Vegetable Report 2002
ABOUT THE 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 2002Herbicide
- Beet Armyworm Control in Lettuce
- Evaluation of Neonicotinoid Insecticides for Whitefly Management in Melons
- Field Evaluation of Eretmocerus eremicus Efficacy in the Control of Sweet Potato Whiteflies Infesting Melons
- Influence of Planting Date and Insecticidal Control on Seasonal Abundance of Lettuce Aphids on Head Lettuce
- Knockdown and Residual Efficacy of Biopesticides and Reduced-Risk Insecticides against Western Flower Thrips in Romaine Lettuce
- Population Growth of Lettuce, Nasonovia ribisnigris, on Resistant Butter and Head Lettuce Cultivars
- Suppression of Western Flower Thrips by Overhead Sprinkler Irrigation in Romaine Lettuce
- The Effects of Spray Adjuvants on the Insecticidal Activity of Success® (spinosad) on Lettuce and Melons
- 2001 Yield Response of Processing Onions in the Palo Verde Valley Treated with AuxiGro® WP
- Effect of Dry Seed+ Application at Planting 1998 on Processing Onion Yields
- Effect of Messenger® on Cantaloupe Growth Pattern and Yield
- Messenger® Effect on Melons
- Activity of Actigard® on Development of Phytophthora Root and Crown Rot on Pepper Plants
- Effect of Messenger® on Chile Pepper Production and Bacterial Spot in 2001
- Evaluation of Fungicides for Control of Powdery Mildew on Lettuce in 2002
- Influence of Salinity and Root-knot Nematode as Stress Factors in Charcoal Rot of Melon
- Performance of Products for Management of Sclerotinia Leaf Drop of Lettuce in 2002
- Comparison of Postemergence Grass Herbicides for Grass Weed Control
- Effect of Halosulfuron on Rotational Crops
- Evaluation of New Preemergence Herbicides Alone and in Combinations for Weed Control in Melons
- Evaluation of Stinger (Clopyralid) for Weed Control in Broccoli
- Performance of Postemergence Herbicides for Cantaloupe Weed Control
Performance of Postemergence Herbicides for Cantaloupe Weed ControlHalosulfuron applied alone gave marginal to good control of common lambsquarters and common purslane, respectively, but did not provide control of the pigweeds. Acceptable control of 85% of the limited population of purple nutsedge was observed. Rimsulfuron applied alone gave good control of the pigweeds, lambsquarters, purslane, and marginal control of nutsedge. Weed control was effective until the late season evaluation at 9 WAT. The combination of halosulfuron and rimsulfuron gave similar results of the rimsulfuron applied alone, however, nutsedge control was not evaluated due to insufficient populations. Halosulfuron treated melons showed the least injury among all of the herbicide treatments applied alone. Rimsulfuron caused marginally unacceptable injury at 18% compared to flumetsulam, thifensulfuron, MKH-6561, and flufenacet which caused unacceptable injury ranging from 20 to 68%.
Evaluation of Stinger (Clopyralid) for Weed Control in BroccoliThree rates of Stinger (Clopyralid) were evaluated for weed control, crop safety and soil persistence in broccoli. Efficacy tests indicated that 0.25 pt./A was ineffective in controlling volunteer alfalfa; while 0.5 pt produced marginal control and 1.0 pt. produced excellent control. No injury was noted at any rate. 140 days after treatment, injury was moderate to severe to alfalfa, moderate to tomatoes, cotton, carrots and lettuce and slight to onions.
Evaluation of New Preemergence Herbicides Alone and in Combinations for Weed Control in MelonsAzafenidin (Milestone®, Dupont) and flumioxazin (Valor®, Valent)) caused cantaloupe injury that was very marginal between acceptable (<15%) and unacceptable (>15%). Flufenacet (Bayer), isoxaben (Gallery, DowAgroSciences), and thifensulfuron (Harmony®, Dupont) at the rates tested caused severe crop injury. Isoxaben provided very good weed control (>90%), azafenidin provided acceptable control of only lambsquarters at 88% and less than acceptable (85%) control of pigweeds, purslane, and grasses, and flumioxazin at the higher rate of 0.05 lb AI/A tended to offer slightly better weed control than the lower rate but overall it was marginally acceptable. Bensulide (Prefar®) combined with flumioxazin caused negligible crop phytotoxicity and better than 93% control for purslane, pigweeds, lambsquarters, and grasses. Combinations of herbicides offered slightly improved weed control compared to herbicides applied alone. Crop injury increased for combinations with dimethenamid (Outlook®, Frontier®, BASF) and s-metolachlor (Dual Magnum®, Syngenta).
