Mycotrol-O is a biopesticide with the entomopathogenic fungus Beauveria bassiana as the active ingredient. Beauveria bassiana is pathogenic to a wide range of arthropod pests and I have used both Mycotrol-O and the conventional formulations BotaniGard 22WP and BotaniGard ES in several studies against multiple pests over years. It showed good potential against thrips in lettuce, aphids in broccoli, lygus bug and spider mites on strawberries. The combination of Mycotrol-O and azadirachtin emerged as a good tool for managing root aphids in organic celery and Mycotrol-O consistently performed better than other options against Bagrada bugs in my laboratory assays.
On 24 August, a grower who has been using Mycotrol-O for controlling Bagrada bug on multiple crops sent me an email he received from the distributor that the OMRI certification of Mycotrol-O will expire as of 28 August, 2015. When I contacted Bioworks, Inc. that markets Mycotrol-O, they confirmed that one of the ingredients of the carrier was challenged by OMRI for organic production and their new formulation, Mycotrol ESO is waiting for registration. LAM International Corp, the manufacturer of Mycotrol-O, notified on 31 August that OMRI accepted their appeal to review the status of the product. This means, Mycotrol-O will remain in OMRI approved status until further notification.
Metarhizium brunneum (=M. anisopliae) and Isaria fumosorosea (=Paecilomyces fumosoroseus) are the other two entomopathogenic fungi that are commercially available, but only the latter is registered for organic use. Beauveria bassiana is an effective pathogen and several growers are using against multiple pests.
Growers and PCAs can continue to use Mycotrol-O based on the current information.
A few species of aphids infest celery in California. According to the UC IPM Pest Management Guidelines, the black bean aphid (Aphis fabae), the foxglove aphid (Aulacorthum solani), the green peach aphid (Myzus persicae), the hawthorn or parsley aphid (Dysaphis apiifolia), and the cotton or melon aphid (Aphis gossypii) attack celery and cause varying levels of damage. These aphids feed on the aboveground plant parts – leaflets and petioles – and some of them are vectors of virus diseases such as western celery mosaic, celery calico, cucumber mosaic, celery yellow spot and others.
In late 2014, an organic celery field in Santa Maria was severely infested with aphids feeding on the root system. Damage stunted plant growth and resulted in up to 80% of yield loss. Gillian Watson at CDFA identified the aphid specimens as the rice root aphid, Rhopalosiphum rufiabdominale (Sasaki) and the honeysuckle aphid, Hyadaphis foeniculi (Passerini). While there was only one earlier record of the honeysuckle aphid infestation on celery, according to the CDFA records, the rice root aphid has never been reported on celery. This is the first record of the rice root aphid on celery. Multiple species of the genus Hyadaphis are referred to as honeysuckle aphid, coriander aphid, and others in the literature, but the one identified on celery was H. foeniculi.
The rice root aphid is known to infest graminaceous (barley, rice, and wheat), rosaceous (apricot and plum), and solanaceous (potato and tomato) crops and is known to vector the barley yellow dwarf virus of grasses and small grains. The honeysuckle aphid is known to be an important pest of apiaceous (fennel), caprofoliaceaeous (honeysuckles), and lamiaceous (mints) plants and involved in the transmission of 13 viruses.
Depending on the host plant they are feeding on, the wingless form of the rice root aphid can be olive to dark green or brownish with yellowish tints or reddish or greenish-brown along with bluish-white wax on the body. The wingless form of the honeysuckle aphid is greyish green or light green with dark appendages.
Field study methodology:
Natural enemies such as coccinellids, syrphid fly larvae, and lacewings play an important role in biological control of aphids infesting aboveground parts of the plant and root aphid management is a challenge especially in organic cropping systems. To address the issue, a field study was conducted using the following treatments: i) untreated control, ii) Ecotec (rosemary oil 10% and peppermint oil 2%) 19.2 fl oz along with 12 fl oz of Kinetic (silicone and non-ionic surfactants), iii) AzaGuard (azadirachtin) 6.3 fl oz along with 20 fl oz of OroBoost (alcohol ethoxylate), iv) Mycotrol-O (Beauveria bassiana) 1.5 qrt, v) Mycotrol-O 1.5 qrt along with AzaGuard 6.3 fl oz, vi) Venerate (Burkholderia spp.) 2 gal, and vii) Grandevo (Chromobacterium subtsugae) 2 lb per acre. Each treatment was about 0.3 acres of single plot and pesticides were administered through the drip system at 250 gpa rate for 40-45 min on December 9 and 23, 2014. Aphid infestations were evaluated on December 6 (pre-treatment), December 22 (13 days after the first treatment), and January 2, 2015 (10 days after the second treatment). On each sampling date, 10 plants were pulled out from random locations within each treatment, roots were washed in mild soap water, and aphids floating on the surface were filtered and counted. Data were subjected to analysis of variance and significant means were separated using Tukey's HSD test.
