ACE Prep Class and Updated ACE Exam to be offered at A&M Workshop

The newly updated Associate Certified Entomologist (ACE) exam, along with a Prep Class for prospective ACEs, will be offered next month in College Station at the Texas A&M University Urban Pest Management Conference and Workshop. For more info click here.

Southwest Beef Symposium

January 9-10, 2014

Clayton Civic Center

124 North Front Street

Clayton, NM 

While rangeland conditions improved in the latter part of the growing season, southern plains cattle producers still have a lot to evaluate as thoughts of rebuilding herd inventories continue. Cattle industry experts will address global industry issues, timely nutrition and health management strategies, and the economics and risk associated with restocking ranches during the Southwest Beef Symposium.

This is the 10th year for the Southwest Beef Symposium which is coordinated by specialists  from the Texas AgriLife Extension Service and New Mexico State University Cooperative Extension Service.   The conference rotates between annually between New Mexico and Texas.

For more information  click here.

FSA Advises Producers to Anticipate Payment Reductions Due to Mandated Sequester

USDA’s Farm Service Agency (FSA) is reminding farmers and ranchers who participate in FSA programs to plan accordingly in FY2014 for automatic spending reductions known as sequestration. The Budget Control Act of 2011 (BCA) mandates that federal agencies implement automatic, annual reductions to discretionary and mandatory spending limits. For mandatory programs, the sequestration rate for FY2014 is 7.2%.  Click here for the full story.

Homeless insects and energy audits

Dr. Mike Merchant, Extension Entomologist, has written a nice post about fall insect invasions of homes and their management.  "When cold weather comes knocking, it should be no surprise that hundreds, or even thousands, of insects may be waiting for you to open the door this fall.  It’s not like you can really blame them.  They are just temporarily homeless critters looking for a warm place to spend the winter."....

Click here for the full post

Northwest Plains Pest Management News Vol XI Issue 15

NWP Sorghum field nearing maturity

A fast and furious corn harvest continues, most of the area corn silage has been harvested and grain harvest
is  progressing rapidly. Reported yields have been variable but most reports have been encouraging. Some sorghum has been harvested but for the most part the area crop is just reaching physiological maturity. Harvest aid application decisions to prepare the area cotton crop for harvest are being deliberated.

At this point cotton harvest aid applications will be weather driven, as it is unlikely that significant heat unit (HU) accumulations to further develop fiber will occur. Using historical weather data from 1980-2010 only 14 total HU are expected in October (14 HU is less than one normal August day). For best results harvest aid applications should be made on warm sunny days with an extended outlook of warm conditions.

Some factors that increase the performance of harvest-aid chemicals include the following:

• Warm, calm, sunny weather
• Soil moisture relatively low but sufficient to maintain cotton plant without moisture stress
• Soil nitrogen levels relatively low
• Leaves active and uniformly expanded on plants
• Little or no secondary growth evident on plants
• Plants with a high percentage of open bolls that have shed some mature leaves

Conversely, some of the factors which negatively affect harvest-aid chemical performance include:

• Applications made under cool (below 60o F), cloudy conditions
• Prolonged periods of wet weather following treatment
• Plants in vegetative growth state with low fruit set
• Plants severely moisture stressed at time of treatment
• High soil moisture and nitrogen levels 
• Plants exhibiting secondary growth 
• Poor spray coverage

Harvest-aid product selection, tank mix partners and rates vary with environmental and crop conditions. The  “2013 High Plains and Northern Rolling Plains Cotton Harvest-Aid Guide” contains a set of tables which suggest harvest aid products based on crop and environmental conditions. The full guide can be viewed at http://goo.gl/WkxFz4

Northwest Plains Pest Management News Vol XI Issue 14

Spring seeded crops have progressed to “the short rows”. Corn harvest for both silage and grain has commenced; preliminary yields, while not record breaking, are encouraging. Cotton and sorghum have progressed very well. Cotton , for the most part has shed much of the small immature fruit and looks to have a chance to adequately mature the harvestable bolls. Sorghum seems to have really made the most of available moisture , many fields look surprisingly good considering.  Winter wheat seeding is off to a rapid start, many of the earlier planted fields have emerged and have began to tiller.

Corn and cotton has matured to the point that pest damage is unlikely. Defoliating pests and aphids could still be problematic in cotton but at this point risk appears to be low. Late maturing sorghum may still susceptible to headworms and should me monitored but once sorghum reaches the hard dough stage it should be safe from headworm damage.

