Cotton insect problems have been relatively light so far with the exception of some areas experiencing heavy thrips pressure from adjacent wheat. At-planting thrips control treatments haven’t looked as good this year but are certainly better than no treatment at all. Plant bugs and cotton fleahoppers are building in alternate crop and weed hosts but have yet to cause much of a problem. But with more cotton squaring every day, producers and consultants are warned about neglecting square retention monitoring until it is too late. Remember last year? Boll weevil trap catches remain below last year’s numbers but weevils still pose a threat to fields near towns, prime overwintering sites and where field history indicates recurring problems. Emergence has probably not peaked yet. The eradication program is still on track in the three active zones and results this year continue to look very good. An early bollworm egg lay continues to cause concern with more favorable weather conditions producing lower mortality levels. Beet armyworms are also a continuing threat but thus far only a few southern fields have experienced problems serious enough to warrant treatment.

Corn is doing very well with recent weather suppressing mite infestations. Earlier planted corn is beginning to tassel. Corn rootworm adults are being found along with light to moderate feeding damage from corn earworms and fall armyworms. First generation southwestern corn borer activity is not especially heavy.

Some earlier planted sorghum is beginning to exert heads with corn leaf aphid infestations showing up in some whorl stage sorghum. More advanced sunflower fields are approaching bloom and producers are alerted to check for sunflower moth problems. Peanuts are pegging in many area fields.

Thrips and Weather Tough On Pre-squaring Cotton

While the rains have provided some assistance in knocking down thrips numbers in pre-squaring cotton, many of these recent rains were not hard enough to dislodge resident thrips infestations. In some instances there were associated high winds and blowing sand, which did result in weather-damaged leaves. In fact, in some fields it was tough to tell the difference between treated and untreated rows of cotton because of this weather damage. But rest assured, on closer inspection, there were differences.

In tests planted near Lazbuddie, thrips pressure has been sufficiently high to cause differences in treatments, even though the cotton is well "weathered". Both replicated tests involve Temik at 3 pounds formulated per acre, the Novartis seed treatment Adage, and an untreated check. In the first planting on May 5, the pre-squaring average thrips per plant was significantly reduced in the two insecticide treatments versus the untreated check. These two insecticide treatments were not different from each other. While leaf area was greater in the two insecticide treatments than the untreated check, only the Temik treatment was significantly different from the check. The second planting on May 19 is still two weeks away from having leaf area measured but based on seasonal thrips count averages, only the thrips numbers in the Temik treatment were significantly lower than the untreated check. The Adage seed treatment had fewer thrips numbers but was not significantly different from the untreated check. Temik provided three weeks of protection from planting in the first and second test while the Adage seed treatment provided less than three weeks in the first test and three weeks in the second test. All in all, Adage did not appear to be quite as good as the Temik treatment but was generally better than other seed treatments evaluated in the past. I was not overly enthused with the Temik treatment residual activity this year. The harsh weather conditions in this test did make interpretation of leaf area and thrips numbers difficult. The true test will come when we evaluate yield potential as the plots approach first flower.

Cotton that is still in the pre-squaring growth stage should be monitored closely for thrips even if previously treated. In between rain events, thrips numbers in some areas have been very high and threatening to earliness and yield if not controlled. Banded ground-applied applications can be very cheap crop insurance. Producers with plants that are severely damaged, but with several true leaf positions, may need to use lower thresholds than that recommended in the management guide to insure rapid recovery. Generally the threshold on pre-squaring cotton is an average of one thrips per true leaf present on a plant (a threshold of one is used from emergence through the 1st true leaf node). Once cotton plants begin to square, thrips are rarely a threat.

