Crop Profile for Watercress in Hawaii General Production Information  Watercress Is a Staple Leafy Green Vegetable Crop in Hawaii

Crop Profile for Watercress in Hawaii General Production Information  Watercress is a staple leafy green vegetable crop in Hawaii.  Commercial acreage has been steady for at least 10 years and was 35 acres in 2002 (Hawaii Ag Statistics Service 2002).  Total production in 2002 was 800,000 lbs. for an average per acre per year yield of 22,857 lb. (Hawaii Ag Statistics Service 2002).  Watercress is continuously cultivated year-round with an average of 6 to 8 crop cycles per year.  Total value of the Hawaii watercress industry was $946,000 in 2001 and $944,000 in 2002. Average farm price in 2002 was $1.18 per pound (Hawaii Agricultural Statistics Service 2002).  Average production costs are approximately $20,000 per acre per year (costs include rent, labor, and farm chemicals) (Watercress of Hawaii Inc., personal communication).  100% of harvested watercress is for fresh market use (Hawaii Agricultural Statistics Service 2002).  Watercress is not exported because the demand is greater than the supply.  Ninety-five percent of commercial watercress production is on the island of Oahu in the Aiea, Pearl City, and Waipahu areas. The remaining 5% is in Haiku and Kihei on Maui. Additionally, there is dryland watercress production on the island of Hawaii in the Mountain View area. The amount of dryland production is not reported by the Hawaii Agricultural Statistics Service (Watercress of Hawaii, Inc. personal communication).  1% of production is grown hydroponically.  Approximately 12 growers on Oahu, 2 on Maui, and 1 on Big Island.  The largest farm size is 10 acres and the smallest farm is ¼ acre.

Production Regions

The Crop Profile/PMSP database, including this document, is supported by USDA NIFA.

Cultural Practices

Watercress is grown continuously throughout the year in Hawaii. Watercress fields are located in areas where there is abundant spring or artesian well water. Watercress cannot be grown commercially using stream or river water because of the potential for animal or human contamination.

Watercress beds or patches are prepared by firming the soil with rocks and gravel. Watercress does not tolerate muddy field conditions. Beds are slightly graded (1% slope from the top to the bottom of a bed) to allow for continuous water flow over the surface of the patch. The film of water is very shallow (0.5 to 1.5 inches) which allows roots to attach to the gravel surface of the bed. The desired pH of the water and the beds is neutral (7.0). Watercress planting is by vegetative cuttings laid on top of the prepared beds in the direction of the water flow.

Because watercress is a leafy vegetable it is sunlight and day length sensitive. The higher the percentage of sunshine the faster the crop grows. In growing areas with leeward sunlight exposure watercress can be harvested 6 to 7 weeks after planting. After the initial planting the subsequent crops are produced by ratoons of the “mother” plants. If growing conditions are favorable then watercress can be grown as a ratoon crop indefinitely.

Nutrient requirements are provided by the mineral content of the irrigation water. There is some supplemental fertilization of watercress by individual growers but no standards have been established.

Watercress is harvested by hand using a hand sickle when the plant has grown 12 to 15 inches above the water surface. After harvest and packaging watercress is quick chilled using vacuum cooling or an ice water bath. There is a high percentage of hand labor required to produce watercress. Those activities requiring hand labor are planting, weeding, harvesting, packaging, and insect pest control (McHugh et al. 1987).

Invertebrate Pests

Aphids Buckthorn Aphid (Aphis nasturtii) Green Peach Aphid (Myzus persicae)

Aphids are an intermittent pest on watercress. Outbreaks usually occur after several successive days of strong tradewinds (greater than 10 mph). Heavy aphid infestations can cause an unmarketable appearance of watercress because the presence of a single live (or dead) aphid on the finished product can lead to customer rejection (Nakahara et al. 1986).

Control

Chemical Control:  Diazinon (Clean Crop Diazinon 500 AG, Diazinon 50W) – PHI = 5 days, REI = 24 hrs. Applied as a directed spray to plant canopy, at a rate of 0.5 lb a.i./acre. Registration was cancelled by EPA in May 2002. Watercress industry was granted a 4-year withdrawal period by EPA to expire in May 2006 (Watercress of Hawaii, Inc. personal communication).

