DRIP TAPE AND TUBINGS: HOW TO CALCULATE THE AMOUNT OF WATER APPLIED
Franklin Laemmlen
 
 Applying only the amount of water the crop needs to grow and mature saves water and energy (pumping costs). Because low-volume irrigation systems are easy to operate and can achieve a high degree of uniformity, they are well-suited to use both water and energy efficiently. To make the best use of a low-volume irrigation system, it is necessary to accurately determine the application rate so the system is only operated long enough to meet plant water needs between irrigations. This article reviews how to determine the application rate and required operating time for drip tape and tubing.
Drip tapes and tubings - placed on or below the soil surface - are most commonly used to irrigate row crops. Determining daily operation times requires a three-step process. The discharge rate of drip tapes and tubings is usually given in gallons per minute per 100 feet of material.
Step 1 is to determine the crop water use in inches per day, which is the standard measure used in evapotranspiration (ET)-based methods of irrigation scheduling.
Step 2 is to determine the application rate of the drip tape or tubing in inches per hour. Table 1 can be used to make this determination if the row spacing and the irrigation system application rate (gal./min. per 100 feet) are known.
Example:
Row spacing = 40 inches
Drip tape application rate = 0.35 gal./min. per 100 ft.
From Table 1, the application rate (in./hr.) = 0.1 in./hr.
Table 1. Application Rate (in./hr.) of Drip Tapes and Tubings for Various Flow Rates and Spacings - Flow Rate (gal./min. per 100 ft.)
| | 0.10 | 0.15 | 0.20 | 0.25 | 0.30 | 0.35 | 0.40 | 0.45 | 0.50 |
| 10 | 0.12 | 0.17 | 0.23 | 0.29 | 0.35 | 0.40 | 0.46 | 0.52 | 0.58 |
| 15 | 0.08 | 0.12 | 0.15 | 0.19 | 0.23 | 0.27 | 0.31 | 0.35 | 0.39 |
| 20 | 0.06 | 0.09 | 0.12 | 0.14 | 0.17 | 0.20 | 0.23 | 0.26 | 0.29 |
| 25 | 0.05 | 0.07 | 0.09 | 0.12 | 0.14 | 0.16 | 0.18 | 0.21 | 0.23 |
| 30 | 0.04 | 0.06 | 0.08 | 0.10 | 0.12 | 0.13 | 0.15 | 0.17 | 0.19 |
| 35 | 0.03 | 0.05 | 0.07 | 0.08 | 0.10 | 0.12 | 0.13 | 0.15 | 0.17 |
| Row Spacing (in.) | 40 | 0.03 | 0.04 | 0.06 | 0.07 | 0.09 | 0.10 | 0.12 | 0.13 | 0.14 |
| 45 | 0.03 | 0.04 | 0.05 | 0.06 | 0.08 | 0.09 | 0.10 | 0.12 | 0.13 |
| 50 | 0.02 | 0.03 | 0.05 | 0.06 | 0.07 | 0.08 | 0.09 | 0.10 | 0.12 |
| 55 | 0.02 | 0.03 | 0.04 | 0.05 | 0.06 | 0.07 | 0.08 | 0.09 | 0.11 |
| 60 | 0.02 | 0.03 | 0.04 | 0.05 | 0.06 | 0.07 | 0.08 | 0.09 | 0.10 |
| 65 | 0.02 | 0.03 | 0.04 | 0.04 | 0.05 | 0.06 | 0.07 | 0.08 | 0.09 |
| 70 | 0.02 | 0.02 | 0.03 | 0.04 | 0.05 | 0.06 | 0.07 | 0.07 | 0.08 |
| 75 | 0.02 | 0.02 | 0.03 | 0.04 | 0.05 | 0.05 | 0.06 | 0.07 | 0.08 |
| 80 | 0.01 | 0.02 | 0.03 | 0.04 | 0.04 | 0.05 | 0.06 | 0.06 | 0.07 |
Step 3 is to determine the irrigation system operation time (hours) necessary to satisfy the crop water needs. This requires the crop water use (ETo determined in Step 1) and the application rate (determined in Step 2). The following formula may be used (or see Table 2):
| Hrs. of | Plant | Application |
| operation/day = | water use ÷ | rate |
| (hrs./day) | (in./day) | (in./hr.) |
| Example: |
| Crop water use = 0.3 in./day (ETo) |
| System application rate = 0.1 in./hr. |
| Hrs. of operation = 0.3 in./day/0.1 in./hr. |
| per day (hrs./day)=3 hrs./day |
|
| Table 2 shows the same operation time for this example. |
Table 2. Operation Time (hrs./day) for Various Application Rates (in./hr.)