Harvest aids can be applied to sorghum to bring grain to a more uniform moisture level and dry down weed escapes. Timing is very important as an application made to early will reduce yield. Once sorghum has reached physiological maturity a harvest aid can be applied without risking yield. Sorghum is considered physiologically mature when the black layer has formed at the base of the kernels (approximately 30% moisture), at this point the grain has reached maximum weight. Once a harvest aid has been applied harvest should be planned accordingly; under normal conditions harvest aids shouldn’t cause a lodging issue for up to 3 weeks but after 30 days lodging could be significant. Ideally sorghum should be harvested 10-14 days after a harvest aid application. Several products are available: sodium chlorate (up to 6 lbs/acre) and glyphosate (up to 2 qt/acre) have been used successfully. Aim is also labeled for use as a harvest aid in sorghum and should be particularly useful in weedy fields.

Large areas of dead wheat as a result of white grubs have been observed in a few fields in the area. White grubs are the larval stage of insects commonly known as May or June beetles. White grubs, sometimes referred to as grubworms, injure wheat by feeding on roots and other underground plant parts.

Emerging wheat damaged by white grubs.

White grubs require 1 to 4 years to complete their life cycle, depending on species. Local observations have documented both Phyllophaga and Cyclocephala species; infestations with near 80% Phyllophaga species have been identified in some fields. Phyllophaga species may have life cycles exceeding one year in which case larger grubs with larger appetites may be present when wheat is most susceptible, in the seedling stage
The adult stage of the various white grub species are heavy-bodied beetles, 1⁄2 to 5⁄8 inch long, brown, with long, spindly legs. In summer adult beetles lay  eggs in the soil, within about two weeks the eggs hatch into small white grubs that feed on plant roots.

White grub feed on wheat roots

White grub larvae are creamy white and C-shaped, with three pairs of legs and tan to brown heads. Larger larvae (1⁄2 to 1 inch-long) are responsible for most damage due to their large size and voracious appetites. Feeding by large numbers of large white grubs can quickly destroy  root systems, killing seedlings.
While there are no registered insecticides for white grub control in wheat, limited field tests suggest that Gaucho® and Cruiser® seed treatments which target aphids and greenbugs may provide some suppression of small larvae but will not likely provide desired results if larvae are large. Lorsban, also labeled for aphid control in wheat, may provide suppression when chemigated.

Small and large white grubs

Fall armyworms, beet armyworms and/or army cutworms have been found in a few area wheat fields, most infestation have not justified treatment at this point but should be monitored closely.  Small larvae are feeding on leaves, creating tiny “window panes” in the leaves Control is suggested when there are four or more larvae, 1 inch or longer, per square foot, and their damage is threatening the stand.  Wheat which is not well established (newly emerged, thin, etc.) may not be able to tolerate as many foliage feeding worms and is at greater risk of damage.  If other species of foliage feeding worms are present, then an aggregate larval population should be considered when making management decisions.    

Beet armyworm feeding on emerging wheat

Northwest Plains Pest Management News Vol XI Issue 13

The harvest season is off to a rapid start as silage choppers are rolling in area corn. Conditions are very good and harvest has not been impeded by weather making harvest quick and efficient. 

The irrigation termination decision making process in corn continues. Assuming an adequate crop condition we normally say that once the starch line has reached 50%, irrigation can be terminated with no detrimental affect. The key to this crop stage irrigation termination point is it assumes a full profile of moisture from which the plant will pull moisture to finish filling grain. If the soil profile is not near capacity at 50% starch line, additional moisture in the form of irrigation or rainfall will be required to finish the crop. With sprinkler and drip irrigation systems we have the capability to tailor late irrigation applications to specific crop needs. Early irrigation termination can significantly reduce corn yield. The starch line is an indicator of crop maturity, corn kernels mature from the outward tip inward toward the cob. A distinct color separation is visible on each kernel and moves down the kernel as it fills. The starch line is easily seen by breaking the ear in half and viewing the cross section. 

Headworm activity in sorghum has really picked up, many observations have revealed headworm numbers 4X the established economic threshold. Current infestation are near 75% fall armyworm (FAW) and 25% corn ear worm. What appears to be happening is the majority of the FAW are hanging out in the foliage until some grain formation appears then they are moving to the head to feed on developing grain. In this scenario fields with few worms in the head a few days ago could be infested with large worms with large appetites very quickly; large larvae consume 83 percent of the total grain consumed during larval development. Treating the worms before they move to the head will not be as effective simply due to the fact that larvae in the heads are directly exposed to the insecticide. A complicating factor in managing headworms is the presence of spider mites. If mites are established then product selection to suppress headworms should be carefully considered as many of the traditional and often cheaper options may flare the mites which could then devastate the sorghum. In situations where mites are present at low levels the use of Belt should provide good headworm control while not flaring mites. If mites are well established then Comite or Onager should be considered as tank mix partners to suppress the mites. Large numbers of spider mites occurring early in kernel development can reduce the ability of sorghum plants to make and fill grain. After kernels reach hard dough, grain is not affected. Additionally, if spider mites are very abundant sorghum plants will have much weaker stalks which and may lodge, which can result in severe harvest losses. 

