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Western Plant Diagnostic Network News

Dear First Detectors, I am always asking the WPDN states and territories for articles for the newsletter, and with this edition I received a many contributions. This edition begins with a very serious infestation of sorghum by an aphid previously known on sugarcane. This epidemic has spread very rapidly in the Midwest and the West. The Asian citrus psyllid keeps spreading in California, this time into Placer County NE of Sacramento. Both of these insects can fly and can spread quickly. Our WPDN director, Professor Rick Bostock, has asked Professor Neil McRoberts to take the helm of the region. There is a new psyllid on Ficus microcarpa in Southern California, an exotic and damaging scale in Hawai’i, stem and bulb nematode on onion and garlic in NM, and an outbreak of two Fusarium species on Cannabis sativa in Nevada.

The WPDN team wishes you the best of Holidays and a peaceful and healthy 2017!

Please find the NPDN family of newsletters at:

Newsletters

Western Plant Diagnostic Network

First Detector News

A Quarterly Pest Update for WPDN First Detectors

Fall 2016 edition, volume 9, number 4

In this Issue Page 1: Editor’s comments Pages 2 – 4: Sugarcane aphid has a new host – Sorghum

Page 5: Asian citrus psyllid spreads in CA – Placer Co.

Page 6: WPDN Director Rick Bostock passes the torch

Page 7: New psyllid on Ficus microcarpa in southern CA Page 8: Exotic scale found in HI Page 9: Stem & bulb nematode found in NM Page 10: Fusarium spp. on Cannabis in NV

Contact us at the WPDN Regional Center at UC Davis: Phone: 530 754 2255 Email: rwhoenisch@ucdavis.edu Web: https://wpdn.org Editor: Richard W. Hoenisch @Copyright Regents of the University of California All Rights Reserved

Sugarcane aphid

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Western Plant Diagnostic Network News

Sorghum is an ancient African cereal grain, domesticated some 8,000 years ago in the region of Southern Sudan and Ethiopia. It is the fifth most important cereal grain after rice, wheat, maize and barley and is a dietary staple for more than 500 million of the most food-insecure people in the world. The modern cultivars of sorghum are from the species, Sorghum bicolor. The whole sorghum plant is used, with the grain being a major food and feed staple, the leaves and stems for livestock, and the sweet juice for syrup and molasses production. Sorghum is not new to the United States. It more than likely traveled to the US via the slave trade; however, the first recorded evidence of sorghum is in 1757, when Benjamin Franklin wrote about broomcorn, a specialty sorghum, to a friend. Sorghum (or milo) represents the third-largest cereal grain in the United States. Its comparative advantage is its drought tolerance; resistance to mycotoxins and fungi; and survivability in relatively harsher climatic conditions. Sorghum is truly a versatile crop that can be grown as a grain, forage or sweet crop. Since 2000, sorghum has come into increasing use in homemade and commercial breads and cereals made specifically for the gluten-free diet. Sorghum is one of the top five cereal crops in the world. The United States is the world's largest producer of grain sorghum, having produced 597 million bushels in 2015.

Sorghum is among the most efficient crops in conversion of solar energy and use of water and is known as a high-energy, drought tolerant crop that is environmentally friendly. Due to sorghum's wide uses and adaptation, “sorghum is one of the really indispensable crops.” It is widely used for ethanol production. Production is primarily focused in a stretch of land beginning in southern Nebraska and ending at the southern tip of Texas. Chief importers in the 2014/2015 crop year, Sept. 1 - Aug. 31, were China with 97% and Japan with 2%.

Sugarcane Aphid Spreads to Sorghum

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Sugarcane aphid on the underside of a sorghum leaves

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Although the bulk of sorghum production is in the Mid-West, the western states plant thousands of acres of the crop. AZ has 24, 000 acres; CA 30,000; NM 105,000, with

additional production in Washington and Utah.

Grain sorghum

Kansas – 3.4 million acres Texas – 2.6 million acres Arkansas – 450,000 acres Oklahoma – 440,000 acres Colorado – 440,000 acres

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Western Plant Diagnostic Network News

The Sugarcane Aphid – A New Pest of Sorghum

The sugarcane aphid (SCA) has historically only been known as a pest of sugarcane. It was first found in Florida on sugarcane in 1977. However, in 2013 farmers in Texas and Louisiana reported that this pest was causing economic losses in grain sorghum and that traditional broad-spectrum insecticides were not providing control. By 2014 similar reports were received from at least 11 southern states from Texas to Florida, and by 2016 this pest has now moved west to Arizona and California. See the full article at: Alfalfa & Forage News, UC Cooperative Extension. This sorghum-feeding SCA biotype developed because of a genetic change in the existing US population or was introduced into the US from elsewhere. The sugarcane aphid can easily be distinguished from other aphid species due to their yellow color with black feet, tips of antennae and cornicles (tailpipes) that point upward from the rear of the insect. This is in contrast to the aphid, called greenbug, Schizaphis graminum, and other aphid species in sorghum that have a greenish appearance. Host plants for sugarcane aphid include sugarcane, sorghum, sudangrass, sorghum X sudangrass hybrids, and the weed Johnson grass . It has not been found on corn or other grains.

