Progress 09/01/12 to 08/31/15
Outputs
Target Audience:California carrots growers in particular, California growers of annual vegetable crops in general Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?A former graduate student (Hannes Wiite) was involved in the field work of this project. it provided general training in setting up and design of nematology field experiments. How have the results been disseminated to communities of interest?Results have disseminated in several presentations on cultural (non-chemical) management options for plant-parasitic nematodes in vegetable crops. Presentations were made at grower and other type meetings. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Trials were done on two field sites infested with root-knot nematodes (RKN). Sites were the Kearney Agriculture Research and Extension Center (KARE), Parlier, CA, (Hanford fine sandy loam) infested with the root-knot nematode M. javanica, and the South Coast Research and Extension Center, (SREC) Irvine, CA, (San Emigdio sandy loam) infested with M. incognita race 3. The experiments had a Split-Plot design with 5 replicates. Plot sizes were 20-ft-long sections of 30-inch-wide beds, along the bed separated by a 3-ft-long fallow section of bed, between beds by a fallow bed. There were eight main treatments: A non-treated dry fallow control, a Vapam™ (metam-sodium) nematicide treatment, and six cover-crop treatments. There were four cover crops: sorghum-sudangrass 'SX-17' (RKN resistant), and 'Trudan 8' (susceptible) and cowpea 'UCR CC-36' (resistant) and Cafe Afrique (susceptible). Cover-crop treatments were sorghum-sudangrass 'SX-17' mowed and incorporated, sorghum-sudangrass 'SX-17' green biomass removed, sudangrass 'Trudan 8' mowed and incorporated, sudangrass 'Trudan 8' green biomass removed, cowpea 'UCR CC-36' mowed and incorporated, cowpea 'UCR CC-36' green biomass removed. The main treatments were assigned to the plots according to a randomized block design Cover crops were hand-seeded (sudan and sorghum-sudan @ 30 lbs/acre, cowpea at 50 lbs/acre) over the center of the beds in late-April/early May. Crops were initially watered with overhead irrigation to germinte the cover crops, and then watered through drip irrigation. In late June cover crops were mowed, and removed from the field or flail-mowed and incorporated into the top 8 inches. At the time of cover crop harvest, Vapam™ nematicide was be applied as a drench on the appropriate beds at 75 gallon/acre according to the label. There was 6 week waiting period between cover crop incorporation and carrot seeding (to avoid phytotoxic of the sudangrass and sorghum-sudangrass incorporated green biomass). The sub-treatment was plus / minus nematicide seed coating of the carrot seed. Coating of the carrot seed (16g abamectin/1,000,000 seeds) was done by Syngenta. Each 20-ft-long plot was divided into two 10-ft-long sections and one of the two sub-treatments was randomly assigned to each 10-ft-long section. Carrot 'PrimeCut 59' was seeded with a pushed hand seeder as a single row in the center of each bed (0.5 g per 10 ft). Fertilizer application and insect control were be according to standard practices. Carrots were harvested in early December. Nematode soil population levels were determined at start of the trial before cover crop planting, after the cover crops (=before carrot planting), and at carrot harvest. Nematodes were extracted from 100g sub-samples using a modified Baermann funnel method and the number of second-stage RKN were counted at 40x magnification. At carrot harvest, a 1m section of carrots from the inner part of each plot was removed, weighed, and counted. Individual carrots were examined for root-galling (indexed on a scale from 0 to 10, with 0 = no galling/forking, 10 = entire root system severely galled) and for forking. The carrot yield (kg) was also determined. The significance of the effects of the main treatments, and sub-treatments on soil nematode population levels, on carrot vigor, yield (nr. carrots, lbs. carrot) and quality (carrot root-galling, percentage marketable carrot) were analyzed with SAS statistical software. Results. Nematode levels: There were no indications that the cover crops significantly affected root-knot nematode populations at either location and in any year of the study. Initial root-knot nematode levels at start of the trial depended on the trial site and the year of the trial. For example in 2014 nematode levels at KARE were low (1 J2 per 100 g soil), but much higher in 2015 at this site (about 100 J2 per 100 g). In general the resistant Sudan grass 'SX-17' and the resistant Cowpea 'CC-36' resulted in numerically slightly lower nematode counts compared to the susceptible Sudangrass 'Trudan8' and the susceptible Cowpea 'Cafe Afrique', but these differences were not significant at the 95% confidence level. In addition, nematode levels after growing a resistant or susceptible cover crop were not significantly different from the untreated control (fallow). Although the nematicide treatment (VAPAM) at both sites and in most years resulted in the lowest nematode levels, the nematicide treatment effects were not significant at the 95% confidence