and Crop Water Use (in./day)
Application Rate (in./hr.)
| | 0.05 | 0.1 | 0.15 | 0.2 | 0.25 | 0.3 | 0.35 | 0.4 | 0.45 | 0.5 |
| .05 | 1.0 | 0.5 | 0.3 | 0.3 | 0.2 | 0.2 | 0.1 | 0.1 | 0.1 | 0.1 |
| 0.1 | 2.0 | 1.0 | 0.7 | 0.5 | 0.4 | 0.3 | 0.3 | 0.3 | 0.2 | 0.2 |
| 0.15 | 3.0 | 1.5 | 1.0 | 0.8 | 0.6 | 0.5 | 0.4 | 0.4 | 0.3 | 0.3 |
| 0.2 | 4.0 | 2.0 | 1.3 | 1.0 | 0.8 | 0.7 | 0.6 | 0.5 | 0.4 | 0.4 |
| 0.25 | 5.0 | 2.5 | 1.7 | 1.3 | 1.0 | 0.8 | 0.7 | 0.6 | 0.6 | 0.5 |
| Plant Water Use (in./day) | 0.3 | 6.0 | 3.0 | 2.0 | 1.5 | 1.2 | 1.0 | 0.9 | 0.8 | 0.7 | 0.6 |
| 0.35 | 7.0 | 3.5 | 2.3 | 1.8 | 1.4 | 1.2 | 1.0 | 0.9 | 0.8 | 0.7 |
| 0.4 | 8.0 | 4.0 | 2.7 | 2.0 | 1.6 | 1.3 | 1.1 | 1.0 | 0.9 | 0.8 |
| | | | | | | | | | | |
Information adapted from Soil and Water Newsletter article by Larry Schwankl.
REDUCED-RISK INSECTICIDES FOR LEAFY VEGETABLES
Franklin Laemmlen
The following information was originally developed by John Palumbo, Entomologist at the University of Arizona Yuma Agricultural Center. Some of the text has been edited to adapt the information to Central Coast conditions.
In the past few years, there has been considerable mention of the development and use of "Reduced-risk" pesticides in agricultural crops. These new compounds are becoming increasingly important in pest management programs. The following information provides a brief overview of what reduced-risk insecticides are and how they may fit into a cropping system.
Reduced-risk pesticides are newer classes of compounds that pose a lower health risk to humans and the environment. This new classification and registration process resulted when the EPA implemented the Reduced-Risk Pesticides Initiative in 1993 to provide incentives to encourage the development and registration of pesticides that present lower risks to public health and the environment, and to encourage the replacement of higher risk pesticides in the market place. Although FQPA was not passed until 1996, the reduced-risk initiative began the process for the replacement of organophosphate pesticides.
