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Alfalfa Update

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Alfalfa weevil feeding activity has slowed significantly in north central Kansas, at least south of I-70.  North of I-70, larvae are still developing and thus feeding, but even in the northern counties this feeding and resultant damage should be significantly reduced by the end of the next week.  There are still some small larvae but the majority of populations are pupating or have pupated.  Adult weevils are still hanging out in alfalfa fields and probably will until that 1st cutting, or temperatures get into the mid-80’s or warmer.

Geraniums and Petunias Beware of the Tobacco Budworm

By Dr. Raymond Cloyd

Have you noticed that your geraniums and petunias are not blooming (flowering)? Well, the “critter” or culprit causing the problem may be the caterpillar or larval stage of the tobacco budworm (Heliothis virescens). Adults are pale-green to light-brown with the forewing marked with four light wavy bands (Figure 1).

Figure 1: Tobacco budworm adult
Figure 1: Tobacco budworm adult

The wingspan is approximately 38.0 mm. Adult females can lay between 500 and 1,000 eggs within 2 to 3 days. Caterpillars are 38.0 mm in length when full-grown and vary in color depending on the host plants fed upon. The caterpillars (larvae) may be black, pale brown, yellow, green, and/or red. They may also possess stripes that extend the length of the body (Figure 2).

Figure 2: Mature larva (caterpillar) of tobacco budworm
Figure 2: Mature larva (caterpillar) of tobacco budworm

Furthermore, caterpillars may have small hairs or setae on localized sections of the body. The caterpillars tunnel into buds (Figure 3)

Figure 3: Tobacco budworm larva (caterpillar) tunneling into petunia flower bud
Figure 3: Tobacco budworm larva (caterpillar) tunneling into petunia flower bud

and feed from inside or chew flower petals, which appear ragged (Figure 4).

Figure 4: Tobacco budworm larva (caterpillar) feeding on petals of petunia flower
Figure 4: Tobacco budworm larva (caterpillar) feeding on petals of petunia flower

Damage usually increases during the growing season. Furthermore, caterpillars feeding inside flower buds on developing ovaries will destroy flowers. Be on the look-out for black fecal deposits (“caterpillar poop”) (Figure 5)

Figure 5: Black fecal deposits ("caterpillar poop") associated with tobacco budworm larva (caterpillar) feeding
Figure 5: Black fecal deposits (“caterpillar poop”) associated with tobacco budworm larva (caterpillar) feeding

on the flower petals or on leaves below the flowers, which is a clear indication that the caterpillars are feeding. Tobacco budworm caterpillars will feed on a number of annual bedding plants besides geraniums and petunias, including: ageratum, chrysanthemum, nicotiana, snapdragon, and strawflower. Ivy geraniums may be less susceptible than other geranium types. The way to deal with tobacco budworm populations is to apply insecticides before the caterpillars tunnel into the buds using materials containing the following active ingredients: spinosad, cyfluthrin, permethrin, or bifenthrin. Be sure to thoroughly cover all plant parts as tobacco budworm caterpillars will also feed on plant leaves.

 

You can find more information on tobacco budworm feeding on petunia in the following article:

Davidson, N. A., M. G. Kinsey, L. E. Ehler, and G. W. Frankie. 1992. Tobacco budworm, pest of petunias, can be managed with Bt. California Agriculture 46 (July-August): 79.

