The cotton crop continues its relentless march toward maturity in the absence of any appreciable rain. Many fields have cutout and some even have open bolls. There has been considerable shedding of fruit in dryland and many limited irrigated fields. In fact, while insects have taken the front seat in the news department, lack of significant rainfall since June’s excess is really going to be the main yield loss leader. Cotton fields with timely irrigations that were planted in the optimal window will have great yields. Many other fields will have reduced yields, probably pulling the average High Plains per acre yield down below average?

While most of the cotton crop is rapidly maturing and moving away from the insect damage window, there remains many late planted and late irrigated fields still vulnerable to the advances of several pests. Boll weevil numbers continue their rapid increases both in trap catches and in the damage appearing in fields outside of active eradication zones. The beet armyworm egg lay is generally tapering off but still continues to produce high numbers of caterpillars in many fields. Loopers, in combination with beet armyworms are causing significant defoliation problems in some fields---up to 60% or more in limited cases. Bollworms continue to dribble into fields with the big peak of activity in corn growing areas expected in 5-10 days. Aphid infestation levels are variable but generally blowing by our suggested treatment levels, especially in fields where caterpillar pests have been controlled with insecticides. And lygus bugs are becoming more of a problem in fields near peanuts and alfalfa.

The insect season has ended for corn, which is now being harvested. Late spider mite problems developed in several fields but treatment was not justified. Alfalfa has had its share of beet armyworm problems and can now be treated with Tracer under a Section 18. A new Section 18 has been granted for Confirm on soybeans, beans, peas, and sunflower for control of caterpillar pests (armyworms, etc.)

The end of the season is rapidly approaching for some cotton fields with open bolls appearing in many of the earlier planted fields. Some boll opening is unfortunately due to moisture stress. Much of the High Plains crop has passed cutout and is moving quickly toward a position where insects can no longer damage potentially harvestable bolls. There are many late planted fields that will see the brunt of the last wave of insect activity of the 2000 season. Producers will need to critically evaluate yield potential and insect control costs before making further management decisions. With boll weevil numbers increasing exponentially, bollworms, loopers and beet armyworms continuing on the attack and aphids flaring right and left; it has been difficult to maintain optimism for this crop over the last few weeks. The long absence of appreciable moisture since June has caused significant fruit shed, often fruit that was protected earlier from insect damage with an expensive insecticide application. While I still think yields will be down this year due to limited moisture since June and insect problems of epic proportions, there are fields that producers have kept up with water needs and where insects have been a minor nuisance. These fields will take advantage of our hot, dry days and yield very well.

The take home measure for this week? Every field has its own set of problems. Do not generalize between fields and across farms. Check each field individually and make management decisions accordingly.

Boll Weevils Making Final Run

Trap catches of boll weevils have really increased this past week (Table 1). This is a similar pattern to what we observed last year (Table 2). But Table 3 presents the real story. Where eradication is an active program, weevil numbers are being held in check by Foundation sprays, even with the Foundation backing off during the mid season to avoid causing any more problems with secondary pests. The counties that caught the most weevils were in descending order: Crosby, Lubbock, Floyd, Hale and Swisher. The counties catching the least included: Parmer, Terry, Deaf Smith, Castro, Bailey and Andrews. Even Gaines County with an average of less than 2 weevils per trap was way below Crosby County, which was at 33 weevils per trap. What a difference a year makes.

While boll weevil numbers were increasing dramatically in traps outside of active eradication zones, punctured square and boll counts were also going through the roof. Without immediate control efforts, some of these fields will be lost. In fact, some already have been lost to weevils. Once punctured boll counts move past 15%, a spray schedule will need to be set up immediately, if there are enough harvestable bolls left that weevils can damage and that can be saved to pay the aerial applicator. Think in terms of 2 applications 4 days apart. Once percent punctured bolls goes above 20-30%, it may not be possible to gain back the upper hand. Think, 3-5 applications if a lot of late fruit needs protection. Also, it is time to move toward products such as methyl parathion or Guthion or even ULV malathion if you can get this application. No need to protect "beneficials" now. And don’t use a pyrethroid unless you want to fight aphids later on.

