Giant ragweed: Sporadic patches of giant ragweed (Ambrosia trifida) are emerging above the grassline in field edges mostly along ditches and not within field margins. Let your neighbors know if you spot giant ragweed and where as they are not easy to find amongst all the other weeds along ditches.

 

Palmer amaranth: Pigweeds, mostly palmer amaranth (Amaranthus palmeri) along field crop margins are rapidly growing and are one of the more frequent observations along outside rows adjacent to lawns and sensitive crops in Salem County. For resistance management, these outside rows of half-dead, curled but still living plants are where resistance can develop. If already sprayed, mow these down to the ground or till under even if it means sacraficing the outside row of crop. If sprayed or mowed, monitor the area to make sure pigweeds completely die.

Ivy Leaf morning glory: Ivy leaf morning glory (Ipomoea hederacea) will continue to sprout with this flush of rain. Monitor newly planted double crop soybeans into wheat stubble for flushes moving into fields from field edges.

Marestail: Over all marestails (Conyza canadensis) are under control except in fallowed unplanted and untilled fields with last year’s crop residue still present. Brushog these down before notilling. Marestail is a wind dispersed seed that like thistles, will end up infesting hundreds of acres downwind if allowed to go to seed.

Thistles: Thistles in the Cirsium and Carduus genus are sporadic but on some idled fields extensively spreading by root rhizomes (Canada) and seed dispersal (Bull, Musk). Canada thistle in sandy soils is a life time headache greatly increasing field management costs over time.

June 26, 2021

A field of ready to harvest wheat was observed infested with 4^th to 5^th star grasshopper nymphs in Salem County. While waiting for positive identification from entomologists familiar with the differences in the nymp identification, these nymphs appear to be differential grasshoppers (Melanoplus differentialis). The uniform yellowish color of nymphs observed, is an indication the population is quite high. Lesser populations tend to be more green in color. Additional fields of wheat, corn and soybean on the same farm all had nymphs present but were not at economic threshold yet.

Visual counts observed walking into the field were more than 4 as they hopped away fro

m a square foot area, repeated in multiple locations. This confirms the population is very high. The threshold for nymph stage grasshopper populations causing economic injury is 15 – 20 per square yard. (Four or more per square foot; nine square feet in a yard = more than 20 per square yard = high infestation.)

Because grasshoppers move from preferred forbs like alfalfa and hay fields, and field edges, into cereal crops it is recommended each cereal grain field not yet ready to harvest due to high moisture content be observed to assess thresholds.

When grasshopper nymph levels are this high, the damage to unharvested cereal grains can be concernin if the adult phase coincides with near ready moisture crops, because their feeding can clip the dried grain head stem and both phases chew on seed head grains.

There is no standard for the level of clipped seed heads per say. Monitoring is the best method to determine if harvest will resolve the issue or if a foliar insecticide is needed to protect the grain quality and yield.

The active ingredient Rynaxypyr (Chlorantraniliprole, IRAC 28) found in Dupont insecticide Coregen and FMC’s insecticide Prevathon are labeled for foliar application of grasshoppers in multiple vegetable, field and forage crops.

“Growers can make a foliar application of Prevathon insect control by ground, air or overhead sprinkler chemigation. It has a short re-entry interval of four hours, a favorable worker protection standard profile and a short PHI.” – FMC website, https://ag.fmc.com/us/en/insecticides-miticides/prevathon-insect-control

Once wheat is harvested, grasshoppers will fly to corn and soybean and alfalfa regrowth. Japanese beetles were present in these crops but currently at low levels. Feeding damage may be misidentified as japanese beetle damage when it is actually an indication of grasshopper pressure building. Nymphs were present in adjacent corn and soybean fields but at low levels.

Monitor soybean and young corn fields closely for signs of adult grasshopper feeding through August. Note that a dense swarm of differential and two-striped field crop grasshoppers can destroy the leaf area of a crop in just a few hours.

The following links have useful identification and detailed management recommendations for various stages of grasshoppers on various crop stages of development. The soybean research link shows the defoliation thresholds in soybeans.