Termites vs. Ants

–Dr. Jeff Whitworth and Dr. Holly Schwarting

Termites and ants have both been swarming intermittently for the past couple of weeks.  Both species usually start swarming in April in Kansas, but the cooler April temperatures seemed to have delayed this behavior for about a month.

termite swarm

Please make positive identification of any insects you suspect may be a pest, but especially ants and termites because there is an enormous difference in the amount of damage potential of termites vs. ants.  Note that although carpenter ants may nest in wooden structures, they will not cause the same degree of damage as a termite infestation.  Because of this, the cost of management for a termite infestation is much greater than carpenter ants.  For more information on termites and ants, please visit:

Termites: https://www.bookstore.ksre.ksu.edu/pubs/MF2887.pdf

Ants: http://www.bookstore.ksre.ksu.edu/pubs/mf722.pdf

European Fruit Lecanium Scale: Adding a “Decorative Touch” to Bald Cypress

–by Dr. Raymond Cloyd

The European fruit lecanium scale (Parthenolecanium cornii) is quite noticeable on bald cypress (Taxodium distichum) twigs and branches. The damage associated with this scale, which depends on the extensiveness of the infestation, includes plant stunting and wilting. The European fruit lecanium scale is a soft scale, so honeydew (a sticky, clear liquid) will be produced during feeding. The honeydew serves as a substrate for black sooty mold and attracts ants. In addition, honeydew can drip onto vehicles parked underneath infested trees leaving unsightly residue.

The scales are dark brown, 1/8 to 1/4 inches in diameter (Figures 1 and 2). Some scales may have white markings on the body. European fruit lecanium scale overwinters as an immature on twigs and branches with maturing occurring in spring. In May and June, females lay many eggs underneath their bodies. In June eggs hatch into small tan-colored crawlers. The duration of an egg hatch can last several days depending on the temperature. Crawlers migrate to leaf undersides and subsequently feed on plant fluids until late summer. At that point, the crawlers migrate back onto twigs and branches to complete their development the following spring. There is one generation per year in Kansas.

Figure 2. MatureEuropeanFruitLecaniumScaleonBaldCypressMay2016 Figure 1. MatureEuropeanFruitLecaniumScalesonBaldCypressMay2016
Figure 1 & 2: Mature European Fruit Lecanium Scale on Bald Cypress

Management of European fruit lecanium scale primarily involves timely applications of insecticides. Applications should be made when crawlers are present because the crawlers are most vulnerable life stage to insecticide sprays. Mature scales possess a shell-like covering that protects them from exposure to insecticides. Repeat applications will be required as the eggs do not all hatch simultaneously but may hatch over a three to four-week period. The most appropriate time to apply insecticides is in late June to early July when the crawlers are feeding on leaves; thus enhancing their exposure to any spray residues. There are a number of insecticides, with contact activity that are effective in suppressing populations of the European fruit lecanium scale. However, many have broad-spectrum activity and will kill many natural enemies including: parasitoids and predators. In fact, most out-breaks of scale insects are caused by the indiscriminate use of pesticides (insecticides and miticides). Therefore, always read the label and exercise caution when applying any pesticide. In the winter, dormant oils can be applied to kill overwintering scales by means of suffocation.

I need to acknowledge Jeff Otto of Wichita, KS for bringing to my attention that European fruit lecanium scale was active. I have also observed infestations in Manhattan, KS.

Alfalfa Weevils

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Alfalfa weevil larvae were first detected in north central Kansas on 3 March. Mr. Chuck Otte, Ag and Natural Resources Agent, also reported finding small larvae on 5 March in Geary County and Mr. Tom Maxwell, Ag and Natural Resources Agent, also reported finding small larvae and pinprick-sized holes in new alfalfa leaves on 9 March in Saline County. So, ready or not, alfalfa weevil larvae are here and, I would bet, many more will be hatching in the next few days to weeks. Alfalfa weevils will continue to hatch and larvae continue to develop any time temperatures exceed 48°F – and those temperatures have been much more common over the last few weeks than usual. Forecasts for the next 7-10 days also look for warm conditions. Thus, it looks like larvae will be emerging, and damage progressing, relatively quickly. Whether this warm weather will compress the alfalfa weevil larval feeding so that the damage is not as stretched out as usual remains to be seen. There are also many lady beetles present in the alfalfa fields we have checked as well as a few pea aphids. Treatment thresholds we use for alfalfa weevil insecticide applications are 30-50% infestation, i.e. 1 larva/2-3 stems.

