S U M M A R Y From field to textile mill, all stages of the cotton industry are adversely af- Cooperative Extension IPM Series No. 13 fected by sticky cotton. Honeydew de- posited by phloem-feeding insects such AZ1156 – 12/1999 as whiteflies and aphids, and sugars produced by the plant itself may build up to levels that impede fiber handling. Sticky Cotton Sources & Typically, stickiness is first encoun- tered when sugar-contaminated cotton lint is carded at the textile mill. Grow- Solutions ers often sustain considerable costs in managing honeydew-producing in- What is Stickiness? Sugars differ in their stickiness. For ex- sects. Further, if stickiness is found by ample, sucrose, melezitose, and trehalu- textile processors, growers in regions To growers, stickiness means higher costs lose are all significantly stickier when de- associated with sticky cotton may suf- for insect control and reduced cotton mar- posited on fiber than are glucose or fer price reductions in future years. At ketability. To ginners, stickiness may mean fructose. Further, trehalulose-contami- present, no test for sugars contamina- special handling and processing require- nated fiber is stickier than fiber with an tion is as rapid as HVI testing. More- ments. At the textile mill, stickiness means equivalent amount of melezitose. Mixtures over, no current test of sugars contami- reduced processing efficiency, lower yarn of sugars, such as occur in honeydew, tend nation has been directly calibrated quality, and in severe cases total shut to be stickier than single sugars. Local- with fiber processing efficiency. Be- cause current measures for mitigating down. For everyone concerned, stickiness ized concentration of sugars like honey- stickiness in the field and at the mill means reduced profitability. Stickiness dew is at higher risk of causing stickiness are unreliable, stickiness is best occurs when excessive sugars present on than more evenly distributed sources like avoided by managing insect and plant fibers are transferred to equipment and plant sugars. sources. Well-implemented integrated interfere with processing. Sugars may be pest and plant management plans are insect- or plant-derived. Though sugars are Impact of Stickiness on Growers & the Marketplace our best defenses against the stickiness ubiquitous in lint, they usually occur at problem. Having put such plans to levels that pose no processing difficulties. Between insect control costs and reduced work, cotton growers in the western This bulletin details the sources and com- cotton prices, sticky cotton is costly to United States have minimized the risks ponents of problem sugars on harvested growers. The major cost is in controlling of sticky cotton. lint, the processing and marketing impacts the potential sources of stickiness. The of stickiness, and strategies for avoiding costs of aphid control in TX or mitigating stickiness. and CA, and of whitefly con- trol in TX, AZ and CA have

Honeydew, when present in sufficient Ellsworth P. all increased in the last de- quantity, is the main source of sugars that cade. Insecticide treatment to can result in sticky lint. Honeydew is ex- specifically prevent sticki- creted by certain phloem-feeding insects ness has cost Southwestern including such common pests of cotton as cotton growers $47 million aphids and whiteflies. These insects are for aphids and $154 million capable of transforming ingested sucrose for whiteflies from 1994–98 into over twenty different sugars in their (Table 1). In AZ, the cost of excreted honeydew. The major sugars in controlling whiteflies in- cotton insect honeydew are trehalulose, creased from $12/acre in melezitose, sucrose, fructose and glucose. 1990 (the onset of the white- Another source of stickiness is free plant fly outbreak) to $145/acre in sugars sometimes found in immature fi- 1995. This cost accounted for bers. Cotton fiber is largely cellulose that 11% in 1990 and 68% in is formed from sugars synthesized by the 1995 of the total spent on in- plant. Dry, mature cotton fibers contain sect control. A new integrated little free sugar, while immature cotton system of whitefly manage- The specter of ‘sticky’ cotton has affected large regions of the fibers contain glucose, fructose, sucrose, ment based on insect growth world’s production. Better plant and insect management are and other sugars. If immature cotton fiber regulators began in 1996. keys to avoiding this costly problem. is subjected to a