 Malathion (Drexel Malathion 5 EC, Griffin Atrapa 5E, Malathion 5, Micro Flo Malathion 5EC, Prozap Malathion 57EC) – PHI = 7 days, REI = 12 hrs. Applied as a directed spray to plant canopy, at a rate of 0.5 lb a.i./acre (HPIRS 2004).

 Imidacloprid (Provado 1.6) – PHI = 7 days, REI = 12 hrs. Applied as a directed spray to crop canopy, at a rate of 0.047 lb a.i./acre.

Alternative Chemical Control:  Dinotefuran is a possible alternative insecticide but needs testing.

Non-chemical Control:  Predators (ladybugs, Syrphid flies) and parasites are present in watercress fields but do not give adequate control (Nakahara et al. 1986).

Cyclamen mite Stenotarsonemus pallidus

Cyclamen mite has been a pest of watercress since the 1950’s. Cyclamen mite feeding begins in the apical shoot of the plant. Damage symptoms are shoot and leaf stunting, bronzing of leaf tissue, and deformation of the entire plant with heavy mite infestations. Cyclamen mite is widespread and found in all watercress growing areas (McHugh et al. 1987).

Control

Alternative Chemical Control:  None

Non-chemical Control:

Intermittent overhead irrigation is very effective in controlling cyclamen mite (McHugh et al 1987, Nakahara et al. 1986).

Diamondback moth Plutella xylostella

Diamondback moth is the most serious insect pest of watercress in Hawaii. The caterpillar stage of the insect does damage to the plant by feeding on the leaves and the young growing shoots. The life cycle of the moth is very rapid. Eggs are laid on the under surface of the leaves and in the growing points. Egg to adult maturation can occur in as little as 12 days but averages 21 days in most watercress growing areas. The diamondback moth is world renown for its ability to quickly develop resistance to any insecticide used to control it. The diamondback moth feeds exclusively on cruciferous host plants (cultivated and weed hosts) (Shelton et al. 1993, Talekar 1992, Tabashnik et al. 1990, Tabashnik et al. 1987).

Control

Chemical Control (HPIRS 2004):  Spinosad (Success) – PHI = 1 day, REI = 4 hrs. Applied as a directed spray to plant canopy at a rate of 0.02 – 0.05 lb a.i./acre.

 Bacillus thuringiensis (subspecies Kurstaki, various products) – PHI = 0 days, REI = 4 hrs. Applied as a directed spray to plant canopy at a rate of 0.2 – 0.8 lb a.i./acre.

Alternative Chemical Control:  None

Non-chemical Control:  Intermittent overhead irrigation is effective in controlling diamondback moth in combination with the parasitoid wasp Cotesia plutella which is established in all watercress growing areas (McHugh and Foster 1994, Nakahara et al. 1986, Tabashnik and Mau 1986).

Imported cabbageworm Pieris rapae

Imported cabbageworm is an occasional pest of watercress. Damage to the crop is by the caterpillar stage of the butterfly. Adults are white butterflies commonly seen searching for nectar along roadside weed stands. Outbreaks often appear from the months of February through June. Leaves are damaged by larval feeding which render the crop unmarketable. Imported cabbageworm is easy to control with registered insecticides (Knowledge Master 2004).

Control

Chemical Control:  Bacillus thuringiensis (subspecies Kurstaki, various products) – PHI = 0 days, REI = 4 hrs. Applied as a directed spray to plant canopy at a rate of 0.2 – 0.8 lb a.i./acre (HPIRS 2004).

 Diazinon (Clean Crop Diazinon 500 AG, Diazinon 50W) – PHI = 5 days, REI = 24 hrs. Applied as a directed spray to plant canopy, at a rate of 0.5 lb a.i./acre. Registration was cancelled by EPA in May 2002. Watercress industry was granted a 4-year withdrawal period by EPA to expire in May 2006 (Watercress of Hawaii, Inc. personal communication).