For more information on alfalfa weevils, please visit:

http://www.bookstore.ksre.ksu.edu/pubs/mf2999.pdf

eggs in stem

Overwintering alfalfa weevil eggs in stem

alfalfa weevil

Early instar alfalfa weevil larvae

pinprick feeding damage

Pinprick feeding damage

 

Bagworms —- Current Status, and What to Do

–by Dr. Bob Bauernfeind

For the past several weeks, in Ward Upham’s compilation of Hot Topics, bagworms have been mentioned.  Last week, they were designated as Pest of the Week.   This is not a real surprise given the time of the year.  Why?  As pictured below, the colored time frames are indicative of bagworm feeding capabilities.  Smaller (generally overlooked) larvae in the green and yellow zones represent periods when larvae are small “nibblers” — negligible visible feeding damage.

The orangish/amberish represents “caution” — larger larvae becoming more destructive but not necessarily causing noticeable damage.  But now (August) is the red danger zone where (as is typical for all lepidopteran larvae) rapidly growing larvae in their last feeding stages consume the greatest amount of foliage (create the most noticeable damage) that has people reacting to the presence of bagworms.

1

The question now is, “Is it too late to spray for bagworms?”  Currently, it is not too late to spray!  Notwithstanding their size, as long as bagworms are actively foraging, they can be effectively controlled.  Those directly hit by an insecticide spray will be killed by contact action.  Those withdrawn into their bag at the time of the spray application will likely succumb after coming-in-contact with treated foliage, but most certainly after consuming treated foliage.

How does one determine if bagworms are actively feeding?  OBSERVATION!  “Active bags” can be identified by newly-clipped greenery at the bag opening.  Also, with a bit of patience, simply watch for a bagworm to reopen its bag, poke out its head, and resume feeding.

2

When is it too late to spray for bagworms?  That also is easily determined.  When a bagworm completes its feeding cycle, it anchors its bag to the host plant with a distinct, highly visible white silken “tie”, after which it permanently closes the “front door”.  Spraying at this point-in-time is futile because the thick leathery bag protects the bagworm within.

3

According to NPIRS (National Pesticide Information Retrieval System), currently in Kansas, there are 500 products registered for use against bagworms.  Some active ingredients currently contained in insecticides available for purchase and use by homeowners include acephate, Bacillus thuringiensis, bifenthrin, carbaryl, cyfluthrin, cyhalothrin (gamma and lambda), deltamethrin, malathion, permethrin and spinosad.  In various trials, I have used the bolded AIs and found them all to be effective against bagworms, even those considered large and close to the end of their feeding cycle.  Some homeowners may still be in possession of discontinued products with the active ingredients chlorpyrifos, dimethoate and/or diazinon.  All were effective against bagworms in trials.  Although it does not appear to have been written into any legalized directive (per personal communication with the KDA), discontinued products may still be used if done in accordance with the instructions appearing on the product label.  Residents may not share or give partial containers to neighbors as this would be considered distribution.

Excluding products containing Bacillus thuringiensis (minimal effectiveness against larger instar larvae), regardless of which product/AI is applied, the critical factor for successful bagworm population reduction is THOROUGH COVERAGE TOP-TO-BOTTOM!  Hastily applied light/misty sprays to tree and shrub peripheries will lead to disappointing results.

.

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.

Ash/Lilac Borer Activity

—Dr. Robert Bauernfeind

Not to beat a dead horse given that Dr. Cloyd’s KIN #2 article addressed the facets of ALB development/damage/control, and last week’s update in KIN#3 substantiating the actual initiation of the 2015 flight activity, but I noted that the table was incorrect in the “Date” column. So to correct that, I have entered the proper dates, and also added in this week’s flight numbers. Again, as can be seen, these moths just don’t fly at temperatures below 70. So this week when temperatures were into the 70’s, moths were active. And, no more wrens.

Screen Shot 2015-05-02 at 9.45.33 AM

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