Unlike with caterpillar pests, bolls are really pretty safe from punctures once 350 HUs are collected past cutout or past white bloom, if you intend to harvest these late flowers as bolls. Boll penetration by weevils drops to 5% or so at this time. We can live with this. In the absence of HU information, use the old pocket knife slice test. If you can’t slice a boll without sawing, then it is safe from penetration. That doesn’t mean that you won’t find a weevil grub in a ‘safe" boll. That grub came from an egg laid several days earlier when the boll was not safe.

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

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
June 19	5684	49
June 26	3346	53
July 3	3318	48
July 10	2057	32
July 17	1522	42
July 24	1772	41
July 31	4534	50
August 7	2960	45
August 14	6133	54

*Includes three counties in the Rolling Plains.

Table 2. Comparison of average weekly boll weevil trap catch in the Southern High Plains/Caprock Zone between 1999 and 2000.*

Week beginning	1999	2000
June 5	12.2	6.8
June 12	7.8	6.1
June 19	9.9	4.1
June 26	9.5	6.0
July 3	3.3	4.6
July 10	2.0	1.8
July 17	2.1	5.1
July 24	2.0	6.0
July 31	5.8	18.8
August 7	5.5	10.0
August 14	13.7	17.0

*These data represents the average number of weevils caught per trap catching weevils. Zeros are not counted.

Table 3. Week 33 (week beginning August 14)— Accumulative average number of boll weevils caught per trap in the GRID trapping program starting with week 18.

Location	1999	2000
Northwest High Plains	49.3	24.6
Northern High Plains	80.7	92.3
Southern High Plains	120.3	115.8
Western High Plains	216.6	35.3
Permian Basin	115.0	39.2
Andrews	201.1	39.1
Bailey	50.9	26.0
Borden	88.6	51.5
Briscoe	92.1	85.2
Castro	16.2	11.0
Cochran	87.9	72.1
Crosby	156.4	196.5
Dawson	161.4	54.3
Deaf Smith	11.0	2.0
Floyd	60.4	128.1
Gaines	268.9	30.2
Garza	193.3	171.3
Hale	75.6	86.5
Hockley	82.9	58.8
Howard	110.7	28.8
Lamb	57.7	22.2
Lubbock	101.1	120.8
Lynn*	101.3	56.5
Martin	55.9	19.4
Midland	46.4	21.7
Parmer	11.7	6.0
Swisher	69.4	76.8
Terry	143.9	27.1
Yoakum	184.5	29.3

These data represent 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.

*Includes traps both inside and outside active eradication zones.

End In Sight For Beet Armyworms ?

I really do believe that the beet armyworm (BAW) egg lay is tapering off in many areas. Acreage to the south of Lubbock has definitely seen a reduction in BAW pressure. Reports indicate a lessening of pressure even in the northern cotton fields. It’s not over yet and many fields are still receiving anywhere from a dribble of eggs to still heavy egg lays from beets. Also, don’t close the door yet on this year’s BAW problem. More could come as late as September. The key is going to be whether the crop is still vulnerable. Please be realistic in assessing damage potential and yield potential from here on out in making control decisions. You all have considerable money in this crop and don’t need to finish the season with bad decisions. Both fruit loss and defoliation are issues that need to be weighed in any decision and of course whether any harvestable boll is still vulnerable to attack. Look under the bollworm section about HU thresholds from this point on. Also look under the defoliation section.

I really do think that many fields are no longer going to be threatened by beet armyworms as far as yield loss is concerned. Fruit feeding is reduced and what fruit feeding that is taking place is mostly on squares that will not produce harvestable bolls for this season. Don’t spray to protect this "junk fruit".

Now that most folks have been drained of their emotions about beet armyworms, we have had a chance to look back on this experience and evaluate what might have worked and why. Most users of Denim and Steward have been generally pleased with their results. If only these two products could have been cheaper and more plentiful. Confirm had a slow start but use picked up momentum once some other insecticide options became limited and more folks began to understand the product. Yes, it was slow to kill worms. But it did stop damage within 24 hours of application. But what really caught most folk’s attention was the 14 day residual activity. No other material could come close to that. A lot of Lorsban was used, mostly because it was plentiful and cheaper than Tracer. Also, many producers were familiar with its performance based on previous year’s experiences. It did deliver about 80% control as long as it was not tested too much against larger worms. It also gave some aphid suppression, but not outright control.

