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Extension Entomology

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European Pine Sawfly

–by Dr. Raymond Cloyd, Professor and Extension Specialist in Ornamental Entomology/Plant Protection

      European pine sawfly, Neodiprion sertifer larvae are out-and-about feeding on pine trees. Young larvae are 1/4 inch in length and olive-green in color with a black head (Figures 1 and 2).

Figure1

Figure 1

Figure2

Figure 2

Older larvae are >1.0 inch long with green stripes. The larvae are gregarious or feed in groups on the needles of a variety of pines, especially Scotch, red, and mugo pine. Larvae will strip the needles of mature foliage, leaving only the central core, which is white and then turns brown (Figure 3); eventually falling off.

Figure3

Figure 3

In general, larvae complete feeding by the time needles emerge from the candelabra. Therefore, those needles are not damaged. There really is only a minor threat of branch or tree death resulting from sawfly larval feeding. However, the loss of second- and third-year needles may be noticeable in landscape trees and ruin their appearance. In late spring, the larvae drop to the ground and pupate in brown, leathery cocoons at the base of trees. Wasp-like adults emerge in fall and lay eggs in the needles before winter. There is one generation per year in Kansas.

Although sawfly larvae look-like caterpillars; they are not caterpillars (Order: Lepidoptera) as they are related to ants, bees, and wasps (Order: Hymenoptera). The best way to tell a sawfly larva from a caterpillar is by the following: 1) sawfly larva have prolegs on every abdominal segment whereas caterpillars are missing prolegs on the abdomen and 2) caterpillar larva have hairs or crochets on their feet whereas sawfly larva do not have hairs or crochets on their feet.

Since sawfly larvae are not caterpillars, the bacterial insecticide, Bacillus thuringiensis subsp. kurstaki (sold as Dipel) will not directly kill sawfly larvae. Therefore, dealing with sawfly larvae involves hand-picking (you can wear gloves if you wish) or dislodging larvae from plants by using a forceful water spray. If necessary, there are a number of insecticides that may be applied to suppress populations of the European pine sawfly including acephate (Orthene), azadirachtin, carbaryl (Sevin), spinosad (Captain Jack’s DeadBug Brew and Conserve), and any pyrethroid-based insecticide with any of the following active ingredients: bifenthrin, cyfluthrin, and lambda-cyhalothrin). Be sure to read the insecticide label to make sure that sawflies are listed. For more information regarding European pine sawfly management contact your county or state extension specialist.

 

 

 

 

 

Alfalfa Weevil Update

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Alfalfa weevils continue to be very active throughout north central Kansas, and the Kansas spring weather continues its usual erratic conditions.  However, the alfalfa weevil larvae continue to feed voraciously.  They have been slowed a little by the cooler weather but, remember, they do continue to feed 24/7, any time the temperatures are at least 48°F.  Much like the last few years, 2016 seems to be a good year for alfalfa weevils with most fields having multiple larvae/stem, at various developmental stages.

AW larvae

AW feeding damage

Sugarcane Aphids

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Sugarcane aphids (SCA) colonies have rapidly declined in some fields in north central Kansas, slowly declined in others, but actually increased somewhat in other fields.  In one field, approximately 90% of all previous SCA’s are gone and enormous numbers of lacewing adults remain (see pics).  However, prior to the latest cold front, most top leaves had winged aphids with nymphs.  This means, evidently, that they are still migrating in and trying to establish colonies.  However, with huge numbers of beneficials now present, it seems unlikely that they will be successful, especially with the recent cooler weather.  Everywhere that SCA colonies became established, they produced honeydew, which coated the sorghum leaves, and was then covered with a dark sooty mold.  However, when the colonies are eliminated the honeydew is no longer sticky and the black mold becomes dry and washes off (see pic).

brown lacewing

green lacewing

 

old honeydew

Corn and Wheat Pest Update

–Dr. Jeff Whitworth and Dr. Holly Schwarting

Corn

Plants in north central and south central parts of the state are finally starting to grow.  All the cloudy, wet conditions have not been the best for corn development and many fields are a little more chlorotic looking than usual for this time of year.  This stalled development usually allows pests more time to feed and thus cause damage.  Seed treatments only provide protection for 3 to 4 weeks (check label) from planting, so most of that protection has dissipated.  However, we have not seen nor heard about much pest activity yet.  A few thin stands have been noted which can be caused by many different pests, probably most common so far has been wireworms.  Generally, however, most fields are past seedling damage.

wireworm 1

wireworm 2

We have received a few calls about armyworm activity in wheat and sorghum, so when these larvae pupate and then emerge as adults to lay eggs, most corn will be in the whorl stage so there may be some whorl-stage leaf feeding which is always highly visible but causes very little actual impact on yield.

Wheat

We have not seen any “worms” in wheat, but have received several calls about armyworms feeding on leaf tissue.  Armyworms should move to another grass host, i.e. corn, sorghum, brome, etc. as the wheat begins to senesce.  They actually devour leaf tissue and thus are not actually feeding on the grain.

Armyworm

If there are thin, light green or tan worms feeding on the wheat head they are probably wheat head armyworms (see photo).  They can and will actually feed on the grain whereas the armyworm feeds on the foliage around the grain – not the grain itself.

wheat head armyworm

If you decide to treat either pest, please refer to the Wheat Insect Management Guide, 2015: http://www.ksre.ksu.edu/bookstore/pubs/MF745.pdf and make sure to check the label for the preharvest interval (PHI) if spraying wheat this close to harvest.

Alfalfa Update

Wet weather has kept equipment out of the fields and has allowed the insects to flourish.  Fortunately, the plants are also doing well and tolerating these healthy populations of pests.  When these fields dry out and are able to be swathed, there will probably be relatively significant populations of alfalfa weevil larvae and adults still present.  They are accumulated into the windrows at cutting; they will feed on the stems under the windrows until the hay is picked up.  This causes the characteristic stripping in the fields where the regrowth under the windrows is chewed off while the areas beside the windrows grow back.  Once the hay is removed, the adult weevils will exit the fields and no longer be a problem.  Weevil larvae in north central Kansas on 7 May were 93% 3rd instar, and 7% 1st or 2nd instar.  There are many pupae and adults also.

weevil

weevil2

There are significant populations of aphids, mainly pea, in these central Kanas alfalfa fields as well.  Swathing will remove this problem, but there are many beneficial insects helping to regulate these aphids, and hopefully they will stay around after swathing to help manage any other aphids and/or potato leafhoppers that may show up (no leafhoppers detected yet).

aphidlacewing 2

Picture1lacewing

Some small grasshoppers were also noted.  Usually, grasshoppers do better in drier conditions, but not always.  So be aware that grasshoppers are present now and eggs will continue to hatch for the next month.

grasshoppergrasshopper2

—Dr. Jeff Whitworth and Dr. Holly Schwarting

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