Problems with cotton insects have remained relatively light through this week although there does appear to be increasing pressure form an ongoing bollworm egg lay. Thrips numbers are all over the board depending upon the age of cotton, location of field and rainfall events in the area. But thrips infestations have been pretty damaging this year and continue to be a problem especially in later planted fields. There have been some reports of fleahoppers and plant bugs in cotton but for the most part they are still confined primarily to alternate hosts. Cotton continues to retain a high percentage of its squares. Boll weevil trap catches indicate that we may be at an emergence plateau. It does look like an extended emergence even though trap catches are generally running lower than last year, even outside active eradication zones. The biggest reductions in weevil numbers by far are in the active zones where reductions range from 93 to 99 percent compared to last year this past week. Rains are hampering timely crop monitoring and insecticide applications but have thus far not had a significant impact on the Foundation’s eradication program.

Corn and sorghum are relatively clean of pest problems. Most southwestern corn borers are now in the stalk with some leaf feeding by corn earworms and fall armyworms. Corn leaf aphids are in many sorghum fields and will provide a food source for developing beneficial insect numbers for later control of greenbugs. Sunflower in the bloom stage need to be checked for sunflower moth. Peanuts are developing with few problems from insects or diseases thus far.

The Good, The Bad and The Ugly.

The good news is that some of these rainfall events have washed thrips infestations off plants, minimizing their impact on early square set. More good news is that thus far boll weevil numbers have been lower than expected and lower than last year in many cases. Also good news is that the majority of cotton fleahoppers and plant bugs are remaining in hosts other than cotton and square retention remains high. The bad news is that weather conditions have enhanced the survival of bollworms resulting from the ongoing, recent egg lay. Other bad news involves beet armyworms and their continued presence in cotton fields scattered across the area. The "ugly" are the cotton plants that have gone through some serious weather and thrips "challenges" and look rather bedraggled.

Thrips numbers continue at high levels between frequent rain showers and have caused considerable damage in many instances, even where preventative control tactics were used. I have to believe that many of these situations involve excessive rainfall resulting in leaching soil- or seed-applied insecticides out of the root zone. Don’t give up on thrips management until plants average 5-6 true leaves and these leaves are not severely damaged by prior infestations. A little sunshine and warm weather will do wonders for many of these "ugly" field situations. An insecticide application may still be needed.

Square Retention Remains High

Probably as much as 75% of the planted, surviving cotton acreage is squaring by now. Some should actually be blooming. Square retention is very high in fields reporting in this week with most averaging above the threshold levels of 90% the first week of squaring, 85% the second week and 75% the third week of squaring. Actually, many fields in the third and fourth week of squaring are carrying more squares than they can take to harvest. Expect some fruit shed later on as plants make an adjustment. This will generally occur at the second and third fruiting nodes and not with first position squares. Also expect some fruit shed once warm, open weather returns.

The good news thus far is that both fleahopper and plant bug numbers have remained low in squaring cotton fields. There are however high numbers of these pests on alternate hosts in some areas. If these pests decide to move into adjacent cotton, square loss could be rapid. All I’m saying right now is to keep your guard up and don’t let these square thieves sneak into your cotton unnoticed and steal your early squares. I hope last year’s experiences with these two pests were clear lessons to most of you. Monitor for first position square retention on at least a weekly basis and scout for these two bugs.

Weevil Trap Catches Plateau

GRID trap catches went up again this week indicating we are in an extended emergence. GRID maps and the listing of trap catches by zone and county can be viewed on the Plains Cotton Growers web site. Two-thirds of the boll weevils caught in the GRID last week were in counties below the Caprock (Motley, Dickens and Kent counties). When these trap numbers are removed and the remaining High Plains county trap catches are compared to last year, there has been an 83% reduction this year. When you make this comparison by zone, a very clear picture emerges (Table 1).

Table 1. Comparison of boll weevil trap catch numbers for the 25 th week (June 19-25) between 1999 and 2000 in the GRID trapping program.

Zone	Active?	Percent reduction (2000 to 1999)
Northwest	Y	99.5
Western High Plains	Y	93.3
Permian Basin?	Y	?*
Northern High Plains	N	43.4
Southern High Plains Caprock	N	74.8

*Had not received trap catch data for counties in this zone.

