NAVEL ORANGEWORM REVIEW

November 2014 Task List

By Bob Beede, U.C. Farm Advisor, Emeritus

As we wrap up another season, processors and most growers are elated over the low navel orangeworm (NOW) damage experienced this year. Discussions with the NOW researchers and crop consultants suggest there are several factors that worked in our favor besides us just getting lucky. Dr. Joel Siegel and crop advisers have trap data suggesting that the overwintering NOW population was markedly less this season than 2013 and 2012. The new adult lure is also reported to have greatly improved the ability to identify the beginning of new generations. However, we still lack the ability to correlate trap catches with potential damage. NOW flight activity also appears to be correlating with the degree-day system; Dr. Siegel has suggested using January 1 as an arbitrary beginning date, rather than initiating heat unit accumulation after establishment of a true biofix (consistent moth catches from the overwintering generation in late March to early April). Several individuals suggested there was better awareness of possible spray timings through the efforts of Nichols Farms, who distributed a regular degree-day update covering most of the pistachio growing regions. Crop consultants I spoke to said this prepared growers for considering recommendations for treatment and illustrated the importance of prompt response, since they saw how rapidly heat units were accumulating. Great job, James!

There is also data to show that sprays timed by the Siegel degree-day method significantly impacted the NOW population. Use of the longer-residual chemistry, such as Altacor and Intrepid Edge, was also suggested as a factor, since crop value and quality incentives easily justified the additional expense. One field treated at 700 degree-days during the overwintering flight suggested additional testing of early population suppression may be warranted. Some academics reading these comments may understandably criticize me for offering what they consider to be anecdotal experiences, but these results represent very large fields in which the NOW population has been progressively reduced with longer residual materials applied at the onset of new flight activity. These flights have also been predicted by degree-day accumulation beginning January 1. Conventional replicated research has been called for, but the question no one has yet to answer is how large a replication is necessary, given the capacity of NOW to migrate up to five miles. Perhaps the population dynamic approach is equally effective in developing management guidelines. NOW research continues to be a very challenging arena!

Continued improvements in winter sanitation, dedication to better spray coverage, and early adoption of mating disruption may have also contributed to less NOW damage. Field reports indicate almonds had a more difficult time with NOW. Some large almond operations reported 10 to 15 percent damage on their Nonpareil variety.

One cannot overlook the effect of early crop maturity and harvest on eliminating its exposure to the fourth generation. The significance of this should be revealed by the insect damage in the second and third shakes.

Crop Quantity and Quality: As of September 20, 85 to 90 percent of the crop was estimated to be delivered. The industry is presently suggesting a total of about 475 million pounds, 5 to 10 percent off of spring expectations. Most growers report good yields, but there is a significant number whose crop was severely affected by insufficient winter chilling. These growers report a dismal 400 to 500 pounds, with blank nut percentages as high as 80 percent! Hopefully they will recover their losses in 2015. Monitoring winter temperatures will be critical in these orchards so that chilling can be accurately assessed. Although some growers had higher than normal closed shell, Nichols Farms reports their growers averaged 17 percent. I believe the higher-than-normal closed shell can be attributed to the extended leaf out and bloom. The late set nuts just did not have enough time to gain sufficient kernel size to split the shell open. The effect of time of fruit set on splitting needs to be studied.

With all the spraying for NOW, growers must have added fungicides for Botryosphaeria and Alternaria, because I received very few calls about these two diseases this year. The newly released fungicides for Alternaria must be doing their job. However, the routine use of pyrethroids for insect control has resulted in the predicted increase of Gills pistachio mealy bug. There were numerous calls during August inquiring about late treatment options when populations became very visible. Now is a good time to survey orchards for Gills mealy bug and Botryosphaeria (BOT). If you find much BOT, it would be very wise to get a crew in before leaf drop and cut the strikes out of the trees. These infected branches are the source of overwintering inoculum, and they spread the disease next spring during the rains. Infected wood also continues to produce spores for SIX YEARS, so if you do not stay up with removal in problem orchards, a wet spring will eventually catch up with you, and BOT will be rampant. OK, you were told!

What’s Next? It is time to think about pre emergent winter weed management. In order to properly address your weed problem, you first have to identify the weeds! Many of the new materials are very effective, but they are expensive because they control noxious weeds such as flaxleaf fleabane and marestail (horse weed), which have developed resistance to the older, less expensive preemergent herbicides. Kurt Hembree, Vegetation Management Farm Advisor, Fresno County, has current weed susceptibility and herbicide registration information at: http://ucanr.edu/sites/Weed_Management/files/74887.pdf. Kurt has suggested rates of application for each product, along with suggested adjuvants. This is an excellent resource to help in effective material selection. Kurt also has a great article on his website about the need for changing from XL nozzles to Turbojets for improved coverage and weed control. If you have not already converted over, read why you should, and then do it!