FAW in sorghum head

Bollworm moth activity and egg lay has picked up over the last few days. Diligent scouting will be necessary to identify fields with economic levels of bollworms. The decision to treat for bollworm should be based on number of larvae/acre, larvae size, and the maturity of the crop. Most of the area cotton is late and still has a lot of squares and small tender bolls which very suitable for larval development. Most of the small fruit has little if any chance to make a harvestable boll but larvae could become established on this then move to more mature bolls as they gain the ability to penetrate larger fruit. Generally we consider bolls which have gained 450 heat units after bloom to be safe from bollworm damage. The late crop makes determination of which bolls are worth protecting much more difficult; we will likely be tempted to protect a much later boll than what we normally would. This adds significant risk associated with getting a positive return on an insecticide application since the later bolls have less time and probability to mature. 

Loopers are common in many cotton fields, they feed on foliage making small holes in the leaves. Very high populations could cause excessive loss of leaf surface area but I have not observed any infestations near that level. There is no established treatment threshold in Texas but NCSU suggests “ If the defoliation reaches 25 percent and a significant number of bolls that the producer expects to harvest are still filling out, treatment may be advised. However, remedial sprays may have only marginal effect on the more common soybean looper.” To round out the current Lepidopteron spectrum beet armyworm, yellow striped armyworm and Arctiid moths, eggs and larvae have also been observed in area cotton. Beet armyworms at present infestations are at tolerant levels but what makes this pest more concerning than other foliage feeders is it may transition to feeding on small bolls. 

Looper and feeding damage to cotton leaf

Late planted corn has been and continues to be very attractive to lepidopteron pests. FAW and southwestern corn borer have been observed in alarming numbers in late planted non-Bt corn. FAW will readily feed on emerging silk which can inhibit pollination. In extreme cases I have seen heavy FAW pressure reduce pollination by more than 90%. Any late planted corn should be carefully monitored for these pests.

Southwestern corn borer larva

Northwest Plains Pest Management News Vol XI Issue 12

Scattered thunderstorms continue to provide much needed moisture to thirsty crops in their paths. Some of the storms contained hail which has caused some crop damage, but for the most part, the benefits of the moisture out weigh losses due to hail. Much of the earlier planted corn is in full dent while the latest planted corn has yet to tassel. Cotton is at peak bloom with most fields between 5  to 6.5 nodes above uppermost white flower (NAWF). Grain sorghum is responding very well to additional moisture from recent storms. Field maturities range from milk stage to those still growing vegetative. 

Grain sorghum should be regularly inspected for headworms from head emergence until hard dough. Estimating the economic injury level for headworms is complicated because the potential yield loss varies with the size of the larvae. That is why it is necessary to record the number of small (up to 1⁄4 inch), medium-size (¼ to ½ inch long) and large (1/2 inch long or longer) headworms. Small larvae  consume very little grain (about 10 percent of the total) and about 80 percent of them die in this stage. Therefore, small larvae should not be considered in determining the economic injury level. If most headworms are this size, sample the field again in 3 to 4 days. About 19 percent of medium-size larvae  survive beyond this stage. Thus, the potential grain loss from medium-size larvae is only 19 percent of the potential loss from large larvae. Most corn earworm larvae larger than ½ inch will survive to complete development, and these large larvae are most damaging; they consume 83 percent of the total grain consumed during larval development. If most of the larvae are larger than ¼ inch, determine which size (medium size or large) is most common and use the corresponding threshold to make treatment decisions. An Android based threshold calculator can be found at the Google Play Store; http://goo.gl/8mXvv . We also have a web app for other operating systems which can be accessed at http://goo.gl/5k7ZtU .

The beat-bucket technique is the best way to estimate the number of headworms in sorghum. Shake sorghum grain heads vigorously into a 2 to 5 gallon plastic bucket (a small white office trash can works well), then count the caterpillars in the bucket. For easy math I like to work with sets of 10; where I shake ten random heads as I walk down the row then I count and evaluate the size of the larvae. If more heads are sampled in a set there may be too much “trash” in the bucket to efficiently make counts. Record the number of small, medium  and large  headworms found in the samples. Then use the threshold appropriate for the size of the majority of the headworms. Using the calculator mentioned earlier, where control cost is $15/ac and grain value is $8/CWT an insecticide application should be considered if 19 medium (1/4 to 1/2 inch) or 4 large (>1/2 inch) worms are present per 10 heads (based on 50,000 heads/ac).

