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Joseph DeFrank

Azolla (Azolla filiculoides) is a floating fern that maintains a symbiotic relationship with an N-fixing blue-green algae. In many parts of Asia, azolla is used as a green manure in flooded rice cultivation. Taro (Colocasia esculenta) grown under flooded conditions is used to produce a traditional Hawaiian staple, poi. Azolla has been present in Hawaii for many years, but is not used in a controlled way for either nutrient augmentation of production sites or weed suppression. In this experiment, azolla was removed from a stream on the island of Kauai and multiplied in a nursery pond. Phosphoric acid was added to the nursery pond as a nutrient (P = 5 ppm) at 5-day intervals to accelerate azolla growth. Azolla was moved from the nursery pond and added to taro production plots at a seeding rate of 488 kg·m–2. Phosphoric acid was used in production plots to hasten coverage of the water surface by azolla. Ten days after azolla inoculation, production plots were covered and taro seed pieces were planted. Weed dry weights from conventional and azolla covered plots were recorded 91 days after taro planting. Taro corms were harvested 315 days after planting. Weed dry weight in azolla plots was 86% less than conventional plots. Azolla delayed taro maturity, causing a 41% reduction in marketable corm yield.

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Kelvin Sewake and Joseph DeFrank

Anthurium bacterial blight is a disease that has devastated much of the Hawaii anthurium industry in recent years. In response to the crisis, the Cooperative Extension Service produced a video entitled “Strategies for Anthurium Blight Control - A Growers' Discussion.” The video format was selected to allow the extension service to utilize experience of four successful large scale commercial growers and deliver blight control information to other growers with a graphic demonstration on control procedures for disease management. Production of the video eliminated the need for farm tours, eliminated the risk of disease spread, condensed information, and allowed growers to borrow copies. This video proved effective in prompting growers to adopt and implement recommended blight control procedures.

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Osamu Kawabata and Joseph DeFrank

A modified power function, y = (A + B·x)–C, was developed for determining the relationship between plant growth and growth retardant treatment. This function accounts for the plant response characteristics by incorporating three coefficients: A, growth level of the nontreated plants; B, the degree of growth reduction; and C, the smallest effective dose of the growth inhibitor. The function accounted for 97% of the variation in purple nutsedge (Cyperus rotundus L.) leaf length as a function of the amount of a growth retardant applied. The procedure resulted in a smaller error sum of squares than several common nonlinear functions because of its greater shape flexibility.

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Osamu Kawabata and Joseph DeFrank

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Charles R. Clement and Joseph DeFrank

Pejibaye (Bactris gasipaes Kunth) is being evaluated in Hawaii for production of fresh heart-of-palm. Yields and offshoot (sucker) production were evaluated in response to woven black polypropylene mat (control), three legumes [Arachis pintoi Krap. & Greg., Cassia rotundifolia Pers., and Desmodium heterocarpon (L.) DC], and a grass (Chloris gayana Kunth) used as ground covers. D. heterocarpon and C. gayana formed closed canopies quickly and controlled weeds well, but required more frequent mowing. A. pintoi formed a closed canopy slowly and only controlled weeds after forming a thick canopy, but required less mowing. Cassia rotundifolia died out after flowering and setting seed. All vegetative ground covers delayed heart-of-palm harvest and had reduced yields 1.5 years after planting. A combination of polypropylene (adjacent to plants) and vegetative ground covers (in service rows) may provide the best solution to minimizing labor for vegetative management in this orchard crop.

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Joseph DeFrank and Charles R. Clement

Pejibaye (Bactris gasipaes, Palmae) is being evaluated for heart of palm production in Hawaii. Yields and weed control were evaluated in response to: oryzalin (4.5 and 9.0 kg ai/ha), oxyfluorfen (0.6 and 1.2 kg ai/ha), paraquat (1.2 and 2.4 kg ai/ha) and woven black polypropylene mat. Four open-pollinated progenies from the Benjamin Constant population of the Putumayo landrace were used as replications. Paraquat was sprayed at 50 day intervals, while the preemergence herbicides were sprayed at 90 day intervals. Harvest started at 18 months after planting out, 17 months after treatment initiation. The polypropylene mat yielded the highest percent harvest (80%), followed by Oxyfluorfen (50%), paraquat (20%), oryzalin (12.5%). There were replication (genotype) effects that suggest varying tolerance to paraquat and oryzalin. Estimated palm heart yields (3731 plants/ha), corrected for % harvest, were highest with polypropylene mat (490 kg/ha), followed by oxyfluorfen 1.2 ai (425 kg/ha) and 0.6 ai (330 kg/ha). Paraquat severely inhibited growth of the suckers that assure future harvests. The performance rating of these weed control treatments was: mat = oxyfluorfen > oryzalin > paraquat.

