Vegetable Report 1994-1995
ABOUT THIS COLLECTION
The Vegetable Report is one of several commodity-based agricultural research reports published by the University of Arizona.
This report was first published in 1965.
The purpose of the report is to provide an annual research update to farmers, researchers, and those in the agricultural industry. The research is conducted by University of Arizona and USDA-ARS scientists.
Both historical and current Vegetable Reports have been made available via the UA Campus Repository, as part of a collaboration between the College of Agriculture and Life Sciences and the University Libraries.
Contents for Vegetable Report 1994-1995
- Broccoli Variety Trials 1994/1995
- Cabbage Variety Trials 1994/1995
- Cauliflower Variety Trials 1994/1995
- Crisphead Lettuce Variety Trials 1994/1995
- Mixed Lettuce and Romaine Variety Trials 1994/1995
- Dry Bulb Onion Variety Trial
- Basal Crop Coefficients for Vegetables in Central Arizona
- Subsurface Drip Irrigation of Leaf Lettuce and Broccoli I: Spatiel Distribution of Roots and Soil Water Tension
- Subsurface Drip Irrigation of Leaf Lettuce and Broccoli II: Water Balance
- Field Evaluation of Potential New Fungicides for Control of Powdery Mildew of Cantaloupe in 1994
- Field Evaluation of Potential New Fungicides for Control of Downy Mildew of Broccoli in 1994 and 1995
- Field Evaluation of Potential New Fungicides for Control of Sclerotinia Leaf Drop of Lettuce in 1994 and 1995
- Field Evaluation of Potential New Fungicides for Control of Lettuce Downey and Powdery Mildew in 1994 and 1995
- Vine-Decline of Melons Caused by Monosporascus cannonballus in Arizona: Epidemiology and Cultivar Susceptibility
- Identifying Short-Range Migration by the Sweet Potato Whitefly
- Efficacy of Insecticides to Green Peach Aphid on Iceberg Lettuce
- Relative Susceptibility of Red and Gree Color Morphs of the Green Peach Aphid to Foliar and Systemic Insecticides
- Efficacy of Biorational Insecticides to Beet Armyworm and Cabbage Looper on Iceberg Lettuce
- Impact of Sweet Potato Whitefly Infestation on Yield and Quality of Cantaloupe
- An Action Threshold for Management of Sweet Potato Whitefly in Cantaloupe
- Imidacloprid Does Not Enhance Growth and Yield of Cantaloupe in the Absence of Whitefly
- Evaluation of Admire Soil Treatments on Colonization of Green Peach Aphid and Marketability of Lettuce
- Efficacy and Temporal Mortality of Selective Insecticides on Beet Armyworm Larvae in Lettuce
- New Insecticides for Potential Use for Whitefly Control in Cantaloupes
- Admire® Insecticde Use and Influence on Cantaloupe Growth
- Comparative Efficacy of B.t. Insecticides Against Lepidopterous Pests in Cabbage
- Insectide Combinations for Whitefly Control in Broccoli
- Herbicide Weed Control in Sweet Corn
- Herbicide Weed Control in Cantaloupes
- Soil-Applied Herbicides for Weed Control in Broccoli
- Preemergence Herbicide Weed Control in Spinach
- Dacthal® Herbicide Rate Comparison for Preemergence Weed Control in Onions
- Postemergence Weed Control in Onions
- Early Postemergence Herbicide Weed Control in Onions
- Use of Non Toxic Materials for Whitefly Control and Growth Enhancement in Crisphead Lettuce
Use of Non Toxic Materials for Whitefly Control and Growth Enhancement in Crisphead LettuceField studies were conducted in Yuma and Tucson in 1993 to determine the effect of several non toxic substances purported to enhance growth and yield of lettuce, and to determine whether these treatments have an effect on whitefly populations. Five applications of the treatments were made beginning four weeks after planting and continuing at weekly intervals. Results indicated that there may be some positive effects of foliar applied methanol and nutrient (nitrogen/iron) treatments, as well as, from the use of Capture insecticide.
Early Postemergence Herbicide Weed Control in OnionsOxyfluorfen (Goal®) herbicide at 0.25 lb. ai./A and bromoxynil (Buctril®) at 0.38 lb.a.i. /A applied early postemergence (POST) to onions at the 1- to 2-leaf stage of growth gave near complete control ( >98 %) of lambsquarters, knotweed, cheeseweed, London rocket, and good control ( -90 %) of shepherd's purse. Buctril® did not control annual bluegrass and Goal® only slightly reduced some of the heavy population. Both herbicides caused marginally unacceptable onion injury at 17-20 %. Buctril® plus pendimethalin (Prowl®) tank-mix combination applied POST also gave very good broadleaaved weed control but annual bluegrass was reduced only 50 %. Similar onion injury was observed for the combination treatment as Buctril® alone. Buctril® caused onion injury when it was applied during cloudy weather. Buctril® and Goal® were effective for broadspectrum broadleaved weed control but onions were sensitive when treated before reaching the full 2-leaf stage of growth. Cloudy weather during applications also intensified the onion injury by Buctril® treatments.
