kentucky pest news, october 1, 2013

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Online at:www.uky.edu/KPN

Number 1359 October 1, 2013

GRAINS

Stink Bugs Could Still Be a Problem in SoybeansDoug Johnson, Extension Entomologist

Because of delayed planting and a cool summer,Kentucky soybean producers are likely to haveconsiderable acreage of late maturing soybeans. This

probably causes most folks to be concerned withfrost. However, this extended maturity may also setup fields for additional damage by stink bugs.Producers and consultants should remain watchful aslong as pods are still filling.

By far, the most common stink bug found inKentucky is the green stink bug (Figure 1). Ourresearch indicates that green stink bugs make upgreater than 80% of the population. Nonetheless,

there are several species of brown stinkbugs (Figure2) in Kentucky-grown beans as well. So expect to

see both types.

Stink bugs can cause decreases in both yield and

seed quality. These pesky bugs feed directly on thebean using their piercing-sucking mouth parts. Theypuncture the pod wall and stab the developing bean,

removing nutrients and sometimes allowing entranceof pathogens into the pod / bean. Usually, there is noclear evidence of this damage until the pods aremature. The only clear evidence one has of theseimportant pests is observing them in the field;

damage symptoms are too late.

Stink bugs will hang around until frost, feeding onwhatever is available to them. In soybeans we

consider the pods at risk up through to R6 stage. Soif you have beans less mature than this you shoulddefinitely be looking for these critters. Once

soybeans are in the R6 stage stink bug damage ismuch more difficult to predict.

Lexington, KY 40546

GRAINS-Stink Bugs Could Still Be a Problem in Soybeans

SHADE & FOREST TREES-Skimpy SpruceDefoliation from the Bottom

Up

INSECT TRAP COUNTS

Figure 1. Green stink bug (Photo: Russ Ottens, University of

Georgia, Bugwood.org)

Figure 2. A brown stink bug.
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Sampling for the pest can be done in two ways. Inwide row beans a shake cloth (aka = drop cloth) may

be used. This is a 3- foot long section of white clothwide enough to reach from row to row. Shake the

beans on both sides over the cloth and count the stinkbugs that fall to the cloth. Remember, adults can fly

so you need to count quickly. Juveniles do not yethave wings so they are a bit slower to escape. Innarrow row beans you will need to use a sweep net.The 15-inch-diameter sweep net is the standard toolfor most thresholds. Take 25 sweeps per locationand count the stink bugs captured. In both types of

sampling, each field should be sampled at multiplelocations. The more locations you sample, the moreaccurate and precise your estimates will be. Averagethe number of stink bugs captured over all locations.

Thresholds that warrant control are: shake clothan

average of one stink bug per row foot, or if sampledwith a sweep net, treat if you collect an average of 9stinkbugs per 25 sweeps at R4-R6.

If control is required, synthetic pyrethroidinsecticides are commonly used for control and are

very effective on green stink bugs. Brown stink bugsare a bit more tolerant of pyrethroids, so if they are

plentiful, inclusion of an organophosphate likeacephate may be needed. Insecticides for use againstthis pest in soybeans may be found at:

http://pest.ca.uky.edu/EXT/Recs/welcomerecs.html .

Producers in the central and eastern Kentucky

production areas also need to keep their eyes openfor the two invasive stink bug species resident inKentucky. Populations of the brown marmorated

stink bug (BMSB) have become established incentral and eastern Kentucky over the last 3 years.

BMSBs look typically like other brown stink bugs

except that they are often a bit larger and have twosmall but very distinct white bands surrounding the

joints in their antennae (Figure 3).

In addition, the Kudzu bug has been found in threesoutheastern Kentucky counties bordering I-75. They

are dark green to olive with a rounded shape andabout the size of an English pea (Figure 4).

Neither of these species is believed to be of majorimportance in this years crop, but as their

populations become established and grow larger insize they have the potential to become major soybean

pests. Any interested party that has collected what isbelieved to be a BMSB or Kudzu bug is asked tosubmit the insect to their county Cooperative

Extension Office for identification.