The Foundation’s eradication program appears to be very effective so far with a reduction ranging from 93 to 99% for two of their active High Plains eradication zones. The two inactive zone trap catch reduction ranges from 43 to 75%. I can’t explain all of the results of the trapping program except to say that I believe we are experiencing an extended emergence and I’m not so sure that trap catches are always reflecting what is going on in nearby fields.

GRID boll weevil trap catches through week 26 will not be available until after next week.

This brings me to the issue of overwintered boll weevil control decisions. There are three ways to make a call on overwintered boll weevil control. These include pheromone traps, field scouting and field history. Traps have generally been the most reliable followed by field history. If you miss getting traps out in a timely manner (before cotton is squaring), then you will have to rely on one of the other means for decision making. If you are nervous about what the trap is telling you, then look at field history and scout the field. Field history of course involves what has happened in previous years---have weevils been bad in the past, were their numbers or damage evident late last season? What about planting date? Earlier planting dates often mean earlier infestations. What about proximity to overwintering sites? Is the field near a town, a clump of trees, a canyon or draw, a CRP field? These clues could give you the history you need to make an educated guess as to whether a field may need a treatment or two.

Lacking field history, you are left with scouting the field. Checking for the presence of overwintered boll weevils in a field is a very tough proposition. Until squares are plentiful and pencil eraser-size squares appear, weevil adults are tough to locate. And they tend to fall off the plant at the least disturbance and play possum on the ground---again making them almost impossible to see. Field inspection involves checking at least 100 plants once pinhead or larger squares appear. If one or more adult weevils are found per 100 plants inspected or four found per 100 row feet inspected, an insecticide application is probably needed. Control can be of questionable value in dryland cotton growing under moisture limited conditions and a high temperature regime. This is because mortality is exceedingly high.

During typical June-July growing conditions, it takes 8-12 days for a pinhead-sized square to progress to a 1/4 inch-size square. Most successful boll weevil development takes place in squares 1/4 inch or larger but some successful development will occur in squares as small as matchhead size. While decisions for the first overwintered boll weevil application should be made during the week of appearance of pinhead-sized squares, the actual application needs to be applied somewhat later, when matchhead-size squares or larger are present.

It takes about 4-7 days for a pinhead-size square to develop to a matchhead-size square and another 3-5 days for a matchhead-sized square to develop to a 1/4 inch-sized square (third grown or pencil eraser in size). There isn’t much margin for error. The publication, Identification, Biology and Sampling of Cotton Insects (B-933), lists square development intervals of 9-10 days for pinhead to matchhead-size squares and 3-6 days for matchhead to one-third grown squares. This is too long for our weather conditions and most of our cotton varieties. Open boll varieties develop squares at a slower rate than our storm proof varieties.

Insecticide selection is determined by several factors including proximity to environmentally sensitive areas (houses, schools, etc.) cost, threat of secondary pests, preservation of beneficial insects, pest complex present, need for residual activity and application method. ULV malathion and pyrethroids tend to provide the longest square protection, closely followed by Vydate and then Guthion and methyl parathion and finally endosulfan (Phaser or Thiodan). Use a 3-4 day application window for endosulfan. This can be extended to a 5-7 day interval for the other materials, depending upon pest pressure. Endosulfan and Vydate are used where beneficial insect preservation is important. Multiple applications of these "safer" materials will probably lead to the elimination of "beneficials" anyway. ULV malathion is the cheapest of the best boll weevil materials but requires a special setup for the plane and is more specific as far as target pest spectrum. Both Guthion and methyl parathion are good materials and relatively cheap and can be used for ground application.

Ground applicators of methyl parathion will need a special filter on their air intake. Applications of ULV malathion, Vydate or endosulfan would be good for fields near sensitive areas. Pyrethroids fit well where both bollworms and weevils are a problem but can result in earlier aphid problems. Pyrethroids may also fit where plant bugs develop as a serious threat, otherwise Vydate could be the choice. Bidrin would work where aphids are also a problem, as would Furadan once it is cleared for our area. In other words, if either Bidrin or Furadan were used to control aphids, no additional weevil insecticide would need to be added to the tank.

Eradication Marches On

The beat goes on. Eradication efforts in our three active zones continues. Some acreage has been sprayed for overwintered boll weevils one or more times but there was still a lot of cotton yet to square according to the last report posted June 25 (Table 2).