Postemergence Weed Control in OnionsOxyfluorfen (Goal®) herbicide at 0.125 to 0.25 lb. a.i./A applied postemergence (POST) to onions at the 3-leaf stage of growth effectively controlled London rocket, yellow sweetclover, and prostrate pigweed with marginal injury to onions. Earlier POST applications on 1- and 2-leaf onions caused injury and some stand reduction. Bromoxynil (Buctril®) herbicide at 0.25 lb. a.i./A applied early POST gave generally good weed control but did not adequately control sweetclover. Buctril® applied in clear weather did not injure 1-leaf onions but caused severe injury on 2- and 3-leaf onions when applied during cloudy weather conditions. Buctril® plus pendimethalin (Prowl®) tank-mix combination applied POST provided good control of London rocket, sweetclover, and prostrate pigweed; however, onion injury was severe due to applying Buctril® in cloudy weather. Buctril® and Goal® effectively controlled weeds present in the onions but timing of POST applications was critical with respect to onion size and weather conditions to minimize injury.
Dacthal® Herbicide Rate Comparison for Preemergence Weed Control in OnionsDCPA (Dacthal®) herbicide was applied preemergence (PE) to the soil surface after onion planting and no crop injury was observed for rates of 5.3, 7.5, and 10.5 lb. a.i. /A at one of two locations. Dacthal® gave good control of London rocket and cheeseweed (90 -94 %) at one location and marginal control at the second location (79 -85 %). Dacthal® did not exhibit a rate response to control the two weeds common to both locations. The lower rate of Dacthal® did not differ in efficacy compared to higher rates to completely control lambsquarters and nettleleaf goosefoot. All rates of Dacthal® marginally controlled yellow sweetclover and other mustard weeds present. Dacthal® provided adequate weed control to allow onion stand establishment.
Preemergence Herbicide Weed Control in SpinachTwo field studies were conducted to evaluate metolachlor (Dual®) for preemergence weed control in spinach to provide support to gain registration through the IR-4 program. Dual® at 1.0 to 1.5 lb a.i./A gave acceptable control of London rocket, black mustard, lambsquarters, and knotweed. Nettleleaf goosefoot, cheeseweed, and yellow sweetclover control was not acceptable. In one test, dimethenamid (Frontier® or SAN -582H, Sandoz) controlled London rocket, lambsquarters, knotweed, and goosefoot at 0.25 lb ai. /A and did not control cheeseweed or sweetclover. Spinach was not injured by Dual® or Frontier®.
Soil-Applied Herbicides for Weed Control in BroccoliThree commonly used herbicides for use in broccoli were effective when applied alone or in combinations as a preplant incorporated (PPI) or a preemergence (PE) application. DCPA (Dacthal®) at 10.0 lb product/A PE gave acceptable control of most weeds. Trifluralin (Treflan® SEC) at 1.0 pt/A and bensulide (Prefar® 4EC) PPI were also effective but mustard weeds were not adequately controlled. Combinations of the herbicides at lower rates did not provide any advantage in improving weed control efficacy.
Herbicide Weed Control in CantaloupesPreemergence herbicide treatments metolachlor (Dual®) and pendimethalin (Prowl®) gave better than acceptable weed control ( >85 %) of prostrate and tumble pigweeds, puncturevine, common purslane, and groundcherry in cantaloupes. Preplant incorporated treatments provided less than adequate control of pigweeds and groundcherry. Bentazon (Basagran®) applied postemergence gave good control of pigweeds but groundcherry control was marginal. Napropamide (Devrinol®), trifluralin (Treflan®), and DCPA (Dacthal (D) caused cantaloupe stand reduction and injury. Bensulide (Prefar®) and Basagran® were safe when applied on cantaloupes.
Herbicide Weed Control in Sweet CornPreplant incorporated and/or preemergence herbicide treatments including metolachlor (Dual®), EPTC with safener (Eradicane®), cyanazine (Bladex®), pendimethalin (Prowl®), and tank-mix combinations provided good (88 %) to excellent ( >98 %) weed control of prostrate and tumble pigweeds and purslane in sweet corn.