Monitor Early Season Square Set

While fleahopper and plant bug (alias Lygus or western tarnished plant bug) numbers remain fairly low and square retention is generally high, producers and consultants must not let down their guard. Recent rains have "greened up" the landscape and provided abundant moisture for additional weed growth. This could provide an ample nursery for the build-up of these two square thieves before moving into cotton later on. Producers are cautioned to remember what happened last year when underrated fleahopper and plant bug infestations took a high toll in many fields, especially west of a line from Lamesa to Tulia.

The key to managing these two pests during the early squaring period is to keep track of square retention through plant mapping. We are involved in a extensive testing of the SQUAREMAN component of the COTMAN model developed in Arkansas which assists in tracking plant development during the squaring period and suggests corrective action. But you can monitor cotton without this fancy model simply by examining 10 plants in each of four or more sites per field for square retention. We are only interested in first position squares. This should save us some time later in the squaring period. Only look at plants that have not lost terminal dominance. (Figure 1)

Map each plant for the presence or absence of first position squares. Start at the top of the plant with the first unfurled leaf (leaf edges not touching). Go down the plant recording squares present (1) or absent (0). The top most square will be larger than a pinhead-size square but still difficult to recognize for most folks. Pinhead squares will be found the node above this. A typical record may look like this: 1011011. This plant would have two missing squares out of a possible 7, resulting in a square retention value of 71.4%. Some damaged squares may still be present but will take on a duller gray-like color and will eventually dry up and fall off. A square that has been fed on in the last 1-2 days may not look much different from an undamaged one. That is why twice-a-week scouting can be quite valuable, especially during periods of increased pest activity.

West Texas fleahopper and plant bug treatment thresholds rely on both square retention data and insect counts. You can’t correct a square retention problem with an insecticide unless an insect pest is present. Producers can expect a higher potential for plant bug problems if their cotton is near alfalfa, peanuts, potatoes and even corn. There are lots of weed hosts too, some of which are also used by fleahoppers, such as silverleaf nightshade (white weed), lanceleaf sage (horse mint), evening primrose, etc. We generally make whole plant inspections for fleahoppers but rely on the drop cloth for plant bugs.

The drop cloth method uses an off-white cloth measuring 36 x 42 inches (on 40-inch rows). Staple a thin strip of wood or dowel to each short side of the cloth. If sampling narrower row spacings, roll up some of the cloth to accommodate the shorter distance between rows. Select a site in the field and unroll the cloth to fit between two rows. Grab only 18 inches of plants from both rows and vigorously shake all plants within the measured distance. Count Lygus adults first before they have a chance to fly off, then nymphs. Sample in about 20 locations. Each location represents 3 row feet. Refer to the West Texas cotton insect management guide for treatment thresholds and control suggestions (http://agpublications.tamu.edu/pubs/eentom/e6a.pdf).

Among the suggested fleahopper insecticides, Address, Orthene, Bidrin, dimethoate, Provado and Vydate have been a particularly good fit. Lygus materials include Address, Orthene, Bidrin, Provado, Vydate, and several synthetic pyrethroids. The pyrethroids are usually reserved for situations where heavy migration or reproduction occurs. Aphid flaring is the biggest concern when using pyrethroids. They certainly would be considered if a multiple pest situation developed such as Lygus and bollworms or weevils. Higher rates are generally needed for Lygus versus fleahopper control. ULV malathion and Vydate applications targeting boll weevils will certainly provide some benefit for fleahopper control.

Once fleahoppers move into a cotton field they generally stay and reproduce. Lygus may move freely into and out of a field in a matter of hours and may feed but not lay eggs. They may also lay eggs and leave as well. The bottom line is that you might scout a Lygus-damaged field without finding any Lygus. You may also find nymphs when no adults had been detected on previous examinations. Pretty tricky pest, huh? At least fleahopper scouting is a little more straight forward, but never easy.

Where Have All The Weevils Gone?

GRID trap catches went down somewhat this week, but remained higher than some producers’ or consultants’ trap catches (Table 1). Remember that the GRID is less than 1000 traps spread across 27 counties and while the GRID maps look pretty full of traps, this is an artifact of scale (http://www.plainscotton.org/bw00.html). They did come up again this week, so the worst is not over with yet.