Effect of Halosulfuron on Rotational CropsA field test was conducted to evaluate and determine the safety of halosulfuron on typical rotational crops such as lettuce, broccoli, spinach, onion, alfalfa, barley, field corn, and melons after an initial application on cantaloupes. Halosulfuron at 0.05 or 0.1 lb AI/A applied on cantaloupes did not detrimentally affect crop stand establishment, height, or whole plant fresh weights when alfalfa, barley, spinach, lettuce, onion, and broccoli were planted at approximately 4 to 5 MAT. Cantaloupes and field corn planted at 1 YAT were not affected in establishing a stand and in growing during the early season as height or vine lengths were measured. At 15 to 16 MAT, lettuce, onion, and broccoli were not affected in establishing a stand. Watermelon planted at 1 YAT exhibited slight stand reduction and crop injury with halosulfuron applied PREE. Alfalfa planted after PREE applications indicated slightly depressed height and yield compared to POST treatments and the untreated check. Spinach planted where POST applications were made on cantaloupes tended to show a slight reduction in fresh weight at 15 to 16 MAT. Halosulfuron does not appear to be a major deterrent to typical crop rotational schemes in the diverse desert agricultural systems.
Comparison of Postemergence Grass Herbicides for Grass Weed ControlSelect (clethodim) and BAS-620 (BASF Corporation) at 0.1, 0.125, and 0.188 lb AI/A gave near complete control (99%) of watergrass at 8 days after treatment of the early application in watermelons and cantaloupes. Poast (sethoxydim) and Fusilade DX (fluazifop-p-butyl) offered nearly similar effective control of the watergrass with control ranging from 93 to 98%. Poast demonstrated a rate response with decreasing efficacy with decreasing rates of application. Fusilade and Poast at the high rate were comparable to Select and BAS-620 at the high rate. In lettuce, Select and BAS-620 performed similarly on large volunteer wheat with 97% control at about 3 weeks after treatment. Fusilade provided an acceptable level of control at 86% control. Poast did not provide any visible control of the volunteer wheat. Differences existed in the performance of the grass herbicides and optimal performance could be obtained with proper timing of application at effective rates and using effective adjuvants.
Performance of Products for Management of Sclerotinia Leaf Drop of Lettuce in 2002Sclerotinia leaf drop in Arizona is caused by two soil-borne fungi, Sclerotinia minor and S. sclerotiorum. Moist soil and moderate temperature favor this disease. Some new products in development were evaluated for control of leaf drop on lettuce during the winter vegetable growing season of 2001-2002. Sclerotia of each pathogen were applied to plots after thinning and just before the first of two applications of test compounds. Significant reduction of Sclerotinia leaf drop caused by S. minor occurred in plots treated with Endura, whereas other products tested against this pathogen did not significantly reduce the level of disease compared to nontreated control plants. The highest level of disease reduction in plots infested by S. sclerotiorum was achieved by the fungicide Ronilan as well as the biological material Contans. Somewhat lower but still significant disease control was achieved with Endura on plots infested with S. sclerotiorum. In this field trial, Endura provided the best level of disease control in plots infested with S. minor, whereas Contans provided the best level of disease control in plots infested with S. sclerotiorum.
Influence of Salinity and Root-knot Nematode as Stress Factors in Charcoal Rot of MelonIncidence of Charcoal rot, caused by the soil borne fungus Macrophomina phaseolina, may be increased in some crops by the addition of stress on the host caused by high salinity of soil or irrigation water and infection by plant pathogenic nematodes. Since both of these factors may be problematic in melon production in Arizona, studies were initiated to determine if higher salt concentrations of irrigation water and infection by Root-knot nematode (Meloidogyne incognita) may be involved in recent increased incidences of Charcoal rot of melon. In greenhouse trials, higher concentrations of salts in irrigation water significantly increased the percentage of plants that died due to Charcoal rot. However, no significant difference was found in the percentage of dead plants inoculated with both root-knot nematode and M. phaseolina compared to plants inoculated with M. phaseolina alone. Results of these trials indicate that salinity may be a factor in the increased incidence of Charcoal rot of melon, but that root-knot nematode infection may not play a role.