Table 2. Records through June 25 of acres mapped, accumulative acres treated, average number of boll weevils caught per trap that week, and percent of acreage at pinhead stage or later in the three active High Plains eradication zones in 2000.*

Zone	Treated Acres (X1000)	Percent of fields that are? squaring**	Average # boll weevils per trap
Northwestern	97	34	0.09
Western	172	47	0.49
Permian Basin	11	18	0.58

*Numbers rounded to the nearest 1000.

**As of June 18.

In spite of all the recent rain, the Foundation has done a pretty good job of staying up with overwintered boll weevil applications. It will become more difficult if weather continues to interfere as more acreage squares and traps trigger treatments. The trigger used is 2 weevils per 40 acres. There is one trap every 5 acres on average so this would translate out to 2 weevils in 8 traps. Fields are to be at the pinhead square stage before they can be treated the first time. This is defined as a field with 50% of the more advanced plants with a pinhead square, or at least one matchhead square found in the field. A pinhead-size square will usually be found by the lower most folded leaf if the plant is squaring. The Foundation does recognize that weevils really need at least matchhead-size squares or larger for successful hosting but the logistics of conducting such a large scale eradication (not management) program does not allow the fine tuning of application timing that producers can do in managing their weevil infested fields. The Foundation has made some errors. This is to be expected with a large program involving so many unskilled personnel.

Foundation personnel can only check traps once-a-week, limiting their ability further to fine tune application timing. The Foundation must err or the aggressive side if they are to err at all. After all folks, this is eradication, not management. The quicker weevil numbers can be brought down the less expensive a program it will be. The Foundation must severely limit reproduction in the field early on to minimize the number of mid-season applications required. If a large percentage of the program acreage must be treated at mid-season, there can be a substantial increase in risk for secondary pest problems.

Some producers are opting to apply their own insecticides when Foundation traps indicate the need to treat. All alternative insecticides to ULV malathion must be with two applications to replace the single ULV malathion application. Producers applying materials such as Vydate or endosulfan do this in lieu of ULV malathion in an effort to preserve their beneficials. I question whether two applications of these materials at a 4-5 day interval are any less harsh than a single ULV malathion application. Other producers are using a pyrethroid for a bollworm/weevil "shot". A second application for weevils must be made 4-5 days later. Whether the producer applies the second of the two applications, program matters not to the Foundation. If the producer doesn’t treat the second time, the Foundation will with ULV malathion.

Some folks have questioned the reasoning behind the need for two applications of an approved alternative insecticide to the one application of ULV malathion. The Foundation is interested in killing adult weevils for the longest period of time following application. In tests that I have reviewed so far, ULV malathion more consistently provides a high level of mortality 5-7 days following application than the other materials. Vydate is a close second but still not as good. Pyrethroids provide excellent long term protection from square damage (often better than anything else), but in mortality type tests, its residual activity is very short. Some entomologists suspect that the extended square protection observed in tests may be due to repellency rather than mortality. As yet, no one has proven this. But the bottom line is that the Foundation is interested in killing weevils, not repelling them. After all, this is an eradication program.

Next week I will bring you a report on the meeting of the Foundation Technical Advisory Committee which met on June 29 and of which I am a new member. I think my discussion will give you a better understanding of the eradication program and the issues facing the Foundation.

Nickel and Dime Egg Lays

The bollworm egg lay continues across the area with problem fields beginning to pop up in the vicinity of Lubbock. Cooler temperatures, cloudy days and higher humidity are contributing to higher than typical survival. Even in areas outside of eradication zones, beneficial insects are being hard pressed to keep up with the constant dribble of eggs and high caterpillar survival. Most of the egg lay further north is still being absorbed by corn. These early problems with bollworms is somewhat unusual but not totally unexpected. As Foundation applications continue in the eradication zones, more of these marginal infestations may develop into economic threats unless the egg lay subsides. I personally use 5,000 to 8,000 small worms as a threshold in pre-blooming cotton but move right up to the 10,000 level once flowers are present. These same thresholds can be used in Bollgard cotton but treatment decisions must be delayed until caterpillars are larger than 1/4 inch in size. Please give the Bollgard technology a chance to work.