 Spinosad (Success) – PHI = 1 day, REI = 4 hrs. Applied as a directed spray to plant canopy at a rate of 0.02 – 0.05 lb a.i./acre (HPIRS 2004).

Alternative Chemical Control:  None.

Non-chemical Control:  Parasites are present but do not give acceptable control of imported cabbageworm.

Sharpshooters Draeculecephala californica, D. inscripta, D. minerva

Sharpshooters are minor pests of watercress. These small insects are commonly found on grass but can build to high numbers on watercress. Nymph and adult stages cause damage to watercress called “hopper burn”. “Hopper burn” is a condition that results in localized yellowing of the watercress leaves and leaflets and can render the crop unmarketable. The grass sharpshooter is easy to control with timely application of approved insecticides (Nakahara et al. 1986).

Control

 Imidacloprid (Provado 1.6) – PHI = 7 days, REI = 12 hrs. Applied as a directed spray to crop canopy, at a rate of 0.047 lb a.i./acre.

Alternative Chemical Control:  Dinotefuran is a possible alternative insecticide but needs testing.

Non-chemical Control:  None.

Snails and Slugs Various species

Snails and slugs can become a problem on watercress when they move high up on the plant stalks at the time of harvest. The presence of slugs or snails on watercress can lead to market rejection of the finished product. Slug and snail pressure increases during rainy periods or from excessive moisture supplied by intermittent overhead irrigation systems used by watercress growers to control diamondback moth (Watercress of Hawaii, Inc. personal communication).

Control Chemical Control:  None.

Alternative Chemical Control:  None.

Non-chemical Control:  Adjust intermittent overhead irrigation during periods of high rainfall or when slugs or snails are noticed high up on the plants.  Remove by hand at time of harvest (Watercress of Hawaii, Inc. personal communication).

Stinkbugs A Lygaeid Bug (Nysius spp.) Southern Green Stinkbug (Nezara viridula)

Stinkbugs are occasional pests of watercress and occur mostly during the months of May and June. Feeding of stinkbugs causes wilting of shoots, stems, and/or leaves above the feeding point. Nymphal and adult stages of stinkbugs can damage watercress but are easily controlled with timely applications of approved insecticides (Knowledge Master 2004).

Control

 Imidacloprid (Provado 1.6) – PHI = 7 days, REI = 12 hrs. Applied as a directed spray to crop canopy, at a rate of 0.047 lb a.i./acre (HPIRS 2004).

Alternative Chemical Control:  Dinotefuran is a possible alternative insecticide but needs testing.

Non-chemical Control:  There are three parasites of Southern green stinkbug, Trichopoda pennipes, T. pilipes, and Trissolcus basalis which give good control most of the year.

Watercress leafhopper Macrosteles sp. nr. severini

The watercress leafhopper is one of the most serious insect pests of watercress because it is the vector of the phytoplasma disease Aster Yellows. The leafhopper is a recent introduction to Hawaii and first discovered on watercress in 2001. Aster Yellows disease causes severe chlorosis, stunting, and a “witch's broom” effect on new watercress shoots. Aster yellows infected watercress is unmarketable (Hawaii Department of Agriculture 2003).

Control

Alternative Chemical Control:  Dinotefuran is a possible alternative insecticide but needs testing.

Non-chemical Control:  None.

Diseases

Aster Yellows

Aster Yellows (AY) is the most serious disease of watercress in Hawaii. AY was first detected in a watercress field in Pearl City, Oahu in 2001. The disease is caused by a phytoplasma that can infect numerous plant hosts (HDOA 2003). AY is vectored in Hawaii by the watercress leafhopper which is known to feed on a variety of host plants. Symptoms of AY on watercress are severe chlorosis and stunting, witch's broom effect on new shoots, and, in some cases, death of the plant. Since its introduction, the AY phytoplasma has been found only in watercress or weed plants adjacent to watercress fields (Smith et al. 2002). Adoption of recommended watercress leafhopper control management practices is critical to control of this disease.

