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Alfalfa Update

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

 

Alfalfa weevil populations in north central Kansas seem to be developing as expected.  Fields sampled this week that had not yet been treated had greatly reduced foliage and were showing obvious signs of significant larval feeding, especially compared to fields that had been treated.

 

 

The good news is that the treated fields seem to be doing well and the untreated fields will probably only continue to be seriously impacted for about another week.  Weevil populations are predominately pupae, pre-pupae, or mature larvae which should cease feeding in the next few days.

 

 

This should give the alfalfa a chance to recover.  However, in untreated fields, and even fields that were treated later, after a majority of the larvae pupated, may have some adult feeding, as they may remain in fields until the 1st cutting or until temperatures start getting into the higher 80’s °F.  Adults feed a little on foliage and/or may cause ‘barking’ on stems, but this usually doesn’t stress plants too much unless there are significant numbers of adults.

 

Very few aphids were detected, but there were a few so periodical sampling should continue to ensure that these aphid populations remain at insignificant levels.

 

Sorghum Pests Update

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Double cropped sorghum may still have some ragworm feeding during the whorl stage (see photo).  In addition, there will probably be at least one more generation of headworms and thus later planted sorghum needs to be monitored for headworms between flowering and soft dough when it is vulnerable.  Also, continue monitoring for aphids as there still seems to be a pretty good mixture of greenbugs, corn leaf, yellow sugarcane, and sugarcane aphids.  Some of the fields treated for headworms have reduced numbers of beneficials so they may not be there in sufficient numbers to help control these aphids.  However, some of the fields sampled this week that were sprayed for headworms at least 2 weeks ago had pretty good populations of beneficials already building back up.

sorghum headwormsfall armyworm_sorghum

 

 

Sorghum Pest Update

— by Dr. Jeff Whitworth and Dr. Holly Schwarting

The situation seems about the same throughout north central Kansas with regard to insect pests.  Still finding mixed populations of aphids (greenbugs, corn leaf, yellow sugarcane, and sugarcane) but beneficial insect populations (mainly green lacewings, lady beetles, parasitic wasps, and occasionally syrphid fly larvae) still remain plentiful.  Headworms are also plentiful in just about every field that is not yet at soft dough.  Remember, expect 5% loss/worm/head between flowering and soft dough.  Chinch bugs, both adults and nymphs, are also plentiful at the base of most plants but can also be found feeding on young developing berries in the heads.

Spirea Aphid: Watch out for this “Sucking” Insect

–by Dr. Raymond Cloyd

Spirea aphid (Aphis spiraecola) is present feeding on spirea (Spiraea spp.) plants in landscapes. Spirea aphid colonies aggregate on terminal growth (Figures 1 and 2) and their feeding causes leaf curling and stunted plant growth. Spirea aphids prefer to feed on stems and leaf undersides of succulent plant growth. All mature aphids are parthenogenic (reproduce without mating) with females giving birth to live nymphs, which themselves are females. Eggs are laid on bark or on buds in the fall by wingless females after having mated with males. Eggs hatch in spring, and young nymphs develop into stem mothers that are wingless. Spirea aphid females are pear-shaped and bright yellow-green. Stem mothers reach maturity in about 20 days. Each spirea aphid female can produce up to 80 offspring or young females.

Figure 2. SpireaAphidsAggregatingonTerminalGrowthofSpireaPlant
Figure 1: Spirea Aphids Feeding on Spirea Plant

Figure 2. SpireaAphidsAggregatingonTerminalGrowthofSpireaPlant
Figure 2: Spirea Aphids Aggregation on Terminal Growth of Spirea Plant

Although the aphids produce honeydew (sticky, clear liquid); continual rainfall will wash the honeydew off plants. In the summer, both winged and non-winged aphids may be present. The winged forms usually appear when conditions become crowded on infested plants, in which they migrate to a more suitable food source, such as another spirea plant to start another colony. Heavy rainfall and strong winds will dislodge spirea aphid populations from plants onto the ground, where they eventually die. Frequent applications (twice per week) of forceful water sprays will quickly remove spirea aphid populations without disturbing natural enemies such as parasitoids and predators. They have a number of natural enemies including: ladybird beetles, green lacewings, and hover flies that may help to regulate spirea aphid populations.

Spirea aphids are, in general, exposed to regular applications of pesticides such as insecticidal soaps (potassium salts of fatty acids) and/or horticultural oils (petroleum, mineral, or neem-based) that may be effective in suppressing populations of spirea aphid. These pesticides have contact activity only, so thorough coverage of all plant parts is important. Furthermore, these pesticides are generally less harmful to natural enemies compared to conventional pesticides.

Wheat Update

By — Dr. Jeff Whitworth, Dr. Holly Schwarting

Wheat fields sampled in NC Kansas over the last week have diminishing populations of aphids.  Many fields had to be sampled relatively vigorously to find any aphids.  However, lady beetles are still quite plentiful which should bode well for not allowing the aphid populations to rebound.