Beat bucket sampling, TAMU photo

Lots of moth activity has been observed in area cotton, most has actually been smartweed borer but the number of bollworm moths has picked up recently.  Adults are yellowish brown moths with a wing span of approximately 1.5 inches; considerably larger than the smart weed borer.   Eggs are about the size of a pin head, white and somewhat domed shaped with ridges running from top to bottom.  Eggs can be easily confused with looper eggs which are flattened on top. Larvae range from 1/16 to 1 5/8 inches long depending on age.  They are variable in color including yellowish, greenish, or brownish forms with a tan to brown head.  Black bumps with a protruding spine are uniformly distributed over the body. Some may be conspicuously striped. Newly hatched larvae feed on tender vegetation for a short period after emergence.  This vegetative feeding is rarely damaging.  Larvae then move to and feed on squares and bolls.  This direct fruit feeding, often times, will result in economic loss depending on the number of larvae present. Treatment may be justified in conventional cotton if 10,000 small (1/4 inch or less) larvae per acre are present.  If larvae are 3/8 inch or more in length then treatment will likely be justified if 5,000 or more larvae per acre are present.  Treatment decisions in Bt cotton should not be made based on small larvae since some feeding must occur before larvae are controlled. Treatment of Bt cotton may be justified if 5,000 or more medium sized larvae (3/8 to ½ inch) per acre are present and square and/or boll damage is observed. 

Cotton bollworm moth on cotton bloom.

Spider mites persist in many corn fields in varying degrees. Some populations have been held in check by miticides and beneficials while others continue to grow. A miticides residual activity has certainly been tested this year. Some fields have not had beneficials in great enough densities to help suppress mites for an extended period. .  Most yield loss is a result of feeding damage at or above the ear leaf.  Yield loss is a result of reduced grain fill, premature dry-down, and weaker stalks which may cause lodging.  Once corn is fully dented mites will not likely impact grain development but could still impact stalk strength.

Spider mite pressure in corn

2013 Boll Weevil Eradication Changes For NWP Zone

The Commissioner of Agriculture has set the 2013 assessment rate for the NWP Zone at $1 per dryland acre and $2 per irrigated acre. As part of the rate reduction the failed acre credit has been eliminated. So what does this mean? All planted acres of cotton will be assessed. For more information contact the Foundation at 1-800-687-1212 or log on to www.txbollweevil.org. 

Sorghum Headworm Calculator

Treatment thresholds for sorghum headworms are dynamic based on grain value, cost of control, and infestation levels. We have developed a sorghum headworm calculator "app" which is available on the Google Play Store at http://goo.gl/8mXvv  The app can also be found by searching for sorghum in the store. The app will run on any android device with an OS of 2.3 or above. We also have a web app which can be accessed at http://goo.gl/5k7ZtU. The Android app calculates larvae/10 heads while the web app calculates larvae/head.

Northwest Plains Pest Management News Vol XI Issue 11

Last weeks isolated thunder storms carried some baggage; pockets of hail destroyed some area crops. The speed at which moisture has disappeared is a testament to the current moisture demands of crops (and

weeds). Corn continues develop at a good pace; some corn is near dent while other fields are growing vigorously. Moisture demands remain near maximum in corn from tassel to milk stage but begin to decline as the crop transitions from milk to the dough stage and continue to decline at a fairly rapid pace through maturity. Much of the area cotton crop is in full bloom and is at or near maximum moisture demand. Irrigation should be carefully managed to promote earliness and maintain fruit load; many times this is walking a fine line. Lower amounts and more frequent irrigation applications will allow producers to speed maturity and maintain yield; adjustments in irrigation frequency and amount should be based on individual field conditions. Much of the grain sorghum is also at or near peak moisture demand which is from boot to heading. Using a moisture probe to monitor soil moisture levels has become futile in many fields with limited irrigation capacity as the probe cannot penetrate the soil. 

Weed management has been a continual battle; weed resistance to herbicides, primarily glyphosate resistant pigweed, is a huge concern. Every effort should be made to remove suspected resistant weeds from the production system. Now through harvest will be a good time to make a few notes on field specific weed issues to refer back to as weed management plans for 2014 are developed. 

Pigweed killed by glyphosate on right and an unaffected potentially resistant pigweed on left

Insect pressure remains very light to non-existent in cotton but verticillium wilt has really intensified. Verticillium wilt is a soil born fungus that cause plants to wilt but does not cause root rot. The pathogen in affect plugs up vascular tissue preventing the translocation of moisture. Stalks of plants can be cut longitudinally and inspected for brown streaking for a quick in field diagnosis. There are no curative treatment for verticillium wilt in cotton, the key management tactic is to plant resistant/tolerant varieties. So, as with weed management make some field notes on “vert” pressure that can be used to help make variety planting decisions next year.

"Vert" symptoms on leaf.

