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Extension Entomology

Tag: swathed

Alfalfa Update

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

 

Potato leafhoppers are still common in all alfalfa fields sampled in the last 7-10 days, unless they have been swathed during that period of time.  Fields swathed within the last week did not have enough potato leafhoppers to reach a treatment threshold.  However, fields swathed just 10-14 days earlier are once again loaded with these little lime green, wedge-shaped leafhoppers.

There do seem to be good populations of green lacewings in uncut alfalfa fields.  However, they do not appear to be impacting the potato leafhopper populations.  We did pick up one alfalfa weevil larva and one adult in an uncut alfalfa field but the alfalfa weevils should not be of concern as major defoliators until next spring.

 

 

Alfalfa Update

–Dr. Jeff Whitworth and Dr. Holly Schwarting

Potato leafhopper populations are very active throughout north central Kansas.  There are small nymphs, many adults, and the adults seem to still be migrating into the fields.

PLH adult2

Leafhopper nymph (2)

PLH burn

Could not find significant populations in fields swathed within the last 7-10 days but as regrowth occurs and immigration continues, these fields need to be monitored.  Fields not yet cut are already showing signs of “hopper burn” and should be swathed ASAP or an insecticide application may be justified.  Potato leafhoppers have few, if any, natural enemies.  Thus, these populations probably will not diminish without management, i.e. either swathing (my preference) or insecticide application.  For more information on potato leafhopper management, please visit the Alfalfa Insect Management Guide: http://www.bookstore.ksre.ksu.edu/pubs/mf809.pdf

 

Alfalfa Update

–Dr. Jeff Whitworth and Dr. Holly Schwarting

Much of the alfalfa in northcentral Kansas that could be swathed has been in the last week.  The cool damp weather has kept the adult alfalfa weevils in the fields.  They are congregated under windrows in the cut fields where they do a little feeding on the stems, resulting in characteristic spots of epidermis removal, called ‘barking’.  As these windrows are picked up there will be the characteristic striping across the fields where the windrows held back the regrowth underneath, plus provided the weevils with a protected site to continue feeding.  Fields not yet swathed also have significant populations of adults but this should not impact the foliage prior to cutting.

AW adult and barking

Windrows

Pea aphids are also present in both cut and uncut fields, but lady beetles and green lacewings are also, so would not expect pea aphid populations to have a negative impact on alfalfa.

Pea aphids adult and nymph

greenlacewing

pinkspotted lady beetle

Sevenspotted lady beetle

Potato leafhopper adults are already present in all alfalfa fields we checked over the past week.  This is earlier than usual for these pests as they typically don’t migrate into the state for another month, between the 2nd and 3rd cutting.  Some of these populations already exceed the treatment threshold with just adults, so hatching nymphs will just increase the populations further.  These potato leafhopper populations need to be monitored throughout the rest of the growing season.

PLH adult and nymph

Alfalfa Update

By — Dr. Jeff Whitworth, Dr. Holly Schwarting

Alfalfa continues to be problematic in NC Kansas.  There seems to be many fields of good alfalfa, apparently treated in an effective manner from both an insecticide and a timing standpoint, and not affected by the freezing temperatures earlier this spring.  Many of these fields have been, or are being, swathed.  However, there are some fields that have had, or are having, a difficult time overcoming the combination of alfalfa weevil larval feeding, early season dry conditions, and the early spring freezing temperatures.  In all fields, the early season warmth sped up alfalfa weevil development and feeding, then the cooler temperatures slowed it back down.  Alfalfa weevil larvae were 1st detected in NC Kansas in early March.  Small, 1st instar larvae are still being detected in some fields.

AW larvae 13

Some larvae pupated and developed into adults as long as three weeks ago, and they are still in the alfalfa fields.  So, NC Kansas still has a significant number of adults.  Treating for adult alfalfa weevils is rarely effective, but swathing within 7-10 days should help manage both larvae and adults without an insecticide application.

AW adult

Adult potato leafhoppers have also been noted in alfalfa fields.  These usually migrate into Kansas between the 2nd and 3rd cuttings, so they are about a month early this year. Leafhopper adult (2)

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