freeze, complex sugars Since then, AZ growers have reduced con- may be broken down to release additional trol costs to less than $35/A, while achiev- Peter C. Ellsworth, Russell Tronstad, University of Arizona simple sugars. Less commonly, oils re- ing excellent whitefly control. The 1996 James Leser, Texas A&M University leased by crushed seed coat fragments can AZ crop was found to be 98% free of Peter B. Goodell, Larry D. Godfrey, University of California Tom J. Henneberry, Don Hendrix, Don Brushwood, also result in stickiness. In this case, raffi- stickiness as determined by random bale Steven E. Naranjo, Steve Castle, USDA-ARS nose is the characteristic sugar. testing with SCT (see next section). In Robert L. Nichols, Cotton Incorporated A reputation for stickiness has a bution of the sugars, the ambient condi- negative impact on domestic tions during processing—especially hu- sales, export orders, and prices for midity—and the machinery itself. Sticki- cotton from regions suspected of ness is therefore difficult to measure. stickiness. The precise loss of Nonetheless, methods for measuring sug- UC Statewide IPM Project sales due to stickiness is difficult ars on fiber have been and are being de- to estimate, because cotton con- veloped. These measurements may be cor- sumption and exports are affected related with sticking of contaminated lint by many factors every year. Cot- to moving machine parts. Currently, no ton price is reduced for stickiness generally recognized system of stickiness by the market at a rate propor- measurement is compatible with the speed tional to the perception of risk. of commercial cotton classing. The physi- L. Forlow Jech The cotton aphid, Aphis gossypii, excretes honeydew rich Reductions in the market value of cal and chemical attributes of the lint and in melezitose (ca. 30–40%). Their droplets (inset, 50X) lint are applied regionally and in- sugars that are correlated with stickiness tend to be larger than those produced by whiteflies. discriminately. Regional penal- have been measured in many ways, each 1997, CA cotton growers spent a statewide ties are a consequence of the dif- with differing efficiency and precision. average of $7/A on whitefly control and ficulty in measuring stickiness in cotton. $38/A on aphid control. Combined, these Because there is currently no rapid costs accounted for over half of their total method that is accepted as an indus- insect control budget. In TX, aphid and try standard for the measurement of plant sugars have been the largest sources stickiness, there can be no formal, S. Bauer (USDA) of stickiness. TX cotton growers have bale-specific schedule of discounts spent up to $19/A (1995) on aphid control for stickiness in the USDA-AMS and $21/A (1991) on whitefly control. In cotton classification system. Esti- addition to these immediate costs, exces- mates of the immediate effects of sive dependence on chemical control tac- stickiness on regional cotton prices tics carries with it increased frequency and are reductions up to $0.03–0.05 / lb L. Forlow Jech risks of insecticide resistance with an in- for AZ since the whitefly outbreak Whiteflies, Bemisia spp., also excrete honeydew, but calculable cost to growers and the indus- of 1992 (Fig. 1), and at least $0.03 / as trehalulose-rich (ca. 40–50%) droplets (inset, 50X). try. lb for West TX in 1995. Since 1992, growers in AZ may have lost as much as Some textile mills use reducing-sugar tests Sticky cotton can reduce cotton gin out- $21 million (1993–1995) and $36 million based on reduction of the cupric ion to put (in bales/hr) by up to 25%. At the tex- (1996–1998). In West TX, prices were af- screen for sugar contamination. These tile mill, excessive wear and increased fected primarily for the 1995 crop. A simi- tests are relatively quick and inexpensive. maintenance of machinery may occur even lar market penalty could be re-imposed in However, some insect sugars are not re- with slightly sticky cotton. In severe in- any region should the potential for sticki- ducing sugars, and some others are mea- stances mill shutdown with a thorough ness be suspected. sured at different levels of efficiency by cleanup is required. various reducing-sugar methods. Thus In addition to causing price reductions for conventional reducing-sugar tests are best cotton lint, estimates of losses due to reserved for screening lint that potentially USDA