Table 1. Total boll weevils caught per week and percent of traps catching boll weevils since April 24, 2000 in the GRID trapping program. 1/

Week beginning	Total weevils caught	% of traps catching weevils
April 24	948	30
May 1	887	34
May 8	5243	67
May 15	1112	34
May 22	2106	45
May 29	1651	46
June 5	4163	56
June 12	3391	47

1/ Includes Motley, Dickens and Kent counties where the bulk of the weevils are being caught (2/3^rd).

Trap catches were generally low last week with the Northwest Zone averaging about 5 weevils per 100 traps, the Northern Zone averaging 3 per trap, the Southern/Caprock Zone averaging 2.6 weevils , the Permian Basin Zone averaging 2 weevils and the Western Zone averaging 1 weevil per trap. These averages include traps recording zeros. Trap catches continue to lag behind last year’s trap catches whether traps are in or outside of an active eradication zone. The difference between the two years is much more dramatic in the active eradication zones where last fall’s diapause applications really hammered weevil numbers down. The average difference for active eradication zones after seven weeks of trapping is 71% through this past week and 27% for inactive zones. GRID trap catches lagged behind last years in all counties monitored but remained high in Briscoe, Cochran, Crosby, Floyd, Garza, Hale, Lubbock and Swisher counties (Table 2). Garza and Crosby counties were the highest so far this season.

Table 2. Week 24 — Accumulative average number of boll weevils caught per trap in the GRID trapping program starting with week 18.

Location	1999	2000
Northwest High Plains	19.5	11.4
Northern High Plains	47.9	40.6
Southern High Plains	68.5	42.2
Western High Plains	149.8	15.8
Permian Basin	75.9	14.7
Andrews	142.9	16.0
Bailey	18.5	11.5
Borden	56.5	32.2
Briscoe	49.7	42.9
Castro	6.5	5.0
Cochran	56.6	44.4
Crosby	97.8	71.1
Dawson	90.5	20.2
Deaf Smith	5.0	0.0
Floyd	35.3	33.3
Gaines	199.4	13.4
Garza	127.9	76.1
Hale	43.2	39.4
Hockley	33.1	22.9
Howard	82.2	12.2
Lamb	22.0	11.5
Lubbock	50.6	39.5
Lynn	51.4	20.9
Martin	35.3	9.2
Midland	27.9	9.5
Parmer	6.7	3.0
Swisher	39.2	26.9
Terry	95.4	14.6
Yoakum	113.8	15.3

This data represents the average number of weevils caught per trap catching weevils. Zeros are not counted. Refer to the Plains Cotton Growers, Inc. web page for actual total numbers caught and percent of traps catching weevils each week.

Overwintered boll weevil emergence continues as more fields begin to square. Some folks are suggesting that weevil emergence has peaked. Don’t count on it. I expect significant emergence at least for another 2-3 weeks. As fields in an area begin to square and especially as pencil eraser-sized squares appear, trap attractiveness declines in relation to the adjacent fields. Do not get fooled by declining trap catches as fields enter their 2^nd and 3^rd weeks of squaring. This may only mean that weevils are merrily feeding and laying eggs in these fields. "Happy" weevils produce an aggregating pheromone that draws more weevils into the field. This detracts from the traps we are monitoring.

Make overwintered boll weevil management decisions the week of appearance of pinhead-size squares. If you catch an average of 2 or more weevils that week, you probably need to spray at least once when matchhead or larger squares appear a few days later. Don’t spray at pinhead square unless predicted weather might interfere with a timely application later on. A second automatic application may be needed 5 days after the first if the week of pinhead-size square appearance trap catches average 4 or more. If 10 or more, a third automatic application may be necessary. If automatic repeat applications are not indicated, base further application decisions on later trap catches and field inspection.