There was a significant difference in aphid numbers among different treatments before and after each application (P < 0.002) and when the average for both applications (P < 0.0001) was considered. When the overall change in aphid populations after both applications compared to the pre-treatment numbers was considered, there was a 3% reduction in untreated control, 24, 18, and 129% increase in Ecotec, AzaGuard, and Mycotrol-O treatments, respectively. However, Mycotrol-O along with AzaGuard provided a 62% reduction in aphid populations followed by a 29% reduction by Grandevo and 24% by Venerate. This study demonstrates the potential of non-chemical options in managing aphid populations in organic celery. Microbial pesticides especially in combination with botanical pesticides can play a significant role in pest management. Understanding the modes of actions of different options and using the right combinations is critical in pest management decisions.
Thanks to the technical assistance of Cintia Perez and Emmy Williams and industry collaborators for donating the products.
AphID. 2014. Hyadaphis foeniculi. (http://aphid.aphidnet.org/Hyadaphis_foeniculi.php)
AphID. 2014. Rhopalosiphum rifiabdominale. (http://aphid.aphidnet.org/Rhopalosiphum_rufiabdominale.php)
Blackman, R. L. and V. F. Eastop. 2006. Aphids on world's plants (http://www.aphidsonworldsplants.info/d_APHIDS_R.htm#Rhopalosiphum and http://www.aphidsonworldsplants.info/d_APHIDS_H.htm#Hyadaphis)
Halbert, S. E. 2003. Coriander aphid, Hyadaphis coriandri(Das) (Insecta: Hemiptera: Aphididae). University of Florida IFAS Extension publication EENY-296. (https://edis.ifas.ufl.edu/pdffiles/IN/IN57400.pdf)
Jedlinski, H. 1981. Rice root aphid, Rhopalosiphum rufiabdominalis, a vector of barley yellow dwarf virus in Illinois, and the disease complex. Plant Disease 65: 975-978. (https://www.apsnet.org/publications/plantdisease/backissues/Documents/1981Articles/PlantDisease65n12_975.pdf)
The Morton Arboretum. 2013. Honeysuckle aphid. (http://www.mortonarb.org/files/Honeysuckle%20aphid%20%28Feb%202014%29.pdf)/span>
Twospotted spider mite, Tetranychus urticae Koch is a major pest of strawberries in California. Spider mite damage reduces plant vigor and contributes to yield loss. Twospotted spider mites are typically found on the lower side of the leaf and form webbing at higher population levels.
Damage: Spider mites cause damage by puncturing the epidermis with their mouthparts and sucking the plant juices. Death of plant cells appears as yellow mottling during initial stages and as feeding continues, damaged areas coalesce and result in scarring, bronzing, and drying out of leaf tissue. This reduces the photosynthetic ability of the plant and thus its growth and vigor. If left uncontrolled, damage leads to stunted plant growth or eventual death. Damage symptoms are unique in Benicia variety where upper leaf surface corresponding to spider mite feeding on the lower side, shows purplish coloration.
Biology: Life cycle includes egg, larva, protonymph, deutonymph, and adult stages. Females lay an average of 100 eggs in 10 days. Eggs are round, initially translucent and turn whitish as they mature. Larvae have three pairs of legs and nymphal stages have four pairs of legs. Males are wedge-shaped and about 0.3 mm long. Females are oval, 0.4-0.5 long, and have a single dark spot on either side of their body. At 85-90 oF, life cycle can be completed in 7-8 days.