Keeping current on herbicide registrations and label changes is like herding cats, so I welcome representatives calling or emailing me changes in their products. I can still be reached at bbeede@ucdavis.edu.

Prowl H2O grass herbicide is similar to Surflan AS (Oryzalin) in its weed spectrum and residual. Prowl remains stable on the soil without rainfall for 21 days. Apply it at the higher label rates (4-6 quarts per sprayed acre) for extended weed control. Surflan also controls annual grasses and a select number of broadleafs such as chickweed, lambquarters, purslane and the pigweeds. It is also stable on the soil prior to a rain. One gallon per treated acre of these two products in the fall usually runs out before the end of the season, especially under drip irrigation. Hence, many growers elect to treat early season “winter weeds” with a low rate of glyphosate (such as Roundup, Touchdown) and Goal (each at about one quart per sprayed acre) and then wait to apply the Surflan or Prowl later in January or February to achieve season-long grass control. Cost and residual are important factors to consider in herbicide selection. Read the label, and discuss your program with a qualified crop consultant for best results.

Chateau is a preemergent herbicide (Valent) available for bearing and non-bearing pistachios that are at least one year old. Applied at 12 ounces per treated acre, Chateau enhances burndown of existing weeds (similar to Goal) and controls difficult weeds such as fleabane and horseweed (marestail). Because of its postemergent characteristics, be careful using it in young trees. Avoid injury with tree wraps and use a shielded sprayer to reduce drift. Apply Chateau only during the dormant period to avoid phytotoxicity to emerging bud tissue in the early spring. Kurt Hembree, UC Farm Advisor, Fresno County, for weeds, also advises split applications in November and January for heavy fleabane control, since this noxious weed germinates early in the fall. A single application in January may result in “escapes” which make one think the product is ineffective. The addition of Gramoxone helps in controlling emerged fleabane and marestail. NOTE: Before using Chateau, check with your Valent representative for any use restrictions applicable to your area or soil type.

Matrix SG preemergent herbicide is active on fleabane, malva, yellow nutsedge, and marestail. Due to its contact activity on selected grasses and several broadleaves (when newly emerged, not a foot tall!), it appears to have a good fit for fall applications where management of the mentioned noxious weeds is required. Matrix works best when combined with a good grass preemergent herbicide such as Surflan or Prowl. It is now a soluble granule formulation applied at no more than 4 ounces of product per broadcast acre per season. The SG formulation is a significant improvement over the old dry flowable, since this product now creates a true solution and the spray tanks no longer require washing with a three percent ammonium solution to insure they are completely rinsed. A second application or use of another preemergence product would be needed in the spring for extended weed control. Trees must be established for one full year before treatment. The spray solution must be no more acidic than a pH of 4.0, and less basic than pH=8.0 to avoid product degradation.

Trellis DF has the active ingredient, isoxaben. Its mode of action (cellulose biosynthesis inhibitor) makes it a good rotation material for other preemergent herbicides with similar control spectrums. Trellis is primarily a broadleaf herbicide, and it is effective on marestail, fleabane, malva, clover, morning glory, and willowherb. Its weed control spectrum is greatly enhanced with the addition of two quarts of Prowl or Surflan. Trellis does not have contact activity, but it is compatible with any postemergent material. Trellis can be applied to newly planted trees, PROVIDING the soil is firmed up and not cracked around the tree at the time of application. It is in the “caution” category, and is registered for both non-bearing and bearing pistachios.

Pindar GT is another relatively new Dow herbicide for pistachios and other nut crops. It has both pre- and postemergent activity. See the label for an impressive list of seedling weeds controlled postemergent. Be sure to add a crop oil, methylated seed oil or non-ionic surfactant for best postemergent results. Pistachios must be established nine months prior to use. Due to its contact activity, application during full dormancy is advised. Use the higher label rates for extended control of fleabane, malva, and marestail. Both Trellis and Pindar require about a half-inch of rainfall for optimum performance within 21 days of application.

Alion SC, by Bayer CropScience, is a cellulose inhibitor with broad spectrum, including fleabane and marestail (horseweed). Application is recommended between November and January before seed germination. Rain incorporation of one-quarter inch or greater should occur within 21 days after application. Consult the most current label for recommended application rates. Residual data shows control for five months. Kurt Hembree says combining Matrix with Alion, along with a burndown material of your choice, provides outstanding weed control.