J. Supak whitefly feeding in southwestern agricul- has high levels of plant sugars. In these tural communities exceeded $200 million cases and with the potassium ferricyanide in 1991 and $500 million in 1992. In the (KFeCN) test, lint with reducing sugar Imperial Valley, CA alone, annual crop levels below 0.3% may be processed with- losses to the silverleaf whitefly from 1991 out difficulty. to 1995 have been estimated to be about $100 million. In 1992 and 1995, whitefly High Performance Liquid Chromatogra- feeding directly reduced cotton yields in phy (HPLC) identifies and measures both AZ, as did aphid feeding during the mid- reducing and nonreducing sugars. The season of 1995 and 1997 in CA. main sugars of insect honeydew, trehalu- lose (from whiteflies) and melezitose Stickiness Detection & (from aphids), and of plant sugars (glu- Measurement cose, fructose & sucrose) are all readily identified in this test. The benefit of HPLC A preharvest freeze can set off a chain of events that leads to immature fibers and excessive ‘Stickiness’ is the physical process of con- analysis is the identification of the source plant sugars. Inset (250X) are cross sections taminated lint adhering to equipment (Fig. of contamination (whitefly, aphid, or of fibers, normal (left) & immature (right). 2). The degree of stickiness depends on plant) which may help identify specific Note wall thicknesses and lumen volume. the chemical identity, quantity, and distri- mitigation measures. The physical interaction of all sugars on number of specks left on the two Table 1. Costs (in $US millions) of aphid and whitefly con- lint with equipment can be measured by sheets of foil. Lower numbers trol in Arizona, California and Texas, 1994–1998 several types of machines. The primary of specks are preferable to (for yield protection & stickiness prevention). difficulty with these physical tests is in higher numbers; however, a spe- A P H I D standardizing the stickiness measurement. cific threshold over which all As with chemical testing, these tests must cotton will result in processing State 1994 1995 1996 1997 1998 Sum be correlated with measures of fiber pro- problems has not been defined. AZ 0.0 0.7 0.1 0.0 0.4 1.2 cessing efficiency in order to interpret the The SCT takes about 5 minutes results. to process each sample, requires CA 33.4 25.5 4.8 40.3 2.3 106.3 smaller initial investment costs TX 11.3 23.0 8.1 9.9 5.5 57.8 One of these tests, the minicard, is a physi- than the minicard, is more mo- cal test that measures actual cotton sticki- Sum 44.7 49.2 13.0 50.2 8.2 165.3 bile, and its results correlate ness of the card web passing between well with predicted stickiness stainless steel delivery rollers of a minia- W H I T E F L Y from the minicard. ture carding machine. Modeled after a pro- AZ 27.5 58.1 18.7 17.3 8.9 130.5 duction carding machine, the minicard The High Speed Stickiness De- must be run under strict tolerances (24°C; tector (H2SD) is a quicker, au- CA 0.0 1.7 3.0 7.9 1.1 13.7 55% RH). A ‘0’ minicard rating indicates tomatic version of the thermo- TX 0.0 9.5 0.0 0.0 0.2 9.7 that no sticking was observed, while pro- detector. The cotton sample is Sum 27.5 69.3 21.7 25.2 10.2 153.9 gressively higher numbers (on a 0–3 scale) pressed between a heated (54°C indicate progressively greater amounts of for 30 sec.) and an unheated pressure plate. Work is currently underway to determine sticking during the process. Cottons with Sticky points are counted and point size methods for measuring insect sugars on high plant sugar contents evenly distrib- distribution determined by image-process- field-collected lint as a tool for predicting uted along the fibers may fail to be mea- ing computer software. Plates are auto- stickiness. Such predictions would be sured as sticky in this test. The minicard matically cleaned between samples. The complicated by various degradative pro- test is slow and has been replaced as the H2SD is able to analyze a sample in 30 cesses that occur prior to processing such international standard by the manual ther- seconds. as rain and microbial activity that might modetector (see next section). Like the thermodetector and H2SD, the Fi- reduce the potential for stickiness. The Sticky Cotton Thermodetector (SCT) ber Contamination Tester (FCT) measures Managing the Sources measures the physical sticking points physical sticking points (at 65% RH). The transferred to aluminum sheets by a con- instrument feeds a thin web between two The most efficient way now to prevent ditioned lint sample that