- Author: Larry J Bettiga
Mark your calendar and register online for the upcoming UCCE Vineyard Pest and Disease Management Seminar to be held on Nov. 4, 2016 in San Luis Obispo. This meeting has been approved for 4.5 hours of DPR Continuing Education credits and CCA credits have been applied for.
Date: Nov. 4, 2016
Time: 9:00 - 15:00
Location: Veterans Memorial Building, 801 Grand Avenue, San Luis Obispo
Cost: $100 per person (includes refreshments and lunch)
8:30 - 9:00 Check in and refreshments
9:00 - 9:10 Introduction and overview of pest and disease issues
Mark Battany, UCCE San Luis Obispo
9:10 - 9:30 Development of disease resistant rootstocks
Andy Walker, UC Davis Viticulture and Enology
9:30 - 9:50 Impact of Red Blotch Disease on grape and wine composition
Anita Oberholster, UC Davis Viticulture and Enology
9:50 - 10:10 Update on Red Blotch Vectors
Cindy Preto, UC Davis Entomology and Nematology
10:10 - 10:30 Developing grapevine leafroll management strategies
Monica Cooper, UCCE Napa
10:30 - 10:40 Break
10:40 - 11:00 Pierce's Disease biology and management in California vineyards
Matt Daugherty, UC Riverside Entomology
11:00 - 11:20 Managing weeds to avoid resistance issues
Paul Verdegaal, UCCE San Joaquin
11:20 - 11:40 Bud necrosis and fertility
George Zhuang, UCCE Fresno
11:40 - 12:00 Sprayer calibration
Lynn Wunderlich, UCCE Central Sierra
12:00 - 13:10 Lunch
13:10 - 13:30 Powdery mildew overview
Lindsay Jordan, UCCE Madera
13:30 - 13:50Sulfur for powdery mildew control
Larry Bettiga, UCCE Monterey
13:50 - 14:10 Powdery mildew and botrytis research update
Allison Ferry-Abee, UCCE Tulare
14:10 - 14:30 The integration of phenology screening into pest resistant rootstock breeding programs
Jean Dodson, Cal Poly Wine and Viticulture
14:30 - 15:00 Improving insecticide controls for mealybugs - following the movement of insecticides in the vine
Kent Daane, UCCE Kearney Ag Research Center
Cabbage maggot (Delia radicum) (Fig. 1) is a serious and destructive pest of brassicas in the Salinas Valley of California. Brassica crops damaged by cabbage maggot are broccoli, cauliflower, cabbage, and Brussels sprouts. Cabbage maggot flies lay eggs in the soil around the base of a plant. Legless, white maggots feed on the taproot and affect plant development. After feeding for about 3 weeks, the maggot pupates in the surrounding soil for 2-4 weeks before emerging into an adult fly. The symptoms of cabbage maggot feeding in the root are yellowing, stunting, and slow growth.
Research showed that infestation by cabbage maggots in direct-seeded broccoli could be severe throughout the growing period, except the first 30 days after seed was planted. Typically, insecticide targeting cabbage maggot is applied immediately after planting seeds and before sprinkler is turned on. Efficacy studies with at-planting application of insecticide did not provide adequate cabbage maggot control. This suggested that insecticide applied at planting might be early relative to cabbage maggot incidence and thus, delaying application might be more effective.
In 2014 and 2015, replicated experiments were done in a commercial planting of baby turnip. The treatments were one chlorpyrifos application at planting and 2 weeks after planting seeds. A tractor-mounted sprayer was used to apply insecticide. Samples were collected and were transported to UCCE entomology laboratory where roots were evaluated for damage by cabbage maggot.
Results suggested that delayed application of effective insecticide suppresses cabbage maggot (Fig. 2). In a previous study, Joseph and Martinez (2014) showed cabbage maggot flies did not lay many eggs at the base of brassica plants until 3 weeks after plant emergence (Fig. 3), despite adult cabbage maggots in the field during early stages of plant development. Also, cabbage maggot infestation tend to be continuous after 3 week stage depending on local pest pressure and crop disturbances (e.g., harvest) in the surrounding fields (Joseph and Martinez 2014).