Spider mite pressure remains high in many corn fields and miticide applications are on going. Mite suppression has been good in some fields while others have had to be retreated. Coverage is critical to maximize miticide efficacy. Increased total volume of spray will provide better coverage and penetration into a dense canopy, 5 gallons per acre should be considered minimum. A much higher incidence of spider mite destroyers (Stethorus) have been observed feeding in in mite colonies recently. The spider mite destroyer is a very small beetle in the lady beetle family (Coccinellidae). The beetle is about 1/16 inch long and shinny black; the larvae are gray to brown with a miniature alligator type appearance (minus the teeth :-) ). Both the adult and larval forms are key predators of mites and will help stabilize mite populations. Mite management tactics should exploit these natural enemies; avoid pesticide applications which will destroy your partners in mite management.

Spider mite destroyer (Stethorus) adult left and larva right

An occasional sorghum headworm has been observed in area sorghum. As grain sorghum transitions from vegetative growth to heading whorl feeding pests will shift to feed in developing heads. Corn earworm and fall armyworm commonly referred to as the headworm complex in grain sorghum, rank as the third most damaging insect pests of sorghum in the United States.   Treatment thresholds for sorghum headworms are dynamic based on grain value, cost of control, and infestation levels. We have developed a sorghum headworm calculator "app" which is available on the Google Play Store at http://goo.gl/8mXvv  The app can also be found by searching for sorghum in the store. The app will run on any android device with an OS of 2.3 or above. Once the app is installed no internet connection is needed. We also have a web app for other operating systems which can be accessed at http://goo.gl/5k7ZtU. The web app will require an internet connection to work. The Android app calculates larvae/10 heads while the web app calculates larvae/head.

Some corn damaged by hail in late June is not pollinating adequately simply due to the lack of pollen production. Injury to the small developing tassel in late June has caused some tassels to be completely bare. 

Injured developing tassel left, barren tassel right

Northwest Plains Pest Management News Vol XI Issue 10

Rainfall blessed portions of the NWP area on the last day of July; NOAA weather stations in Friona and Muleshoe recorded .5 and 1.78 inches respectively. Individual reports in excess of 3 inches were also received. The area corn crop continues to progress very well with a wide range of maturities from less than two feet tall to blister stage. The cotton crop continues to play catch up, but is developing at a good pace. Yield potential is fair to good for the most part. Grain sorghum, as with corn has a wide range of maturities ranging from vegetative to heading and blooming. Most fields are on track to fully mature but late planted fields could be hurt by frost especially if development is slowed by stress. 

Corn pest pressure has increased, in addition to existing spider mite issues Southwestern corn borer (SWCB) activity has dramatically  increased this week; trap captures are up 10 fold compared to last week. Yield losses from SWCB may occur as a direct result of stalk and or ear shank feeding, as well as lodging.

Bt hybrids are very effective in controlling Southwestern corn borer but required non-Bt refuge and other non-Bt corn will have to be managed traditionally. The established economic threshold for second generation Southwestern corn borer is when 20% of plants are infested with eggs or small larvae. Timing is critical when making an insecticide application; insecticides must be applied prior to larvae boring into the stalk to be effective. Small larvae will feed on leaves, ear shoots, husks, and silk for about 5 to 10 days before tunneling into the stalk or ear shank and continuing to feed. Insecticides should be selected carefully; some are harsh on beneficial arthropods and may cause a secondary outbreak of spider mites.  

Spider mites persist in many fields while others remain nearly mite free. Many fields with established mite

populations have exceeded treatment threshold and have been treated. Current miticides are slower to fully suppress mites than what we see when treating most other insect pests. At 7 DAT it may look like a miticide has had no impact at the field level since there may actually be more mites present than before it was treated. In research conducted locally, labeled miticides averaged  about 55% control 7 days after treatment. This is not to say that there are half as many mites in the treated plots than before treatment because mites have continued to develop, but, and it is a big but, the plots treated with miticides have reduced mite pressure compared to that observed in the untreated plots. Remember we want to minimize mite colonization of the ear leaf.  

Fall armyworm have been observed feeding in non-Bt corn in varying degrees. Larvae have been observed feeding in silk, behind ears, and behind leaf collars. There is no established treatment threshold for FAW in corn but recent research confirms they can consume a significant amount of grain when feeding in the middle of the ear in addition to ear losses due to ear shank feeding.  There is a detailed presentation by Pat Porter which discusses potential grain loss due to FAW feeding in corn, it can be viewed at http://goo.gl/X9jy4O

FAW behind ear leaf

Cotton pests remain quiet even though I observed a “lost” bollworm feeding in a square this week. In corn growing areas, corn continues to be the favored host plant for bollworm/corn earworm at this stage. With recent precipitation plant growth should be closely monitored as we may not have enough boll load at this point to prevent excessive vegetative growth. In fields with good moisture and a later developing boll load a plant growth regulator may be necessary to keep cotton development on track. 