Insectide Combinations for Whitefly Control in BroccoliTwo pyrethroid insecticides, fenpropathrin (Danitol®) and bifenthrin (Capture®), were evaluated in several combinations with other insecticides for whitefly control in broccoli and demonstrated good efficacy to reduce eggs and immature stage insects. At one week after the second of three applications, Danitol® or Capture® plus methamidaphos (Monitor®), acephate (Orthene®), or endosulfan (Thiodan®) significantly reduced egg counts relative to the untreated check.
Comparative Efficacy of B.t. Insecticides Against Lepidopterous Pests in CabbageSeveral commercial formulations of Bacillus thuringiensis (Al) insecticides were applied on cabbage and lepidopterous pests including Tricoplusia it (cabbage looper, CL), Spodoptera exigua (beet armyworm, BAW), and Plutella xvlostella (diamondback moth, DBM) were effectively reduced in population. The ten commercial products did not appear to vary significantly in controlling CL, the dominant species present in the cabbage.
Admire® Insecticide Use and Influence on Cantaloupe GrowthCantaloupe growth was influenced by using imidacloprid (Admire®) insecticide to control, suppress, or reduce whiteflies. The growth rate of cantaloupe was evaluated at regular intervals after crop emergence and a rate response was observed with greater growth with respect to increase in Admire® rate. Following at planting time applications, at 3 and 4 weeks after treatment (WAT) cantaloupe plants had more foliar growth and a greater number of leaves with increasing Admire® rate. At 5 to 8 WAT, cantaloupe vines exhibited greater growth with increasing rates of Admire®.
New Insecticides for Potential Use for Whitefly Control in CantaloupesMost experimental treatments effectively reduced Bemisia tabaci [sweetpotato whitefly (WF) also known as silverleaf WF, B. argentifolii] adults and eggs in cantaloupes relative to the untreated check at 6 days after treatment of each of five applications. Acephate (Orthene®), buprofezin (Applaud®), bifenthrin (Capture®), endosulfan, fenpropathrin (Danitol®), naled (Dibrom®), and pymetrozine(CGA -215944, Ciba) treatments had the fewest adults and eggs. Insect growth regulator (IGR) materials in combinations, pyriproxyfen (S-71639, Valent) and fenoxycarb (Ciba),were more effective in reducing WF relative to the untreated check than when applied alone. Registered products, Dibrom®, endosulfan, and methamidaphos (Monitor®) were effective in combinations or in alternating applications.
Evaluation of Admire Soil Treatments on Colonization of Green Peach Aphid and Marketability of LettuceAdmire (imidacloprid), applied as a soil treatment, protected lettuce plants from developing infestations of green peach aphid, Myzus persicae (Sulzer), for 60-100 d after planting based on two small plot and two commercial field trials. Admire applied 7.6 cm sub-seed furrow provided longer and more consistent protection from green peach aphid than treatments applied to the soil surface, as a side-dress, or 15.2 cm sub-seed furrow. Surface band applications of Admire provided inconsistent control probably because of inadequate hydrological incorporation into the soil. In small plot trials, effective control of aphids by Admire applied 7.6 cm sub seed furrow resulted in greater than 90.0% marketable heads while the untreated plots contained 20.0% marketable heads. When used in a commercial setting, Admire applied 7.6 cm sub-seed furrow on leaf lettuce prevented aphid colonization (<3 aphids per plant) for approximately 100 d after planting, while the untreated and commercial standard treated areas contained 30.7 and 26.8 aphids per plant respectively at 100 d after planting. In addition, marketability of lettuce was greater in Admire treated plots. As a sub-seed furrow treatment, Admire provides a more suitable approach to aphid control than is currently available with foliar insecticides.
Imidacloprid Does Not Enhance Growth and Yield of Cantaloupe in the Absence of WhiteflyImidacloprid is a new, chloronicotinyl insecticide currently being used to control sweetpotato whitefly (Bemisia tabaci Genn, also known as silverleaf whitefly, Bemisia argentifolii Bellows and Perring). Large growth and yield increases of cantaloupes (Cucumis melo L.) following the use of imidacloprid have caused some to speculate that this compound may enhance growth and yield above that expected from insect control alone. Greenhouse and field studies were conducted to evaluate the growth and yield response of melons to imidacloprid in the presence and absence of whitefly pressure. In greenhouse cage studies, sweetpotato whiteflies developed very high densities of nymphs and eclosed pupal cases on plants not treated with imidacloprid, and significant increases in vegetative plant growth were inversely proportional to whitefly densities. Positive plant growth responses were absent when plants were treated with imidacloprid and insects were excluded. Results from a field study showed similar whitefly control and yield responses to imidacloprid and bifenthrin+ endosulfan applications. Hence, we conclude that growth and yield response to imidacloprid is associated with control of whiteflies and the subsequent prevention of damage, rather than a compensatory physiological promotion of plant growth processes.