Once boll weevils get established in your fields, they are extremely difficult to eliminate or at least gain the upper hand. Therefore, timely applications are of the utmost importance. If you planned on a ground application but wet field conditions won’t allow this, use an airplane---do not wait! One missed overwintered boll weevil application can mean several more additional applications later on. Insecticides that are effective include: Guthion, malathion ULV, methyl parathion, Penncap M, Vydate and several of the pyrethroids (when bollworms or Lygus are a consideration). Most folks rely on Vydate because of its reduced impact on beneficial insects. Multiple applications of almost any weevil material will "hammer" beneficial insects.

Data I have reviewed looking at the residual activity of various weevil materials evaluated either adult mortality or square damage. Most of these materials do not kill adult boll weevils past 3-4 days after application. Rainfall events within 24 hours can drastically reduce this residual activity. When evaluating insecticides based on square protection, many materials including ULV malathion, Vydate and several of the synthetic pyrethroids (including Baythroid, Capture and Karate Z), have significantly reduced square damage compared to the untreated check up to 7 days following an application. This does not necessarily mean that these treatments are actually killing adult weevils this long but are preventing reproduction by newly arrived or emerged boll weevils. Under this scenario, I’m not so sure that pyrethroids don’t afford the same level of control as ULV malathion.

In any case, don’t rely on border treatments to control overwintered boll weevils. Data from recent studies conducted by Dr. Dale Spurgeon of USDA ARS in College Station indicate that this practice would not work. Put treatments across the entire field. Better safe than sorry.

If your overwintered boll weevil treatments are not entirely successful then you may pick up punctured squares. Adult weevils feed on these squares, leaving a residue of yellow pollen behind. Female weevils will lay eggs in feeding puncture tunnels on the lower third of a square, sealing up the hole with a plug---producing a wart-like bump. Depending upon temperature, these eggs will hatch in 3-5 days, producing a larva (grub) that will continue to feed inside the infested square for 1-2 weeks. These grubs do not move outside the square but squares will be shed by the plant a few days after they are punctured, exposing the egg and/or grub to high soil temperatures that can produce significant mortality. The fully developed grub will pupate in the infested square and transform into an adult weevil during the next 4-6 days. The newly emerged adult will then chew its way out of the square and appear as a red weevil. During the next 4-5 days this adult weevil will change color, mate and then begin laying eggs---up to 200 during her lifetime. The entire cycle will take approximately 20-30 days. [life cycle slide]

The Texas Boll Weevil Eradication Foundation (TBWEF) program continues in our three active zones. A combination of a successful fall diapause program and lower than expected winter survival has helped this first full season program. There is still a considerable block of acreage yet to reach the squaring stage but so far, lower trap catches have been encouraging. So far there have been no definite secondary pest problems develop as a result of the eradication treatments. Let us hope this trend continues. Later planted cotton in an active eradication zone has gained an advantage this year. Late cotton usually has to contend with lots of boll weevil pressure, which translates into lots of dollars for control and/or lots of yield loss. But the TBWEF will be taking care of weevils this year and so producers with these late fields will mainly have to worry about late bollworm problems. The TBWEF Technical Advisory Committee is meeting in Corpus Christi next week to discuss several important issues that could have a big impact on eradication programs in Texas. I will be there as a member of this committee and will keep you informed.

Early Caterpillar Threat Continues

An early bollworm egg lay has continued for the last couple of weeks with no sure sign of abating. Rainfall, higher humidity and lower temperatures have contributed to lower than usual mortality levels and these worms have become established in some southern fields at levels causing concern and some early applications. Because of our typically short growing season, I usually use a threshold of 5,000-8,000 larvae per acre on pre-bloom cotton but move right up to 10,000 per acre once blooms are present.

