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INSECTS AND WEEDS IN FOCUSWeb site: http://entowww.tamu.edu http://agfacts.tamu.edu/~rparker/

VOL. XXIX NO. 12 ENTO/WS July 27, 2004

T WOOLY APHID ATTACK HACKBERRYT FALL ARMYWORM REPORTED IN

PASTUREST COTTON MATURING RAPIDLY IN

LOWER GULF COAST COST COUNTIEST CHARCOAL ROT FOUND IN COTTON

BOLLST RENEWED FOCUS ON NEPS IN COTTONT INTERESTING INSECTS

WOOLY APHID ATTACKHACKBERRY

A species of woolly aphid has been attacking hackberryin the Coastal Bend for several weeks resulting in blackleaves as a result of sooty mold growing in thehoneydew excreted by the aphids. The species may bethe Asian woolly hackberry aphid that was introducedinto the United States a number of years ago whichsubsequently spread throughout the southern states.Defoliation of trees has been noted, but these treesshould replace the leaves over the next several weeks.The aphids appear as puffs of small white balls on theleaves; winged individuals readily fly about and canoften be seen in large numbers in the air. In casecontrol is needed, many insecticides used on ornamentaltrees will reduce their numbers. One of the mostcommon insecticides being used is acephate (Orthene).

The woolly aphid group are interesting insects.Cornicles (pair of tubular structures on the end of theabdomen of many aphid species) are reduced or absentin the group, and wax glands are abundant. The waxglands produce the long waxy threads which give theaphids the woolly look. This wax acts as a deterrent tomany natural enemies. The sexual forms lackmouthparts, and the egg laying female produces onlyone egg. Other females produce multiple living young.

RDP

FALL ARMYWORM REPORTED INPASTURES

Reports of fall armyworm were received from VictoriaCounty three weeks ago, but none have been reportedsince that time. However, conditions are right foroutbreaks at this time. Moths of the species lay theireggs in masses often resulting in large numbers in anarea. As they grow in size, larvae migrate out in alldirections. Fall armyworm larvae can be identified bythe characteristic inverted “Y” on the head. Untilcaterpillars reach the last instar (growth stage) their

feeding may not be noticed, but during that last stagethey consume about 85% of their entire foodrequirements resulting in rapid destruction to host planttissue. Small caterpillars feed on one surface of grassleaves resulting in a “windowed effect,” but largecaterpillars consume the entire leaf surface. Examinegrass weekly by looking deep into the foliage to detectsmall caterpillars before they reach large size. If theforage is needed and caterpillars are found when theyare small, quick grazing or harvest for hay can becarried out. If caterpillars are large they will still feedon the cut grass while it is being cured for baling. As ageneral rule-of-thumb 3-4 fall armyworms per squarefoot can be used an a treatment threshold.

Approved insecticides for pastures include malathion,carbaryl (Sevin), methomyl (Lannate), methylparathion, and spinosad (Tracer). All these insecticidesshould be applied with hollow cone nozzles; we haveobserved superior control with the hollow cone nozzle.Tracer has a section 18 label which is due to expire onSeptember 23, 2004. Unless we show in correctlydesigned field studies that currently labeled insecticides(primarily carbaryl) are not effective, the Section 18 forTracer will not be issued again. The last day Tracer canbe used is September 23, 2004. It has no grazingrestrictions, but there is still a three day waiting periodon cutting hay. RDP

COTTON MATURING RAPIDLY INLOWER GULF COAST COUNTIES

Hot dry conditions resulted in rapid opening of cottonbolls during the week of July 18 in many fields. Exceptfor very late maturing cotton, insect pressure isgenerally light. Insects of concern include green stinkbug, brown stink bug, and Euschistus quadrator (namedthe “small brown stink bug” by one our localconsultants). There is another stink bug being found incotton which is actually a beneficial predator speciesknown as the spined soldier bug. It looks like thebrown stink bug. It has shorter stout mouthpartsdesigned for catching prey.