levels. Similarly, when comparing removal of cover crop residue after mowing with incorporating cover crop residue into the soil, no consistent and significant effects on nematode population development was detected. In previous studies, coating carrot seed with abamectin resulted in significant reductions in the level of nematode-associated damage (galling and forking) of the carrots at harvest, thereby also resulting in an increase in the percentage of marketable carrots. In this study, we were unable to repeat this result. In some years at one of the two sites the abamectin seed-coated carrots resulted in slightly higher (!) levels of forking and galling (i.e. fewer marketable carrots) compared to the no-abamectin seeded carrots, whereas in other years the situation was reversed. However, the effect of abamectin seed coating on the level of galling and forking of the carrots was overall minor and not consistent between the study sites and the years. In each year of the study, there was obvious galling on the carrot roots, but never extreme. For example, on a 0-10 scale, galling was generally not much higher than 4, even in the most affected carrot plots. When examining the number of carrots, the total carrot weight harvested per linear meter of bed, or the average weight per carrots, there were some minor differences between the years and between the field sites, but any differences observed were not consistent over the entire trial period or between the two trial locations.
Publications
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Progress 09/01/12 to 08/31/13
Outputs
Target Audience: Vegetable growers, carrot growers in particular, in mediterranean-type climates. Changes/Problems: We will locate the trial the coming year (2015) at field station in Shafter, instead of KARE. Root-knot nematode levels at the Shafter station are very high (we have had probelms maintaining high levels at KARE) and there are much fewer weed problms. In addition, the Shafter station has very similar climate as the KARE station (both in San joaquin valley, approx 50 miles apart). What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest? As this was out first year compl;ete field trial, and as so far there have not been any significant effects of the treatments, we have not yet disseminated the results. What do you plan to do during the next reporting period to accomplish the goals? We will repeat the trial at the SCREC site in irvine. In addition we'll move the site from the KARE station to a field station in Shafter. very high root-knot nematode levels have been identified at this site by us, and it is in the general vicinity of the KARE site with similar climate conditions.
Impacts
What was accomplished under these goals?
The root-knot nematode susceptible cowpea var. Cafe and nematode resistant var. CC36, and nematode susceptible sorghum-sudan var. Trudan8 and nematode resistant var. SX-17 were seeded in spring in nematode infested field trials at the UC Kearney Agricultural Research and Extension Center (KARE) in Parlier, and at the UC SouthCoast Reseach and Extension Center (SCREC) in Irvine. Control plots remained fallow. Prior to seeding root-knot nematode soil infestation levels were determined. Low (Parlier) and medium high (Irvine) nematode levels occurred at seeding time. The crops grew well at both sites, and were mowed and removed or mowed, chipped and tilled back into the plots. At this time, half of the fallow plots were treated with the nematicide metam-sodium. The plots were split into 2-subplots and five weeks later, nematode susceptible carrots var. Imperator were seeded in each of the sub-plots. Half of the sub-plots were seeded with carrot that had receieved a seed-treatment containing abamectin (a nematicide), the other sub-plots were seeded with carrots that had no abamectin in the seed treatment. At carrot seeding, nematode soil levels were again determined. At carrot harvest, yields and carrot quality (nematode symptoms e.g. forking, galling) was determined from a 1m section of all carrot plots. At SCREC, nematode levels at harvest were medium high (ca. 40 meloidogyne J2 per 100 cc soil), but not different between the cover crop treatments or the carrot seed treatments. Forking of carrots was a common symptom, but the number of carrots with obvious gall formation was relatively low. Athough numerically, the metam-sodium treated plots had fewer forked carrots and lower galling, the treatment was not significantly (P=0.05) different from the others. At KARE trial site, there was a very high weed pressure (nutsedge) that caused some problems early on after carrot emergence. Post-emergence herbicides did control the weeds, but also cased obvious stunting of the carrots. At harvest time, carrot stand was very poor with many plants remaining very small, and with stubbed carrots. These symptoms occurred throughout the plots and were not related to any of the treatments and also were non-characteristic of nematode symptoms. Because of this, it was decided not to collect carrot harvest data from the KARE plots, as it would not yield any useful data.
Publications
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