The postemergence (POST) herbicide treatments did not cause any crop stand reduction following applications. Bentazon (Basagran®) at 0.50 lb AI /A caused marginally acceptable injury on the cantaloupe leaves. At 2 weeks after treatment (WAT), the amount of injury decreased and cantaloupe treated with Basagran at 1.0 lb AI/A showed marginally acceptable injury symptoms. Halosulfuron (Monsanto) at 0.05 to 0.10 lb AI/A caused slightly more injury (10 to 17 %) with increasing rates. Basagran at 1.0 lb Al/A gave good control ( >90 %) of morningglory and was marginal in controlling morningglory at 0.75 lb AI/A Halosulfuron at 1 WAT was marginal in controlling morningglory but improved to give acceptable control at 2 WAT. Fewer and smaller plants were removed by hand-hoeing from Basagran and halosulfuron treated plots compared to the untreated check.

DCPA (Dacthal®) at 9.0 lb AI /A, the commercial standard herbicide, slightly reduced the number of plants and shortened the plant height compared to the untreated check. Preemergence (PREE) herbicide treatments that caused injury as height reduction similar to Dacthal included pendimethalin (Prowl®), propachlor (Ramrod®), metolachlor (Dual®), dimethenamid (Frontier®), ethofumesate (Nortron®), and benefin (Balan®). Visual observations did not indicate significant stand reduction or crop injury compared to plant counts. Treatments that caused minimal visible crop injury (<10 %) were Ramrod, Balan and lower rates of Frontier and Nortron. Moderate to acceptable injury (15 %) was observed on onions treated by Prowl, Dual, Frontier, and Nortron. Treatments that significantly reduced crop stand were Prefar at 6.0 lb AI /A, lactofen (Cobra®), thiazopyr (Visor®), and some combinations of the three herbicides. Combination treatments that caused marginally acceptable injury included Prowl plus Dual, Nortron plus Prowl, Prefar plus Nortron, Nortron plus Frontier, Ramrod plus Frontier, Ramrod plus Nortron, and Ramrod plus Balan. Early weed control ratings showed that Prowl at 0.5 and 0.75 lb Al/A, Nortron, Cobra, Visor applied alone gave acceptable control (>85 %) of London rocket (Sisvmbrium irio), sowthistle (Sonchus oleraceus), and sweetclover (Melilotus officinalis). Prowl at 0.75 lb AI/A and Cobra gave season -long control of all weeds. Early weed control ratings of combination herbicide treatments demonstrated that Prowl or Nortron combined with other herbicides gave acceptable weed control. Prowl at 0.50 lb AI /A plus Ramrod, Nortron, or Dual at the lower rates slightly improved weed control compared to each of the herbicides applied alone.

The effect of Roundup on lemon trees (Citrus limon) was evaluated by repeatedly spraying 0.5, 0.75, 1, 1.25, and 1.5 lb. a.i./acre (corresponding to 0.5, 0.75, 1, 1.25, 1.5 quarts of Roundup Ultra/acre) on the bottom 20 to 24 inches of the tree canopies, over a three year period. The Roundup applications caused significant leaf injury in the sprayed area of the canopies and there was also significant defoliation of branches at the higher Roundup rates in all three years of the study. In 1996 after three Roundup applications, increasing rates of Roundup had no effect on flower or fruitlet production in either the sprayed or unsprayed portions of the tree canopies as judged by the counts collected from branches in each canopy zone. Similarly, in 1997 after five Roundup applications, and in 1998 after nine Roundup applications, increasing rates of Roundup had no effect on flower or fruitlet production in the sprayed or unsprayed portions of the tree canopies. Spraying Roundup on the bottom of the tree canopies did not reduce total lemon yield per tree in 1996, 1997 or 1998 at any of the application rates. In all three years of the study, increasing Roundup rates had no effect on the yield of the first or second ring picks or the percentage of the total crop picked on the first harvest date. Increasing Roundup rates also did not affect fruit size at any harvest date in 1996, 1997 or 1998. Similarly, increasing Roundup application rates did not affect fruit quality at any harvest in 1996, 1997 or 1998. Thus, there was no relationship between the rate of Roundup sprayed on the trees and yield, fruit size or quality in all three years of this study. The three years of data collected in this study indicate that accidental drift or inadvertent application of Roundup onto lemon trees when spraying weeds on the orchard floor has no significant effect on lemon tree productivity.

Mechanical (disk and Perfecta cultivator) and chemical weed control strategies were compared in a Yuma, AZ lemon orchard. In addition, an optical weed sensing sprayer (WeedSeeker) was evaluated for making post-emergence Roundup Ultramax herbicide applications. The use of pre-emergence herbicides in conjunction with the WeedSeeker spray units has the potential to significantly reduce the amount of post-emergence herbicide and water needed to spray flood irrigated citrus orchards. There was a relationship between weed ground cover and the area sprayed by the WeedSeeker units that indicated the maximum herbicide saving will occur a low weed densities. The use of the Kawasaki Mule with its superior suspension system allowed for faster spraying speeds than were possible with the tractor mounted sprayer and this also reduced spray volume per plot. Weed control was similar for the conventional and the WeedSeeker sprayers. Future investigations will include efforts to improve the estimation of percent weed groundcover, the use of higher rates of pre-emergence herbicides and the development of crop budgets based on experimental operations.

A field study was designed to determine if foliar boron (B) sprays could increase fruit set and yield of 'Parent Washington' navel oranges (Citrus sinensis). Treatments consisted of two application timings (prebloom and postbloom) and five application rates 0, 250, 500, 750 and 1000 ppm B as Solubor. Leaf B levels had a significant response to both application timing and rate in 1998, but there were no significant differences in 1999. There were no significant difference in fruit quality or yield in either year.

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Typescript (photocopy). / Digitized by Kansas Correctional Industries

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