Although a lot of cotton is past caterpillar problems,some late planted fields are still vulnerable. During thepast week 100% of the Heliothine caterpillars examinedhave been tobacco budworm. This is exactly what isexpected this time of year. RDP

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1A

1B

2B

2A

Fig 1B, 2B are enlargements of outlined areas in 1A, 2A

CHARCOAL ROT FOUND IN COTTON BOLLSGary N. Odvody, TAES Plant Pathologist, Corpus Christi, Texas

Last week a rot of cotton bolls caused by the fungus Macrophomina phaseolina was observed causing 29-35%boll loss in a field near Portland, Texas. Most of the charcoal rot appeared to be of recent origin (1-2 wk) andwas probably associated with wet fields and high air temperatures. This fungus has an optimal growthtemperature is 95 F (35 C). Affected bolls were located on all areas of the plant but predominantly at mid-plantand above regardless of height. This pathogen is probably a slightly different strain than the one causingcharcoal stalk rot of sorghum and corn in that it readily produces pycnidia and pycnidiospores. The pycnidiaare sub-spherical slightly beaked structures just underneath the plant epidermis. They produce pycnidiospores that are “oozed out” of the pycnidium under wet conditions and then aerially dispersed by rain and wind toplant parts above the soil surface. Boll peduncles appear to be the only site of initial infection with progressionprimarily up and through the boll (Fig 1A,B). The boll is prematurely killed and then opens to reveal the locksthat are permeated with sclerotia of M. phaseolina (Fig 2 A,B). The pycnidia are produced only on the outersurface of the peduncle (Fig 1A, arrow) and outside boll wall. The hardened locks of cotton with sclerotia falleasily out of the bolls. A nearby cotton variety test had infrequent, scattered occurrence of the charcoal rotacross a number of varieties. The distribution and severity of this charcoal rot across the Coastal Bend isunknown but probably much less than observed in this unusual field where severity may be at least partly-related to late heavy rains and high heat. The only other report of M. phaseolina causing a boll rot is by W. W.Ray in Oklahoma in 1946.

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RENEWED FOCUS ON NEPS INCOTTONThe following information on “NEPS” was obtainedfrom Textile Topics, Vol. 2004-2, Spring 2004published by the International Textile Center,Lubbock, Texas. The entire article can be viewed attheir website (http://www.textiletopics.ttu.edu/).Click “Current Issue” or look for the Summer 2004issue. Information here was selected as anintroduction to the topic.

According to the American Society for Testing andMaterials, a nep is “a tightly tangled knot-like mass ofunorganized fibers”. Exhibit 1 shows a magnifiedpicture of a nep in raw cotton.

In a study by Hebert et. al., it was determined that inmost cases fiber neps are made up of five or morefibers with the average number of fibersapproximating 16. Furthermore, “Ninety-six percentof the fiber neps studied contained immature fibers,yet only 50% of allneps contained 100% immature fiber”.

The appearance of common neps on yarns and fabricsis shown in Exhibit 2. Two distinct categories of nepsare “seedcoat neps”—which have a piece of theseedcoat attached to the fibers—and “shinyneps”—which consist of dead fibers, with insufficientcellulose to even absorb dye. These two subclasses ofneps comprise a very small portion of all neps;however, when they do occur they present veryserious quality problems.

A small portion of observed neps may exist in theunprocessed cotton, with the majority of neps causedby handling and processing. Almost any mechanicalprocess can cause the formation of neps, but the mostlikely ones include harvesting, ginning, andopening/cleaning in the textile mill. Neps aregenerally removed from the cotton fibers at only twoplaces in the textile mill: at the carding machine and

the combing machine.

While mechanical processes are the chief cause ofneps, some cotton fibers are more susceptible to nepformation than others. Genetically determinedphysical characteristics are known to play a role. Forexample, longer and finer fibers are inherently moreprone to forming neps when subjected to stressfulmechanical processes. Also, stress caused byenvironmental conditions (e.g., drought, heat, etc.)and by competition (e.g., insects, weeds, etc.) mayresult in immaturity, weak places, or other problemsthat predispose the cotton toward nep formation.