Control

Chemical Control:  Elimination. Rogue infected plants but first spray an approved insecticide before watercress leafhoppers can move to uninfected plants. In addition to symptomatic plant removal all asymptomatic watercress within a 3 ft. radius of the infected plant must be removed.  Border leafhopper control. Regular sprays of an approved insecticide for all vegetation within 50 ft. from edge of watercress field.

Alternative Chemical Control:  None.

Non-chemical Control:  Avoidance. Use of disease free watercress planting material once diseased plants have been removed from the field. Careful monitoring of replant areas to identify and remove symptomatic plants.  Transgenic resistance. Research is needed in this area.

Black Rot Xanthomonas campestris

Black rot can be a serious disease during prolonged rainy periods. The disease begins as a yellow spot at the edge of the watercress leaflets. The disease is spread by splashing water droplets (Knowledge Master 2004). Under heavy rainy conditions, especially during “kona weather”, black rot can spread to the apical growing shoot causing plant stunting and deformation. The use of intermittent overhead irrigation can also spread the disease if relative humidity is high (> 80%) and wind is light (< 10 mph).

Control

Chemical Control:  Copper hydroxide (Champ, Griffin Kocide, Nu-Cop) – PHI = 2 days, REI = 48 hrs. Applied as a directed spray to plant canopy at a rate of 0.75 – 1.5 lb a.i./acre (HPIRS 2004).

Alternate Chemical Control:  None.

Non-chemical Control:  Stop intermittent overhead irrigation (used for diamondback moth control) until trade winds return.  Minimize free moisture on crop leaves. Sprinkler system used to control diamondback moth turned off during prolonged rainy periods (> 2 days) or during times of high relative humidity (> 80%) during the daylight hours.

Cercospora Leaf Spot Cercospora nasturtii

Cercospora leaf spot is an occasional pest caused by high humidity (>80%). Mostly older leaves are affected but the disease can sometimes be found high up on the plant if the conditions which favor the disease (heat and high humidity) are prolonged (Knowledge Master 2004). Growers rarely spray for this disease.

Control

Chemical Control:  Copper hydroxide (Champ, Griffin Kocide, Nu-Cop) – PHI = 2 days, REI = 48 hrs. Applied as a directed spray to plant canopy at a rate of 0.75 – 1.5 lb a.i./acre (HPIRS 2004).

 Azoxystrobin (Quadris) – PHI = 7 days, REI = 4 hrs. Applied as a directed spray to plant canopy at a rate of 0.10 – 0.25 lb a.i./acre (HPIRS 2004).

Alternate Chemical Control:  None.

Non-chemical Control:  Remove infected leaves by hand when harvesting.

Weeds Weed control is generally not a major concern in watercress fields. Intermittent overhead irrigation used for diamondback moth control creates conditions which do not favor the proliferation of weed species. Additionally, flooded fields that are needed for watercress production limit the establishment of weeds in actively grown fields. Weed intrusion mostly occurs near the edges of watercress fields. The main weed pests are: California grass (Brachiaria mutica) (Holm et al. 1977), honohono grass (Commelina diffusa) (Holm et al. 1977), and water hyssop (Bacopa sp.).

Control

Chemical Control:  Glyphosate (Various products) – PHI = N/A (not for crop application), REI = 4 hrs. Applied as a border control spot spray. Applied at various rates. Not effective on honohono grass. Partially effective on water hyssop.

Alternate Chemical Control:  None.

Non-chemical Control:  Hand weeding as needed.

Contacts Profile drafted by:

John J. McHugh, Jr. Crop Care Hawaii, LLC 2923A Kaamalio Dr. Honolulu, HI 96822

Lynne N. Constantinides Crop Care Hawaii, LLC 2923A Kaamalio Dr. Honolulu, HI 96822

Cathy Tarutani-Weissman Plant and Environmental Protection Sciences College of Tropical Agriculture and Human Resources University of Hawaii-Manoa Honolulu, Hawaii, 96822 (808) 956-2004

Reviewed and Approved by:

Michael Kawate Extension Pesticide Coordinator Plant and Environmental Protection Sciences College of Tropical Agriculture and Human Resources University of Hawaii-Manoa Honolulu, Hawaii 96822 (808) 956-6008