Evaluation of Fungicides for Control of Powdery Mildew on Lettuce in 2002Powdery mildew on lettuce is caused by the fungus Erysiphe cichoracearum. This disease is favored by moderate to warm temperatures and dry weather conditions. Several potential new fungicides were evaluated for control of powdery mildew on lettuce in 2002. Powdery mildew appeared in our plots by February 15 and reached moderate levels of severity by plant maturity on March 6 to 8th. Nontreated lettuce plants were moderately infected with powdery mildew at plant maturity, whereas the level of disease was low to virtually nonexistent in plots treated with Microthiol Disperss, Rally, Quinoxyfen, Flint, and Rally alternated with Kaligreen. Furthermore, other tested products provided moderate suppression of powdery mildew. The future availability of one or more of the tested chemistries not currently registered for lettuce could help in efforts to control powdery mildew on this crop and to establish and maintain a fungicide resistance management program for plant disease control products.
Effect of Messenger® on Chile Pepper Production and Bacterial Spot in 2001Messenger is based on naturally occurring proteins called harpins that trigger natural plant defense systems to protect against disease and pest damage as well as activating plant growth pathways for potential improvements in crop yield and quality. An experiment was established in a commercial chile pepper field in Cochise County to evaluate the effect of Messenger on chile pepper production and bacterial spot. Bacterial spot of pepper occurs wherever this crop is exposed to moisture due to rainfall or overhead irrigation. Foliar application of Messenger, Kocide 2000 + Maneb 75DF (a standard bacterial spot treatment) or Messenger + Kocide + Maneb was performed June 5, 19 and 28; July 16; and August 8 and 22. A foliar defoliation (bacterial spot) rating was performed September 5 and yield (weight and number of chile peppers) was determined September 20 and 21. Compared to nontreated plants, the mean weight of chile peppers harvested from plants treated with Messenger, Kocide + Maneb and Messenger + Kocide + Maneb increased 11, 15 and 24%, respectively, whereas the number of peppers increased 14, 15 and 21%, respectively. The severity of bacterial spot symptoms was numerically (but not significantly) lower on plants treated with Messenger, Kocide + Maneb and Messenger + Kocide + Maneb compared to nontreated plants.
Activity of Actigard® on Development of Phytophthora Root and Crown Rot on Pepper PlantsPhytophthora blight of peppers (Capsicum annuum), caused by the oomycete pathogen Phytophthora capsici, occurs in most regions where this crop is grown. The root and crown rot phase of the disease develops on plants in areas of the field where soil remains saturated with water after an irrigation or rainfall. Subsequent periods of soil saturation encourage further disease development. Actigard (acibenzolar-S-methyl), is a chemical activator of plant disease resistance, has no known direct antifungal effects and is thought to mimic salicylic acid in the signal transduction pathway that leads to systemic acquired resistance (SAR). Foliar applications of Actigard were evaluated for suppression of root and crown rot on pepper plants growing in the greenhouse in pots and inoculated with Phytophthora capsici or grown in soil naturally infested with the pathogen. Inhibition of stem cankers on pepper cultivars Bell Tower and AZ9 after two to four treatments with Actigard was significantly greater than on plants receiving a single treatment of the chemical. Inhibition of stem canker elongation on Bell Tower or AZ9 peppers ranged from 93.2 to 97.2% and 87.4 to 92.4% when plants were inoculated with P. capsici at 1 or 5 weeks, respectively, after the fourth application of Actigard. Survival of chile pepper plants in field soil naturally infested with P. capsici was significantly increased by three foliar applications of Actigard compared to nontreated plants in all three trials when pots were watered daily and in two of three trials when pots were flooded for 48 hr every 2 weeks. When soil was flooded every 2 weeks, establishing conditions highly favorable for disease development, plants treated once with Ridomil Gold survived significantly longer than those treated with Actigard. On the other hand, when water was provided daily without periodic flooding, establishing conditions less favorable for disease development, there was no significant difference in plant survival between the two chemicals in two of three trials. Growth of shoots on chile pepper plants treated with Actigard, watered daily and grown in soil containing P. capsici generally was greater than nontreated plants. Pepper plants subjected to periodic saturated soil conditions and receiving three foliar applications of Actigard plus a soil treatment of Ridomil Gold survived significantly longer and produced a greater amount of shoot growth than plants treated with either chemical alone. This work suggests that Actigard could be an important management tool for Phytophthora root and crown rot on pepper plants.
