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Extension Entomology

Tag: beneficials

Spiders

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

 

 

Many spiders are reaching maturity this time of year and numerous species stretch webs everywhere trying to catch a few insects before cold weather sets in.  Although large, and to many frightening, most are totally harmless and all are beneficial by eating other insects including mosquitos and flies which are currently numerous.

golden-garden-spider

 

golden-garden-spider-on-web

orb-weaver

 

Sorghum Pest Update

— by Dr. Jeff Whitworth, Dr. Holly Schwarting and J.R. Ewing

Much sorghum throughout north central Kansas is at least in the soft dough stage and thus has passed through the most susceptible stages for sorghum headworm infestations.  However, any sorghum yet to head out will still be susceptible to these headworms as there will still be at least one more generation.

All four aphids species, corn leaf, greenbugs, sugarcane, and yellow sugarcane, are still in every sorghum field we sampled throughout north central Kansas.  All populations seem to be increasing but there are relatively healthy populations of beneficials present as well.

SCAwLB

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 Update

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Chinch bugs are really common in sorghum fields throughout north central Kansas.  Their feeding will weaken stalks if dry conditions are prevalent.

Green lacewing eggs were present, indicating the presence of future beneficials to help with control of potential future aphid populations.

lacewing egg

chinch bug nymps2

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”

 

Sugarcane Aphids

–by Dr. Jeff Whitworth, Dr. Holly Schwarting and JR Ewing

Sugarcane aphids were still active in north central KS on 23 and 27 October, as were the beneficials (see pics).  Fields were being harvested and getting acceptable yields (growers reported 80 to 160 bu/acre, which they said was usual for the fields involved) without much interference caused by the stickiness of the honeydew (and it is sticky).

SCA Oct_leaf

 

SCA oct head

 

beneficials - aphids

Below are the results of sugarcane aphid efficacy trials conducted in Saline Co.  Aphid populations were, in our opinion, ideal for conducting trials of this nature because there were enough aphids to show any differences caused by the treatments, but not so many that the plants were overwhelmed or that the grower sprayed the field (thereby over-spraying these plots).

SCA efficacy trial 1

 

Means within a column followed by the same letter are not significantly different (P>0.05; PROC ANOVA; Mean comparison by LSD [SAS Institute 2003]).

SCA efficacy trial 2

 

Means within a column followed by the same letter are not significantly different (P>0.05; PROC ANOVA; Mean comparison by LSD [SAS Institute 2003]).

Wheat – Aphids

—by Dr. Jeff Whitworth – Dr. Holly Schwarting – J.R. Ewing and Salehe Abbar & Dr. Brian McCornack

Wheat aphids, primarily greenbugs, but bird cherry oat and English grain aphids as well, continue to migrate into wheat fields all over the state. However, there are increasing numbers of lady beetles and parasitic wasps (see photo of mummy). Hopefully these beneficials will keep these aphids well below treatment thresholds.

Screen Shot 2015-05-02 at 9.46.18 AM

More information about greenbug identification,  current management recommendations, or their natural enemies can be found on the myFields.info website (www.myfields.info).

 

Alfalfa – Weevils and Aphids

—by Dr. Jeff Whitworth and Dr. Holly Schwarting

Alfalfa weevils continue to be very active in north central Kansas. The recent cooler weather has slowed down development a little but they are still feeding. We determined development from larvae collected on 20 and 22 April. Here is what the population breakdown looks like:

20 AprilNo. larvae   23 April No. larvae
12 1st Instars 4
25 2nd Instars 16
15 3rd Instars 30
   numerous Pupae numerous

alfalfa weevil

So what does this mean? Alfalfa weevil larval feeding will continue for another 7-10 days, depending on the weather. Egg hatch and consequent larval feeding has been going on since 13 March in north central KS. Insecticides applied since that time have provided adequate protection, for the most part.

field trial

This photo shows KSU chemical efficacy trials with many different products being tested, and the obvious untreated plots plus the border around the plots. The rest of the field was treated with Stallion® by MKC in Abilene, KS and, as illustrated here seemed to work relatively well with 1 application. Remember, feeding will continue for at least another week and therefore treatment (or re-treatment) may still be appropriate.

Alfalfa aphids, mainly pea aphids, are becoming more numerous throughout north central Kansas. Treating for alfalfa weevils probably pretty much decimated the natural enemies/beneficials and they will not repopulate as quickly as the aphids migrate in to infest fields.

 

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