Sunflower head moth larvae have been observed feeding in pre-bloom sunflowers which may be an indication of heavy infestations once blooming has commenced. The head moth, is the single most important sunflower pest in Texas. Sunflower moth infestations are usually heaviest early in the growing season, with another smaller moth flight possible later in the season. The adult is a small, slender, silver-to-buff gray moth about 1⁄2 inch long. It is most often seen resting on sunflower heads during the blooming period, especially in early morning and early evening. Moths are highly attracted to plants beginning to bloom. Nearly 80 percent of the eggs are laid on the plant within 4 to 7 days after buds begin to open. Eggs hatch in 24 to 72 hours. Newly hatched larvae are yellowish. Mature larvae are brown with four yellowish-green to cream colored longitudinal stripes. For the first 5 to 6 days after hatching, young larvae are relatively exposed as they feed on pollen and floral parts on the flower surface. Insecticide applications should target the very early bloom period when yellow ray petals are visible.

Sunflower head moth larva feeding in bud.

Heat Unit Accumulation and Current Crop Moisture Demands

DD 60 based on May 1 planting date

Northwest Plains Pest Management News Vol XI Issue 9

Crops have progressed very well this past week, what a difference a rain makes! The area corn crop ranges from 4 leaf to blister stage and even though some fields have taken a beating from mother nature it looks good on a whole. Much of the area cotton crop is finally blooming; nodes above white flower (NAWF) have ranged from 6-9 indicating good yield potential, time permitting. The crop is about two weeks later than what we would like to see, but currently most fields are progressing at a high pace. The reduced effective bloom period will likely limit top end yield but August and September weather conditions will determine to what extent.  Cotton will need to be carefully managed to promote earliness to preserve as much yield potential and fiber quality as possible. Area sorghum is also rapidly growing but, as with cotton, later planted fields are in a race with mother nature to mature before frost.

Spider mites must not have read the text book as they did not seem to slow a bit during recent cooler and more humid conditions. Many field have exceeded treatment thresholds and many more are near it. Even small mite colonies have a tremendous number of eggs indicating the potential for continued rapid population expansion. Treatment threshold at this point can be simplified to an established mite population in the lower 1/3 of the plant with small colonies beginning to develop near the ear leaf with end goal preventing colony establishment on the ear leaf. As I mentioned last week population dynamics are extremely important in managing spider mites, regular field evaluations should be made to document population trends and natural enemy activity.  A rapidly developing mite population should be dealt with more aggressively while a slower developing population may allow some flexibility to determine if natural enemies will keep them in check. We have several trials out evaluating different products and rates, hopefully they will provide information that will help make good pest management decisions.

Banks grass mites and eggs

Weeds continue to be problematic and difficult to control. Control problems can be attributed to several reasons and in many cases combinations of factors including environmental conditions, weed size and condition, herbicide coverage, weed resistance to herbicides. As weed management decisions are made consider all management options and don’t automatically rule out “low tech” tactics such as cultivation and hand hoeing. To my knowledge no weed has developed resistance to the separation of above ground parts from below ground roots. If weed resistance is suspected deal with it aggressively, make every effort to prevent the loss of herbicide efficacy due to resistance.

Southwestern corn borer (SWCB) field level infestations have been reported even though moth captures in traps have remained relatively low with slight increases recently. The changing agriculture landscape including  planting use of Bt hybrids, as well as previous years use of Bt technology may be making trapping less effective in predicting area wide potential pest activity. Populations of SWCB appear to be much more localized and more difficult to predict than the more uniform infestations of yester year. The established action threshold for SWCB is met when 20% of plants are infested with eggs or small larvae. Most eggs will be laid on the middle 7 leaves; the ear leaf, 2 above and 4 below.

Hatched SWCB eggs

As cotton transitions into the early bloom stage we no longer consider cotton fleahopper a risk but we need to continue monitoring cotton for significant Lygus infestations. During the early bloom period the action threshold for Lygus is 15/100 sweeps (4/beat sheet sample) with unacceptable fruit shed. Current Lygus infestation levels remain low. Fields adjacent to weedy areas should be closely monitored when the weeds are destroyed as Lygus will migrate into cotton.

Lygus Adult

Heat Unit Accumulation

The area is running a bit ahead of the 30 year long term average in heat unit accumulation but crops are behind in development due to delayed planting.

DD 60 based on May 1 planting date

Crop moisture demands near .25 inch for corn, .2 inch for cotton, and .15 inch for sorghum. More detailed crop moisture demands as of July 25, 2013 can be found here.

Northwest Plains Pest Management News Vol XI Issue 8

The area has been blessed with a wide spread slow soaking rain! The moisture will provide a much needed boost to crop production and has already provided a significant boost in producer optimism. Local NOAA weather stations recorded from near 1 inch to over 2.5 inches over the last several days; individual reports in excess of 3 inches were also received. 