Bollworms typically lay eggs singly on the upper surfaces of leaves, particularly the newer top growth. But eggs can be found almost anywhere at times including on flower petals, square and boll bracts, leaf petioles, etc. High temperatures tend to drive egg laying further down the plant. Bollworm moths have a wingspan of about 1 1/2 inches and can lay as many as 200 pinhead-sized eggs under field conditions. These eggs are white at first and stand taller than they are wide. Egg development takes about 3 days and eggs turn brown within 24 hours of hatch. Black eggs often signify that the egg has been parasitized. Larvae that emerge from the egg are very small (1/16 inch) and difficult to find. I usually locate them by finding their damage first. These small caterpillars feed in the terminal area on small leaves and squares but eventually move down the plant to find larger fruit. They will eventually penetrate one or more bolls once they are available. Small bollworms can easily move down the plant by producing a silken thread and rappelling on down. There will be some movement between plants down the row.

Larval development averages two weeks but can take as long as 3 weeks under cool conditions. Larvae grow to be 1 1/2 inches or larger. There are many color variations ranging from green, brown, tan, black and even pink. They generally have some stripes running the length of their body. One has to examine the mandibles of larger caterpillars to determine if they are actually bollworms or tobacco budworms. For now, this determination is not important but could be later in the season when budworms can be more prevalent. Once development is completed, caterpillars drop to the ground and dig into the soil to a depth usually no deeper than 2-3 inches and pupate. After a period of about 12-18 days, moths emerge from these pupae and start the next generation. (See bollworm picture series)

Beet armyworms (BAW) persist across area cotton fields but have generally been more of an emotional nuisance than a real threat. But don’t take them for granted. Without warning our situation could change rapidly, resulting in threatening levels of beet armyworms that must be dealt with quickly if the present arsenal of insecticides are to be effective. We no longer have Pirate to bail us out of trouble. Thus far I have not had any reports of BAW problems in Bollgard cotton. The same cannot be said for some conventional cotton fields and some treatments that have gone on. Most of these have been successful.

We continue to find a small caterpillar mostly in Gaines County fields. As yet we have not been able to get anyone to identify it. It is not a bollworm or armyworm. We have been told it probably is a noctuid (a family of caterpillars) but I still hold out that it could be a Pyralid (another family of caterpillars). Garden web worms (careless weed worms) are Pyralids. But it may also be some kind of leaf roller? JFL

Corn rootworm beetles began to emerge last week in our area, and numbers will increase over the next three weeks (pictures of rootworm beetles). These beetles feed on leaves, pollen and tassels, but prefer silks. Most feeding damage is inconsequential except when silks are pruned to the point that pollination is reduced. Insecticides are economically justified when adults are numerous (8 to 10 per plant) during the green silk stage and the silks are chewed back to within 1/2 inch of the shuck. However, insecticide use for rootworm beetle control may promote later spider mite outbreaks, depending on insecticide used and, to a great extent, the weather in July and August. Because spider mites are difficult and/or expensive to control, it is prudent to carefully consider whether a rootworm insecticide should be applied. RPP

The corn leaf aphid is bluish-green and has black legs. The greenbug (also an aphid) is lighter green and has a characteristic dark green stripe down its back. (Pictures of sorghum pests discussed here)

There is an excellent website at Texas A&M called "Insect Pests of Sorghum" (http://sorghumipm.tamu.edu/). This is the home website of eminent sorghum entomologists Dr. George Teetes and Dr. Bonnie Pendleton. The Lubbock IPM website also has a sorghum section with many references from Texas and elsewhere.

I am pleased to note that Dr. Pendleton will join the faculty of West Texas A&M on August 1, thus giving us a major league sorghum entomologist on the High Plains.

Southern blight (SB) continues to be found on a few plants within the region the past few weeks in poorly rotated fields. The infection loci have primarily been restricted to the underground plant parts, such as the roots and crown. While I have not seen any surface activity (vegetative growth), I do find this to be highly unusual and if the nighttime temperature exceeds the upper 70's we could expect to see SB within the coming weeks, so please keep an eye out for this destructive soilborne disease.

Early leafspot lesions have been found in this area of the Southern Plains. Due to the fact that we have been experiencing wet periods (rain events) this is really no big surprise. Now, as with many diseases in peanuts, it can be easy to confuse one symptom with another altogether different problem. Case in point, we are currently seeing a chemical burn on some peanuts that could be thought to be leafspot. To distinguish early leafspot from chemical burn or other foliar deformities, you must look carefully for tiny brown bumps or "fuzz" on the top of the spot accompanied by a yellow halo around the spot. Now that we are seeing the initiation of leafspot in combination with pod rotting fungi such as Rhizoctonia and Pythium, which we are also finding now, I would advise area growers that you need to apply an appropriate fungicide prior to a significant outbreak. Remember that fungicides are preventative and not curative in their mode of action. (Pictures of the diseases mentioned here) (Reprinted with editing from Gaines County Extension Agent-IPM Clyde Crumley’s newsletter.)

