Insect Strip

Insect Strip

Friday, June 27, 2014

An Abundance of Uncommon Insects

Leaf-footed Bugs

Last week Dr. Pat Porter, Extension Entomologist - Lubbock, reported in the Focus on South Plains Agriculture newsletter, Vol.53 no. 4, about an unusual pest he had seen feeding in corn. He identified it as one of the leaf-footed bugs, Mozena obtusa Uhler, that has been noted as an important insect attaching  mesquite trees. About this time a crop consultant, John Quillin, sent me a photo from his son in Lubbock showing this insect in heavy numbers on mesquite. Kerry Siders, Extension Agent - IPM for  Hockley and Cochran Counties, had a call from a PCO that described a bug like this on mesquites in home landscapes and in the pasture. Blayne Reed, Extension Agent - IPM for Hale and Swisher Counties, has also found large numbers of these leaf-footed bugs on mesquite. 

Cluster of Mozena obtusa on mesquite branch, Photo by Blayne Reed

Mozena obtusa on mesquite bush, Photo by Blayne Reed

Then on June 25, Dr. Porter sent an e-mail stating that these bugs and another similar looking bug were decimating pea plants in a pea seed increase trial at the Lubbock Research  and Extension Center. What he wrote was, “We have a leaf-footed bug at the Lubbock Center that is decimating the pea seed increase plots. This one is about 3/4 inch long and is grey. It looks a lot like Mozena obtusa that I reported on in FOCUS last week, but it is grey instead of yellowish. It might even be Mozena – there were Mozena in the pea field as well. It is certainly a Coreid – I keyed it out but have not had time to work on species ID. 

Mozena obtusa Uhler Adult, Photo by Pat Porter

Other Coreid bug on peas and weeds, Photo by Pat Porter

Anyway, there was around one insect for every 5 – 7 pea plants and they had been feeding many days before being discovered. The damage looks like thrips damage on steroids: young leaves wrinkled and yellow and the growing points decimated. Every plant in the field was damaged. Monti Vandiver stopped by yesterday ….. and he drove by the pea field. I asked him if he wanted to look at the insect damage and he said he thought the field was a herbicide damage trial. Blayne scouted some farmers market gardens today and found the insect on adjacent weeds. His theory is that once the weeds, which had been treated with herbicide, decline, the bugs will jump on the peas. I think he is right. 
I chose to spray bifenthrin (on the pea field at Lubbock) because that is the pyrethroid I had the most of. After application there were very few insects in the field, but I did not see many dead ones. It could be that the repellent effect of pyrethroids drove them out of the field before they were killed. Or maybe they were not killed? I don’t know. They were still abundant in my corn field that is adjacent to the pea field. . . . . I have been looking in cotton and can find no evidence that the insect is feeding there; I can find them but they seem to be incidental. I know for sure that they feed on corn, and if their numbers stay high they might be a pest during the ear stages, much like a stink bug. I am finding egg clusters in corn.” But since the e-mail Blayne has documented M. obtusa feeding in the terminals of cotton.

Damage to peas from Leaf-footed bugs, Photo by Blayne Reed

Mozena obtusa feeding damage (pin holes) to corn, Photo by Pat Porter

Dr. Porter and Blayne Reed have done an exceptional job identifying and documenting the potential threat of these two Coreid bugs to peas and possibly other legumes. 

White-lined Sphinx Caterpillars

The caterpillar stage of the white-lined sphinx (Hyles lineata) has caught the attention of a number of folks north of Amarillo. Again, John Quillin sent a photo of the caterpillars feeding on weeds in a pasture and Robert Bowling e-mailed asking about them. I came across these caterpillars a couple of years ago while working on a potato project in Dallam County. These caterpillars were feeding on a specific weed along the edges of potato fields and in pastures.

White-lined Spinx Moth
Photo credit: Whitney Crenshaw, Colorado State University,

The moth is commonly known as the hummingbird moth and the hawk moth and the  caterpillars are known as hornworms. Caterpillars widely vary in color from green with yellow, white, and/or black markings, but others are black forms with yellow markings.  They can reach unto 3 to 3 1/2 inches long and have a distinct spine on the back end. The hornworms develop on a variety of plants (willow, apple, elm) but mostly on Portulaca (moss rose), primrose, and wild grapes. Fortunately, they should not be an issue in field crops, but could visit the vegetable garden.  

