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Extension Entomology

Month: May 2016

Oak Vein Pocket gall: Back with a Vengeance!

Posted on by Jena Ernsting

–by Dr. Raymond Cloyd

We have received numerous inquiries (in fact…LOTS) regarding gall-like growth on the underside of pin oak (Quercus palustris) leaves. In some cases, many pin oak trees have extensive galling on nearly all the leaves, with the leaves twisted or distorted. In fact, one tree on the Kansas State University (Manhattan, KS) campus, located behind Umberger Hall, is nearly 100 percent infested with this gall. I really think the gall makes the tree more attractive J. The culprit is the oak vein pocket gall, which is caused by the gall-midge, Macrodiplosis quercusoroca. Galls are elongated, pocket-like swellings on the lateral veins and mid-rib of pin oak leaves (Figures 1 through 3). The gall-making organism is a small fly called a midge (Family: Cecidomyiidae). Adults are 3.0 mm long and resemble small mosquitoes (but they are not mosquitoes so do not worry). Female midges attack newly developed leaves that are unfolding – just before they are flattened. After the eggs hatch, small larvae or maggots migrate to the lateral and mid-veins, and subsequently begin feeding. After several days, tissue forms and surrounds each larva. Full-grown larvae are white and approximately 2.0 mm in length. Development is completed by mid-spring to early summer. The larvae eventually emerge from the gall, fall to the ground, and overwinter or enter diapause (a physiological state of arrested development) until the next spring. There is one generation per year. There are no control measures for this gall. Remember, this is not the gall-former that the oak leaf itch mite feeds on…that is the marginal oak leaf fold galler (Figure 4).

Figure 1. Oak Vein Pocket Gall
Figure 1: Oak Vein Pocket Gall

Figure 2. Oak Vein Pocket Gall
Figure 2: Oak Vein Pocket Gall

Figure 3. Oak Vein Pocket Gall
Figure 3: Oak Vein Pocket Gall

Figure 4. Leaf Marginal Fold Gall
Figure 4: Leaf Marginal Fold Gall

I want to acknowledge Matthew McKernan; Horticulture Agent (Sedgwick County; Wichita, KS) for keeping me abreast of the situation (and sending images) regarding the oak vein pocket gall in south-western Kansas.

Corn Update

Posted on by Sharon Schroll

By — Dr. Jeff Whitworth, Dr. Holly Schwarting

Most corn has been planted in SC and NC Kansas, although some has been struggling somewhat with the cooler temperatures, wet soils, etc.  Whatever the case, please remember insecticide seed treatments do a good job of protecting the seed and germinating plants, but not forever.  About 3-4 weeks of protection from the time of planting can be expected but after that, wireworms, white grubs, etc. may affect the seedlings, especially under less than ideal growing conditions.

Wheat Update

Posted on by Sharon Schroll

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.

Alfalfa Update

Posted on by Sharon Schroll

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)

Mosquitoes: How to Avoid Getting “Bitten” By This “Sucking” Insect

Posted on by Sharon Schroll

–by Dr. Raymond Cloyd

The current wet weather and issues associated with the Zika virus have people “on edge” regarding mosquitoes (Figure 1). However, the common strategies that must be implemented to avoid mosquito bites is the same regardless of the mosquito-disease (e.g. virus) relationship. The three primary strategies that will help to avoid mosquito problems include: 1) source reduction, 2) personnel protection, and 3) insecticides.

ReFigure1. MosquitoMagnetSign

1) Source Reduction

First of all, it is important to routinely eliminate or reduce all mosquito breeding sites, which will effectively decrease mosquito populations, by removing stagnant or standing water from any items or areas that may collect water. These include the following:

  • Wheelbarrows, pet food or water dishes, saucers underneath flower pots, buckets, tires, toys, wading pools, birdbaths, ditches, and equipment. In addition, be sure that gutters drain properly and do not collect water.

2) Personnel Protection

Protect yourself from mosquito bites by delaying or avoiding being outdoors during dawn or dusk when mosquitoes are most active. Use repellents that contain the following active ingredients: DEET (Figures 2 and 3) or picaridin (Figure 4). DEET may provide up to 10 hours of protection whereas picaridin provides up to 8 hours of protection. In general, a higher percentage of active ingredient in the product results in longer residual activity or repellency. For children, do not use any more than 30% active ingredient. Furthermore, do not use any repellents on infants less than 2 months old. Clothing can be sprayed with either DEET or permethrin (pyrethroid insecticide). Afterward, always wash clothing separately. Before applying any repellent be sure to read the label carefully.

ReFigure2. DEETRepellent

ReFigure3. DEETRepellents

ReFigure4. PicaridinRepellent

3) Insecticides

For stationary ponds there are several products that may be used, such as, “Mosquito Dunks” (Figure 5) and/or “Mosquito Bits” (Figure 6), which contain the active ingredient, Bacillus thuringiensis subsp. israelensis. The active ingredient is a bacterium that is ingested by mosquito larvae, and subsequently kills them. The bacterium only directly kills mosquito larvae and has no effect on fish or other vertebrates. Try to avoid making area-wide applications of contact insecticides because these types of applications are generally not effective, and the applications may potentially kill many beneficial insects and pollinators (e.g. bees).

ReFigure5. MosquitoDunks

ReFigure6. MosquitoBits

What Does Not Work Against Mosquitoes 

The following items will not control mosquitoes:

  • Mosquito repellent plants (citronella plants), bug zappers, electronic emitters, and light traps/carbon dioxide traps.

 

If anyone has questions or comments regarding mosquito control please contact your state extension office or Department of Entomology at Kansas State University (Manhattan, KS).

Transform approved for use in Kansas to control sugarcane aphid

Posted on by kansasbugs

—by the KSRE Field Crop Extension Entomology Team

This week, Kansas received a section 18 approval for the use of Transform (sulfoxaflor) against sugarcane aphid for 2016, which will give sorghum growers two effective materials to manage aphid infestations. Note, there are differences in price between these two products, which should be factored into any treatment decisions, especially when multiple applications may be necessary.

Recent reports have sorghum receiving insecticide treatments for relatively light populations of sugarcane in south Texas, but the aphid is beginning to slowly move north, so the potential exists for much earlier infestation of Kansas sorghum this year. There are also confirmed reports that the aphid overwintered on Johnsongrass rhizomes just north of Lubbock, TX. This is about about 80 miles further north than in 2015. Reports from Texas indicate some of the cultivars rated as resistant seem to be holding up well, probably with the assistance of good natural enemy populations.

The Sorghum Checkoff has a list of ‘tolerant’ (= resistant) hybrids, but it does not indicate any regional adaptations for the hybrids. We have not yet ranked Kansas-adapted hybrids for resistance to sugarcane aphid, but efforts are underway to evaluate hybrids this summer. We strongly recommend that growers and extension agents contact their local entomology specialists for advice, as management recommendations will vary regionally.

Scout early, scout often, and know before you spray!

 

Wheat

Posted on by Sharon Schroll

–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”

 

Alfalfa

Posted on by Sharon Schroll

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

   Alfalfa weevils continue to be very active throughout NC KS. This past week the weevil populations were still plentiful and in all stages, including very small 1st instar larvae. This is really unusual, as we started finding 1st instar larvae back in the 1st part of March. This is really a testament to the fluctuating temperatures that we have seen over the last 2 months, with a relatively warm winter/early spring then a major cool down with several nights of freezing temperatures which have slowed down weevil development significantly. Please remember, if an insecticide application is still warranted, check the Pre Harvest Interval (PHI) for the product of choice.