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In July 1999, adult stages of root weevils were established in 1-gal containers planted with Rhododendron `PJM.' Each pot was inoculated with one black vine weevil, three rough strawberry root weevils, and four strawberry root weevils. On 12 July, insecticide spray treatments were applied. Treatments were evaluated for percent adult mortality at 7 and 14 days after treatment (DAT). Black vine weevils were more sensitive to the insecticides studied than either strawberry root weevil or rough strawberry root weevil. There was considerable mortality of the black vine weevils and rough strawberry root weevils in the untreated plots by 14 DAT. Talstar Flowable (bifenthrin), Alta (deltamethrin), Topside (lamda cyhalothrin), and CGA 293 343 (thiamethoxam) all gave 100% control 7 DAT. Additionally, Closure (bendiocarb) and acephate gave 75% or better control at 7 DAT. Rough strawberry root weevil had 100% mortality in only the Alta-treated plots at 7 DAT, followed by 93% and 80% mortality in Topside and acephate-treated plots, respectively. Mortality of the strawberry root weevils in the untreated plots by 14 DAT remained relatively low. Strawberry root weevils were more resistant to the applied insecticide treatments. Only Topside-treated plots had 90% or greater mortality at 7 DAT, followed by Talstar (60%), Alta (58%), and acephate (54%). Topside-treated plots had 90% or greater mortality at 14 DAT followed by Talstar (76%), Alta (68%), and Closure (60%). Combined root weevil species mortality showed highest mortality at 7 DAT in Topside-treated plots (87% or greater), followed by Alta (74% or greater), and acephate (73%).
Experiments were conducted to determine the effect of varying solution N concentrations on fruit yield and NO3-N concentration in leachate from rockwool-grown `Midal' peppers (Capsicum annuum L.) in Florida. Treatment 1 plants received a series of nutrient solutions containing N at 60, 90, and 120 mg·liter–1 (60–90–120 mg·liter–1) during their growth cycle. Plants in treatments 2 and 3 were grown with N at 120 or 175 mg·liter–1, respectively, throughout their entire growth cycle. Two trials were conducted; trial 1 from 17 Nov. 1991 to 1 July 1992, and trial 2 from 31 July 1992 to 23 Feb. 1993. In both trials, total marketable fruit weight was significantly (P ≤ 0.05) higher (16% to 67%) for plants grown with N at 175 than with 60–90–120 mg·liter–1. In trial 2, plants receiving N at 175 mg·liter–1 produced significantly more fruit (8%) and 14% higher total fruit weight than plants receiving N at 120 mg·liter–1. The trend toward higher yield with N at 175 rather than 120 mg·liter–1 also occurred during trial 1, but differences were not significant. Nitrogen concentration did not significantly affect the percentage of total fruit having blossom-end rot in either trial (41% in trial 1; 13% in trial 2). Nitrogen at 175 mg·liter–1 resulted in 10% to 40% increases in total nutrient solution use and 2.5- to 3.5-fold increases in leachate NO3-N concentration compared to N at 120 mg·liter–1.
Stem and bud tissues of promocanes from more than 260 Rubus genotypes were evaluated for mid-winter cold hardiness after laboratory freezing in January 1990. T50 values were calculated for cane samples of red, yellow, black and purple raspberry, and blackberry cultivars, hybrids and species. Red raspberries exhibited the hardiest stem tissue, although several purple raspberries (Rubus sp. cvs. Brandywine, Royalty) survived as low as -33 C. Fall fruiting red raspberries, such as R. idaeus L. cvs. Zeva Remontante, Indian Summer, St. Regis, and Fallred, survived from -23 to -25 C. Summer-bearing cultivars, Canby and Puyallup, survived to -30 C. Stems of several black raspberries (R. occidentalis L. cvs. New Logan, Bristol) survived to -27 C. Stems of the hardiest blackberry cultivars, (R. sp. cvs. Black Satin, Smoothstem) survived to -22 C. In most genotypes the region of the bud at the axis of the stem was less hardy than tissues within the bud scales. Buds tissue was 2 to 10 C less hardy than stem tissue. Field plants were also visually rated for cold injury following record low temperatures occurring in 1989, 1990, and 1991.
Abstract
A modified Scholander pressure bomb was sensitive enough to detect significant differences in relative leaf water stress among ‘Orlando’ tangelo (Citrus reticulata Blanco × C. paradisi Mact) on several rootstocks. Leaf water potential for the rootstocks ranged from -7.9 bars for rough lemon (Citrus jambhiri Lush.) to -13.7 bars for those on trifoliate orange (Poncirus trifoliata Raf.). There was a diurnal pattern in leaf water stress. Modifications and procedures for the pressure bomb measurements are described.