Recent precipitation and cooler weather could not have come at a better time for corn which is pollinating. Stress occurring a few days prior to tasseling can cause ear development to slow resulting in a lag between pollen shed and silking which can lead to poor pollination. Moisture demand has decreased from over .40 inch/ day to .13 inch/day during the recent cool humid conditions. Moisture demand will rapidly rebound to previous levels as temperature increases and humidity decreases. Hopefully current soil moisture along with irrigation will get the early corn past peak moisture demand. A good soil moisture profile will also be a good base for later planted corn as moisture demands increase. 

Spider Mite Pressure

Spider mites have continued to progress in many corn fields, cool wet conditions may slow them down but many infestations are well established and will likely require treatment shortly to avoid excessive yield loss. The action threshold for spider mites in corn is based on crop value, percent infested leaves, and leaf area damaged by mites. The following table was developed based on fast acting miticides and may need to be amended slightly for slower acting miticides. 

Population dynamics are extremely important in accessing spider mites, regular scouting should be conducted to document population trends and natural enemy activity.  A rapidly increasing mite population should be dealt with more aggressively while a slower developing population may allow some flexibility to determine if natural enemies will keep them in check. I’ve said it before but it’s worth repeating the conservation of natural enemies is the corner stone in spider mite management.  Key natural enemies include six spotted thrips, spider mite destroyers, minute pirate bugs, and predatory mites. Management of other pest such as corn borer and fall armyworm can significantly impact mite populations.  The use of broad spectrum insecticides can flair mites by removing natural enemies which are suppressing mite populations.  Miticides may not provide adequate suppression in the absence of natural enemies which could necessitate multiple applications to get a raging spider mite population under control. 

Six Spotted Trips

Southwestern corn borer (SWCB) trap captures remain low but I expect the second generation moth flight to pick up shortly.  Moths are ¾ inch long, white,  with no distinct markings.  Eggs are flattened, approximately 1/8 inch in diameter and can be laid singly or in groups of 2 to 3 or more.  When in groups, eggs are laid in an overlapping pattern resembling fish scales. Freshly laid eggs are creamy white but develop three parallel red lines in about 24 hours. Small larvae will feed on leaves, ear shoots, husks, and silk for about 5 to 10 days before tunneling into the stalk or ear shank and continuing to feed. Second generation SWCB will lay 75% of their eggs on the upper surface of the middle 7 leaves; the ear leaf, two above and four below.  Inspection should be concentrated in this zone. The established economic threshold for second generation SWCB is when 20 to 25% of plants are infested with eggs or small larvae. Bt corn hybrids are extremely effective in suppressing SWCB making insecticide treatments unnecessary. 

SWCB Egg

Fall armyworm (FAW) infestations have increased in area sorghum, some fields have as high as 30% of plants infested. Dr. Pat Porter has been monitoring FAW moth activity and has noted that this years population is tracking very similar to 2011. If this trend continues moth activity will begin to increase the latter part of July and peak the second week of August.  FAW is a non discriminatory pest which will infest many area crops including corn, cotton, sorghum, blackeyed peas, green beans just to name a few.

Insect pest pressure remains very quiet in the cotton field. square sets are outstanding as we near bloom ranging from 90-98%  with most fields 95% or better. Weeds continue to be troublesome in many fields. Remember there are several good residual herbicide products to consider when “laying by” cotton. These layby options are another tool to prevent or manage weed resistance to glyphosate. Some products can be applied over the top while some will need to be directed or applied under a hood. The benefits of a good layby program will far out weigh costs and inconvenience of application especially in light of documented pigweed resistance to glyphosate.

Northwest Plains Pest Management News

Crops have responded very well to precipitation and cooler temperatures over the last couple weeks. The area corn crop has about as wide a range of maturity as I’ve ever seen this time of year, from just planted to tassel/silking. More mature corn fields are nearing or at peak moisture demand which could exceed .45 inch/day under hot windy conditions. The following chart graphs daily ET values based on average conditions from various planting dates.

Most cotton has “turned the corner” and is squaring but I have yet to see a bloom. Square sets have been outstanding ranging from the low 90s to near 100% with most fields around 96%.  While we are not behind in heat unit accumulation the cotton crop is behind due to delayed planting and harsh environmental conditions which will likely result in a shorter than normal effective bloom period.  Considering this, managing cotton for earliness at this point looks to be even more important.  The bulk of nitrogen fertilizer should be applied by early bloom. Pest pressure at this point is very low.


Sorghum is progressing very well, the crop ranges from emerging to growing point differentiation (GPD).  It seems some sorghum has taken a bit longer to recover from a phenoxy herbicide application than expected. A wide range of crop response was observed between hybrids in a local trial treated with dicamba + atrazine. Try to avoid yield robbing moisture and nutrient deficiencies during GPD to maximize yield potential.