Sugarcane aphids intercept nutrients intended for the development of leaves and grain heads by feeding on plant sap. Heavy infestations can kill leaves, stunt growth, and reduce the size and quality of grain heads. Honeydew and sooty mold on leaves can compromise photosynthesis and may also reduce harvest efficiency by gumming up harvest equipment. Populations of sugarcane aphid can build very quickly. Informational resources from Texas A&M Extension report that in one location field populations went from 50 to 500 aphids per leaf over a two-week period. Adult aphids (all females) give live birth to nymphs that can develop into adults within about five days and that live for approximately four weeks during summer conditions. Aphids are usually wingless until population density is high, at which time some of the offspring begin to develop wings (alates) to disperse to new feeding locations. A very informative PowerPoint presentation on the sugarcane aphid by from Texas A&M is A New Pest of Sorghum: the Sugarcane Aphid.

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Greenbug aphid adults infesting Sorghum

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Note the difference

Sugarcane aphid adults and nymphs Note the dark cornicles, antennae, & tips of the feet

Winged offspring, called "alates” disperse to other sorghum fields

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Western Plant Diagnostic Network News

of asexual reproduction in which growth and development of embryos occur without fertilization. The SCA gives birth to live young rather than laying eggs and are all female. Therefore, the SCA populations are genetically identical and can grow quite rapidly. Immature aphids mature to adults in about five days and live for about 4 weeks. Aphid numbers can increase very rapidly during the summer. The alate , or winged form of the SCA fly and move with the wind to new areas. Due to parthenogenesis, they then establish new infestations. Proper management of the SCA in grain sorghum should begin with routine scouting of fields. The population development of this insect is very rapid, and small infestations can escalate out of control in less than one week in some cases. Because SCA is a new pest for sorghum production in the U.S., current recommendations are based on limited field trials. Insecticides labeled for use against other aphid pests in sorghum are largely ineffective for control of sugarcane aphid. Because Texas was the epicenter of the SCA infestation and has 2.6 million acres of grain sorghum, Texas A&M AgriLife Extension has been a leader in SCA control. The Sugarcane Aphid: Management Guidelines for Grain and Forage Sorghum in Texas is a very good and thorough guide for monitoring and management. Other publications from the Texas A&M research group – The Sugarcane Aphid: A New Pest of Grain and Forage Sorghum and Sugarcane Aphid: Host Range and Sorghum Resistance Including Cross-Resistance From Greenbug sources – define the host range of the SCA and field trials to test sorghum breeding lines for tolerance and/or resistance to the greenbug aphid. The greenbug has been a pest of small grains since it was first found in Virginia about 1882. It is a major pest of wheat. There are 9 biotypes of the greenbug. Breeding programs have been in place to find resistant varieties of small grains, including grain sorghum to the greenbug. Texas A&M is testing sorghum varieties resistant to the 9 biotypes of the greenbug to find resistance to the sugarcane aphid. Kansas State University, Louisiana State University, University of Tennessee, and others are working quickly to develop control strategies and resistant cultivars. Guidelines from the University of Georgia are 1) plant early to avoid later infestations; 2) use an insecticide seed treatment to give 30 – 40 days protection; 3) scout early and often; 4) encourage beneficial insects; 5) treat when SCA are reach threshold levels; 6) use a proven effective insecticide; 7) good spray coverage is key; 8) avoid pyrethroid insecticides, and 9) check fields 2-3 weeks before harvest. Heavily infested sorghum will gum up the harvest and threshing equipment with honeydew.