We continued to here complaints about Tracer performance, at least more so than with other products. Again, we knew what to expect from Lorsban and therefore did not complain when it didn’t clean up a field. We also had somewhat reduced expectations with Confirm. I really think there are three major issues pertaining to non-performance of some of these materials. The first and easiest one to dispense with was the size of the infestations. Producers can live with eighty percent control of 10,000 caterpillars but not necessarily 80% of 65,000 per acre!

What we have seen is a serious coverage problem. Many of these materials appear to be very sensitive to coverage. In research plots where high spray volume, three nozzles per row and drops are used, we rarely have a problem controlling pests with efficacious materials. The fact is, we often "blow them away" even with the low rates. Now, once these materials get in the hands of commercial ground or aerial applicators, or producers doing their own applications, all bets are off. This is especially true where taller, lusher cotton is the rule. Even spray planes set up correctly have had some problems with the bigger cotton. And many of the ground applications went out with overhead nozzles, no drops. This was a very big mistake! Especially where low spray volumes were used. Many have found that coverage can be improved using a crop oil with water to help reduce evaporation and drift. But what really would work best would be a non-emulsifiable oil. By mixing first this oil with the insecticide, the water becomes the carrier of the oil-encapsulated insecticide. A much better system than the first. Remember, that without drops on ground equipment and with taller cotton treated with aircraft, the cotton plant acts like an umbrella, allowing spray deposition only on the outside of the plant. What about all the worms on fruit in the interior areas?

The third issue of performance is target size. Too many applications are going out late either because of indecision on the part of the producer or consultant or because applicators are getting behind. Look at the Tracer label. Target size is 1/8 inch long caterpillars, not 1/4 inch or 1/2 inch! How many of you sprayed fields with some small but mostly larger caterpillars and still expected miracles?

Looper and Beet Armyworm Defoliation Substantial

While I believe that fruit feeding by beet armyworms is on the decline, defoliation by beets and cabbage loopers is still widespread. Cotton can tolerate a lot of leaf area loss, especially on the older leaves, the bottom leaves and the mainstem leaves. The leaves that subtend bolls are the most important now. There has been a lot of defoliation in some fields. More than I have seen before. Some fields have lost over 60% of their leaf area. This will have an impact on yield. These fields look brown from a distance. But most fields with some level of defoliation are not as bad off as they look. We tend to overestimate defoliation by quite a bit. Look at an example of soybean leaf defoliation . Much of our defoliated cotton crop is less than 30% defoliated. I think we need to be above 35-40% at this time to have a substantial impact on yield. If you think this fits your situation, consider using a higher rate of one of the newer pyrethroids for just looper control, or something like Tracer if beet armyworms are in the mix.

New section added 11:30 AM, August 23:

While cabbage loopers have been the dominant species of loopers present in area cotton fields, there have been increasing concerns about the probable presence of soybean loopers in the mix. Soybean loopers are generally harder to kill than cabbage loopers and fewer insecticides lay the claim of control of this species. These two looper species have different mandible configurations but most of you want something simpler and quicker than looking at "smiling" caterpillars in a cotton patch. Cabbage loopers almost always have white stripes down their sides while soybean loopers often do not. But the more definitive characteristic would be the black thoracic legs behind the head of soybean loopers versus pale legs behind the head of cabbage loopers.[Pictures of cabbage and soybean loopers]

Looper control regardless of species is not great, especially with pyrethroids. Products with Bt work well for leaf feeders and Tracer also, when good coverage is obtained. Other pyrethroids that list control of cabbage loopers on their label include Decis, Baythroid, Asana, Ammo,, Fury, Capture and Karate Z. Decis claims suppression of soybean loopers and Larvin claims control of both looper species. Tracer does too.

Where Are All the Bollworms?