Messenger® Effect on MelonsMessenger applied at three timely applications at early runner, bloom, and fruiting stages of watermelon versus bi-weekly applications, showed no significant statistical differences for vine length, number of blooms, or harvestable yields. Visual observations for the watermelon plant health at the end of the season tended to indicate that the three timely applications resulted in slightly more vigorous plants than the bi-weekly treated watermelon plants. Cantaloupe vine growth, number of fruit set, yield weight, and fruit size were not different between Messenger treatments and were not enhanced compared to the untreated check.
Effect of Messenger® on Cantaloupe Growth Pattern and YieldAn experimental site was selected at Yuma Agricultural Research Center, University of Arizona, to evaluate the effect of Messenger on melon plant growth and yield. Four treatments in completely randomized block design replicated four times were applied to melon planted on 84- inch beds. High Mark open pollinated melon variety was planted on 3-20-2001 using a commercial planter. Treatments included Messenger applied at 3-leaf stage on 5-4-2001 Messenger applied every 14 days starting on 5-15, 5-29, 6-13, 6-27-2001, standard management practices and control. Observations collected included plant mapping and yield. Results were variable, showed no significant effect of Messenger on plant growth and yield. However, there was indication that Messenger may have an effect on plant growth pattern and yield. Messenger applied at 3-leaf stage and repeated applications seemed to induce an early melon formation, increased number of nodes and yield. It was not possible to make recommendation based on one-year results. Further investigation is needed to verify the results obtained from this experiment.
Effect of Dry Seed+ Application at Planting 1998 on Processing Onion YieldsDry Seed+, a fertilizer/plant growth regulator, was applied to processing onions at planting in the fall of 1998 to evaluate the effect on yields. Yield data obtained June 1999 indicated no effect in this experiment, although this was dissimilar to other trial results. Salt content at the field was thought to have limited yields, and have stressed growing plants, which may have contributed to lack of yield differences noted. Further testing is necessary to further evaluate this product.
2001 Yield Response of Processing Onions in the Palo Verde Valley Treated with AuxiGro® WPProcessing onions were treated with AuxiGro in spring 2001. Applications were applied at four and 7.5 weeks prior to harvest. A single application of 4 oz. product/acre at either four or 7.5 weeks prior to harvest increased yield by approximately 0.7 tons/acre. Two applications resulted in a 1.3 tons/acre yield increase. Differences noted were not statistically different, but the two application treatment provided an increased net return of approximately $95/acre.
The Effects of Spray Adjuvants on the Insecticidal Activity of Success® (spinosad) on Lettuce and MelonsStudies were conducted in the field and laboratory to investigate how the addition of spray adjuvants to Success affected its insecticidal activity against leafminers, thrips and lepidopterous larvae. Studies were also designed to evaluate the knockdown and residual mortality of Success against worms when applied with a buffer to produce an acidic spray solution. Results indicated that Success applied without an adjuvant appeared to provide the most consistent adult mortality of Liriomyza leafminers. In contrast, the addition of a penetrating surfactant (crop oil concentrate) resulted in significantly greater larval mortality consistent with the leafminer feeding behavior. Efficacy of Success against lepidopterous larvae and western flower thrips was not improved using a spray surfactant. However, addition of buffering agents to Success spray solutions significantly affected efficacy against beet armyworm and cabbage looper. Lab bioassays and field studies showed that knockdown mortality was not affected, but residual efficacy was significantly reduced when Success was applied in an acidic (pH 4.2) spray environment.
Suppression of Western Flower Thrips by Overhead Sprinkler Irrigation in Romaine LettuceA two year study was conducted from 2000-2002 to evaluate the use of overhead sprinkler irrigation for suppressing thrips populations in romaine lettuce. Specifically we looked at how the duration and frequency of sprinkler irrigation use reduced adult and larval populations following various irrigation applications employed specifically for thrips suppression. We also evaluated combinations of insecticide spray regimes, used in association with sprinkler irrigation runs, for suppressing thrips populations in both fall and spring seasons. The results of the study demonstrated that overhead sprinkler irrigation has the ability to suppress thrips populations in romaine lettuce. At best, we experienced about 50% population reduction using only sprinkler irrigation compared with the untreated control during these trials. Sprinkler ruins of durations of > 4 hrs and more than 4 cm of water appeared to provide the minimal necessary for suppression. Furthermore, sprinkle runs of 2 or 3 times weekly appeared to provide the most consistent suppression. In contrast, insecticide sprays consistently provided >80% suppression and provided higher yielding and better quality lettuce than sprinklers. The use of sprinkler irrigation, in addition to insecticide sprays did not significantly improve thrips suppression or yields. However, sprinkler irrigation is being used season long in some romaine fields and in organic production and should be of benefit for thrips suppression, particularly in organic systems where effective insecticide alternatives are not currently available.