SHADE & FOREST TREES

Skimpy SpruceDefoliation from the Bottom Up

Nicole Ward-Gauthier, Extension Plant Pathologist

Rhizosphaera needle cast, the most common diseaseof spruce in Kentucky, causes needle drop in lower

branches, resulting in a distinct thinned appearance.The fungal pathogenRhizosphaera kalkhoffii

primarily infects spruce, but can also affect some

pine species.

Symptoms are often noticed during summer whenneedles on lower branches turn purplish or brown

(Figure 5). Within a few weeks, needles fall andlower limbs are left bare (Figure 6). Small, darkfruiting bodies called pycnidia form in stomata(pores in needles) and can be used to confirmdiagnoses (Figures 7 & 8). Pycnidia can easily be

recognized with a hand lens or with the naked eye.

Figure 4.Kudzu bug.

Figure 3. Brown

marmoratedstink bug.
http://pest.ca.uky.edu/EXT/Recs/welcomerecs.htmlhttp://pest.ca.uky.edu/EXT/Recs/welcomerecs.htmlhttp://pest.ca.uky.edu/EXT/Recs/welcomerecs.html


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Figure 5. Needles infected with Rhizosphaera turn purplish

brown during summer. (Photo: USDA Forest Service,

Bugwood.org)

Figure 6. Needle drop and thinning of lower canopy are classic

symptoms of Rhizosphaera needle cast in spruce. (Photo:

Minnesota Department of Natural Resources, Bugwood.org)

The life cycle of the fungus extends over a 15-monthperiod. Infection takes place as spores (conidia)

within these pycnidia are rain splashed from needle

debris onto foliage. This infection process occursprimarily during spring but it can continue as long asconditions are rainy, such as this past summer.During the winter or following spring, pycnidia

develop in infected needles, plugging stomata(Figures 7 & 8). Needle discoloration and needledrop occur during summer of the second season,resulting in thinning of lower canopies. Ifdefoliation occurs 3 to 4 consecutive years, branch

death is likely. Stressed trees are more susceptible toinfection byR. kalkhoffii than healthy plants.

Figure 7. Fungal pycnidia are often visible without a hand lens.

Figure 8. Fungal pycnidia protrude from stomata.

Disease management should consist of good cultural

practices such as improved vigor and reduced plantstress, proper spacing to improve air circulation, andmost importantly, good sanitation habits. Duringrainy seasons or in plantings with a history ofdisease, fungicides may be applied 2 consecutive

years during spring when fungi are most active.Fungicides that include chlorothalonil, copper, ormancozeb are effective when applied during needleemergence (mid-April) and again four weeks later.For more information, seeHomeowners Guide to

Fungicides.

For additional information on needle cast diseases ofconifers, see ID-85http://www2.ca.uky.edu/agc/pubs/id/id85/id85.pdf
http://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-GEN-07.pdfhttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-GEN-07.pdfhttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-GEN-07.pdfhttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-GEN-07.pdfhttp://www2.ca.uky.edu/agc/pubs/id/id85/id85.pdfhttp://www2.ca.uky.edu/agc/pubs/id/id85/id85.pdfhttp://www2.ca.uky.edu/agc/pubs/id/id85/id85.pdfhttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-GEN-07.pdfhttp://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-GEN-07.pdf


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2013 INSECT TRAP COUNTS

September 20 to September 27

Graphs of insect trap counts for the 2013 season are

available on the IPM Web site at -http://www.uky.edu/Ag/IPM/ipm.htm.

Note: Trade names are used to simplify the information

presented in this newsletter. No endorsement by the

Cooperative Extension Service is intended, nor is criticism

implied of similar products that are not named.

Location Princeton, KY Lexington, KY

Black cutworm 0 2

Armyworm 0 2

European corn borer 0 4

Corn earworm 6 3

Southwestern corn

borer

0 4

Fall armyworm 3 0
http://www.uky.edu/Ag/IPM/ipm.htm.http://www.uky.edu/Ag/IPM/ipm.htm.http://www.uky.edu/Ag/IPM/ipm.htm.

kentucky pest news, october 1, 2013

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