Pulling the trigger on bollworm infestations that are near the treatment threshold and are very small can be a mistake for two reasons. If you have planted a Bollgard type cotton, you should expect very good control of these early bollworm infestations. You must wait until bollworm larvae are larger than _-inch in size before making a treatment decision. A similar problem can develop on conventional, non-Bollgard cotton if you have a marginal infestation of very small worms. Predators can do an excellent job of reducing bollworm numbers below the treatment level as long as the larvae are _ inch or smaller in size. Once larvae grow bigger than this, most predators are unable to win a confrontation with the larger worm. And minute pirate bugs are our number one predator against bollworms according to studies conducted by Mark Arnold, Research Associate with the Texas Agricultural Experiment Station at Lubbock.

Beet armyworm infestations continue to be found in several southern fields and have been an economic issue in a few instances. Most of the time these early infestations continue to stay below our treatment levels based on hits or larvae per acre (20,000 with 10% of plants examined infested). Dupont’s Steward received a section 18 registration last Friday after we went to press and joins a growing arsenal of insecticides labeled for beet armyworms including: Lorsban, Confirm, Intrepid, Tracer, and Denim.

Beet armyworm (BAW) trap catches have often been quite high but since we have been unable to establish a relationship between trap catches and field infestation levels, use this trap information only as an alert. T The BAW moth has a smaller wing span than a bollworm (1-1 1/4 inches), and its forewing is grayish-brown with two golden spots near the center. The back wings are translucent white with narrow brown borders. The female lays masses of eggs totaling about 80. She will produce about seven egg masses during her lifetime. These eggs are covered with hairs and scales from her body. Eggs take about 2-5 days to hatch and larvae feed for 16-21 days. These larvae feed gregariously for several days [picture 6] before dispersing. Larvae are a light to olive green in color, have fewer hairs than bollworm larvae, and have a black spot above the legs on the second segment behind its head. Pictures of BAW adult, eggs, and larvae. JFL

There has been some light to moderate leaf feeding damage by corn earworms (a.k.a. cotton bollworms) and fall armyworms but nothing to worry about. Spider mite infestations have generally been kept in check by recent weather events but could resurge with the return of hot, dry conditions. Beneficial arthropods have also been useful in keeping mites in check at this time.

Corn rootworm adults were sighted in Castro County last week. These adult beetles feed on leaves, pollen and tassels but are most damaging on silks. When adults reach levels of 8-10 per plant and silks are chewed back to one inch, poor ear filling may result from inadequate pollination. Controlling adults can reduce the number of eggs laid for the next generation but may also trigger a mite outbreak. So far, little root pruning has been reported. Corn pest photographs JFL

Now we really need sunshine, normal temperatures and low wind as favorable environmental conditions for this highly variable crop. In many places, the early planted irrigated seems to be moving along better than later planted. Taking up where we left off last week, the seasonal heat units are still above normal for the season. But the "surplus" was whittled away by a considerable amount last week. In the previous newsletter, we reported +21%, +31%, and +26% above normal from May 1 through last week, for Halfway, Lubbock and Lamesa, respectively. As of this writing, we are at +11, +19, and +17% of normal for those locations. Last Saturday we obtained essentially zero heat units at Halfway, 1.6 at Lubbock, and 8 at Lamesa due to the very cool temperatures.

Crop Development. Fields without environmental damage normally begin squaring at about 35 days after planting, or at about 525 heat units after planting (Table 3). First fruiting branches should begin appearing at main stem nodes 5-6. Some very vigorous fields may actually initiate the first fruiting branch on node 4. Watch fields carefully in order to determine the status of fruiting and for timing overwintered boll weevil insecticide applications. Check in the terminal to find pinhead squares - squares will be small, fuzzy, and pyramid shaped. When in doubt, pry bracts open on squares and look for a dome shaped structure. This is the flower bud.

Table 3. Cotton development by heat units and calendar days.