Growers electing to dispense with a preemergent herbicide this winter and apply multiple postemergent treatments throughout the season have a good selection of herbicides available, including Roundup, Touchdown, Gramoxone, Shark, Fusilade, Treevix, Goal, and 2,4-D. Postemergent application frequency, product selection and cost will vary greatly depending upon weed species and pressure. It is critical to know your weed species and the control spectrum of your selected postemergent to insure satisfactory control. For example, Treevix, Shark, and Venue are primarily broadleaf materials. Hence, they require the addition of glyphosate or gramoxone to get the grasses. Glyphosate is moderately effective on purple nutsedge with repeated applications prior to the six-leaf growth stage. Nutsedge has become a major problem in new orchards, particularly with in-line drip, whose emitters wet an area well beyond the young tree root zone.

Those electing not to apply a preemergent herbicide should tune up their application equipment to insure optimal coverage. Low rates of Goal in combination with glyphosate have been documented as more effective in burning down existing weeds than if used alone. Use of a high-quality adjuvant is also essential to achieving maximum performance. The addition of ammonium sulfate at about 10 pounds per 100 gallons of spray solution also improves the efficacy of all the postemergent products.

What’s better? Repeated postemergent applications or a good preemergent program? I would strongly advise you to use the preemergent program. Weeds have a way of getting away from you and wet weather makes this even more likely. Cost comparisons between pre- and postemergent programs often show that the expense of repeated contact application equals or exceeds the one-time cost of the preemergent treatment. This is especially true if you have noxious weeds like fleabane which are best controlled with the newer preemergent materials. Also, experience has shown glyphosate-based materials to be risky on first- year pistachio trees, even with tree wraps. Most PCAs avoid this recommendation, so do not plan to make it your first postemergent material of choice for the first season.

NOTE: Herbicide application equipment should NEVER be used for treating tree foliage! You are begging for big trouble if you do. This is especially true with Chateau, so please be wise and avoid injury to your trees. Incidentally, herbicides formulated as wettable powders are best added to the spray tank FIRST to enhance compatibility. Flowables, dissolvable granules, and other non-liquid materials are then added second. Liquids, the least problematic, are then added last.

Manufacturer labels providing essential information about the proper use and application rate for all pesticides can be accessed at http://www.agrian.com. or http://www.cdms.net.

New Variety News: There appears to be much confusion over the royalty requirement for Golden Hills, Lost Hills, and Randy, the male pollinator. All three were developed by academic members of the University of California; hence there is a $1.00 per tree fee that must be paid to UC at the time of successful budding. In addition to the per tree fee, there is also a one-time, $500 licensing fee that must be paid at the time of planting.

For further information and fee payment, go to my website http://cekings.ucanr.edu/Agriculture/Grapes_Tree_Fruits_Nut_Crops/Crop_I....

First-Year Tree Concerns: As I drive around the valley, I am alarmed by the number of first-year tree plantings that are being pushed MUCH later than “us old wise men” would recommend. I completely understand that the budding crews are running late; late-planted clonal rootstock requires more time to reach acceptable budding caliper, and the newer varieties have a larger bud shield, thus one must wait longer to obtain the needed tree size. HOWEVER, those of us who have been around the block a few more times than many of the newer members recall several years in which the succulent trunk shoot pushed into late October gets FRIED almost to the bud union, and sometimes into the rootstock, should a sudden freeze occur in early November. I fully realize how tempting it is to push the late bud and go for the required 44 inches of Kerman or Golden Hills main trunk growth. Achieving this the first year allows one to tip the shoot to 42 inches while it is dormant, which increases the number of lateral buds for primary scaffold development. Waiting to push the bud this coming spring requires that it be headed to the desired height in-season, and this typically results in less lateral bud push for primary branches. By the way, there is NO way you could hit these really tender shoots with zinc, in my opinion. The normal 10 gallon rate of zinc 12 percent liquid would very likely burn the tips and side tissue, and possibly cause them to break later at the burn location.

Weather Station Installation: Now is the time to get your temperature recorders in place so that you can monitor chill portions and cold events! I cannot tell you how important I think this is, especially if (God forbid!) we have another erratic, warm winter! Weather data is also very valuable during bud push and bloom, so every ranch should have one!

Author: 

Bob Beede, U.C. Farm Advisor, Emeritus