Category Archives: Insect

Eastern Shore Insect Trap Activity

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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.

Peanut insect pest update, potato leafhoppers on the move

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It is worth noting that potato leafhoppers are active in some peanut fields. In some of our plots, especially those that were not treated with in-furrow insecticides for thrips, we are approaching threshold levels of damage. Our recommendation is to treat fields if 20-25% of leaves show typical hopper burn leaf damage symptoms (the yellow V-shaped pattern on the leaflet tips) and hoppers are still present in the field. It is important to determine if leafhoppers are still present because we have found that they typically migrate into and back out of peanut fields throughout the season, and may not actually be present even when leaf damage symptoms are obvious. Mid July is a fairly common time to begin seeing thresholds, if they are going to occur. We recommend checking fields just prior to making other sprays (example, leafspot) so insecticides can be tank mixed if a threshold for leafhoppers is detected. Several pyrethroid insecticides are listed for potato leafhopper control. Also, Lorsban 15G will provide some control, if applied for soil insect control.

Cotton insect pest update

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All is still pretty quiet in terms of cotton insects. Although plant bugs are out there, we know of only one field that was treated. Square retention is good in all the fields we have checked and similar reports are coming in from local crop scouts. Although you can find spider mites in most fields, none are even close to threshold. Aphids are also present, but in very low numbers. Rain (or lack thereof) may be the bigger issue in many areas. Cotton will be blooming soon, and we will begin to shift to sampling developing bolls for stink bug damage. More on that next week.

Our corn earworm pyrethroid susceptibility monitoring program indicates a possible problem in the making

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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

Virginia Issues Fire Ant Quarantine in 11 Localities

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The following advisory is being sent on behalf of Dr. Pete Schultz, Entomologist and Director of the Virginia Tech Hampton Roads Agricultural Research and Extension Center.
Virginia Department of Agriculture and Consumer Services has issued a temporary state quarantine for 11 localities in southeastern Virginia. Details as to the locations and regulated articles are available at their website (copy and paste address into your browser):
http://www.vdacs.virginia.gov/news/releases-b/062409fireants.shtml

Cotton insect pest update: few plant bugs and good square retention in fields

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Having passed through ‘thrips season’, we are having a little relief from insect pests. So far, there have been almost no reports of mid-season pests like aphids or mites. One field developed aphids in pretty high numbers but by the time it was discovered, tiny parasitic wasps had killed many of them. If we see more than 25% aphid mummies (the dried remains of parasitized aphids), and no insecticide is applied that would kill the wasps, the wasps will usually completely eliminate the aphid population within a week to 10 days.

Will plant bug populations be higher this year due to the somewhat wetter conditions? This is being talked about south of us where they are having a wetter than normal season. It is thought that wetter years result in more weeds and alternate hosts plants where plant bug populations can increase. However, most of our cotton area did not receive excessive amounts of rainfall, and some areas are actually getting pretty dry. We are seeing tarnished plant bugs in weeds and crop fields, but not in unusually high numbers. We are just beginning to assess fields for square retention, which is still the best way to determine the need for any action against plant bugs. Plant bugs feed on developing squares causing them to blacken and drop off, leaving a telltale scar where the square had been. With some training, it is fairly easy to inspect a cotton plant and find either blackened squares or the scars where squares were. We consider a field in the ‘safe zone’ if square retention is 80% or above. This is because cotton can compensate from loss of as much as 20% of the total square load without any reduction in yield. We proved this for ourselves some years back by doing a 2-year study where we removed up to 20% of the first position squares, on several varieties. No yield loss occurred.

As of this week, based on checking several fields and reports from field scouts in the private sector, our cotton fields are at greater than 90% square retention, which is what we generally see. A few fields to the south of us in North Carolina have been reported to be in the low 80% range, and one is at 75%. Plant bugs are spotty for sure, but all indications are that this year, like most, will be a low plant bug year.