EPA defines a reduced-risk pesticide as one which "may reasonably be expected to accomplish one or more of the following:" (1) reduces pesticide risks to human health; (2) reduces pesticide risks to non-target organisms; (3) reduces the potential for contamination of valued environmental resources, or (4) broadens adoption of IPM or makes it more effective. The agency has established criteria for each category which a candidate compound must meet before reduced-risk status is granted. Perhaps the most significant advantage of the program to manufacturers and growers is that reduced-risk compounds are given special consideration during registration. FQPA requires the EPA to expedite the review of compounds that meet the reduced-risk criteria, and EPA considers these low risk compounds a priority in the registration process where pesticide submissions are reviewed based on the following prioritization: (1) methyl bromide alternatives, (2) OP alternatives that pass the reduced-risk screen, (3) other reduced-risk candidates, (4) OP alternatives, but denied reduced-risk status, (5) USDA-EPA identified potentially vulnerable crops, (6) minor use priorities, and (7) non-minor use priorities. This process has in some cases resulted in products gaining federal labels in as little as 14 months.
A recent report by IR-4 (as of May 2002) estimates that 35 reduced-risk compounds are presently registered (10 herbicides, 13 fungicides, and 12 insecticides) on a variety of crops, and 10 products are currently considered reduced-risk candidates for registration (2 herbicides, 5 fungicides, and 3 insecticides).
Another significant initiative to encourage the development of lower risk pesticides was the establishment of the Biopesticide and Pollution Prevention Division in 1994 to review and register biopesticides. As defined by EPA, biopesticides are classes of pesticides derived from natural materials found in certain animals, plants, microbial organisms, and minerals.
Biopesticides fall into three major classes: (1) Microbial pesticides that consist of a microorganism (e.g., a bacterium, fungus, virus or protozoan) as the active ingredient. The most widely used microbial pesticides are subspecies and strains of Bacillus thuringiensis, or Bt. (2) Plant-Incorporated Protectants, which are pesticidal substances that plants produce from genetic material that has been added to the plant. Bollguard cotton is an example of a biopesticide, which resulted from a gene taken from the Bt pesticidal protein, and introduced into the genetic material of cotton, and (3) Biochemical pesticides, which are naturally occurring substances that control pests by non-toxic mechanisms.
Biochemical pesticides include substances, such as insect pheromones, plant extracts (mustard oil, limonene), natural insect growth regulators (IGR’s) (azadirachtin, neem oil), and repellents (garlic, capsaicin). Biopesticides are inherently less toxic than conventional pesticides, both to human and target pests. Finally, biopesticides can be extremely effective control agents, for example, Bt cotton against pink bollworm. However, other biopesticides have shown only limited activity against pests in vegetables.
Shown in Table 1 below is a list of conventional, reduced-risk, OP alternative insecticides and biopesticides presently registered or pending approval for use on leafy vegetables. You will note that we presently have 7 insecticide products that EPA has designated as reduced-risk compounds. Although, several biopesticides are available, only Bt (e.g., Dipel, Xentari, Javelin) and azadirachtin-based products (e.g., AZADirect, Ecozin, Neemix, Trilogy) have shown any measurable activity against some insect species. Additional tables and discussions are presented on the use of conventional, reduced-risk, and OP alternative insecticides for managing target pests individually in specific use windows during the leafy vegetable crop season. These tables and descriptions are meant to be used as general guidelines by growers and PCA’s for integrating these products into their pest management programs.
Table 1. Insecticide Alternatives for Leafy Vegetables
| | Conventional | Reduced-risk | OP Alternative | Biopesticide |
| Worms: Including beet armyworm, cabbage looper, & budworm | Lannate, Larvin, Orthene, Endosulfan | Success, Avaunt, Confirm, Intrepid | Proclaim, Warrior, Mustang, Decis | Bt, aizawai, Bt, kustaki, Azadirachtin |
| Aphids | Endosulfan, Orthene, Capture, MSR | Assail, Fulfill | Admire, Platinum, Actara, Pirimor | Azadirachtin |
| Leafminers | AgriMek, Trigard, Vydate | Success | | Azadirachtin |
| Cucumber Beetles | Lannate, Ambush/Pounce, Diazinon | Assail | Admire/Provado, Mustang, Warrior | |
| Thrips | Lannate, Orthene, Dimethoate, AgriMek | Success, Assail | Warrior, Mustang | |
Italicized compounds are presently pending registration on leafy vegetables.