Population Growth of Lettuce, Nasonovia ribisnigris, on Resistant Butter and Head Lettuce CultivarsStudies to examine lettuce aphid population growth on resistant head and butter lettuce cultivars were conducted in small filed plots at the Yuma Agricultural Center. By artificially infesting plants on several lettuce plantings during the spring, the influence of the resistant lettuce plants were evaluated for their capability of preventing lettuce aphid populations from colonizing plants. Results of five field trials showed that several varieties of head and butter lettuce have been developed that almost completely prevent lettuce aphids from surviving and reproducing on plants during the spring. Although the cultivars tested did not posses marketable characteristic for harvests, they do provide germplasm for breeding new varieties suited for desert production. In addition, these studies also support conclusions drawn from the past several seasons that suggest lettuce aphid population growth is greatest when ambient temperatures average between 65-70 °F.
Knockdown and Residual Efficacy of Biopesticides and Reduced-Risk Insecticides against Western Flower Thrips in Romaine LettuceThree separate field trials over two years were conducted to evaluate the comparative knockdown and residual efficacy of several conventional, Reduced risk and biopesticide compounds against western flower thrips in romaine lettuce. These trials consistently demonstrated that both Lannate-pyrethroid combinations and Success provided significant knockdown and residual control of thrips adults and larvae when compared to the other spray biopesticide treatments. Unfortunately, the biopesticide alternatives at best provided poor to marginal efficacy against western flower thrips. The implication of these results on desert lettuce production and resistance management programs is discussed.
Influence of Planting Date and Insecticidal Control on Seasonal Abundance of Lettuce Aphids on Head LettuceSmall plot studies were conducted from 1999-2001 to examine the population abundance and control of the lettuce aphid on winter and spring head lettuce crops. In each year, Seven, 0.25 acre planting of head lettuce were established beginning in Sep-Oct with final harvest occurring in April. Replicated plots within several planting were treated with an Admire treatment at planting, a side dress application of Platinum post-planting or allowed to remain untreated. Lettuce aphids were first detected in our experimental area in December in PD 3 in 2001, but in 2002 first occurred in lettuce almost 2 months later (Feb 21). Similarly, lettuce aphid abundance was much greater in 2001 than in 2002, probably a result of temperature difference. Temperature had an important influence upon lettuce aphid development based on our field observations. Population appeared to increase in early March when the average daily temperature was about 65 E F. We observed a sharp decline in population abundance in April where daytime highs exceeded 90E F. Insecticide treatments also influenced seasonal abundance. Under heavy aphid pressure in 2001, lettuce treated with Admire in the early planting dates appeared to prevent lettuce aphids from significantly infesting lettuce heads at harvest. However, lettuce aphids in the last 3 planting dates were able to colonize plants and infest a larger proportion of heads at levels not considered commercially acceptable. Under lighter pressure in 2002, lettuce aphids did not significantly colonize Admire treated lettuce. Green peach aphid, potato aphid and foxglove aphids were also present in both years, but seldom reached economic levels, and where completely controlled in plots treated with soil, systemic insecticides.
Field Evaluation of Eretmocerus eremicus Efficacy in the Control of Sweet Potato Whiteflies Infesting MelonsThe effect of three different release rates (1x, 10x, and 20x the recommended rate of 10,000/acre) of Eretmocerus eremicus, a whitefly parasitoid, on sweet potato whitefly populations in cantaloupe were evaluated against populations in untreated control plots. Parasitoids were released from a point source in the center of each of nine treatment plots. All stages of whitefly development were monitored within a 10-m annulus surrounding each release point in all 12 plots, as were rates of parasitism. This occurred over a 52-d period from July 21 through September 11, 2001. The rates of sweet potato whitefly population increase during this time were equivalent and independent of the parasitoid release rate. Whitefly densities were not controlled in any of our treatment plots, nor in the controls. Moreover, rates of parasitism did not increase with time in any of the treatment plots and did not differ among the three release rates (22.0 ± 16.2%). Hence, Eretmocerus eremicus, by itself, is not efficient as a means to control whitefly populations in melon crops in the Southwest US. The ineffectiveness of E. eremicus to control whitefly populations in the field may be due to its propensity to dispersal at low host densities.