is squeezed and rollers. Contamination of the rollers inter- stickiness is by managing sugar sources heated (to 82.5°C for 12 sec.). Levels of rupts a laser beam, resulting in a record- in the field. Detailed integrated pest man- stickiness are categorized according to the ing. Because the cleaning and recording agement plans (see references) for both is automated, samples may be aphid and whitefly have been developed 0 processed as quickly as one in AZ, CA, and TX. These honeydew-pro- per 45 seconds. ducing insects may be managed by avoid- -1 After whitefly-related 1987Ð1992 = -2.94¢ problems in 1992, AZ ing conditions leading to outbreaks, care- prices seem to be ad- -2 versely affected by per- While there is no reliable in- fully sampling pest populations, and using ception of stickiness field method for detection of effective insecticides when populations -3 stickiness predisposition, the reach predetermined thresholds. insects responsible for honey- 1993Ð1998 = -5.63¢ -4 dew deposits can be sampled The risk of having excessive plant sugars can be minimized by harvesting mature -5 and populations measured. Not all population levels of seed cotton. This may be accomplished insects lead to sticky lint; through plant management tactics that in-

Difference in Cents / lb. -6 however, chronic numbers of clude: early and uniform planting, nitro- -7 insects, especially during boll gen management according to plant opening or an extended sea- growth and yield goals, high first-position -8 son, can lead to excessive in- boll retention, and timely chemical termi- sect sugars that result in nation and harvest. If a freeze is imminent 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 Calendar Year stickiness. In addition, field and immature bolls are present, the use of Figure 1. Average† weekly spot price disadvantange of factors associated with risk of boll-opening chemicals can greatly dimin- Arizona (DSW) vs. California (SJV) upland excessive plant sugars are ish the problem of plant sugar contamina- (31-3/35). There are other market forces in lateness of the crop, fiber im- tion. All these measures work towards effect as well as perception of stickiness. maturity, and freezing tem- early harvest, before freezing conditions † Source: USDA-AMS, Cotton Price Statistics, 1987–1998. peratures before harvest. that contribute to excess plant sugars. problem yet to be solved. In Endorsing Organizations some areas of the world, The University of Arizona, The University of Cali- overhead and in-canopy ir- fornia, Texas A&M University, United Stated De- rigation has been used to re- partment of Agriculture, Cotton Incorporated, Na- move honeydew from open tional Cotton Council bolls. The frequency of this References Sticky type of irrigation may be more important than the Diehl, J.W., P.C. Ellsworth & S.E. Naranjo. 1997. Whiteflies in Arizona No. 11: Binomial Sampling Cotton volume applied. Use of of Nymphs (rev. 6/97). The University of Arizona sprinklers has been limited Cooperative Extension. 2 pp. in the Western United Ellsworth, P.C., J.W. Diehl, T.J. Dennehy & S.E. States, where furrow irriga- Naranjo. 1995. Sampling Sweetpotato Whiteflies in tion is prevalent. Cotton. IPM Series No. 2. The University of Ari- zona, Cooperative Extension. Publication #194023. If stickiness is a problem Tucson, AZ. 2 pp. Figure 2. ‘Sticky’ cotton is a complex, 3-component inter- Ellsworth, P.C., T.J. Dennehy & R.L. Nichols. 1996. action among source (insect or plant sugars), lint, while ginning, the ginning rate of honeydew contami- Whitefly Management in Arizona Cotton 1996. IPM and processing equipment. Series No. 3. The University of Arizona, Coopera- nated cotton can be in- tive Extension. Publication #196004. Tucson, AZ. Mitigating the Problem creased by increasing the heat of the dry- 2 pp. ing towers to reduce humidity. The Ellsworth, P.C., J.W. Diehl & S.E. Naranjo. 1996. When field management of sugar sources potential for stickiness can be further re- Sampling Sweetpotato Whitefly Nymphs in Cotton. is inadequate to prevent excess accumu- duced by lint cleaning. Both of these prac- IPM Series No. 6. The University of Arizona, Co- lation of sugars, mitigation tactics may be operative Extension. Publication #196006. Tucson, tices, however, can result in shorter fibers. necessary to remove excess sugars from AZ. 2 pp. Conventional textile lubricants may also the lint. This mitigation may be achieved Godfrey, L., P. Goodell, E. Grafton-Cardwell, N. be used. Stickiness due to high levels of through both natural and managed pro- Toscano, E.T. Natwick & J. Brazzle. 