Nitrogen fertilization in irrigated fields making good progress should be considered. Figure 2 shows a typical N uptake curve for cotton and corresponding crop development stages. Suggestions for applications of approximate percentages of total N are also shown. Fertigation is a practice that is gaining in popularity in the High Plains. Where possible, nitrogen fertilizer (UAN, 32-0-0) can be applied through center pivots or "fertigated". This results in lower application costs. One should consider whether a LEPA system with drop hoses is used vs. a spray system. If a pivot rigged with spray nozzles has marginal water quality and extremely hot, dry conditions are encountered, then some salt burn may be encountered on foliage. This type of N management fertigation scenario has been used and validated for the last several years at the Lamesa AGCARES farm using alternate furrow LEPA irrigation.

To obtain maximum utilization of applied N, the total amount of N should probably be applied prior to peak bloom, in order to compensate for the "lag time" associated with application, bacterial conversion of urea and ammonium forms to nitrate-N, and physiological uptake delays. One challenge is that most fields may not require irrigation at this time due to the recent rainfall. It will still be important to sidedress or topdress N fertilizer in a timely manner in order to maintain the crop with an adequate nutrient status. It is important to not over fertilize with N if reduced yield potential is anticipated. This is due to the fact that it makes late cotton more difficult to manage on the back side of the season. Some late-season insect problems, such as aphids, can be aggravated by high N status plants.

Questions concerning mepiquat chloride (Pix, Pix Plus, and others) applications have also been asked. Pix Plus is a mepiquat chloride material formulated with a Bacillus cereus (BC) bacterial additive. Some lower cost mepiquat chloride generic materials are available this year. Mepiquat chloride (MC) reduces production of gibberellic acid in plant cells which in turn reduces cell expansion, ultimately resulting in shorter internode length. MC will not help the plants compensate for earlier weather or disease damage by increasing growth rate. It may under good growing conditions increase fruit retention, control growth and promote earliness. Results from our replicated testing indicates that we can get from 5 to 15% reduction in plant height (compared to the control) from 16 oz of 4.2% a.i. MC material applied in up to 4 sequential 4-oz/acre applications starting at matchhead square and ending at early bloom. We have been able to "shave" about 1 node from the growth of the main stem at some locations, which can result in about 3-5 days earlier cutout. We have not observed consistent yield increases from any of the MC materials we have investigated, including those with the BC additive. A good boll load will normally help control plant growth.

Fields with poor early-season fruit retention, excellent soil moisture, and high nitrogen fertility status may be candidates for poor vegetative/fruiting balance and should be watched carefully. Growers who have planted picker varieties (which are more indeterminate than most of our stripper types) and have conditions resulting in high growth potential may also be concerned. Growth potential of these varieties is considerably greater than many of our stripper types. Some decision tools are available, including the Pix Stik from BASF, which is used to measure the uppermost 5 nodes (down from the terminal which is counted as zero). The Pix Stik suggests use rates for various average internode lengths beginning at 50% matchhead square and in the absence of stress. For an average of 1.5 to 1.8 inches, 4 - 8 oz / acre are suggested. For average internode lengths greater than 1.8 inches, 8 - 16 oz / acre are suggested. Follow up assessments every 7-14 days are also suggested. Labels for Pix, Pix Plus, and other MC materials are available via the Internet at RB

Potential Evapotranspiration, often referred to as "PET", is an estimate of crop water demand based upon weather data. Actual water use by a crop, referred to as "crop ET", will vary with soil and crop conditions, and often will be less than the crop’s PET.

Table 4. Data from the South Plains PET Network, June 14-20, 2000:

	Reference		Estimated Crop PET in inches
	PET (inches)	Rain (inches)	Cotton		Sorghum		Corn
			Seedling	1st square	3-leaf	GPD	8-leaf	tassel
Lubbock	1.29	1.43	0.09	0.28	0.71	1.03	1.29	1.61
Lamesa	1.58	0.84	0.11	0.35	0.87	1.26	1.58	1.98
Halfway	1.44	0.87	0.10	0.32	0.79	1.15	1.44	1.80
Seminole [a]	1.90	0.93 [b]	0.13	0.42	1.05	1.52	1.90	2.38
Ropesville	1.79	2.12	0.13	0.39	0.98	1.43	1.79	2.24

[a] Site is actually closer to Denver City.