Management: Growers typically rely on biological and chemical control options for managing twospotted spider mites in strawberries. Type I specialist Phytoseiulus persimilis Athias-Henriot, Type II specialists Neoseiulus fallacis (Garmin), N. californicus (McGregor), Galendromus occidentalis (Nesbitt), and Type III generalist Amblyseius andersoni (Chant) are common predatory mites that attack twospotted spider mites. Releasing one or more species of predatory mites is a popular practice in strawberry production. Abamectin, acequinocyl, bifenazate, etoxazole, fenbutatin-oxide, fenpyroximate, hexythiazox, and spiromesifen are the most commonly used chemical miticides according to pesticide use reports of the California Department of Pesticide Regulation. Chemical miticide use shows a 2% increase in the Watsonville-Salinas area, an 82% increase in the Santa Maria area, and a 125% increase in the Oxnard areas from 2009 to 2013. There is a continued need for identifying effective chemical and non-chemical miticides to manage twospotted spider mite in strawberries.
A small plot field study was conducted in 2013 at Manzanita Berry Farms in Santa Maria to evaluate the efficacy of various botanical, chemical, and microbial pesticides. Treatments included bifenazate (Acramite 50 WS at 1 lb/ac), abamectin (Agri-Mek SC at 4.29 fl oz/ac), entomopathogenic fungus Beauveria bassiana (BotaniGard ES at a lower label rate of 1 qrt/ac) + bifenazate (Acramite 50 WS at the lowest label rate of 0.75 lb/ac), rosemary and cotton seed oil (Eco-Mite at 1% concentration), fenpyroximate (Fujimite 5 EC at 2 pt/ac), fenpyroximate (Fujimite XLO at 2 pt/ac), Chromobacterium subtsugae strain PRAA4-1 (Grandevo at 2 lb/ac), Burkholderia sp. strain A396 (Venerate XC at 2 gal/ac), and cyflumetofen (Nealta SC at 13.7 fl oz/ac). A spray volume of 150 gal/acre was used with 0.25% non-ionic surfactant except for the treatment with B. bassiana, where an organo-silicon surfactant was used. Each treatment had a 15' long strawberry bed and treatments were replicated in randomized complete block design. Treatments were applied using a CO2 pressurized backpack sprayer twice at weekly intervals and eggs and mobile stages of twospotted spider mites and predatory mites were sampled 3 and 7 days after each application. On each sampling date, 10 mid-tier leaflets were collected from 10 random plants within each plot and mites were collected using a mite brushing machine and counted under microscope. Data were analyzed using analysis of variance and significant means were separated using Tukey's HSD test.
Pre-treatment counts were not available due to a technical issue, so comparisons were made for pest and predatory mite counts after each spray application and the post-treatment period as a whole. Compared to untreated control, treated plots had fewer spider mites throughout the observation period, but the pest suppression was not statistically significant (P > 0.05, Table 1). When the percent reduction in treatments relative to untreated control was compared, rosemary+cotton seed oil, fenpyroximate EC, and B. bassiana+bifenzate had relatively higher reduction in mobile stages while Burkholderia sp., rosemary+cotton seed oil, and cyflumetofen had a higher reduction in eggs after the first spray application (Fig. 1A). Reduction in mobile stages following the second spray was the highest in cyflumetofen followed by bifenzate, rosemary+cotton seed oil, fenpyroximate XLO, and EC (Fig. 1B). After the second spray, the highest reduction in eggs was seen in fenpyroximate EC followed by Burkholderia sp., cyflumetofen, rosemary+cotton seed oil, and B. bassiana+bifenzate. In general, rosemary+cotton seed oil treatment did a better job of reducing egg and mobile stages after both applications followed by Burkholderia sp., cyflumetofen, and fenpyroximate EC (Fig. 1C).
Fig. 1. Percent reduction in eggs and mobile stages of twospotted spider mites in different treatments compared to untreated control after first (A), second (B), and both spray applications (C).
There were no statistically significant differences in predatory mite populations among treatments except in mobile numbers on 7 days after the first spray (P = 0.0046, Table 2). Plots that were treated with Burkholderia sp. and cyflumetofen had a relatively higher number of predatory mites and bifenzate and abamectin had lower numbers, in general.
Table 2. Number of eggs or mobile stages (mean+SE) of predatory mites 3 and 7 days after first and second spray treatment along with post-treatment average.
Although treatment differences were not statistically significant, this study demonstrates the efficacy of various botanical, chemical, and microbial pesticides against twospotted spider mites and their safety to predatory mites. Results show the potential of non-chemical alternatives, which can be used in rotation with chemical pesticides for a sound IPM program.
General IPM recommendations:
- Obtain transplants from a clean source to avoid early spider mite infestations, which could lead to season long problems in production fields.
- Periodically scout the fields to evaluate infestation levels and make appropriate management decisions.