An Action Threshold for Management of Sweet Potato Whitefly in CantaloupeA range of action thresholds for the control of sweet potato whitefly, Bemisia tabaci Gennadius were evaluated in field experiments with high population density of B. tabaci. Action thresholds for whitefly adults, based on seasonal whitefly averages that could result in 5% and 15 % dollar losses, of 3 and 10 adults per leaf, respectively, were tested. All thresholds were compared to weekly insecticide treatments and an untreated check The resulting best threshold treatment was 3 adults per leaf area which provided a 170% increase in net return over the untreated check. The 3 adult per leaf threshold resulted in 6 applications of insecticide, compared with 10 applications used in the weekly regime.
Impact of Sweet Potato Whitefly Infestation on Yield and Quality of CantaloupeA range of population levels of sweet potato whitefly, Bemisia tabaci Gennadius was evaluated in three field experiments allowing measurement of the effect of whitefly numbers on melon quality and yield. An increase in total numbers of immature whitefly was associated with significant declines in harvested melon weight, a decline in number of boxes harvested, a decrease in fruit size, a decrease in percent sugars, and an increase in sooty mold. Regression analysis of individual whitefly life stages with yield parameters indicated that adult number was a more precise parameter and higher R2 values were obtained with increased range of whitefly population densities. Adults were sampled at the third leaf node in both locations. Nymph samples were taken at varying nodes from the base of the plant. Estimates of the mean adult whitefly density resulting in 5% and 15 % dollar yield loss were 3 and 10 adults per leaf Estimates of the mean total nymph density resulting in 5% and 15% dollar yield loss 0.5 and 2 (AZ) nymphs per cm² of leaf area, respectively.
Efficacy of Biorational Insecticides to Beet Armyworm and Cabbage Looper on Iceberg LettuceFour tests were conducted evaluating biorational insecticides for control of beet armyworm (BAW) and cabbage looper (CL) on iceberg lettuce. Treatment means for BAW were difficult to separate due to low population densities. The new formulation of Javelin appeared to be the most efficacious Bt overall. However, when Bts were compared on a equal cost/A basis, there were no significant derences among products for CL control. All Bts were comparable to Lannate for CL control. The neem oil extract Align, provided adequate BAW and CL control, and its efficacy at low rates seemed to be slightly enhanced by the addition of Sunspray Ultrafine Oil. Larvin at lower than label recommended rates gave good BAW and CL control as did Javelin. The tank-mix of these two products did not enhance worm control over that of the products used alone. Mustang gave good control of CL but appeared to be slightly weak against BAW.
Relative Susceptibility of Red and Gree Color Morphs of the Green Peach Aphid to Foliar and Systemic InsecticidesFoliar and systemic insecticide bioassay techniques were developed for testing insecticide susceptibility to two color morphs of the green peach aphid. Six foliar and one systemic insecticide were used in our evaluations. These insecticides included three organophosphates, two pyrethroids, one organochlorine, and one chloronicotinyl. One of the green colored populations tested was collected from spinach, and red and green color populations were collected from the within the same cabbage field. The red morph was found to be less susceptiblethan the green morphs to Dimethoate, Karate, and Endosulfan. Their were only slight differences in susceptibility to the foliar insecticide between the green morphs. The greenmorph from spinach was found to be the most susceptible to Admire, while the two morphs collected from cabbage did not differ. Leveling off of aphid mortality at about 85% with high doses of Admire may indicate highly tolerant types in the populations, or an artifact of the methodology.
Efficacy of Insecticides to Green Peach Aphid on Iceberg LettuceThree tests were conducted evaluating foliar and soil applied aphicides for efficacy to green peach aphid infesting iceberg lettuce. Aphid population densites were low in all three studies and differences among treatments were difficult to discern. At low aphid populations we could not detect whether or not soil applications of Admire enhanced or inhibited the activity of subsequent foliar applications of other aphicides. Although when used alone, some products did offer statistically significant aphid control. However, in a commercial setting these differences would probably not be significant. At low aphid populations none of the pyrethroid tank mixes evaluated gave significantly better aphid control than the products used alone. All of the experimental aphicides evaluated appeared to have some degree of efficacy to green peach aphid.