Delaying insecticide application would increase the likelihood of intercepting cabbage maggot larvae seeking roots. In the Salinas Valley of California, use of organophosphate insecticides including chlorpyrifos is regulated. This stringent regulation is forcing growers to seek alternate insecticides for cabbage maggot control. Previous study showed that clothianidin, thiamethoxam, and spinetoram as well as pyrethroid insecticides such as zeta-cypermethrin, fenpropathrin, bifenthrin, lambda-cyhalothrin, and pyrethrins were effective against cabbage maggot larvae, and efficacy was comparable to chlorpyrifos (Joseph and Zarate 2015). However, alternate insecticides are likely to be less persistent because they break down quickly (e.g., spinetoram) or become immobile in soil under field conditions because they bind to organic matter in contact (e.g., pyrethroid insecticides). Thus, as fewer effective older chemistries (e.g., organophosphate insecticides) are used against cabbage maggot because of use restrictions, delayed application of insecticide might be more critical.
For more details on this study, please read the published paper. http://cemonterey.ucanr.edu/files/248875.pdf
Joseph, S. V. 2014. Efficacy of at-planting and basal applications of insecticides on cabbage maggot in seeded-broccoli. Monterey County Crop Report. January/February 2010-2013. http://cemonterey.ucanr.edu/newsletters/i__b_ Monterey_County_Crop_Notes__b___i_50471.pdf
Joseph, S. V.,and J. Martinez. 2014. Incidence of cabbage maggot (Diptera: Anthomyiidae) infestation and plant damage in seeded brassica fields in California's Central Coast. Crop Prot. 62: 72-78.
Joseph, S. V., and J. Zarate. 2015. Comparing efficacy of insecticides against cabbage maggot (Diptera: Anthomyiidae) in the laboratory. Crop Prot. 77: 148-156.
A series of laboratory and field studies were conducted to determine if the insecticides coated lettuce seeds are an option to control key lettuce pests in the Salinas Valley: springtail (Protaphorura fimata; Fig. 1A), leafminers (Liriomyza spp.; Fig. 1B) and western flower thrips (Frankliniella occidentalis; Fig. 1C). In addition, a laboratory test was conducted to determine if “primed” lettuce seeds reduced springtail feeding damage.
Springtails. Springtail (P.fimata) is soil dwelling primitive arthropod primarily attacks germinating lettuce seeds, reducing the plant vigor or death, which cause patchy or area-wide stand loss. Most springtails possess a forked organ (furcula) in the rear-end, which is extended forward and backward to jump; hence, the common name, springtail. However, the springtail species, sampled from lettuce fields causing the stand loss, does not have furcula. This means it cannot jump.
The head lettuce seed ‘Regency' was coated with clothianidin, thiamethoxam, and spinosad (Table 1). The seeds were coated by Dr. Alan Taylor at Cornell University and coating technique mirrored commercial seed coating procedure. Laboratory studies were conducted in containers with springtail (P. fimata) infested soil. The data show that all three insecticides spinosad, clothianidin and thiamethoxam treated seeds significantly reduced the incidence of springtail feeding injury when compared with untreated seeds. Among insecticides, superior performance in efficacy was noted in the following order: clothianidin > thiamethoxam > spinosad (Fig. 2). Two field trials were conducted against springtails using the same seed treatments, however, the springtail pressure was so low that conclusive data were not obtained. Clothianidin (NipSit) in particular, is now registered on head lettuce and could be used for springtail control. This is an important information in that springtails attack the germinating seeds of lettuce especially in the spring time. During spring, we get some rain showers and the wet conditions in the field after planting makes insecticide application along seed line almost impossible. If the insecticide coated seeds are planted, the grower or PCA could avoid at-plant insecticide application which is typically targeted toward springtails. Application of insecticides such as neonicotinoids and pyrethroids along the seed line will protect the germinating seeds from springtail feeding. More field studies will be conducted in the following years to validate these results in the field.
Studies were also conducted to determine if there are any varietal effects exists (Table 2). The much needed attribute for springtail control is faster seed germination so that the springtail would not get sufficient time to feed and cause seed mortality. “Primed” lettuce seeds are used for uniform and a quick germination (cut short 2 to 3 days than “unprimed” seeds). “Primed” and “unprimed” seeds were evaluated to determine if the quick seed development would reduce springtail damage. Data show that germinating “primed” seeds were impacted with springtail feeding affecting their germination and were not different from the “unprimed” seeds when the springtail pressure was moderate to high (Fig. 3). The seeds used for this experiment were from same seed lot (“primed” and “unprimed”) for a lettuce variety. Also, there was no clear variety difference in springtail feeding damage.
Leafminers and western flower thrips. The leafminer eggs are laid within the surface layer of the leaf. The eggs hatch within couple of days and the maggots mine through the surface layer of the leaves. The egg laying and maggot mining creates stippling and mining injuries which make the leaves unmarketable. Although UC recommends few insecticides such as Agri-mek (Abamectin), Trigard (Cyromazine), Aza-direct (Azadirachtin) and Entrust (Spinosad), the management of leafminers are primarily relied upon on Agri-mek applications.