Well, we did it. We broke the June record for rainfall at Lubbock. As of this writing, we were approaching 9 inches. The recent rainfall events across the High Plains have resulted in many areas receiving as much as 15 inches or so. Good rains have fallen over a substantial portion of our acres and are continuing. Official reports indicate 1-3 inches from Tulia, Dimmitt, Friona, and Hereford for the last few days. Anywhere from 1-5 inches was reported in Dawson County. Grower reports of greater than 10 inches over the last few weeks are not uncommon in some places north of Lubbock. There are still some areas such as north of Muleshoe that are "dry slotted" and have received less than 1 inch since June 1st. Getting the ground covered with sandfighters to protect stands, especially on smaller cotton is a priority. Cultivation as soon as possible will help with soil aeration and should help with crop recovery.

Spotty hailstorms near Needmore, Petersburg, New Home, and other areas since last week have decimated another 20-30K acres. Additional hail was encountered Wednesday night in Dawson County. This brings our total to about 50K acres destroyed over the last 2-3 weeks. Considerable dryland cotton in Dawson and Gaines Counties have also been "disastered" due to earlier drought associated problems. The total lost in those two counties is nearing 100K acres. As of this writing, it appears that we are close to 150K acres lost from this year's planting. What is important about this situation is the fact that we are past our final planting dates for insurance purposes for cotton across the region, and any cotton losses incurred will come off this year's High Plains production. Adjusters are working fields and many growers will collect insurance payments and look seriously at alternative crops. Dr. Calvin Trostle, Extension Agronomist at Lubbock, has some very good information available for replanting considerations.

We really need some open weather to get this crop moving forward. Heat unit accumulation has generally been lower than the long term average for the last few weeks, and the "surplus" which we once observed (at nearly +30% above normal) has diminished. Our DD60 or heat unit "surplus" compared to the long-term average from May 1st is about +7% at Halfway, and about +17% at Lubbock and Lamesa. Cooler temperatures and water logged soil conditions are beginning to "yellow-up" the crop in some places. Some cotton fields with excessive soil moisture and poor growing conditions are exhibiting Rhizoctonia root disease problems (pictured here). I also wouldn't be surprised to find some bacterial blight (also called angular leaf spot) out there due to the wet conditions we have recently experienced. Bacterial blight can move from leaves to bolls if wet conditions persist. Once on bolls, the lesions start out as waxy-appearing spots, and eventually the infected areas die. This is a concern because if the boll carpel wall is breached by the bacteria, then the lint may be discolored or eventually destroyed by boll rot. If anyone has observed bacterial blight symptoms, please call the center and report what variety (or varieties) on which it has been found.

Dryland Cotton Fertilization

We are getting some questions about fertilizing the dryland crop. Many dryland producers have opted to sidedress or topdress nitrogen (N) fertilizer after stand establishment in order to reduce front-loading expenses. Applications of N are more likely to stimulate growth and promote fruit retention. Adjust N rates to fit yield potential. With all of the moisture stored in the soil profile, one should seriously consider N fertilization. A one-bale cotton crop will actually remove about 45 lb of actual N per acre, but due to inefficiencies in uptake and in the soil, about 50-60 lb N/acre are actually required. Generally speaking, about 30-50 pounds of actual N per acre are adequate for dryland cotton. The higher rates should definitely be considered if the yield potential (stored soil moisture) is adequate for higher lint yields. Sidedressing/topdressing should be completed before blooming, with extreme care taken to not prune roots during the application. Benefits from low rates of foliar fertilizers are questionable.

Available N Fertilizer Sources

Anhydrous ammonia (82-0-0) contains more N per ton than any other source. It is the basic building block for the manufacture of other N sources. Overall, in terms of price per pound of actual N, it is the least expensive. Problems with handling, safety, application, and toxicity concerns combine to make this a less than desirable N source.