Scattered white heads are starting to be easily distinguished in the green wheat.  If the stem pulls out easily, with some apparent feeding in the stem, this is from the wheat stem maggot.

wheat stem maggot

The number of infested stems in always negligible relative to yield loss but often causes concern because of the easily noticed white heads.

Wheat

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

 Still finding aphids in wheat throughout NC and SC KS. But in all fields sampled last week there were many lady beetles and mummies, indicating the beneficials are also very active. Spraying aphids will kill most of the aphids at the top of the plants– but won’t kill all the aphids down in the canopy just because the leaves in the canopy intercept the spray. But it will, typically anyway, kill all the beneficials as they move around searching for aphids to consume. Therefore, it is rarely a good idea to add an insecticide to a fungicide application to save application costs UNLESS the insecticide is warranted-not “just in case”

 

Here Comes The Asian Ladybird Beetle!

–by Raymond Cloyd

This is the time of year when the Asian ladybird beetle, Harmonia axyridis adults start entering homes and becoming a nuisance. The Asian lady beetle is a native of Asia and was introduced into the southeastern and southwestern portions of USA to deal with aphids on pecan trees. However, the Asian ladybird beetle has spread rapidly to other portions of the USA. The Asian ladybird beetle is a tree-dwelling ladybird beetle, more so than the native species of ladybird beetles, and is a very efficient predator of aphids and scales.

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During fall and early winter, when the weather is cooler, Asian ladybird beetle adults start aggregating on the south side of buildings and entering homes. The beetle does this because in their homeland of China they inhabit tall cliffs to overwinter. There are very few “tall cliffs” in Kansas—so the next best thing is a building.

The Asian ladybird beetle can be easily distinguished from other species of ladybird beetles by the presence of a pair of white, oval markings directly behind the head, which forms a black M-shaped pattern. Adults are 1/4 inch long, 3/16 inch wide and yellow to dark-orange colored. In addition, their body is usually covered with 19 black spots. Adults can live up to 3 years. Female beetles lay yellow, oval-shaped eggs in clusters on the underside of leaves. The eggs hatch into larvae that are red-orange and black in color, and shaped like a miniature alligator. The larvae are primarily found on plants feeding on soft-bodied insects such as aphids and scales. They eventually enter a pupal stage. Pupae can be seen attached to plant leaves. The adults emerge from the pupae and start feeding on aphids. Adults can be found on a wide-variety of trees including apple, maple, oak, pine, and poplar.

Asian ladybird beetle adults are a nuisance pest because they tend to aggregate and overwinter inside buildings in large numbers. The beetles release a pheromone that attracts more beetles to the same area. Although the beetles may bite, they do not physically harm humans nor can they breed or reproduce indoors. Beetles are attracted to lights and light-colored buildings, especially the south side due to the warmth provided when they bask in the sunlight. The beetles then work their way into buildings through cracks and crevices. Dark-colored buildings generally have fewer problems with beetles (so now is the time to paint your house). Adult beetles will feed on ripening fruit such as peaches, apples, and grapes creating shallow holes in the fruit. Large numbers of beetles feeding on fruit may cause substantial damage so that the fruit is less appealing for consumption.

Beetles may be prevented from entering homes by caulking or sealing cracks and crevices. Beetles already in homes can be physically removed by sweeping them or vacuuming. Be sure to thoroughly empty the vacuum bags afterward. Do not kill the beetles. Just release them outdoors underneath a shrub or tree away from the house. Commercially available indoor light traps can be used to deal with beetles indoors. The traps need to be placed near the center of a room and they are only effective at night in the absence of competing light. In addition, they work best when room temperatures are 75°F or higher.

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If crushed, the beetles will emit a foul odor and leave a stain. The dust produced from an accumulation of dead Asian ladybird beetle adults behind wall voids may incite allergies or asthma in people. Although there are some sprays available, the use of insecticides is not recommended for indoors.

Homeowners that want to avoid dealing with overwintering beetles entering their homes can hire a pest management professional to treat the points of entry on the building exterior with a pyrethroid insecticide. The treatments need to be made in late September or early October before the beetles enter the building to overwinter. Beetles that are feeding on fruit can be “controlled” with insecticides commonly labeled for use on fruit trees.

An old friend revisited – Wooly maple/briar aphids (WMBA)

–Dr. Robert Bauernfeind

An old friend revisited – Wooly maple/briar aphids (WMBA)

It has been a number of years since I have had occasion to address wooly briar/maple aphids.  And matching dates of past encounters, the timing is right on (in 2007, June 1, and in 2009, May 29).