References

1. College of Tropical Agricultural and Human Resources, University of Hawaii at Manoa. 2001. http://www.ctahr.hawaii.edu/ctahr2001/CTAHRInAction/Dec_01/watercress.html 2. Hawaii Agricultural Statistics Service. 2002. http://www.nass.usda.gov/hi/stats/stat- 51.htm 3. Hawaii Department of Agriculture, New Pest Advisory No. 02-01. 2003. http://www.hawaiiag.org/hdoa/npa/npa02-01-wcleafhopper.pdf 4. Hawaii Pesticides Information Retrieval System. 2004. http://state.ceris.purdue.edu/htbin/sitesetp.com 5. Holm, L. G., D. L. Plucknett, J. V. Pancho, J. P. Herberger. 1977. The World’s Worst Weeds. University of Hawaii Press. 6. Knowledge Master. 2004. University of Hawaii, College of Tropical Agriculture and Human Resources, University of Hawaii-Manoa. Computer Resource Database. http://www.extento.hawaii.edu/kbase/crop/Type/cer_prim.htm 7. Knowledge Master. 2004. University of Hawaii, College of Tropical Agriculture and Human Resources, University of Hawaii-Manoa. Computer Resource Database. http://www.extento.hawaii.edu/kbase/crop/Type/pieris.htm

8. Knowledge Master. 2004. University of Hawaii, College of Tropical Agriculture and Human Resources, University of Hawaii-Manoa. Computer Resource Database. http://www.extento.hawaii.edu/kbase/crop/Type/xanthomo.htm 9. McHugh, J. J., Jr., and R. E. Foster. 1995. Reduction of diamondback moth (Lepidoptera: Plutellidae) infestation in head cabbage by overhead irrigation. J. Econ. Entomol. 88: 162 – 168. 10. McHugh, J. J., Jr., S. K. Fukuda and K. Y. Takeda. 1987. Hawaii Watercress Production. HITAHR. Res. Ext. Series 088. 11. Nakahara, L. M., J. J. McHugh, Jr., C. K. Otsuka, G. Y. Funasaki and P. Y. Lai. 1986. Integrated control of diamondback moth and other insect pests using an overhead sprinkler system, an insecticide, and biological control agents on a watercress farm in Hawaii. In N. S. Talekar and T. D. Griggs (eds.), Diamondback Moth Management: Proceedings of the First International Workshop, pp. 403 – 413. Asian Vegetable Research and Development Center, Shanhua, Taiwan. 12. Shelton, A. M., J. A. Wyman, N. L. Cushing, K. Apfelbeck, T. J. Dennehy, S. E. R. Mahr, and S. D. Eigenbrode. 1993. Insecticide resistance of diamondback moth (Lepidoptera: Plutellidae) in North America. J. Econ. Entomol. 86: 11 – 19. 13. Smith, H. A., J. J. McHugh, Jr. and B. R. Kumashiro. 2002. Monitoring a Newly Introduced Watercress Leafhopper in Central Oahu. Hawaii Agriculture Experiment Station, Vegetable Report 4. 14. Tabashnik, B. E., N. L. Cushing, N. Finson and M. W. Johnson. 1990. Field development of resistance to Bacillus thuringiensis in diamondback moth (Lepidoptera: Plutellidae). J. Econ. Entomol. 83: 1671 – 1676. 15. Tabashnik, B. E., N. L. Cushing and M. W. Johnson. 1987. Diamondback moth (Lepidoptera: Plutellidae) resistance to insecticides in Hawaii: intra-island variation and cross-resistance. J. Econ. Entomol. 80: 1091 – 1099. 16. Tabashnik, B. E. and R. F. L. Mau. 1986. Suppression of diamondback moth (Lepidoptera: Plutellidae) oviposition by overhead irrigation. J. Econ. Entomol. 79: 1447 – 1457. 17. Talekar, N. S. (ed.) 1992. Diamondback Moth and other Crucifer Pests: Proceedings of the Second International Workshop. Asian Vegetable Research and Development Center, Tainan, Taiwan. 18. Watercress of Hawaii, Inc. (watercress growers association). 2004. Personal communication.