasshoppers are always worse in dry years. They tend to move from border vegetation or infield weed sources as they dry down (which occurs more readily in dry weather), or from cover crop after herbicide burn down. They will undergo several generations—we find hoppers in all sizes (nymphs and adults) almost any time during the season, especially as we move into late summer/fall. They will eat soybean leaves, but are also capable of feeding on young pods later in the year. Treatment this time of year has to be based on the extent of defoliation. Under normal growing conditions, soybeans are capable of withstanding a lot of defoliation (30-40%) in the vegetative growth stages because they are growing so rapidly constantly putting on new canopy. Of course under these dry conditions, they are standing still, almost. You have to gauge the need for treatment on this tough decision point and it is often a seat-of-the-pants call, as many of them are. If the defoliation is severe and hoppers are abundant, I think you need to consider a treatment. Treating field edges can be effective, especially if hoppers are still moving in from bordering weed sources. If we do not get rain enough to make a decent crop, control efforts and the $ spent will have been wasted—a hard call to make If treatments are made, our limited experience showed that products containing chlorpyrifos (Lorsban 4E at ½ to 1 pt/acre, or Cobalt at 7 to 13 oz/acre) were more effective than pyrethroids. All things considered, I would use the lowest labeled rate. Also, Lorsban 4E is pretty good for controlling twospotted spider mite, which may also be present, or at least a pending threat.

Insect pest activity on the Eastern Shore for Week Ending July 2

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The blacklight trap counts in Painter were very low this week with virtually no key moth pests caught, except for 1 European corn borer, and 20 brown stink bugs, which was a big drop for stink bug catch from the previous week.

One arthropod pest that has cause some issues lately is spider mites. This pest will often have outbreaks when the weather is hot and dry. Commercial tomato growers are managing this pest with Oberon, Acramite, and Agrimek primarily. Another very good new miticide labeled on vegetables is Portal available from Nichino America.
Relative to vegetables soybeans have very few highly effective miticides. Growers can suppress high populations with Dimethoate, Lorsban, or Warrior. However, repeated sprays of these products can also flare up spider mites because they destroy predatory mites. The following text was taken from the Virginia Tech Pest Management Guide for Field Crops:

Mite outbreaks usually are associated with hot, dry weather, which accelerates reproduction and development. During periods
of high humidity and field moisture, a fungal disease can reduce populations but high temperatures can nullify these effects.
Outbreaks also are associated with the application of certain insecticides that kill natural enemies and/or seem to make the soybean
plant more nutritionally suitable for mites.
Check weekly for mites, starting in early July through August, especially during a hot, dry season. Concentrate on the field
borders and look for the early signs of white stippling at the bases of the leaves. Do not confuse mite damage with dry weather
injury, mineral deficiencies, and herbicide injury. If feeding injury is evident, press the undersides of a few damaged leaves on
white paper to reveal any crushed mites. Determine the extent of the infestation and assess the level of injury by examining 20
to 30 plants in the infested area. Field infestations often show defoliated or injured plants at some localized point, with injury
becoming less evident and extending in a widening arc into the field.
If isolated spots of mite activity are confined to the perimeter of the field, spot-treatment using ground equipment is recommended
to prevent further spread of mites into the field. If the infestation is distributed throughout the interior of the field, treatment
of the entire field is suggested if live mites are numerous (20 to 30 per leaflet) and more than 50 percent of the plants show
stippling, yellowing, or defoliation over more than one-third of the leaves. If rains come, mite development and survival will
decrease but may not drop to economic levels if heavy populations are developing under high temperatures.

Neonicotinoid choices for plant bug control in cotton

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There are three neonicotinoid insecticides labeled for plant bug control in cotton. The attached table presents the rates (oz and lb ai/acre). The low and high rates of all products are essentially equal in terms of the amount of active ingredient applied per acre. Although all are neonicotinoides, each of the products is a different compound so activity against plant bug (and stink bug) may differ (Centric contains thimethoxam; Trimax Pro contains imidacloprid, and Belay contains clothianidin). We are in the process of comparing these three for effectiveness in controlling plant bugs in cotton. We will share the results soon. We do have some stink bug control data in both soybeans and cotton, but will wait for another week or so before posting that information.

Additional information: neonicotinoid-insecticide-options-jul-1-2010-v2003-doc

Spider mite threat to peanut is high

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With the dry weather, spider mites are already showing up in many crops and weedy field edges. Once established, mites are tough to control in peanuts. One of the most risky options is the application of Lorsban 15G under dry conditions. Lorsban can contribute to mite flares in peanuts and it is our experience that Lorsban flared mite populations are especially hard to get under control. Lorsban may be needed for rootworm control at some point in the season, but if fields remain dry, rootworms will not survive in the soil and will not be a threat. Lorsban would be safe if the crop is under irrigation, otherwise, I would recommend holding off for another week or so to see what the weather is going to do. There will still be time to apply Lorsban (through July) if the weather turns and we start getting consistent rains. We are also beginning to see some potato leafhopper damage in peanuts. Lorsban will provide good leafhopper control for a few weeks, but the risk of flaring mites offsets that advantage. A better option would be to apply Danitol at the 6 oz/acre rate which will control leafhoppers, and will suppress the mite population.