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Vegetable IPM Updates Archive

Insect Management

Jul 11, 2018

Management Guidelines for Whiteflies and CYSDV on Fall Melons 2018

Fall melon planting is getting close and local fields are being prepared for planting. Growers and PCAs are well aware of cucurbit yellow stunting disorder virus (CYSDV) and the impact it can have on fall melons. This whitefly transmitted crinivirus was first identified on desert melons in the fall 2006 where widespread infections on cantaloupes, honeydews and other melons occurred. CYSDV can cause significant losses in melon fruit yield and quality, and without question, desert melon crops have been seriously affected by this virus. Melon IPM has also been impacted by CYSDV where insecticide usage on fall melons has increased significantly. We have been studying the epidemiology of CYSDV for over 10 years in an attempt to understand the complex relationships between the virus, vector and our local cropping system. Our ultimate goal is to develop practical approaches for reducing CYSDV impact on fall melon production. In addition, we continue to develop new information on chemical control of the whitefly vector (Bemisia whitefly adults). Last fall, whitefly populations were lighter than normal, and CYSDV incidence on fall melons was the lowest we’ve recorded on melons since the virus as first reported 11 years ago. Thus far, whitefly numbers this spring and summer have been relatively light compared to previous years. Although, the incidence of CYSDV was generally light on spring melons., it was still present in many fields. How these low numbers translate into virus incidence on the fall melon crop is unknown? Regardless, experience suggests that growers should anticipate CYSDV to be present. Further, given the aggressive management programs that PCAs and growers are now using, it will be interesting to see how CYSDV impacts melon production this fall. We’ll be tracking both whiteflies and CYSDV incidence again in 2017. Our research to date suggests that fall melons produced near cotton or near areas where spring melons were recently produced are at the highest risk of infection. When possible, growers should attempt to isolate fall melon plantings as far away as possible from these sources of whiteflies and CYSDV. Growers forced to plant fall melons near these crops should be vigilant in minimizing adult whitefly infestation levels with insecticides during pre-bloom growth stages. To view a summary of the status of CYSDV in Yuma County and guidelines for management visit 2018 Guidelines for Whitefly and CYSDV Management on Fall Melons.

To contact John Palumbo go to: jpalumbo@ag.Arizona.edu

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Soil Science

Aug 23, 2023

Colorado River Water & Arizona Agriculture
On Tuesday, 15 August 2023 officials from the U.S. Bureau of Reclamation (USBR) presented their 24-Month study reports with projections and operational plans for 2024 (USBR, 15 August 2023).  We are still dealing with the drought but there is some improvement in the 2024 plans for Colorado River water allocations for Arizona.

The wet winter and spring experienced in the Southwest in 2023 has provided some relief on the dire situation we were facing on the Colorado River system and reservoir levels have improved.  But unfortunately, one good precipitation season does not solve all the problems and they will still need to be dealt with.

The current plan for lower Colorado River water management is basically a return to the Drought Contingency Plan (DCP) Tier 1 schedule (Figure 1).

Fgure 1.  Drought Contingency Plan Tier reductions for Arizona.

Tier 1 plans take us back to an 18% reduction or 512,000 acre-feet (KAF) of Arizona’s Colorado River allocation of 2.8 million acre-feet (MAF).  Arizona was operating under Tier 1 guidelines in 2022.

The irrigation districts in central Arizona that have lost access to Central Arizona Project (CAP) water will not be receiving any additional water in 2024 based on this plan.  The districts immediately adjacent to the mainstem of the Colorado River will continue to receive the same amount of water as they have been receiving the past two years.  For Arizona and the other lower basin states, these are basically the same water allocation guidelines that were in place in 2022.

The urban areas and American Indian tribes will not experience any additional reductions based on the USBR plans. However, some cities and tribes have volunteered to reduce their Colorado River water allocations in exchange for payments from the federal government.

For example, in 2023 Arizona, California, and Nevada agreed to a plan that will conserve an additional 3 MAF of Colorado River water through 2026 in exchange for $1.2 billion from the federal government.  If approved by the USBR, this plan would reduce Colorado River allocations to the Imperial Irrigation District in California, which has some of the most senior water rights on the river.

The Gila River Indian Community (GRIC), which has a Colorado River allocation of 653 KAF, committed in April 2023 to relinquish temporarily 125 KAF in exchange for $400 per AF from the federal government.  The federal government is also funding GRIC infrastructure projects to increase wastewater reuse in irrigation.

Thus, some of the Colorado River water that is technically allocated to Arizona under Tier 1 guidelines will stay in Lake Mead due to previously agreed upon conservation measures.

Regarding other lower basin states and the current USBR plan, Nevada will have slightly more Colorado River water in 2024 than in 2023.  Mexico will deal with a 5% reduction in Colorado River water from their base and once again California will not be suffering any required cuts in their Colorado River water allocation.

Overall, this is good news.  We have some temporary relief on the Colorado River system and no additional reductions will be required in 2024.  This puts the seven Colorado River basin states and Mexico in a better position to negotiate the guidelines and agreements required for 2026 since all the existing agreements expire in two years.