1998. UC IPM plant sugars can be reduced by storing the Pest Management Guidelines: Cotton. University of cesses; however, the specific impact of cotton for approximately six months. California DANR Publication 3339. 67 pp. these processes on stickiness is variable www.ipm.ucdavis.edu/PMG/selectnewpest. However, storage of baled cotton will not and may depend on the initial level of con- cotton.html appreciably reduce stickiness from insect tamination. Natural processes include Goodell, P.B., L.D. Godfrey, E.E. Grafton-Cardwell, sugars. At the textile mill, stickiness may weathering, rainfall, and degradation by N. Toscano & S. Wright. 1999. Insecticide Resis- be managed by blending bales and by re- tance Management Guidelines in San Joaquin Val- microorganisms. Since sugars are water ducing humidity during carding. A lubri- ley. University of California. 21 pp. www.uckac.edu soluble, rainfall will wash some honeydew cant in fog form may be introduced at the Slosser, J., J. Leser, D. Rummel, T. Fuchs, E. Bor- from lint. If sufficient moisture is avail- end of the hopper conveyor, and card- ing, M. Muegge & C. Sansone. 1999 Suggestions able, bacteria and molds living on the for Management of Cotton Aphid in West Texas. crush rolls may be sprayed sparingly with plants will decompose many honeydew entowww.tamu.edu/extension/bulletins/ a lubricant to minimize sticking. sugars. Complex sugars are broken down aphweb99.html. to simpler sugars, and the simpler sugars, Conclusion For more information about cotton sticki- given sufficient time and moisture, are fur- ness and insect/crop management, includ- ther broken down to carbon dioxide and Lints contaminated with sugars from vari- ing this publication, visit the internet site: water. Unfortunately, microbial action also ous sources (plant and insect) can result ag.arizona.edu/cotton. leads to discoloration and to a weakening in stickiness. Yet stickiness is not an in- of the fibers as well as heating of cotton trinsic property of the lint and therefore Funding for the printing of this bulletin in modules that may result in reduced seed cannot be measured directly. Rather, was provided by Cotton Incorporated. viability and problems in ginning. stickiness is a complex, three-component ® interaction that involves the source sug- The statements contained herein are based on information believed to be reliable. No guarantee is made of their accuracy, however, and the Potential in-field mitigation techniques in- ars, harvested seedcotton, and processing information is given without warranty as to its accuracy or reproduc- ibility either express or implied, and does not authorize use of the infor- clude supplemental oversprays of en- equipment. The complexity of this inter- mation for purposes of advertisement or product endorsement or certi- zymes or water. Certain carbohydrate de- action indicates the need for an integrated fication. The use of trade names does not constitute endorsement of any product mentioned, nor is permission granted to use the name Cotton grading enzymes when sprayed on sticky solution that includes prevention, in-field Incorporated, USDA, or The University of Arizona or any of their trade- cotton can reduce honeydew to simpler mitigation, and processing adjustments. marks in conjunction with the products involved. Issued in furtherance of Cooperative Extension work, acts of May 8 sugars. Microbial activity on the fibers Because currently our best means of elimi- and June 30, 1914, in cooperation with the U.S. Department of Agri- then further degrades these simpler sug- nating stickiness is source sugar minimi- culture, James A. Christenson, Director, Cooperative Extension, Col- lege of Agriculture, The University of Arizona. ars, resulting in a significant decrease in zation in the field, US agricultural research The University of Arizona is an equal opportunity employer authorized fiber stickiness. However, these enzymes and implementation agencies continue to to provide research, educational information and other services only to require water for activity, and metering the emphasize successful insect and crop man- individuals and institutions that function without regard to sex, race, religion, color, national origin, age, Vietnam Era Veteran’s status, or proper amount of water for activity is a agement plans. disability.