[b] Rain gauge calibration is yet to be verified.

 

These PET estimates are based upon High Plains crop coefficients. PET will vary with growth stage, which is affected by cumulative growing degree days (heat units). Since planting dates vary, and accumulation of heat units varies with planting date and location, we are seeing a broader range of crop growth stages in the field. You are encouraged to customize your crop water use estimate by multiplying the reference PET value by the appropriate crop coefficient. Crop coefficients for additional crops and growth stages are available from the Texas PET Website at the following:

High Plains Corn - http://texaset.tamu.edu/include/crop/corn.html

High Plains Cotton - http://texaset.tamu.edu/include/crop/cotton.html

High Plains Sorghum - http://texaset.tamu.edu/include/crop/sorghum.html

Other Crops - http://texaset.tamu.edu/include/crop/cropcoe.html

Turf – http://texaset.tamu.edu/turf.asp

 PET data and weather data for Halfway, Lamesa, Lubbock, Seminole, and Ropesville are available at: [http://achilleus.tamu.edu/data/data.html].

The Northern High Plains PET Network provides detailed PET estimates by crop and by planting date for Bushland, Dalhart, Dimmitt, Earth, Etter, Farwell, Morse, Perryton, Wellington, and White Deer. Current data are available at http://amarillo2.tamu.edu/nppet/station.htm. DP

Intensive sampling for root-knot nematode in cotton. Variable rate applications of Temik required intensive sampling for root-knot nematode. If one sample is taken every two acres, then the cost of sampling a 120 acre field would be approximately $1,300. It would be very difficult to recover the sampling costs if a field had to be intensively sampled yearly. From 1996 through 1998, three cotton fields were intensively sampled for root-knot nematode. There were areas of the fields, which had high root-knot nematode densities initially, and areas which had lower root-knot nematode densities initially. These areas relative to each other did not change. However, with respect to the nematode management decision rules, (to be provided in a later issue), any spot in the field could have caused a dramatic shift in root-knot nematode management class over a two year period.

Remote sensing for detection of management categories of root-knot nematode in cotton. Plants reflect certain wavelengths of light, and the intensity of the reflectance of these wavelengths can change depending on the type of stress the plant undergoes. Root-knot nematodes can increase the water stress in cotton. Infrared aerial photography was conducted on 10 fields infested with root-knot nematode during 1998 and 1999. Differences in the reflectance patterns of these images were used to sample for root-knot nematode, to see if the patterns were related to root-knot nematode density. Root-knot nematode density was related to the reflectance patterns in 9 of 10 fields. This means that reflectance patterns could be used to target sampling for root-knot nematode. The problem is that the wavelength of light, which was used to relate nematode density to reflectance, was not consistent between fields. So while remote sensing may be a useful tool for sampling, it is first necessary to identify which wavelength or combination of wavelengths are important for an individual field, and then researchers need to determine if that relationship is consistent over years. Pictures for this article are displayed on this linked page. Picture 1 is the infrared image taken on July 22, 1999 of a narrow row cotton field in southern Terry County and overlaid with the density of root-knot nematode from soil samples. Picture 2 is the same image, after it has been processed to show plant vigor more clearly. Picture 3 shows the recommended rate of Temik 15G over the field. There is a significant relationship between better plant vigor and lower population densities of root-knot nematode. However, other factors besides nematodes may be involved with the reduced plant vigor. The producer for this field analyzed the soil nutrient status and discovered that phosphorus was limiting in the low vigor areas. Interpretation of remote sensing information takes skill, experience, and often additional information (like sampling for nematodes or nutrient status). TW

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