Urea (46-0-0) is manufactured using ammonia and carbon monoxide, a by-product of ammonia synthesis. It is generally the least expensive solid N source. It has excellent shipping and handling characteristics. Some problems are encountered from an agronomic standpoint. In order to reduce possible N losses, it is important that urea be applied properly.

Ammonium nitrate (34-0-0) is manufactured by reacting anhydrous ammonia and nitric acid. It has excellent agronomic properties. It can be explosive if a carbon source is added (used in the making of the 1995 Oklahoma City bomb). Its hygroscopicity causes handling problems (prills melt and "brick up"). This material is generally more expensive on a per pound of actual N basis, and is getting hard to find in most areas.

Ammonium sulfate (21-0-0-22S) is one of the oldest forms of N fertilizer, and is many times more expensive per pound of actual N than other sources. It can be manufactured from coke oven gas from steel and other metallurgical industries. It can also be manufactured by reacting anhydrous ammonia with sulfuric acid. The added benefit of sulfur may be important if that essential nutrient is required in low testing soils.

Urea-ammonium nitrate or UAN is the main fluid nitrogen source commonly marketed as 28-0-0 in winter months and 32-0-0 in the warm season. It is corrosive to many metals, and corrosion inhibitors are generally added. It is a mixture of 35% urea, 45% ammonium nitrate, and 20% water (by weight).

Ammonium thiosulfate (12-0-0-26S) or ATS is the main fluid fertilizer source of sulfur. It is compatible with fluid N sources and many times is blended with UAN to supply sulfur.

Ammonia loss problems from N fertilizers are mostly associated with anhydrous ammonia, urea, and urea based fluids (UAN). Ammonium nitrate does not generally have a significant problem with ammonia loss.

Factors favoring ammonia volatilization from urea-based materials include:

1. High soil pH conditions

2. Low cation exchange capacity (such as in low organic matter sandy soils)

3. Large amounts of plant residues (urease enzyme present)

4. High temperatures

5. Moist conditions followed by rapid drying

Some producers use airplanes to apply urea. In order to reduce ammonia loss from urea-based materials (this would also apply to fluid UAN), the following strategies are suggested:

1. Incorporate into the soil by cultivation or at least by rotary hoeing after application.

2. Broadcast applications increase exposure to urease enzyme, so if possible inject or knife fluid UAN into soil.

3. Lightly irrigate immediately following a broadcast application if other soil incorporation is not used.

Plant Monitoring

Monitoring fruiting patterns is an important management consideration. First position fruit is very quickly counted. This is generally adequate for "getting a handle on the crop" (Figure 1). At early bloom, up to 80% of the harvestable crop will be on the plant in the form of squares and blooms. We like to see at least 90% square retention going into the first week of bloom. Many times, High Plains fields will enter blooming with square retention greater than that. Our square retention goal is 75 - 85% 14 days into blooming. Our percent boll retention goal is at least 50%, with 75% excellent for 3 - 4 plants / ft on 40 inch rows. Plant mapping can be used to help monitor the progress of the crop and determine some important crop factors.

Important plant mapping data at early bloom are:

1. Total 1st position squares present and missing

(retained squares / total square sites = % square retention)

2. Total 1st position bolls present and missing

(retained bolls / total boll sites = % boll retention)

 3. Nodes above white flower

Nodes above white flower (NAWF) gives an indication of crop vigor and yield potential. For the High Plains region, greater than 7-8 NAWF could be considered excellent, 6-7 - good, 5 moisture stress evident, 4 or less - cutout imminent on determinate varieties. RB

Table 3. Data from the South Plains PET Network, June 23-29, 2000:

	Reference		Estimated Crop PET in inches [a]
	PET (inches)	Rain (inches)	Cotton		Sorghum		Corn
			1st square	1st bloom	5-leaf	flag leaf	10-leaf	tassel
Lubbock	1.41	0.87	0.31	0.62	0.99	1.34	1.62	1.76
Lamesa	2.14	1.27	0.47	0.94	1.50	2.03	2.46	2.68
Halfway	1.30	0.84	0.29	0.57	0.91	1.24	1.50	1.63
Seminole [b]	--	--	--	--	--	--	--	--
Ropesville	2.02	2.15	0.44	0.89	1.41	1.92	2.32	2.53

[a] 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.

[b] Site is actually closer to Denver City. Electrical problems at the site have resulted in questionable data. Please accept our apologies for the inconvenience.

PET varies 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

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