Bollworm moths continue to lay eggs at below peak levels across the region, concentrating mostly on the later, lusher fields. Most infestations of caterpillars have been below 10,000 per acre. Where cutout has occurred, thresholds should be raised above 10,000 per acre on any new activity. Once 450 or more heat units (HUs) have accumulated past cutout, harvestable bolls become relatively safe. Actual boll safety can be modified by several factors. If young caterpillars can gain some size on squares or small bolls, then these larger worms can penetrate the so called "safe bolls". Also, there is a big difference between 10,000 small bollworms trying to penetrate safe bolls and 30,000 trying to do the same. Since boll penetration at 400 HUs is still as high as 43% in Texas studies, and even 20% after 600 HUs, higher caterpillar counts can still get you into trouble. That is why we have raised the threshold to 15,000 and even 20,000 worms per acre as bolls "toughen up". With the COTMAN model, we can use the 450 HU level for up to 10,000 small worms per acre, 15,000 for 500 HUs and 20,000 for 600 HUs. These are safety threshold estimates that I think will work. Use these also for beet armyworms, as far as fruit feeding is concerned. Also to be considered is the impact of late sprinkler irrigations on boll softness. Based on observations only, I believe that bolls remain vulnerable to insect penetrations past the suggested HU thresholds when overhead sprinkler irrigations are applied.

Peak levels of bollworms have yet to appear in cotton fields in corn growing areas. Based on surveys in corn, we expect this movement from corn to cotton to occur later this week and into next week. Fields that are still attractive to egg laying and can support these infestations will have considerable pressure. Don’t let loopers and beet armyworms hide these much more damaging pests. Scout carefully.

Aphids Infestations Continue to Flourish

Infestation levels of cotton aphids have continued to increase in many but not all fields. As with all insects this year, aphid infestations are not a problem in all fields. My concern this season has been the lateness of many applications made to aphid problem fields. Too many producers are waiting until aphid numbers easily exceed 200 per leaf, well above our treatment threshold of 50 per leaf. Waiting this long means that some yield loss has already occurred before control can be achieved. A late application also means that control may not be as satisfactory as it would have been if it had been more timely.

I know that many folks checking cotton for aphids don’t think there is much of a problem until the leaves are real shiny and honeydew (sugar water excretion deposits of aphids) are dripping from leaves and coating plant parts. The truth of the matter is that a field with a threshold level of aphids looks pretty good from the turnrow. A closer inspection would show a light mist-like deposit of honeydew on cotton leaves. And most producers think that 100 aphids per leaf looks more like 50. Some of the delay of applications can be attributed to producers being distracted by other pests, such as beet armyworms and loopers.

Control has been somewhat inconsistent across the area. Bidrin continues to be erratic in performance, even at the 8 ounce per acre rate. Adding 4 ounces of Curacron often will enhance performance on difficult to control infestations. Furadan has not been the magic bullet as in years past but still appears to be the best, and the cheapest. Other materials listed in the cotton insect management guide such as Lannate, Lorsban or Provado provide even less control than the above mentioned materials.

Pyrethroids continue to flare aphid numbers, as do some of the other non-pyrethroid materials such as Steward. Pyrethroids increase aphid reproduction, kill beneficial insects and keep "beneficials" out of treated fields a long time. Other insecticides don’t appear to affect reproduction but do kill insect predators and parasites. Both Larvin and Steward can be pretty rough on lady beetles. And there are a lot of lady beetles out there in some fields. But remember, you are growing cotton, not "beneficials"! If aphid numbers blow by the treatment threshold of 50 aphids per leaf, the "beneficials" didn’t succeed in controlling the population and an insecticide is needed.

Don’t fall into the trap of using an unproven product for aphid control. There is one of these out there right now called Aphid-Pruff. You probably saw an advertisement on TV 11 and even a story on this product on TV 11 by Loren Stromen. This product even has an EPA number. Must be good stuff, huh? Well, no it isn’t! This product is not research based like those developed by major chemical companies that invest millions of dollars into the development of their products. Aphid-Pruff was developed by Jerry Kitten of Kitten Fertilizer in Slaton. This is not a new product as I had a chance to look at it in a scientific study a few years ago. In a replicated test conducted east of New Home according to Kitten’s protocol, I did not observe any differences between the Aphid-Pruff treatments and the untreated check. In other words, it didn’t work. And having an EPA number does not mean that it is effective. In fact, EPA could care less whether the product performs according to the label. Their concern is for safety and environmental impact. A product that doesn’t kill anything would get a very quick nod from EPA. Bottom line? Without any research to support product claims, Aphid-Pruff is an expensive lesson ($7.50 a gallon; 1 gallon per acre; may need more than 1 application) for producers needing real control of damaging aphid infestations. A Furadan application costs less than $6 per acre for material.