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Hector R. Valenzuela and Joseph DeFrank

Living mulches offer a low-input alternative to achieve weed control while minimizing herbicide applications, decreased fertilizer leaching, insect and nematode management. and improved soil texture. A study was conducted to evaluate the effect of a Rhodes Grass (Chloris gayana cv. Katambora) living mulch on the growth and productivity of ten eggplant. Solanum melongena, cultivars grown under fertigation. The living sod was established at the Univ. Hawaii Waimanalo Experiment Station in June 1992. Soil analysis was taken before experiment initiation. Ten eggplant cultivars were transplanted on both living-mulch and control (woven-polyethelene mulch) plots on 4 March 1993. Weekly or bi-weekly harvests were conducted for six months. beginning on 19 May 1993. In addition plant height and canopy dimensions were determined on 16 April. and 10 Nov. Plant growth was monitored throughout the experiment. Soil samples were taken from the eggplant rhizosphere, hare-ground and in Rhodes grass monoculture, for nematode count determinations. Soil samples were also taken for nutrient determination after completion of the experiment. Overall yields were greater in the polyethelene mulch than in the living mulch plots. A differential response was observed on the response of cultivars to cropping system. However the most vigorous cultivars performed well in both systems. The living mulch system showed potential for nematode management in eggplant agroecosystems.

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Charles R. Clement and Joseph DeFrank

Pejibaye (Bactris gasipaes Kunth) is being evaluated in Hawaii for production of fresh heart-of-palm. Yields and offshoot (sucker) production were evaluated in response to woven black polypropylene mat (control), three legumes [Arachis pintoi Krap. & Greg., Cassia rotundifolia Pers., and Desmodium heterocarpon (L.) DC], and a grass (Chloris gayana Kunth) used as ground covers. D. heterocarpon and C. gayana formed closed canopies quickly and controlled weeds well, but required more frequent mowing. A. pintoi formed a closed canopy slowly and only controlled weeds after forming a thick canopy, but required less mowing. Cassia rotundifolia died out after flowering and setting seed. All vegetative ground covers delayed heart-of-palm harvest and had reduced yields 1.5 years after planting. A combination of polypropylene (adjacent to plants) and vegetative ground covers (in service rows) may provide the best solution to minimizing labor for vegetative management in this orchard crop.

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Joseph DeFrank and Charles R. Clement

Pejibaye (Bactris gasipaes Kunth, Palmae) is being evaluated for production of fresh heart of palm in Hawaii. Precocity, yields, and weed control were evaluated in response to woven black polypropylene mat (control), oryzalin, oxyfluorfen, and paraquat. Control plots attained 100% of plants harvested by 26 months, followed by oxyfluorfen (97.5%), oryzalin (77.5%), and paraquat (60%). Estimated heart of palm yields (3731 plants/ha) were similar with oxyfluorfen 1.2 kg a.i./ha (707 kg·ha–1), polypropylene mat (612 kg·ha–1), oxyfluorfen 0.6 kg a.i./ha (600 kg·ha–1), and oryzalin 4.5 kg a.i./ha (478 kg·ha–1). Based on precocity, yields, and weed control efficiency, the performance rating of these weed control treatments was mat ≈ oxyfluorfen > oryzalin > paraquat. Chemical names used: 4-(dipropylamino)-3,5-dinitrobenzenesulfonamide (oryzalin); 2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene (oxyfluorfen); 1,1′-dimethyl-4-4′-bibyridinium ion (paraquat).

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Hector R. Valenzuela, Joseph DeFrank and Greg Luther

The diamondback moth (DBM). Plutella xylostella, is the number one pest of cabbage in the the world. The pest is resistant to most pesticides registered for its use, and resistance has also been detected in several areas for registered biopesticides. Four experiments were conducted to: 1) Determine the tolerance to DBM feeding among 20 commercial head cabbage cultivars, 2) Evaluate the effect of three nitrogen fertility levels on DBM numbers. and 3) Evaluate the effect of Indian mustard. Brassica juncea trap crops as a tool to manage DBM populations in head cabbage agroecosystems. Experiments were conducted at University of Hawaii experiment stations located in Kamuela. Hawaii, and in Kula, Maui. The trap crop treatments consisted of planting two border rows of Indian mustard in cabbage field borders. Three or 4 biweekly insect counts were conducted for each trial. Insect counts consumed of destructive sampling of 3-6 plants per plot and determination of larvae and pupae number and parasitation levels. The nitrogen studies found more DBM in monoculture cabbage receiving 300 kg Ha-1 N than in controls even though cabbage yields did not vary among treatments. A range of tolerance to DBM feeding was found among the cultivars tested. The trap crop system was shown to be more effective during the summer than in the winter months. Data indicates that the trap crop also acted as attractant for beneficial insects, which may aid in the biological control of DBM in cabbage