Worm Control in Lettuce
We presently have a great deal of information on the new reduced-risk and OP alternative chemistries and their fit in lettuce pest management programs. These products have specific use patterns on head lettuce relative to their unique characteristics. (Table 2). This would include temporal mortality, residual efficacy, route of activity, efficacy relative to application method and interaction with larval development and feeding behavior.
The table below was constructed from data gathered over the past six years and suggests uses for each compound for the protection against beet armyworm, cabbage looper, and budworm/bollworm in lettuce crops. Table 2 is organized by identified stages in plant growth throughout the crop season. The fit within the table for each active ingredient corresponds with its recommended use.
Table 2. Alternatives for Worm Control at Specific Lettuce Crop Stages
|
|
Stand Establishment |
Thinning to Heading |
Heading to Harvest |
| Success |
|
|
|
|
|
|
|
|
| Proclaim |
|
|
|
|
|
|
|
|
|
| Avaunt |
|
|
|
|
|
|
|
|
|
| Intrepid |
|
|
|
|
|
|
|
|
|
| Confirm |
|
|
|
|
|
|
|
|
|
| Lannate |
|
|
|
|
|
|
|
|
|
| Larvin |
|
|
|
|
|
|
|
|
|
| Orthene |
|
|
|
|
|
|
|
|
|
| Endosulfan |
|
|
|
|
|
|
|
|
|
 Pyrethroid tank mixtures recommended (Warrior, Mustang)
Thinning Stage: Depending on population pressure and temperature, a treatment may be required for larval control. Some applications may be by air because of sprinkler irrigation and wet fields. Lannate+pyrethroid is a good option for initial control at stand establishment because of the excellent contact and ovicidal activity, broad-spectrum efficacy against many soil-dwelling pests. Success and Proclaim have demonstrated good activity against BAW/CL, but should be used after emergence because of selective efficacy. If leafminer is also a concern, Success at higher rates (6.0 oz.) can be used.
Post-thinning/Pre-heading Stage: All of the compounds are options for control during this period. Confirm use should be directed towards the post-thinning period, and addition of pyrethroid should be used because of its inconsistent performance on budworm/bollworm. Avaunt and Intrepid (registration pending) should be applied at the higher rates with ground equipment whenever possible. Orthene and Endosulfan combinations are useful because of activity on aphids and thrips.
Heading-harvest Stage: Perhaps the most important period in which plant protection is required. Fewer options, but several effective compounds are available. Addition of pyrethroid with all active ingredients 7-10 days before harvest may enhance control of small larvae and miscellaneous pests such as beetles, plant bugs and thrips.
Aphid Control in Leafy Vegetables
Growers now have a number of alternatives for aphid control from which to choose (Table 3).
Soil uses: Admire and Platinum (pending registration in lettuce) can both be applied pre– and post-planting, but are most consistent as pre-plant applications.
Foliar approaches: Two reduced-risk products, Assail and Fulfill, are available. Both are very effective against aphids (primarily green peach and potato aphids) and can be used throughout the growing season. Additionally, Actara (pending registration in lettuce), and Pirimor (pending registration) provide good aphid control. Provado, used in combination with Orthene, not only provides good aphid control but offers thrips suppression as well. These products represent several modes of action that can be alternated successfully to manage aphid populations and reduce resistance risks. In areas where lettuce and foxglove aphids are present, Metasystox-R has shown to be very effective, as have Provado+Orthene, and Assail+Capture applied at 7-10-day intervals.