Lygus Bugs May Be A Problem

Lygus bugs have become dramatically more numerous in some cotton fields, especially those near peanuts and alfalfa. The treatment level at this time of year is 2 plant bugs (adults or nymphs) per 3 row feet, sampled using a drop cloth. This level is only a guideline and would only apply where fruit damage is becoming excessive. Later cotton would be most vulnerable. We have an insecticide test (16 treatments) established in a field on north University where counts probably average 5 per 3 row feet. With a late crop and low yield potential, this field can not be economically treated. Many of the pyrethroids and Orthene are excellent plant bug materials.

Eradication Update

Boll weevils are really beginning to move between fields and showing up more in traps and even in fields within the active eradication zones. But to my knowledge, no producer has had a damaging weevil infestation develop in their field within an active zone. The same cannot be said for fields outside active zones. Boll weevil numbers in traps keep increasing and punctured boll counts are heading toward the stratosphere! One only needs to review Table 3 and compare zones and counties to see what is beginning to unfold out there. Wait until September and October. It can only get more dramatic. Also look at the most recent GRID map to see the distribution of boll weevils in the GRID trapping program.

While the Texas Boll Weevil Eradication Foundation has held back on spraying the last several weeks since early season overwintered boll weevil sprays, they are fast approaching the time when they will crank up spraying activity again as the diapause phase begins again. The treatment reductions during the midseason period were an effort to avoid increasing problems such as aphids, beet armyworms and loopers. And whether you believe it or not, the Foundation’s efforts were successful. They did not create this caterpillar catastrophe we are experiencing, nor did they exacerbate it either. Records from 1980 (pre boll weevil) show the same pattern of infestations with loopers, beet armyworms and bollworms and their spread across the area. The only difference this time is that we had more qualified consultants and IPM agents to work with and more effective chemicals as well.

Table 4 provides Foundation data on the total accumulative acres sprayed, average number of boll weevils trapped (both in 2000 and in 1999) and beet armyworm trap activity. Basically, Foundation traps are showing significant reductions in boll weevil numbers compared to 1999. Their beet armyworm trap catches show a general increase in the Northwest Zone and similar to lower numbers in the two southern zones.

Table 4. High Plains Eradication Program weekly report for week ending August 13.

Zone	Accumulative acre applications	Avg. # boll weevils per trap	Avg. # beet armyworms per trap
Northwest	681,469	0.08 (2.0)*	531
Western	1,200,094	0.22 (5.0)	172
Permian Basin	692,520	0.17 (1.0)	53

*( #) = 1999

A new trap has appeared next to some of the boll weevil traps put out by either the Foundation or in conjunction with the GRID trapping program. This trap is for catching pink bollworms. This is a separate survey and has nothing to do with the eradication program. JFL

Two Lubbock County fields were severely damaged by a larva that destroyed taproots. The lab at College Station identified these as desert weevils, an occasional but devastating pest. To look for this pest, dig deeply in dead spots. The larvae are 1/4 to 3/4 of an inch long and seem to be legless when viewed with the naked eye. Taproots will have large feeding gashes up to five inches long and 3/8 inch wide. Adults are "shortnosed" or "flatnosed" weevils. RPP

The ever-popular guide, "Managing Insects and Mites in Texas Small Grains" has just been revised. The new version is available at http://agpublications.tamu.edu/pubs/ent/b1251.pdf, and will be in county Extension offices in a month or two. RPP

This crisis exemption is effective as of August 21 and will expire on September 5, 2000.

Tolerances have been established for residues of tebufenozide on the foliage of legume vegetables at 0.1 ppm. A 14 day pre-harvest interval must be observed. Applications should not be made to field areas which are less than 100 feet from permanent natural bodies of surface water or reservoirs.

TDA also announced a Section 18 for the use of Confirm on sunflower to control lepidopterous larvae. Again, applications must be made according to the Confirm label (read label). Additionally, the product may be applied at a rate of 8 to 16 fluid ounces (0.125 to 0.25 lbs active ingredient) per acre in a minimum of 5 gallons of finished spray per acre by air or 10 gallons of finished spray per acre by ground application. A maximum of one application may be made under this crisis exemption.