Mechanical neps may result if cotton is ginned with amoisture content that is either very high or very low.Also, the more trash the cotton contains, the more thefibers must be cleaned, which will result in theformation of more neps.

Regardless of the types of neps, if they areincorporated into the yarns, it is likely that a portionof them will be visible on the fabrics made from theyarns. However, the proportions of different categoriesof neps may be different among card slivers versusyarns versus fabrics. Thus, when Herbert, et. al.followed through to fabrics from the carded cottonmentioned above, the visible distribution of nepsshifted to 30% biological, 24% mechanical, and 46%“other”. The very large increase in the proportion of“other” neps (from 1% in fiber to 46% in fabric)reveals why cotton containing dead and/or immaturefibers is a primary concern for textile dyers of high-

quality goods. In dark shades of dyeing, the presenceof immature/dead fiber in moderate quantities almostcertainly will produce off-quality finished goods.

It is estimated that even in fabric with severecontamination, the percentage of immature/deadfibers (by weight) is less than 0.1% of the total fibers.These amounts would be too small to have significanteffects on the average fiber properties, as measuredby current commercial instruments, but are substantialenough to negatively impact the commercial value ofthe fiber to the end user. RDP

INTERESTING INSECTS

Taken from An Introduction to the Study of Insects,6th edition by Borror, Triplehorn and Johnson.

Digestive System - Insects feed upon almost everyorganic substance found in nature, and their digestivesystems exhibit considerable variation. Thealimentary canal is a tube, usually somewhat coiled,which extends from the mouth to the anus. It isdifferentiated into three main regions: the foregut, themidgut, and the hindgut. Both the foregut and hindgutare derived from ectodermal tissue and are linedinternally by a thin layer of cuticle, the intima. Thiscuticle is shed at each molt along with the outerexoskeleton.

Many insects eject digestive enzymes upon food, andpartial digestion may occur before the food isingested. Flesh fly larvae discharge proteolyticenzymes onto their food, and aphids inject amylaseinto the plant tissues and thus digest starch in the foodplant. Extraintestinal digestion also occurs in the preyof larvae of antlions and predaceous diving beetlesand in bugs that feed on dry seeds.

Most chemical digestion of the food takes placewithin the midgut. Some of the midgut epithelialcells produce enzymes, and others absorb digestedfood. Sometimes secretion and absorption are carriedout by the same cells. Enzymes may be released intothe midgut by the disintegration of the secretory cells(holocrine secretion) or by the release of smallamounts of enzymes across the cell membrane(merocrine secretion).

Only a few species of insects produce enzymes thatdigest cellulose, but some are able to use cellulose asfood as a result of symbiotic microorganisms presentin their digestive tracts. These microorganisms,usually bacteria or flagellated protists, can digest thecellulose, and the insects absorb the products of thisdigestion. Such microorganisms are present intermites and many wood-boring beetles and are oftenhoused in special organs connected to the gut. RDP

For more information contact:

Roy D. Parker Stephen D. LivingstonExtension Entomologist Extension Agronomist

10345 Agnes, Corpus Christi, TX 78406(361) 265-9203, Fax (361) 265-9434

View our newsletter earlier on the internet at http://agfacts.tamu.edu/~rparker. Also pest management information is available at www.txaac.org.

********************************************************************************Educational programs conducted by the Texas Agricultural Extension April 7, 2004Service serve people of all ages regardless of socioeconomic level, race, color, sex, religion,handicap or national origin. The information given herein is for educational purposes only. References to commercial products or trade names is made with the understanding

that no discrimination is intended and no endorsement by the Cooperative Extension Service is implied.The Texas A&M University System, U.S. Department of Agriculture, and the Commissioners Courts of Texas Cooperating