Identification https://www.youtube.com/watch?v=bgi6De5NDIw

Identification https://www.youtube.com/watch?v=bgi6De5NDIw

Identification http://idtools.org/id/grasshoppers/factsheet.php?name=13190

Economic importance  http://idtools.org/id/grasshoppers/factsheet.php?name=13190

New Jersey species in 2005 https://njaes.rutgers.edu/pubs/publication.php?pid=fs290

Coragen label http://www.cdms.net/ldat/ld8KF045.pdf

Soybean reasearch https://soybeanresearchinfo.com/soybean-pest/grasshoppers/

Prevathon label https://ag.fmc.com/us/en/insecticides-miticides/prevathon-insect-control

Below is a pdf on ‘Italian Ryegrass Management in Soybeans’ by Take Action Partners on herbicide resistance management.

Italian rye grass and its hybrids are a common grass in head right now along field edges and in fall planted grains or as a weed of pure stands of hay crops. Ryegrass is difficult to control in most crops due to its emergence biology, tillering and resistance to herbicides.

“Technical editing for this publication was led by Larry Steckel, Ph.D., University of Tennessee, Knoxville; and Jason Bond, Ph.D., Mississippi State University, in partnership with other universities in the soybean-growing regions of the United States. Take Action is supported by BASF, Bayer, DuPont, Dow, FMC, Monsanto, Syngenta, Valent and corn, cotton, sorghum, soy and wheat organizations.” For more information and links to additional resources, visit www.IWillTakeAction.com.™

https://iwilltakeaction.com/uploads/files/57229-7-ta-hrm-factsheet-italianryegrass-r2-final.pdf

For management in forage hay crops, see the Oregon State publication “MANAGEMENT OF ANNUAL RYEGRASS CONTAMINATION IN TALL FESCUE AND ORCHARDGRASS GROWN FOR SEED” https://cropandsoil.oregonstate.edu/system/files/curtis_annual_ryegrass.pdf

 

 

Ivy-leaf morning glory seedlings with one set of true leaves seemingly sprang up over night with the storms that tracked across Southern NJ Wednesday night. This large seeded annual twining vine can significantly reduce yields in soybeans. Where in the field these seedlings are located should be monitored closely over the next few days. Don’t assume preemergence herbicides that have activity on seedlings up to four-inch morning glories are still going to do the job. It all depends on how many days (or weeks) went by since herbicides were applied and if this was the first activating rainfall since application.

Morning glory seeds can germinate at multiple depths in the soil profile escaping what soil residual activity was present before the rains came. Scouting cues of suppressive herbicidal activity from products like Valor, Canopy, Classic, Authority, Flexstar, Firstrate are: Noticeably larger plants along field edges that did not receive spray coverage, and more of them; but few plants further into field interiors where herbicides were applied. Look also for signs of herbicide activity over the next few days.

Preemergence products with some activity on morning glories have group 2, 5 and 14 modes of action and have somewhat similar symptoms of weed injury. “Seedling weeds will then either turn brown and die shortly after being exposed to light, or will cease growing, turn yellow and then turn brown from the growing point out.” – page 4, 2010 Valor XLT Soybean Label, Valent Product EPA Reg. No. 59639-117).

Even one morning glory left unchecked in a foot of row can reduce soybean yield in that row by 50%. If flushes of morning glories are emerging throughout the soybean crop, consider lightly cultivating if at all possible if row spacing permits before that early (full season) flush of morning glories have a chance to entwine. However, keep in mind that cultivation will incorporate surface applied herbicides. Too deep and this could reduce effectiveness against small-seeded broadleaf weed seeds brought up closer to the soil surface.

In beans, post-emergence herbicides applied to emerged morning glories generally only provide suppression and may not prevent seed production. This is generally true for all large-seeded annuals.

Don’t let those roadside edge plants outside the field go to seed. Other plants seen along with ivy morning glory yesterday are emerging jimsonweed and cocklebur seedlings, both large-seeded annuals. If you see a hand sized goose foot shaped plant it could be giant ragweed, also a large seeded annual.