Thrips is another of the major pest of lettuce, and combination of direct feeding injury and viral disease [thrips-transmitted tospoviruses [Impatiens Necrotic Spot Virus (INSV)] can cause significant losses in lettuce production. In addition, because most of the export markets have set higher standards on prevalence of live and dead thrips in the produce, the lettuce industry is constantly battling ways to significantly reduce thrips in the produce targeted for export.
A replicated-field trial was conducted to determine the efficacy of seed coated insecticides (Table 1) on leafminers and western flower thrips incidence and their infestation. The results show that insecticide seed coating may not be an effective option for leafminers and thrips control in head lettuce (Table 3 and 4) under the conditions this experiment was conducted. There was no reduction of leafminer or thrips feeding with insecticide coated seeds compared with untreated control. Further evaluations under varying conditions might be necessary to validate the consistency of these results.
- Author: Shimat Villanassery Joseph
- Author: Mark Bolda
Lygus bug (Lygus hesperus) (Fig. 1) is a major pest of strawberry in the Central Coast. Lygus bug populations develop on weed hosts surrounding the strawberry fields such as wild radish, common groundsel, lupines, and mustards (Zalom et al. 2012). Time to time, adults migrate into the strawberry fields and lay eggs. Eggs hatch, and molt through five nymphal stages before molting into adults. Lygus bug feeding on the developing embryos affects the normal development of tissues surrounding the embryo (Handley and Pollard 1993) and affected fruits are misshapen often referred as “catfaced fruit” (Fig. 2) which are deemed unmarketable. Although both nymphs and adults can cause catface injury, nymphs are considered more destructive than adults. The young fruits up to ~10 days after petal fall are considered vulnerable to economic injury from lygus bug feeding (Zalom et al. 2012).
Chemical control continues to be an effective tool for lygus bug control and growers are always seeking effective and softer insecticides for its control. A replicated trial comparing the efficacy of insecticide treatments against lygus bug was conducted in first-year strawberry ‘San Andreas' in Watsonville, CA in 2016. The details on insecticide products and rates used in the trial are shown in Table 1. The insecticides were applied twice at 10 day interval using commercial tractor mounted sprayer. The water volume used for both the applications was 150 gal per acre and was applied at 140 psi. Dyne-Amic (surfactant) was added at 0.25% v/v to all the treatments. Insect samples were collected using regular sized Rubbermaid container by hitting 20 flowering strawberry plants with lid. In addition, 60 fruits were sampled from each plot to determine catface injury.
Pre-count sample did not show any difference in number of adult and nymphal lygus bugs among treatments (Figs. 3 and 4). Overall, all the insecticide treatments reduced the number of lygus bug adults and nymphs compared with untreated plants. The combination treatments using pyrethroid insecticides such as Danitol and Brigade suppressed lygus bugs and general predators such as bigeyed bug, minute pirate bug, and damsel bug as well as spiders (Figs. 5-8). Data show that reduced-risk insecticides, Rimon and Beleaf suppressed lygus bug nymphs as well. Sequoia, not yet registered on strawberry, provided a decent lygus bug control. Sivanto initially provided a good suppression of adults and nymphs but could not adequately sustain the control for more than a week. Two rates of Avaunt (unregistered insecticide on strawberry) was included in this experiment and were comparable to other effective insecticides in this experiment.
Insecticide use certainly reduced catface injury on strawberry fruit. Number of fruits with catface injury was lower in all the insecticide treated plants than untreated except the lower rate of Avaunt (Fig. 9). Catface injury on fruits treated with Sequoia was lower than untreated but not different from other insecticides (except lower rate of Avaunt).
Handley, D. T., and J. E. Pollard. 1993. Microscopic examination of tarnished plant bug (Heteroptera: Miridae) feeding damage to strawberry. J. Econ. Entomol. 86: 505-510.
Zalom, F. G., M. P. Bolda, S. K. Dara, and S. Joseph. 2012. Strawberry: Lygus bug. UC Pest Management Guidelines, UC ANR Publication 3468. http://www.ipm.ucdavis.edu/PMG/r734300111.html
A symposium dedicated to lygus, bagrada, brown marmorated stink bug will be held on 18-20 April, 2017 in Seaside, CA. Several researchers around the globe working on true bug will present their findings in the symposium. It will be a great opportunity for you all to participate and learn the recent development in bug science. Last day of the symposium (20 April 2017), the talks will be steered toward growers, PCAs and any personnel involved in pest management. Please do not forget to register ahead of time. Registration and other information about the symposium could be found at this following link -