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Extension Entomology

Tag: potato leafhopper

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)

Leafhoppers in Alfalfa

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Alfalfa can be kind of a forgotten crop during this very busy time of year.  Most growers are busy planting sorghum, soybeans, sunflowers, and/or harvesting wheat, working wheat ground, etc.  This year, so far, has been a rough one for swathing and baling alfalfa.  Now, there are substantial infestations of potato leafhoppers, both adults and nymphs.  Potato leafhoppers can be quite damaging from now until fall.

Leafhopper adult

Leafhopper nymph

 

Both nymphs and adults feed by sucking juice from the plant and in so doing inject a toxin into the plants.  This can cause serious yellowing of the leaves, and even stems, if it continues for very long.  Generally, swathing and hay removal will disrupt this feeding and remove the leafhoppers from the fields.  They rarely re-infest fields after this physical removal or after an insecticide application, if that is justified.  If swathing is possible within the next 7-10 days, that should take care of the potato leafhopper problem.  However, be sure to keep scouting these fields as the damage caused by potato leafhoppers usually occurs much before the yellowing is noticed.  This feeding damage is cumulative – the stressed plants don’t seem to regain their original vigor and therefore don’t ever yield as much tonnage as expected.

Alfalfa – Pest Update

–by Dr. Jeff Whitworth, Dr. Holly Schwarting & J.R. Ewing

Cool, wet weather continues to dominate the state. This has allowed the alfalfa weevil adults to remain in the alfalfa fields. As they remain in fields they are feeding in/on terminals and the new foliage. However, they don’t feed anywhere near as much as the larvae, plus there aren’t near as many so, the feeding really is negligible. However, they do cause concern and their feeding on the new foliage and “barking” of the stems can slow regrowth if they remain in fields. Swathing alone will not eliminate the adults if the weather continues to be only in the 80’s for daytime highs.

 

AW adult barking

The first potato leafhoppers of the summer were detected in north central Kansas on 19 May. This is a little earlier than usual but fits right in with the unusualness of this spring.

Pea aphid populations have been steadily increasing the past couple of weeks. However, sampling some of the same alfalfa fields on 19 May indicated the aphid populations have reduced relatively dramatically. There are many larval and adult lady beetles in these fields and they can even be readily observed feeding on the aphids. So, these beneficials really seem to be helping with aphid control.

lady beetle larvae w aphid