This crisis exemption is effective as of this date and will expire on September 5, 2000.

Tolerances will be established by EPA. A 30 day pre-harvest interval must be observed.

Applications should not be made to field areas which are less than 100 feet from permanent natural bodies of surface water or reservoirs. RPP

Table 5. Data from the South Plains PET Network, August 11–August 17, 2000:

[a] Potential Evapotranspiration, often referred to as "PET" or "ET", is an estimate of maximum crop water demand based upon weather data. Actual water use by a crop will vary with soil and crop conditions.

As the end of the season nears, it is time to consider scheduling the last irrigation. With cotton in particular, excess soil moisture can cause problems later with regrowth (unnecessary terminal growth); yet we want to provide sufficient moisture to allow the later bolls to mature.

Cotton water demand declines after first open boll. At first open boll, water use may be as much as 110% of reference crop (cool season grass) ET. At 25% open bolls, the water use rate is approximately 83% of the reference crop ET; and between 50% open bolls and 95% open bolls, water demand is only about 44% of the reference crop ET. According to long-term climatological data records, typical reference crop ET at Lubbock is about 0.27 inches/day in August, 0.22 inches per day in September, and 0.16 inches per day in October. Hence, expected water use in a "typical year" are summarized by growth stage and date in Table 6.

Table 6. Expected cotton water use (inches per day) by growth stage at Lubbock, based upon long-term climatological data and High Plains cotton PET coefficients.

Soil moisture storage capacity was discussed in detail in the July 21, 2000 edition of Focus on Entomology.

Although cotton withdraws most of its water requirement from the upper 2-3 feet of soil, cotton can have an effective root zone depth of 2.6 to 5.6 feet in a deep soil. Plow pans, clay pans, caliche layers, water tables, and excessively dry lower layers can impede root growth. A soil probe or rod inserted into the soil will help you to determine depth of impeding soil conditions, and therefore the maximum depth you should sample for soil moisture.

Soil moisture monitoring instruments can provide quick and easy estimates of soil moisture storage (and depletion). Alternately, you may estimate the moisture level by appearance and feel. To estimate soil moisture by feel and appearance, use a soil probe, auger, or spade to extract a small soil sample within each foot of root zone depth. Gently squeeze the sample in your hand to determine whether the soil will form a ball or cast, and whether it leaves a film of water and/or soil in your palm. Press a portion of the sample between your thumb and forefinger to observe whether the soil will form a ribbon. Compare your sample with the guidelines indicated below for your particular soil type.

Table 7. How soil feels and looks at various soil moisture levels.

Available water storage by soil texture classification is summarized below:

(Source: Estimating Soil Moisture by Appearance and Feel. NebGuide G84-690-A. University of Nebraska Cooperative Extension Service. (http://www.ianr.unl.edu/pubs/irrigation/g690.htm)

More specific data for soils in the Southern High Plains were summarized by Dr. Randy Boman in the August 11, 1999 edition of Focus on Entomology http://lubbock.tamu.edu/ipm/AgWeb/newsletters/focus/1999/aug_20/frameset.html. According to Dr. Boman, the ideal management strategy would result in simultaneous depletion of soil moisture and nitrogen and maturation of the final boll.

Table 9. Average plant available water holding capacities for typical High Plains soils.

Sources: High Plains Underground Water Conservation District and NRCS.

To calculate the water remaining in the root zone, multiply the Available Water Holding Capacity (Table 8 or Table 9) for your soil by your estimated percent moisture remaining in the soil (Table 7). For a soil with a water holding capacity of 1.9 inches of water per foot soil depth, and an estimated 25% available soil moisture, the water remaining is 1/2 inch per foot of soil depth (1.9 inches/foot X 0.25 = 0.5 inches/foot).

With an estimate of soil moisture available in the soil, and an approximation of crop water requirements through the end of the season, we can do a better job of determining whether to terminate irrigation or continue irrigation (perhaps at reduced levels) for a little while longer.

Generally speaking, furrow irrigation usually should be terminated in mid-August. Sprinkler, LEPA, and subsurface drip irrigation offer more flexibility in application rate, and therefore allow us to "taper off" irrigation applications to account for declining crop water demands. DP