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Sugarcane Aphid Epidemiology and Control

Sorghum crop heavily infested with the sugarcane aphid in Texas

Rapid spread of the sugarcane aphid on sorghum from the original infestation at Beaumont TX (red) in 2013 in one

year’s time (yellow and green)

Sugarcane aphids are very difficult to control. Most populations start out small and exponentially increase in 5 to 7 days. The SCA reproduce by parthenogenesis, a natural form

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Western Plant Diagnostic Network News

Asian Citrus Psyllid Quarantine Expands in California

The Asian citrus psyllid , Diaphorina citri, a small insect that can carry a bacterium to cause a devastating citrus tree disease, has been detected in Placer County in northern California. The disease, called Huanglongbing, and also known as HLB or citrus greening disease, will kill any tree it infects. There is no known cure, other than preventing infection. A call to the California Department of Food and Agriculture’s tip line on Sept. 8, 2016, brought state inspectors to a property in western Lincoln where specimens were collected from four trees that day. The specimens were positively identified the following day and the trees were destroyed. Agricultural inspectors from the Placer County Agricultural Commissioner’s office and the state immediately began an inspection of citrus trees in the area and the Asian citrus psyllid was discovered on another tree on an adjacent property. That tree was destroyed, as well. Inspectors have placed traps in trees in a 1.5 mile radius of the infected trees. The state, at the request of Placer County, approved emergency regulations establishing a 5-mile quarantine radius from the discovery site. The quarantine encompasses most of Lincoln, a portion of Rocklin and a large swath of unincorporated Placer County. Rocklin and Lincoln are approximately 30 miles NE of Sacramento. This action prohibits the transportation of any backyard citrus fruit, trees, tree cuttings, or root stock to anywhere else, inside or outside of the quarantine boundaries.

Please see the past WPDN newsletters on ACP/HLB: Summer 2010, Fall 2013, Summer 2015 includes the first incidence of the bacterium causing Huanglongbing in San Gabriel County, CA. And Winter 2016 as the spread of ACP continues. For information on Interior Quarantines, Compliance, Approved Treatments for Nurseries, etc. please see CDFA ACP/HLB Site

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These guidelines were in the Winter 2016 edition. Since it is citrus

season once again, please do not send any citrus gifts if you are in a

quarantine area outside of that area. It is illegal to send home grown citrus across state lines.

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Before you give citrus, there are four things you should know to gift smart:

1. Be Aware of Quarantines. If you are thinking about giving citrus fruit, plants, or items made with citrus (such as floral arrangements, wreaths, potpourri or seasonings like kaffir lime leaves) be sure not to move them from quarantined states or territories. Not only are you risking spreading citrus diseases by transporting citrus outside of these areas, but it’s also against the law. Learn more about quarantines.

2. Check the Citrus Supplier. Be a savvy buyer. Gift citrus fruit sold in a regulated state must be packed in a certified packinghouse and accompanied by a USDA certificate. Commercial fruit packers, Internet shippers and roadside vendors within regulated states should be able to prove they are in compliance with the federal quarantine. Before you buy, ask the vendor if their product is in compliance.

3. Keep Homegrown Citrus at Home. Help reduce the spread of citrus diseases by not moving your homegrown citrus fruit or plants across state lines. Enjoy your fruit with friends and neighbors, but be sure to obtain a federal certificate if you’re thinking of transporting your citrus outside of your state. To inquire about transporting your citrus out of state, contact your USDA State Plant Health Director’s office.

4. Avoid Fines and Penalties. Because citrus diseases have destroyed millions of acres of citrus around the world, they present an immediate and urgent threat to America. If you knowingly purchase citrus in violation of quarantine regulations and requirements, the penalties you could incur range from $1,100 to $60,000 per violation. If you suspect citrus is being moved improperly, report your concerns to USDA’s Smuggling Interdiction and Trade Compliance (SITC) toll-free hotline at (800) 877-3835.

Asian citrus psyllid feeding

Citrus tree infected with the bacterium causing HLB

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Western Plant Diagnostic Network News

Please see this article by Rick Bostock and the WPDN Team from California Agriculture. It features the work of the NPDN/WPDN and its partners in protecting plant systems:

Plant health: How diagnostic networks and interagency partnerships protect plant systems from pests and pathogens

A Note to the WPDN and First Detectors from the Regional Director Prof. Rick Bostock -

Transition

On January 1, 2017, I will be stepping down as Director of the Western Region of the NPDN. My colleague, Neil McRoberts, will assume the lead role for the project and become the principal investigator of our cooperative agreement with the USDA National Institute for Food and Agriculture (NIFA). Neil is a professor and plant pathologist in my department who brings to the project tremendous expertise in epidemiology. For the past several years he has been working with us on developing analytical tools for the data repository and related efforts. No doubt, Neil will bring fresh ideas and energy as we move forward.

To all of you, I want to express my appreciation for your cooperation and efforts since inception of the project almost 15 years ago. I still vividly recall July of 2002 when the directors of the five regions were tapped and asked to “create a diagnostic network”. We had marching orders but no blueprints. I think it is truly remarkable what together we all accomplished so quickly in conceiving and creating this network, which brought together so many great people at both the regional and national levels. Without you, this would not have happened. Truly a team effort and program we all should be proud of.

