- Author: Cheryl Reynolds
The UC Statewide Integrated Pest Management Program (UC IPM) put together a 26-page card set in English and Spanish on understanding pesticide labels. Intended for pesticide handlers, applicators, safety trainers, and pest control advisers (PCAs), the cards explain when to read the label, describe what kind of information can be found in each section of a pesticide label, and point out specific instruction areas so that applicators can apply pesticides safely and avoid illegal pesticide residues.
Traces of pesticide residue are normal and even expected after pesticides are applied to food crops, but by the time produce is ready to be sold, purchased, and consumed, residues are usually far below the legal limit.
In its latest report from 2013, the California Department of Pesticide Regulation (DPR) reported that there was little or no detectable pesticide residue in 97.8% of all California-grown produce. This demonstrates a strong pesticide regulation program and pesticide applicators that apply pesticides safely and legally. However, there have been instances in California where a pesticide not registered for a specific crop has been used unintentionally, resulting in illegal residues and eventually crop loss and destruction.
The Environmental Protection Agency (EPA) sets tolerances for the maximum amount of pesticide residue that can legally be allowed to remain on or in food.
DPR regularly monitors domestic and imported produce for pesticide residues and is considered the most extensive state residue-monitoring program in the nation.
The primary way pesticide applicators can assure that they make proper applications and avoid illegal pesticide residues is to follow the pesticide label. UC IPM's new card set was developed from information in the upcoming third edition of The Safe and Effective Use of Pesticides as well as Lisa Blecker, UC IPM's Pesticide Safety Education Program coordinator. Bound with a spiral coil, this eye-catching instructional card set was designed for both English-speakers and when flipped over, for Spanish-speaking audiences as well. UC IPM also plans to release a new online course on preventing illegal pesticide residues sometime late fall.
To download copies of the card set in English or in Spanish, see the UC IPM web site.
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.