Category Archives: Insect

Worms reported in SC and NC peanut fields, what doest that mean for VA growers?

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I have seen reports of mixed species worm populations in some peanut fields in both South and North Carolina. Populations include corn earworm (may be some tobacco budworm also, but you cannot tell these species apart without some experience and good magnification of the mandibles/jaws), beet armyworm, and fall armyworm. Although I have not heard of worms in Virginia peanut fields, we should be on the lookout for them.

With these mixed species worm complexes it will be pretty important to know which species are in your fields—so—how good are your worm ID skills? We have a good insect ID guide available that shows the characteristics that most easily distinguish these different worm species. We will be glad to mail some to you, let us know, or you can access the guide on the web at: http://pubs.ext.vt.edu/444/444-360/444-360.html. Knowing the species is important in choosing the right insecticide—if control is needed (see below).

The next important question is—should I treat for worms? In my experience, many growers treat fields that are not at any risk to yield loss—that is, they ‘jump the gun’. It takes a lot of leaf feeding for worms to do economic damage to peanuts, and I have seen only a handful of cases where this has occurred over the past many years. This will be especially true this year when peanut canopies are very large, so are able to withstand even more leaf ‘tattering’ with no negative consequence. But if you do determine that a field is in danger, feel the urge to spray, or just love killing worms—better not rely on a pyrethroid or you may not be satisfied with the results. Corn earworms have become a little more difficult to control with pyrethroids in recent years, and beet armyworm and fall armyworm have never been very susceptible to pyrethroids. You will need to turn to some of the non-pyrethroid options like Steward EC @9.2-11.3 oz/acres, Belt SC @2-4 oz/acre, or Blackhawk (was Tracer) @1.7-3.3 oz/acre.

Black light trap captures for week ending August 8, 2013

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Please click “More” to view the tables with the average number of corn earworm moths and brown marmorated stink bugs (BMSB) captured per night in local black light traps. Mark Kraemer in Petersburg reported approximately 3 to 4 BMSB per foot on some maturity group 4 vegetable-type soybean with pods present (Guelph and Kanrich), but BMSB were not on surrounding maturity group 5 soybean in the flowering stage. Dr. Kraemer also reported seeing BMSB on Asian long beans again this year. Mike Arrington found corn earworm (=bollworm) egg-threshold levels in cotton research plots at the Tidewater AREC (Suffolk) and at an on-farm cotton research trial in Southampton County this week. Thanks to our black light trap operators for their reports this week: David Moore, Kelvin Wells, Laura Maxey, Mary Beahm, Chris Drake, Watson Lawrence, Mark Kraemer, Janet Spencer, Ames Herbert and his entomology crew, Scott Reiter, Keith Balderson, Helene Doughty, and Jim Jenrette. Additional information: blt-8-aug-2013-pdf

Corn earworm (CEW), kudzu bug, and stink bug update

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The corn earworm situation is shaping up to be late and fairly light, at least that’s what we seem to be seeing so far. Our annual field corn/corn earworm survey is completed with 27 counties reported. Percent infested ear averages are very low compared to most years. The overall average across all counties is at an all time low of less than 18% ears infested. Even the southeastern counties which traditionally have had the highest infestation level are at just over 23% ears infested, when averages are normally in the 40-60% range. The moth movement from corn is also slow in developing. We have yet to see more than just a few moths in our local black light traps and we are not seeing moths fling from fields as we walk them, or at night. We can speculate about the reasons for this unusually low level, but the bottom line is that unless things change pretty drastically over the next few weeks, we may not see many soybean, cotton, peanut or sorghum fields infested this year.

Kudzu bug activity in soybean is increasing. From our statewide surveillance program, we are now up to 37 counties with infestations in soybean fields. The good news is that most of these infestations are at low or very low levels—well below the economic threshold—but there are exceptions. Heavy infestations are now reported for several of the counties close to the NC border. The heaviest infestations are in early planted fields that are flowering or beginning to form pods. We are now seeing second generation adults in many fields. We are not sure what this will mean in terms of the late planted fields, time will tell. In an earlier advisory we attached a table generated by entomologists at Clemson and UGA that listed the percent control provided by a long list of insecticides. We STRONGLY recommend that if a field treatment is needed that growers use products that are listed at the top of that table—those that provide the best control. We have learned that not following this guide can lead to having to retreat.

Stink bug pressure in cotton is turning out to be less severe than what we had predicted earlier, although we are seeing a number of fields at threshold. Cotton will remain vulnerable to stink bugs for a few more weeks—at least through the 6th week of bloom. If a treatment is needed this week (or has already been applied), we recommend re-sampling for new damage at about 7 days post-treatment—using our cotton stink bug threshold card. Additional treatments may be needed, especially if the ‘traditional’ bollworm treatment is not needed because of the very light CEW pressure discussed above. That ‘traditional’ bollworm treatment (if it included a pyrethroid) has been providing stink bug control as an added bonus. So a field that does not have to be treated for bollworm (use the 3% worm/fresh worm damaged boll threshold) may have to be treated again for stink bugs. So scout fields for fresh stink bug damage weekly for the next few weeks and abide by the recommended percent damaged boll thresholds.