White-lined Sphinx caterpillars showing different coloration patterns, Photos by Ed Bynum

Saturday, June 21, 2014

Early Fall Armyworm Moth Activity for the Texas High Plains

The last couple of weeks have seen a dramatic increase in the activity of the Fall Armyworm (FAW), Spodoptera frugiperda (J.E. Smith), moths.  Dr. Pat Porter, Extension Entomologist at Lubbock, has trapped an exceptional number of moths at the Texas A&M AgriLife Research and Extension (Figure 1). Moth trap catches from June 13 to June 19 reached an all time high of 900+ compared to trap catches for 2011 and 2013, which were well below 100. Even before these high numbers he reported finding FAW egg masses and whorl feeding damage (Figure 2).

Figure1. Comparison of weekly FAW moth trap captures for 2011, 2013, and 2014. Courtesy of Dr. Pat Porter

Figure 2. Whorl feeding damage of FAW to non-Bt corn, photo credit: Dr. Pat Porter

This early FAW activity has also been noted in Mississippi and Arkansas (Be Watchful for Fall Armyworms in Grassy Beans) where fall armyworms are moving from grassy fields to soybeans.

Moth trap catches for FAW have also begun to increase in many of the corn producing county across the Texas High Plains (Figure 3). Moth numbers have steadily increased from the first sample period from May 27 to June 2. Some counties or trap location within a county have not had much of a FAW moth activity. But, moths have been active in Hale, Hartley, Lipscomb, Moore, Randall, and especially in Parmer. If this moth activity continues to increase or becomes more wide spread across the region, we could begin to see whorl feeding activity in non-Bt refuge fields, refuge non-Bt strips,refuge-in-bag plants, grain sorghum, and on forage grasses and range pastures. This early moth activity could be a springboard to multiple generations this year. 

Figure 3. Comparison of FAW moth activity for counties in the Texas High Plains, 2014.

 Fall armyworms are generalist feeders and are known to feed on 80 different host species. The females are active at night laying egg masses on host plants and light-colored surfaces, such as fence posts and other objects. An egg mass is light gray with grayish fuzz and can contain just a few to hundreds of eggs. The eggs hatch within 2 to 4 days. The newly hatched larvae will disperse away from the egg laying site to other plants and will feed on exposed leaves for a few days (instars 1 to 3). As the larvae becomes 1/4 to 1/2 inch long they will move to the whorl when plants are in the vegetative growth stages. The larvae will continue to develop in the whorl from the mid-size (4th instar) to the last large larval stage (instar 6) before pupating. The last larval stage will be about 1 1/2 inches long. During this time in the whorl a caterpillar will consume 98% of all plant material eaten. The symptoms of ragged-edge chewed holes and frass can be seen in the whorl, but become more noticeable when leaves unfold out of the whorl. This damage can look substantial, but may not be as damaging as it appears. Research has shown that late whorl stage infestations of corn were less susceptible to feeding damage and yield losses than early to mid-whorl damage and pre-tassel growth stages. However, feeding damage to grain sorghum is most severe during the mid- to late whorl stages (5 leaf to boot) when the panicle is developing. Although studies have identified when corn and sorghum are most susceptible to whorl stage infestation, we still do not have any established thresholds based on economic losses from feeding damage to the whorl. Therefore, there are many different recommendations from state to state. For example, Purdue recommends treating corn if 75% of the plants have whorl damage and larvae are less than 1 1/4 inch long. Kentucky’s recommendation is when egg masses are found on 5% of the plants or when 25% of the plants have whorl damage and live larvae are present. For us on the Texas High Plains, economical control of FAW whorl infestations in corn is seldom achieved. And, for grain sorghum, our guide states “Insecticide application may be justified if larval feeding reduces leaf area by more than 30 percent or is damaging the developing grain head or growing point within the whorl.

So, will these high moth trap catches mean we will have damaging whorl infestations. Dr. Potter has a great deal of experience with FAW infestations. He stated “Non-Bt corn should be scouted but I do not expect any of the fields to reach the treatment threshold of 30 percent of leaf tissue removed. All of the types of Bt corn currently sold will do a good job of killing fall armyworm larvae. My biggest concern is the higher overall numbers of fall armyworms in the system. This could mean more yield loss in corn and sorghum down the road, but we will have to watch and wait”, (20, June, 2014, Focus on South Plains Agriculture, Vol. 53, no. 4).