Reference

USBR, 15 August 2023. 24-Month Study reports.
August 2023 Lake Powell and Lake Mead: End of Month Elevation Charts
To contact Jeff Silvertooth go to: silver@ag.arizona.edu

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Plant Pathology

Oct 2, 2024

2024 Downy Mildew of Spinach Fungicide Trial

This study was conducted at the Yuma Valley Agricultural Center. The soil was a silty clay loam (7-56-37 sand-silt-clay, pH 7.2, O.M. 0.7%). Spinach ‘Revere’ was seeded, then sprinkler-irrigated to germinate seed Jan 18, 2024 on beds with 84 in. between bed centers and containing 30 lines of seed per bed. All irrigation water was supplied by sprinkler irrigation. Treatments were replicated four times in a randomized complete block design. Replicate plots consisted of 15 ft lengths of bed separated by 3 ft lengths of nontreated bed. Treatments were applied with a CO₂backpack sprayer that delivered 50 gal/acre at 40 psi to flat-fan nozzles.

Month	Max	Min	Average	Rainfall
January	68	42	54	1.14 in
February	73	47	59	0.50 in
March	77	50	63	0.31 in

Downy mildew (caused by Peronospora farinosa f. sp. spinaciae) was first observed in plots on Feb 19 and final reading was taken on February 26, 2024. Spray date for each treatments are listed in excel file with the results. Disease severity was recorded by determining the percentage of infected leaves present within three 1-ft² areas within each of the four replicate plots per treatment. The number of spinach leaves in a 1-ft² area of bed was approximately 144.

The data (found in the accompanying Excel file) illustrate the degree of disease reduction obtained by applications of the various tested fungicides. Products that provided effective control against the disease include Orondis ultra, Thrive 4 M, Fungout, Cevya, Eject and Zampro. No phytotoxicity was observed in any of the treatments in this trial.

VIPM_10-3-2024_01

To contact Bindu Poudel go to: bpoudel@email.arizona.edu

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Mechanization

Aug 23, 2023

Pre-Season Vegetable IPM Workshop

Mark C. Siemens, Department of Biosystems Engineering
Vol. 14, Issue 16, Published 8/9/2023
Pre-Season Vegetable IPM Workshop
Mark C. Siemens
Vol. 14, Issue 17, Published 8/23/2023

The Pre-Season Vegetable IPM Workshop will be taking place TOMORROW, Wednesday, August 23^rd at the Yuma Agricultural Center. Come learn about the latest IPM products, practices and trial results from university and industry experts. Registration begins at 7:30 am and the program starts at 8:00 am. Agenda below. Looking forward to seeing everyone there!

To contact Mark C. Siemens go to: siemens@cals.arizona.edu

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Weed Sciences

Aug 23, 2023

Broccoli Herbicides

In the absence of Dacthal (DCPA) growers are looking for different herbicide options for Broccoli and Onions.
The following is data from a broccoli trial done in 2010 by Tickes/Pena, which compares Prowl, Goal Tender, Prefar, Treflan, Devrinol and Dacthal at different application timings. Plots were visually evaluated for weed control of Goosefoot (Chenopodium murale), Malva (Malva parviflora), and Yellow Sweet Clover (Melilotus oficinalis). The label recommendations for Devrinol are “Use the lower rate on light soil (coarse textured-sandy), and the higher rate on heavy soil (fine textured-clay)”. The rate goes from 1-2 lbs on the DF-XT 50% formulation.
We hope this information is useful in our decision making for broccoli herbicide programs.

To contact Marco Pena go to: marcop@ag.arizona.edu

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Specialty Crops

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Areawide Insect Trapping Network

Oct 20, 2021

Area wide Insect Trapping Network (October 20, 2021)

Area wide Insect Trapping Network   VegIPM Update, Vol. 12, No. 21, Oct 20, 2021.

Results of pheromone and sticky trap catches can be viewed here.

Corn earworm:
CEW moth counts declined considerably over the past 2 weeks across all locations and below average for this time of the season.

Beet armyworm:
Trap counts increased slightly in many locations, but well below average for mid-October. Most activity in Dome and Yuma Valleys.

Cabbage looper:
Cabbage looper trap counts remain steady in most areas. Activity average to below normal compared to previous years.

Whitefly:
Adult movement increased sharply in the Dome Valley, Wellton Gila Valleys and Bard two weeks ago, but down in all locations last week.

Thrips:
Thrips adult movement variable across locations; up in Wellton and Tacna, but remains below average for mid-October.

Aphids:
Aphid movement Increased sharply in Bard and Yuma and Gila Valleys consistent with N and E winds over the past 2 weeks.

Leafminers:
Adult activity increased sharply in the Gila Valley 2 weeks ago, but remains low in most location; below average for this time of season.

Diamondback moth:
Significant increase in moth activity in the last 2 weeks, particularly in Dome Valley, Gila Valley and S. Yuma Valley. Traps located adjacent to cauliflower and broccoli transplants had significantly higher counts.  Areawide counts are trending upward.

To contact John Palumbo go to: jpalumbo@ag.arizona.edu

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