Category Archives: Pest Group

Be prepared for scab in small grains

Posted on by

Wheat in the southeastern portions of Virginia will start flowering soon if it has not already. Wheat is susceptible to scab (Fusarium head blight) from early flowering until approximately 10 days after first flower. An online scab risk assessment tool (www.wheatscab.psu.edu) provides information on relative risk of wheat infection by the scab fungus which also has the potential to contaminate grain with DON (vomitoxin). The risk model is based primarily on relative humidity during the 15 days prior to flowering since high moisture favors inoculum production by the scab fungus on crop residues. However, the model also takes into consideration variety resistance to scab. No wheat varieties have complete resistance (immunity) to scab, but commercially available varieties vary in their susceptibility. Current variety rankings for scab resistance can be found here:

Wheat variety rankings for scab resistance

If you do not know the relative susceptibility/resistance of your variety, it is probably best to err on the side of caution and assume that your wheat crop is susceptible or at least moderately susceptible to scab. Currently, the predicted scab risk for wheat that is flowering in Virginia is low for all but the most susceptible varieties. Dry weather is predicted after the current storm passes through, so scab risk will likely remain low to moderate over the next week. However, it is prudent to be prepared to apply a fungicide for scab management as the wheat crop approaches the flowering growth stage. Keep in mind the best management tactic for minimizing yield and quality losses to scab and DON is to plant resistant varieties and to make a properly timed fungicide application when wheat is in the susceptible growth stage (flowering) and weather conditions favor dispersal of the scab fungus.

If a fungicide is applied for scab, strobilurins should NOT be used as they may increase DON (vomitoxin) contamination of the grain if applied after flag leaf. Foliar diseases are starting to increase in some fields in Virginia, but if the wheat is at or near flowering, a strobilurin or premix fungicide containing a strobilurin is not recommended. Fungicides recommended for scab also provide very good to excellent control of common foliar diseases of wheat (see last week’s post), so a scab fungicide application may provide the added benefit of controlling leaf spots and rusts. The triazole fungicides Prosaro, Proline, and Caramba are the most effective fungicides for scab and should be applied at early to mid-flowering and up to one week later. For maximum efficacy, fungicides for scab and DON control should be applied with nozzles angled at a 30 degree angle from the horizontal using both front and back facing nozzles. This will ensure that the product is applied to the grain head rather than the leaves or the ground.

Growers, agents, and consultants can subscribe to the U.S. Wheat & Barley Scab Initiative’s (USWBSI) FHB Alert system at http://www.scabusa.org/fhb_alerts. Region-specific scab alerts that provide growers with updates during critical times are sent as emails and/or text messages.

Wheat disease update

Posted on by

As the wheat crop approaches flag leaf emergence and heading growth stages, it is time to start thinking about disease management. When conditions are conducive to disease development (e.g. high humidity, warm temperatures) foliar fungicide applications may be necessary to protect wheat yield and quality.

Wheat diseases observed in Virginia so far in 2015 have included viruses (which cannot be managed with fungicides), powdery mildew, and leaf blotch. Disease severity thus far has been relatively low in most areas but an increase in disease can be expected with warm, humid weather. Leaf blotch, for example, has been observed on the lower leaves where it is unlikely to impact yield, but once the flag leaf emerges, this leaf surface, which feeds the developing grain, should be protected from disease if symptoms are observed on the lower leaves and conditions are conducive to disease development. Once heading and flowering occur, the developing grain need to be protected from infection by the Fusarium head blight (scab) fungus if scab risk is high. Factors contributing to scab development and proper timing of fungicides for scab management will be discussed in a later post.

Slide1

Each year plant pathologists from throughout the U.S. update the following wheat fungicide efficacy table based on the most current data. Efficacy ratings for each fungicide listed in the table were determined by field testing the materials over multiple years and locations. Efficacy is based on proper application timing to achieve optimum effectiveness of the fungicide as determined by labeled instructions and overall level of disease in the field at the time of application. Judicious use of an appropriate fungicide for the target disease can protect both yield and quality of the wheat crop.

NCERA-184-Wheat-fungicide-table-2015

First kudzu bugs found in 2015 in VA

Posted on by

We just received confirmation that kudzu bug adults have been found in two counties, one on a trap at the VT Tidewater Ag Research and Extension Center in Suffolk, and several on the side of a building in Mecklenburg County (see the attached map).  These adults are the overwintering population getting active as the weather warms.  They are about a month later than our first reports in 2014–the first in that summer emerged the first week in March in Chesapeake.  This winter has been pretty cold and wet compared to some and could have caused this delay.  Most likely more reports will start coming in soon.  Updates will be posted. Kudzu_bug_traps_7_Apr_2015

Corn seed trait tables

Posted on by

Dr. Dominic Reisig (Entomologist, North Carolina State University) has shared these slides showing (1) corn trade names, their Bt protein(s), and their effectiveness against corn earworm and fall armyworm; and (2) corn seed treatment trade names, their active ingredient(s), and their effectiveness against billbug, white grub, and wireworm.  In these two attached tables, P = Poor, F = Fair, G = Good, VG = Very Good, E = Excellent, and NL = Not Labeled.  Please click on the pdf document at the end of this sentence to access the tables:  corntraits

Boxwood Blight on Boxwood Holiday Greenery

Posted on by

Boxwood blight has been present in Virginia since 2011 and has since spread from its original location in Carroll County to a number of other counties around the state by movement of infected plants. Because much of Virginia’s greenery production industry is located in areas where boxwood blight is known to occur, the potential for spread of the disease on boxwood greenery also exists. Last year we notified agents regarding the potential for spread of the disease via holiday boxwood greenery. Now that potential has become a reality in North Carolina. The North Carolina Department of Agriculture and Consumer Services recently discovered boxwood blight in holiday boxwood greenery sold at several retail locations in North Carolina. Although the fungus that causes boxwood blight is not active at cold temperatures, it produces structures that can survive on plant debris over the winter. The fungus could potentially infect nearby susceptible plants in the landscape when favorable weather conditions return. Therefore, it is very important that boxwood greenery be properly disposed after the holidays by double-bagging and removing to the landfill. Do not compost boxwood greenery and do not leave it in cull piles in the landscape. Inspect boxwood greenery carefully for symptoms of boxwood blight before introducing it to a site containing susceptible boxwood plants and discard symptomatic greenery as described above. Symptoms of boxwood blight include brown leaf spots with dark border, black streaks on green stems, and leaf drop. Be aware, however, that even asymptomatic greenery could potentially harbor the pathogen. If clientele have highly valued boxwood in their landscape, they may want to avoid introducing boxwood greenery altogether.

For more information on the North Carolina situation, refer to the NCSU Plant Disease and Insect Clinic blog at: http://ncsupdicblog.blogspot.com/2014/12/pest-alert-boxwood-blight-on-holiday.html.

For more information on boxwood blight in general, including Best Management Practices for the greenery industry, landscapers, home growers, and retail and wholesale nurseries, visit the Virginia Boxwood Blight Task Force web site at:http://www.ext.vt.edu/topics/agriculture/commercial-horticulture/boxwood-blight/index.html.

Please make sure that property managers of historic sites in your area are informed about this update.

Leaf spots on boxwood caused by the boxwood blight pathogen (photo by A. Bordas)

Leaf spots on boxwood caused by the boxwood blight pathogen (photo by A. Bordas)

Black streaking on boxwood stems caused by the boxwood blight (photo by A. Bordas)

Black streaking on boxwood stems caused by the boxwood blight pathogen (photo by A. Bordas)