Table 3. Alternatives for Aphid Control at Specific Lettuce Crop Stages
|
Soil |
Foliar |
| At plant |
Post-plant |
Thinning |
Pre-heading |
Pre-harvest |
| Admire | |  |
|
|
|
| Platinum | | |
|
|
|
| Assail |
|
|
| | |
| Fulfill |
|
|
| | |
| Actara |
|
|
| | |
| Pirimor |
|
|
| | |
| Provado/Orthene |
|
|
|
|
|
| Provado/Thiodan |
|
|
| |
|
| Metasystox-R |
|
|
| |
|
Leafminer Control: Success is the only reduced-risk compound with activity against Liriomyza leafminers. It is particularly effective against L. sativae, but will provide L. trifolii control at higher rates. It is useful in lettuce where leafminer suppression is provided following application for worm control in fall crops. Under heavy pressure, AgriMek is an effective alternative in leafy vegetables.
Cucumber Beetle Control: Assail is the only reduced-risk compound evaluated that provided control of striped and spotted cucumber beetles. Several conventional products (Lannate, pyrethroids, diazinon) still provide excellent knockdown of cucumber beetles on a number of crops.
Thrips Control in Leafy Vegetables
Two reduced-risk compounds have activity against western flower thrips in head and leaf lettuce. Success is perhaps the most efficacious of the two, and is an effective alternative that should be used in rotation with Lannate+pyrethroid mixtures for thrips management in lettuce. Assail provides marginal suppression of thrips (~50% control), but will only be useful in rotational spray programs where Admire or Platinum have not been applied for aphid control. Agrimek (8 oz./acre) is
an effective thrips material in lettuce, with efficacy similar to Success (6 oz./acre).
Sustaining Product Efficacy
The above information offers several options that can be used for managing insect pests at various times throughout the growing season. This information can also serve as a guide to PCAs and growers for avoiding the overuse of a single product, and as a reference for rotating chemistries throughout the season for the purpose of maximizing control and sustaining product efficacy.
In addition, other tactics can be practiced to avoid the development of resistance to any of these new active ingredients. First, whenever possible, avoid making consecutive applications of the same active ingredient to the same field. This also includes pyrethroids. Second, do not apply any active ingredient below labeled rates. Finally, avoid tank-mixtures containing 2 or more of the new reduced-risk chemistries when controlling insect pests. Not only is this expensive, but generally not necessary based on the past performance of the conventional and reduced-risk products. Ideally, these strategies will optimize control of key insect pests and maximize the longevity of all these compounds. In certain situations these management guidelines may be difficult to follow, but they may be necessary for the long-term sustainability of these valuable chemistries on vegetable crops.
Additional Information on Reduced-Risk Pesticides is Available at these Internet Sites:
Information adapted from Yuma County Farm Notes Newsletter, May 2002.
WEED INFESTATIONS COMING FROM FEED AND/OR MULCH
Franklin Laemmlen
Dr. Andrew Chang, Department of Soil and Environmental Sciences, UC Riverside, is looking for examples and locations where exotic weeds have been introduced to an area in baled hay or straw or in any forage material used for mulching or animal feed. His request follows:
As part of the Weed-free Forage and Mulch (WFFM) education campaign we are seeking anecdotal or documented recollections of weed infestations that were believed to be started by contaminated hay, feed, straw, fresh manure or mulch. Also weed infestations found in horse or cattle camps. The Farm Bureau, Cattleman, and forage growers have requested we justify the WFFM program and assure them that this is really a problem (please circulate this request widely).
The information needed is BRIEF. For example:
In Fullaweeds County outside of the town of Thistleville, in the early eighties an infestation of Iberian starthistle was discovered next to a cattle staging area where hay had been stacked in previous years.
When Caltrans did a road widening on Highway 71 outside of Thistleville, yellow starthistle appeared in the area spread with straw for erosion control the next year.
After the Rocky Top Fire in 1997 on Boardfeet National Forest, perennial pepperweed infested the area where rice and wheat straw were spread for erosion control.
If you know of examples or have case histories you can provide, please contact the Cooperative Extension office at 805.934.6240. Thank you.
BACK TO VEGETABLE PAGE
|