Abstract
Two applications of 3500 ppm daminozide applied 4 to 5 weeks from sowing and at visible bud stage resulted in excellent height control of Calendula officinalis L. ‘Mandarin’ by reducing both peduncle and internodal elongation. There were no differences in flowering time between any daminozide concentrations (1500, 3500, or 5000 ppm) and control. Light reduction of 50% during the spring months did not increase plant height or prolong flowering times compared with ambient, but 75% light reduction increased internode elongation and duration of flowering. There were no interactions between light reduction and number of daminozide applications. Chemical name used: butanedioic acid mono(2,2-dimethylhydrazide) (daminozide).
Application of linuron was compared with hand-weeding and a nontreated control (= control) for weed control in carrots. Linuron, applied pre- or postemergent, was slightly less effective than the 100% weed control obtained by hand-weeding. Carrot yields were similar for all treatments, and were at least six times as great as in the control. In 1996, linuron treatments returned net profits ranging from $980 to $1887 per ha, compared to $740 for hand-weeding and - $2975 for the control. In 1997, return on linuron treatments was greater, ranging from $5326 to $6426, compared with $2852 for hand-weeding. Marginal rates of return ranged from 21% to 86% in 1996. In 1997, rates of return for every dollar invested in linuron were over 59%. Chemical name used: N′-(3,4-dichlorophenyl)-N-methoxy-N-methylurea (linuron).
Application of linuron was compared with hand-weeding and a nontreated control (= control) for weed control in carrots. Linuron, applied pre- or postemergent, was slightly less effective than the 100% weed control obtained by hand-weeding. Carrot yields were similar for all treatments, and were at least six times as great as in the control. In 1996, linuron treatments returned net profits ranging from $980 to $1887 per ha, compared to $740 for hand-weeding and -$2975 for the control. In 1997, return on linuron treatments was greater, ranging from $5326 to $6426, compared with $2852 for hand-weeding. Marginal rates of return ranged from 21% to 86% in 1996. In 1997, rates of return for every dollar invested in linuron were over 59%. Chemical name used: N′-(3,4-dichlorophenyl)-N-methoxy-N-methylurea (linuron).
In an effort to identify new herbicides for vegetables crops, broccoli (Brassica oleracea) cantaloupe (Cucumis melo), carrot (Daucus carota), head lettuce (Lactuca sativa), bulb onion (Allium cepa), spinach (Spinacia oleracea) and processing tomato (Lycopersicon esculentum) were evaluated in the field for tolerance to eight herbicides. The following herbicides and rates, expressed in a.i. lb/acre, were applied preemergence: carfentrazone, 0.05, 0.1, 0.15 and 0.2; flufenacet, 0.525; flumioxazin, 0.063, 0.125 and 0.25; halosulfuron, 0.032 and 0.047; isoxaben, 0.25 and 0.50; rimsulfuron, 0.016 and 0.031; SAN 582, 0.94 and 1.20 and sulfentrazone, 0.15 and 0.25 (1.000 lb/acre = 1.1208 kg·ha-1). Tolerance was evaluated by measuring crop stand, injury and biomass. Several leads for new vegetable herbicides were identified. Lettuce demonstrated tolerance to carfentrazone at 0.05 and 0.10 lb/acre. Cantaloupe and processing tomato were tolerant of halosulfuron at 0.032 and 0.047 lb/acre. Broccoli, cantaloupe and processing tomato were tolerant of SAN 582 at 0.94 lb/acre. Broccoli and carrot were tolerant of sulfentrazone at 0.15 lb/acre.
The Food Quality Protection Act may result in the withdrawal from use of many herbicides in the “minor” crops: fruits, vegetables, herbs, flowers, and ornamentals. An obvious mitigation strategy is to test and register newer, low-rate herbicides that are currently used only in large-acreage field crops. The newer herbicides have low mammalian toxicity, few off-target effects, and are often used at rates of less than 0.1 kg/ha. Many of the older herbicides are applied at rates of several kg/ha and have off-target effects that can make their use problematic. Low-rate herbicides could replace the older chemicals commonly used in horticultural crops. We have tested several promising low-rate herbicides: carfentrazone, cloransulam, dimethenamid, halosulfuron, rimsulfuron, and sulfentrazone. Broccoli, cantaloupe, carrot, lettuce, onion, spinach, and processing tomato varieties were screened for tolerance to low-rate herbicides at four locations in California that included desert, inland, and coastal environments. All of the crops tested had tolerance for one or more of the low-rate herbicides. Data on similar tests for other horticultural crops will also be presented. The potential for registering these herbicides in vegetables and other horticultural crops varies with the crop and the pesticide's manufacturer. Pesticides that may soon face removal from widespread use will be reviewed. Herbicides and other potential alternatives to currently registered herbicides will be examined to determine possible practical alternatives for specific crops and weeds.