 

The inclusion of two very different host plants might have a person asking, “Well, are they on maple or are they on briar?”  In fact, both a primary woody host (maple) and an unrelated secondary/alternate herbaceous host (brier) are required for these aphids to complete their seasonal life cycle.

 

Despite their rather simple and familiar appearance, some aphid species (such as wooly maple/brier aphids) have very unusual and complex reproductive adaptations.   While most people are aware that the aphids which they encounter in their gardens and landscape plantings are all females which (in the absence of males) reproduce parthogenically by giving birth to living offspring, sexual forms are required for mating purposes and the eventual production of overwintering eggs.  This is where maple trees come in —  where (in the Fall) WMBA deposit overwintering eggs.

 

Thus, beginning in Spring, each 1st generation aphid emerging from an overwintered egg is a wingless female called a fundatrix (foundress-of-a-colony).  The offspring of each succeeding generation (all females, called fundatriginae) also produce living young.  These aphids eventually become overcrowded as they colonize twigs and branches.

 

1-Shannonjpg

While the above-pictured aphids appear to be “normal aphids”, they aren’t called wooly aphids for no reason.  That is, these aphids possess specialized wax-producing glands.  And at some point, they will begin producing white flocculent strands which provides them with their “wooly appearance”.

2-WMBAjpg

While not being sure of the exact stimulus at work, at some point, possibly overcrowding and constant touching/bumping-into-each-other “triggers” an internal response mechanism promoting wing production in developing aphids.  By mid- to late June, those aphids (again, all females which are now called exules) emigrate from their woody maple host to their alternate herbaceous host which, in Kansas, would likely be the plentifully-abundant greenbrier.

Upon reaching the summer host, exules deposit their offspring (you guessed it, all wingless females) which in turn account for additional summer generations on their briar hosts.  Upon entering Fall, shortened daylight hours hourst, decreased temperatures or a combination of both set off another change in aphid forms (now called sexuparae) of which there are two types:  Gynoparae are winged females which emigrate back to the primary host where they produce wingless females called oviparae;  and androparae are winged females which emigrate back to the primary host where they produce wingless males.  Males mate with oviparous females which then deposit the aforementioned fertilized overwintering eggs.

Now to the discussion on wooly maple/briar aphids that most readers care about.  Are they harmful?  Is there a need to control them?

The only real complaint leveled against wooly maple/briar aphids revolves around the “sticky mess” which they are responsible for.  WMBA congregate on the twigs and branches of the different varieties of sugar maples.  They insert their piercing-sucking mouthparts into the phloem elements which conduct the flow of plant juices/sap.  Fairly stationary, aphids continually withdraw the sugar-rich sap.  The excess juices are eliminated/excreted in the form of “honeydew”.  The honeydew “rain” will coat anything beneath WMBA-infested  trees  — vehicles, sidewalks, driveways, house decks, picnic/patio furniture, children’s swing sets and toys, items on clothes lines, and so on.  Being sticky and nutrient-rich, captured airborne fungal spores can proliferate into unsightly accumulations of dark-colored sooty mold.  But other than that, trees easily withstand wooly maple/briar aphid infestations as seen below.

3-Mapletreejpg

While insecticidal sprays and/or the use of forceful water sprays might seem called for, neither is practical in practice.  And, unnecessary!  By the time such infestations are discovered, within a very short period of time (2 weeks, possibly less), as described in the prior explanation of their seasonal developmental cycle, they will quickly dissipate on their own when they seek out their alternate summer host.  IT IS HIGHLY UNLIKELY THAT THEY WILL FIND THEIR WAY BACK TO THE SAME TREE HOST FROM WHICH THEY IMMIGRATED —- at least by my experiences/inspections.

Maybe one last-and-legitimate gripe:  handle with care.  They do leave a hard-to-remove stain that might relegate good clothing to a wear-only-at-home status.

4-Hand-stain

 

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

Alfalfa – Weevils and Aphids

—Dr. Jeff Whitworth – Dr. Holly Schwarting – J.R. Ewing and Salehe Abbar

Alfalfa weevil feeding is winding down in north central Kansas, but not as fast as usual. If treatment is still considered prior to swathing do not forget to read the label and follow the PHI (post-harvest interval) required by the product you choose. The untreated control plots in our insecticide efficacy trials are still above our treatment threshold of 1 larva/2 stems, or 50% infestation, and contain many small larvae. Remember, larvae were 1st detected on 13 March so they have been actively feeding for six weeks. However, the good news is many insecticides are still providing excellent protection from one application three weeks ago. See below:

Screen Shot 2015-05-02 at 9.46.15 AM

Aphids continue to increase in alfalfa fields. They are primarily pea aphids with a few spotted aphids. Have not seen or heard of any at, or even close to, treatment thresholds, but populations are increasing. Lady beetle and parasitic wasp populations seem to be rebounding which should help slow down these aphid populations.

 

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