- Rotate chemicals among different modes of action groups and consider botanical and microbial control options to reduce the risk of resistance development.
- Understand the dietary preferences and environmental requirements of different species of predatory mites and release the right species appropriate for the situation.
- Avoid water stress for plants as spider mites thrive when plants are under stress.
- Excessive nitrogen fertilization encourages spider mite population build up, so optimize fertilizer input.
Acknowledgments: Thanks to Dave Peck, Manzanita Berry Farms, Santa Maria for his collaboration, pesticide industry partners for the financial support, and Sumanth and Suchitra Dara for their technical assistance with mite brushing.
Blecker, S. 2015. Pesticide use trends in strawberries. Presentation at Santa Maria Strawberry Field Day. http://cesantabarbara.ucanr.edu/files/213517.pdf
Dara, S. K. 2014. Managing spider mites in California strawberries. UCCE eNewsletter Strawberries and Vegetables. http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=13943
Dara, S. K. 2014. Predatory mites for managing spider mites on strawberries. UCCE eNewsletter Strawberries and Vegetables. http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=14065
Hoffland, E., M. Dicke, W. V. Tintelen, H. Dijkman, and M.L.V. Beusichem. 2000. Nitrogen availability and defense of tomato against two-spotted spider mite. J. Chemical Ecol. 26: 2697-2711.
- Author: Cheryl Reynolds
As summer continues to heat up, keep in mind that regulations remain in effect to reduce the volatile organic compounds (VOCs) that can be emitted into the atmosphere by pesticides and other harmful chemicals and contribute to the amount of ozone or smog in the environment.
Calculators from the Department of Pesticide Regulation (DPR) that determine the VOC emissions from fumigant and non-fumigant pesticides before application are available to help growers, pest control advisers, and pesticide applicators comply with the regulations. The UC Statewide Integrated Pest Management (IPM) Program provides a link to these calculators from each of the treatment tables in the UC Pest Management Guidelines. Click on the Air Quality – Calculate emissions button.
Take steps to reduce VOCs. Avoid emulsifiable concentrate (EC) formulations as they release the highest VOC emissions. Pesticide control advisers and growers can also reduce VOC emissions by employing IPM practices such as using resistant varieties, traps, exclusion, and biological control. When using pesticides, spot-treat and seek low-emission materials. Solid formulations, such as granules or powders, are best.
Check the fact sheet on the DPR web site for the most up-to-date-information on VOC restrictions and regulations.
Few herbicides are available for use in lettuce and more effective weed control tools are needed. Previous studies have found Prowl H2O (pendimethalin) to be safe to transplanted lettuce and effective on weeds that commonly infest lettuce fields. The study objective was to compare the safety and efficacy of pendimethalin applied to lettuce before (PRE) and after (POST) transplanting in commercial plantings and field station evaluations on the California central coast. Pendimethalin applied PRE transplanting resulted in little lettuce injury and provided acceptable weed control. Lettuce yields were not reduced by pendimethalin. While the level of injury was low with the pendimethalin POST transplant application, the PRE transplant application caused even less injury than the POST. Pendimethalin at 2.1 pt/Acapplied PRE or POST transplant controlled 68% and 53%, of the weeds, respectively, compared to 12% for Kerb (pronamide). In the commercial evaluations there was no difference in the numbers of marketable lettuce heads or head weights between pendimethalin and the hand weeded control. Results here show that pendimethalin has potential for use in transplanted lettuce and controls weeds as well or better than pronamide.
The objective of this work was to determine the safety of PRE and POST applications of pendimethalin to transplanted lettuce and efficacy on common weeds of lettuce.
Pendimethalin PRE and POST Applications. One month old lettuce plants (3 to 5 true leaf stage) were transplanted into twin row 40-inch wide beds. The in-row plant spacing was 9 inches, between row spacing was 12 inches and plots were one bed wide by 25 feet long. Prowl H2O 3.8 lb/Gal. (pendimethalin) was applied at 2.1 and 4.2 pts/A and Kerb 3.3 SC (pronamide) was applied at 2.5 pts/A PRE one day before transplanting and POST, one day after transplanting. The pendimethalin 2.1 pts/A treatment was included as the normal 1X rate, the 4.2 pts./A rate was included as a 2x rate to verify safety to lettuce. Each trial had a no herbicide non-weeded control and a weed-free control. Weed densities were measured in 2.8 ft2 sample areas about 3 weeks after transplanting. Crop injury estimates were recorded on a scale of 0% (no injury) to 100% (dead). Lettuce yield (fresh weights) was determined by harvesting a 9 feet long sample area from one plant line in the middle of the plot. Experiments were repeated in 2013 and 2014, and were arranged in a randomized complete block design with four replications. Injury, weed density and yield data were subjected to ANOVA and means were separated by Fisher's protected LSD at α ≤ 0.05.