Black light trap captures of corn earworm moths and BMSB for week ending Aug. 1, 2013

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The average nightly captures of corn earworm moths and brown marmorated stink bugs in area black light traps are attached (please click “More”). Counts for both pests were pretty low this week. Thanks to trap operators Scott Reiter, Laura Maxey, Keith Balderson, Mary Beahm, Ames Herbert and his entomology team, Mark Kraemer, Mike Parrish, Kelvin Wells, Helene Doughty, Jim Jenrette, and Chris Drake for their reports this week. Additional information: cew-bmsb-1-aug-2013-pdf

Results of the 2013 corn earworm survey of field corn

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Attached (click “More”) are the results of Dr. Herbert’s 2013 corn earworm survey of field corn in Virginia. In general, numbers of ears infested with earworm larvae were lower than in previous years. Hopefully this means fewer moths that emerge, leave this nursery crop, and lay eggs in soybean, cotton, peanut, etc. Our network of black light traps will help you determine moth flight activity in your area. It is also vital to scout your crops and use appropriate thresholds for eggs or larvae. For soybean, please use the Corn Earworm Economic Threshold Calculator found at http://webipm.ento.vt.edu/cew/ For cotton you should use the appropriate thresholds (conventional or genetically-protected) found in the 2013 Virginia Cooperative Extension Field Crops Pest Management Guide (beginning on page 4-108 found at http://pubs.ext.vt.edu/456/456-016/Section_4_Insects-11.pdf). Other insect chapters (soybean, peanut, sorghum, etc.) of the Field Crops Pest Management Guide, with appropriate thresholds, can be found at http://pubs.ext.vt.edu/456/456-016/456-016.html Additional information: cew-survey-results-2013-pdf

Virginia distribution maps of kudzu bug and brown marmorated stink bug–Aug. 1, 2013

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Attached (click “More”) are the Virginia distribution maps for kudzu bug and brown marmorated stink bug as of Aug. 1, 2013. We will continue to provide updates throughout the season. Thanks to our scouts Ed Seymore, Jamie Hogue, and staff at the Tidewater AREC for their hard work and reports. Additional assistance from Virginia Cooperative Extension ANR Agents, Virginia Tech faculty and staff, Wayne Gardner (Univ. of Georgia), and others is greatly appreciated. Additional information: kb-bmsb-map-pdf

Black light trap counts for the week ending July 25, 2013

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Please see the attached document containing this week’s average nightly captures of corn earworm moths and brown marmorated stink bugs in area black light traps. Thanks to trap operators Mary Beahm, Keith Balderson, Mike Parrish, Laura Maxey, Chris Drake, David Moore, Ames Herbert and crew, Mark Kraemer, Kelvin Wells, Helene Doughty, Jim Jenrette, and Scott Reiter for the information they provided this week. Additional information: blt-cew-bmsb-7-25-pdf

Table with insecticides available for control of bollworm and stink bugs in cotton

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We had a request to develop a list of the insecticides available for managing bollworm and stink bugs in cotton—sprays that will go out over the next few weeks. The reason is that with the many products, both single and mixed active ingredients (ai) and different amounts of ai per gallon, it is very confusing and hard for growers to make good selections. Making the best product choice means knowing what the active ingredients are, what they are designed to kill, and how much product is needed to apply enough ai per acre to achieve good results. The attached table provides that information. It was a collaborative effort and included input from Jack Bacheler and Dominic Reisig at NCSU. Please note that not all products are included and that the rates on the table are from the product labels. Hopefully this information will be useful.
Additional information: bw-sb-cotton-insecticides-2013-herbert-docx

Cotton insect situation update

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Things are pretty quiet in cotton pest-wise with the exception of scattered fields with spider mites and reports (mostly from northeast North Carolina) of pockets of plant bug activity. We are not used to seeing spider mites in wet years and do not really understand the ‘why’. I have seen this in the past and have a couple of observations. One is that under these conditions it is very hard to achieve perfect control of spider mites regardless of the products used, but, mite injury is not a great concern since plants are vigorously growing. My recommendation is to hold off on treating unless 1) rainfall amounts decrease and we begin to see some drought stress, or 2) mite injury gets so bad that otherwise healthy leaves (mid and upper canopy) start to drop due to intense feeding. Injury to and dropping of lower leaves is not really to concerning as these lower leaves are not as important to overall plant health and will be shed in the natural maturing process.

We are not seeing much evidence of plant bugs in the fields we are checking, and not hearing about much from others. We assess plant bug activity by checking for bugs and determining percent square retention. Plant bugs target squares and feeding results in shed. The danger point is reached if retention drops below 80-85 percent—and the fields we have checked have greater than 90% retention.

At this point most cotton in Virginia is into the flowering stage. Once flowering begins, we shift our emphasis to boll protection. We will follow with more specific advice in the next few weeks.