Spider mites have been building in some corn fields but  remain hard to find in others. Most colonies remain relatively small but have moved up the plant to the upper part of the lower third of the plant. Occasionally we have observed colonies in the middle section of the plant. Remember if spider mites are established in a field which will be likely treated for another pest with an insecticide which is harsh on beneficials then a preventative miticide application about two weeks prior should be considered. Currently labeled miticides are designed to work in concert with natural enemies of spider mites, when these beneficials are removed from the equation miticide performance may not meet expectations. Sixspotted thrips, a key predator of spider mites,  have been observed in area corn and will help stabilize mite populations if conserved. Adult sixspotted thrips can be distinguished from other thrips species by the 6 spots on their back (3 on each wing cover). Both adults and larvae are predaceous feeding primarily on mites and can be very effective in suppressing mite populations.

Fall armyworm pressure has picked up in area sorghum and non-Bt corn. Area surveys in sorghum have ranged from 2-11% infested plants. Damaged leaves unfolding from the whorl are ragged with “shot holes.” Although this may look dramatic, leaf damage usually does not reduce yields greatly, and control of larvae during the whorl stage is seldom economically justified. Also, larvae within the whorl are somewhat protected from insecticide. Insecticide application may be justified if larval feeding reduces leaf area by more than 30 percent or is damaging the developing grain head or growing point within the whorl.

Plant growth regulators (PGR) in cotton in and of themselves do not “make more cotton” but do allow producers to push a crop with irrigation and fertility while maintaining acceptable plant structure and enhancing earliness. In other words a PGR applied to cotton without adequate moisture and plant nutrients will not enhance yield. A heavy boll load will limit vegetative growth and enhance earliness but in a high input environment where moisture and fertility are not limiting factors a heavy boll load alone may not be enough to adequately control vegetative growth in stripper harvested cotton.  Mepiquat chloride (MC) is a foliar applied PGR that is absorbed into leaves and translocated throughout the plant.  Since its introduction, MC has been used extensively to manage cotton growth in an attempt to reduce risk associated with a delayed harvest.  Mepiquat chloride regulates cell elongation by inhibiting the synthesis of gibberellin.  This reduction in cell length in turn reduces overall plant height and internode length. There are numerous PGR options most of which are based on mepiquat chloride but may contain other active ingredients to further enhance effectiveness. Early low rate multiple (LRM) applications during squaring and early bloom have shown to be more effective than later single high rate applications.  For example in a local research trial early LRM applications of Stance (4 to 1 ratio of mepiquat chloride and cyclanilide) reduced the number of days to physiological cutout which in turn translated into an earlier harvest while the single high rate application did not differ from the untreated plots.

Northwest Plains Pest Management News

Recent precipitation has provided much needed moisture to the area but did come at a cost. Streaks of hail accompanied some of the storms which damaged and in some cases destroyed crops in their path. Replant decisions are having to be made as quickly as possible as time to mature a subsequent crop is limited.

The growing point of sorghum remains at or near the soil surface and likely avoided catastrophic injury in most cases and should recover. Larger corn was at more risk since the growing point and hardened stalk below it were  much more exposed. Damage evaluations should consider crop stage, stand loss, leaf area loss, growing point injury and stalk injury.

Injured growing point

Damaged stalk

Like many other crop plants, corn does not need all of the leaf surface area that it produces. Corn fields may look ugly and ragged and still be capable of producing an almost normal corn crop. Even shredded and broken leaves are capable of some photosynthesis if they are still connected to the main plant. A strong healthy root system, good soil moisture, and favorable, sunny weather are most important to a rapid recovery.  The growth stage of the corn plant and the percent defoliation are important. Hail that is received later in the growing season can be increasingly destructive. Damage tables constructed by University of Minnesota (below) indicate the percent yield reduction observed with various percents of defoliation at defined growth stages. Notice that a near-50 percent leaf loss at the 10th leaf stage results in only a 6 percent yield reduction.

What about silage production? Leaves  only compose 10-15% of total plant weight so yield losses due to actual physical leaf removal may not be has great as one might assume. Most damage will come from the inability of the plant to produce acceptable plant structure and  ears. Research conducted by Penn State Extension suggest that corn silage yield losses due to hail are comparable to grain yield losses.

After 4 to 5 days have lapsed since the hail storm, inspect the surviving plants. Some of these plants should be split open to see at what height and condition the growing point is found. If the growing tip is black or brown, the damage is severe and the plant may soon die. Undamaged growing points will be pushing new leaves, and corn will increase in height and leaf area. A “buggy whip” condition can occur when new leaf growth becomes tangled in dead or mangled leaves, normally most plants will break through given enough time. Each field will have to be carefully evaluated to get a best estimate of crop potential and risks associated with keeping the current crop vs. replanting.

Estimating corn yield reduction due to various amounts of leaf removal at several stages of plant development (taken from tables prepared by Hail Insurance Adjustment and Research Association and Crop Insurance Research Bureau as listed in Crop News Bulletin No. 23, Extension Service, University of Minnesota).