Commercial Field Evaluation. The on-farm evaluations were held with cooperating growers in Las Lomas and Santa Maria. Pendimethalin was applied PRE at 2.1 pts/A one day before transplanting. Lettuce yield in Las Lomas was sampled from an 18 ft long sample area on one bed (4 plant lines). Lettuce yield in Santa Maria was sampled from one plant line by 30 feet long. The on-farm evaluations included a hand weeded control. Experiments were arranged in a randomized complete block design with three replications. Data were subjected to ANOVA and means were separated by Fisher's protected LSD at α ≤ 0.05.
Results and Discussion
Pendimethalin PRE and POST Applications. The PREpendimethalinapplications at 2.1 and 4.2 pts/Awere safe for transplanted lettuce and resulted in minor crop injury of 12% or less (Table 1). POST transplant applications of pendimethalin resulted in 0 to 7% injury in 2013. POST applications of pendimethalinin 2014 resulted in 22% and 24% injury for the 2.1 and 4.2 pts/Atreatments, respectively. While the level of injury was very low, injury was more evident in the POST transplant pendimethalin applications than in the PRE transplant applications. Lettuce yields were not reduced by PRE or POST pendimethalin or pronamide applications relative to the nontreated control, indicating that transplanted lettuce plants have similar levels of tolerance to both herbicides (Table 1).
The primary weeds in these experiments (average between 2013 and 2014) were 68% annual sowthistle (Sonchus oleraceus L.), 12% shepherd's-purse, 10% burning nettle (Urtica urens L.) and 8% hairy nightshade (Solanum physalifolium). Under high weed densities in 2013, pendimethalin at 2.1 pts/Aprovided 69% and 53% weed control respectively in the PRE and POST transplant treatments (Table 1). By comparison pronamide provided 12% and 39% weed control respectively in the PRE and POST transplant treatments. Annual sowthistle was the main weed in 2013; a species poorly controlled by pronamide. Hairy nightshade was the main weed in 2014, a species well controlled by pronamide, and the reason why pronamide performed better in 2014 than 2013.
Table 1: Injury estimates, transplanted lettuce yield (fresh weights) and total weed control resulting from pendimethalin PRE and POST applications, in 2013 and 2014 on the field station evaluations. Note: yields were combined for 2013 and 2014.
a Means with the same letter within columns are not significantly different according to Fisher's Protected LSD at P < 0.05.
b Visible injury estimates were taken 15 and 25 days after treatment for the 2013 and 2014 experiments, respectively; estimates were taken on a scale of 0%-100%, with 0% = no injury and 100% = dead plants.
c Yield was evaluated 48 and 59 days after treatment for the 2013 and 2014 experiments, respectively.
d Weed control was measured 25 and 23 days after treatment for the 2013 and 2014 experiments, respectively. The main weeds in this experiment were 68% annual sowthistle, 12% shepherd's-purse, 10% burning nettle and 8% hairy nightshade.
Commercial Field Results. Evaluations of pendimethalin in commercial fields found similar results to the research station evaluations. At both locations, there was no significant difference in the numbers of marketable lettuce heads or yield between pendimethalin and the hand weeded control (Table 2). Differences in yield between locations were mainly due to differences in lettuce varieties and corresponding cropping practice such as plant densities.
Table 2. Transplanted lettuce yield, number of marketable heads and fresh weights, from the on-farm study of pendimethalin held in Las Lomas and Santa Maria in 2013 and 2014, respectively.
a There were no differences between the treatments according to Fisher's Protected LSD at P < 0.05.
We concluded thatpendimethalin (PRE and POST) at 2.1 pts/Awas safe for use on transplanted lettuce, and resulted in better weed control than pronamide. For transplanted leaf lettuce, pendimethalin is a viable product and registration of this product on lettuce should be pursued.
Acknowledgments: Thanks to California Leafy Greens Research Board for funding this study and Craig Sudyka, Betteravia Farms and Jason Gamble, Babe Farms, Santa Maria for their collaboration in Santa Maria studies.