I have been with the project since the get-go, and what has kept me going, besides the sense that we are making a difference and accomplishing something important, is the positive spirit I derive from our personal and professional interactions. It has truly been a privilege to work with you. I am especially grateful to my UCD regional center staff, Carla Thomas and Dick Hoenisch, to former staff members, Andrew Coggeshall and Eugene Erickson, and to the team at the Plant Pest Diagnostics Center at the California Department of Food and Agriculture. I also want to give a shout out to my account manager, Wendy Johnson-Mesa, for her able handling of the complex accounting associated with a project of this size with its many subcontracts. Also, I thank our former program managers at USDA, Kitty Cardwell and Marty Draper, for their national leadership and help on so many fronts. Although there will continue to be challenges ahead, I am confident that with Neil’s leadership and your talents that our regional and national networks will continue to thrive in the years ahead.

Rick Bostock

Neil McRoberts

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Western Plant Diagnostic Network News

The Ficus Leaf-Rolling Psyllid A New Pest of Ficus microcarpa

By Donald R. Hodel, Gevork Arakelian, Linda M. Ohara, Cheryl Wilen, and Surendra K. Dara

A psyllid , perhaps new to the Western Hemisphere, has been found on Ficus microcarpa (Chinese banyan, Indian laurel fig) in Los Angeles, Orange, San Bernardino, Ventura, San Diego, and Riverside counties of California. It causes a distinctive, tight, and typically complete rolling of the leaves. Ficus microcarpa is one of the most common, useful, and widespread ornamental landscape trees, and has long been a target for numerous pests. The psyllid was first detected on trees in Carson south of Los Angeles in February, 2016. This psyllid was identified as the Ficus leaf-rolling psyllid (FLRS), to be in the family Triozidae and identified as Trioza brevigenae .

Damage is fairly obvious and unusually conspicuous on heavily infested trees. Leaves at the branch and twig tips are tightly and typically completely rolled into a narrow cylinder, sometimes eventually compressed to only about 3-5 mm in diameter. The rolling process begins at the distal end or leaf apex and, like two cresting waves, progresses adaxially (upper leaf surface) along each margin and proximally toward the leaf base.

Because the FLRP is likely a new arrival, we know nothing about its long-term impact on tree health. If damage is mostly restricted to few or several leaves, long-term health would likely not be significantly affected; in such cases it could be considered simply a nuisance esthetic issue. On the other hand, if most or every new leaf is infested and rolled, as it appears it is going to be on at least one of the trees we saw, esthetic damage would be significant and tree health would likely decline because of reduced photosynthesis. The FLRP appears to be nearly exclusively attracted to the newest developing leaves, which are softer, more pliable, and easier to roll, rather than simply the leaves’ position on the canopy periphery where they would be first encountered. If further study shows this observation to be true, it will impact how this pest can be managed culturally and mechanically.

The complete article with excellent photos can be found at: Ficus leaf-rolling psyllid: a new pest of Ficus microcarpa in southern California

Leaf rolling by the ficus leaf-rolling psyllid, Trioza brevigenae.

Ficus microcarpa is one of the most common and useful landscape trees

common

Adult Ficus leaf-rolling psyllid

Adult Ficus leaf-rolling psyllid Compare this with the ACP on p. 5

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Western Plant Diagnostic Network News

Asterococcus sp. prob. yunnanensis, Borchsenius (Hemiptera: Cerococcidae)

A New Exotic Scale Insect Pest in Hawaii and the U.S. By Janis N. Matsunaga, Hawaii Department of Agriculture

The host vary over a wide range of botanical families. Rhaphiolepis indica (Rosaceae), or Indian hawthorn, a very common landscape shrub (pictured above), is the preferred host in the Waimea area. Gardenia taitensis (Rubiaceae), commonly known as Tahitian gardenia, and Rhododendron sp. (Ericaceae) are also hosts in Waimea. According to Scalenet, hosts also include Chinese wingnut, Pterocarya stenoptera (Juglandaceae ), Cinnamomum camphora (Lauraceae), and Rosa (Rosaceae). Ornate pit scale feeding can cause twig die-back, premature loss of foliage, and the death of the plant. Copious amounts of honeydew is excreted, inducing the growth of sooty molds. Thick layers of sooty mold cover the leaves and stems of woody plants, negatively affecting photosynthesis.

A new exotic scale insect was found in Waimea, Hawaii County, on 28 August 2015. It was collected by the Hawaii Department of Agriculture and identified by an entomologist in Cardiff, Wales who specializes in scale insects in the family Cerococcidae, Christopher J. Hodgson. So far he scale is limited to Waimea. It is native to China, named after Yunnan province. This discovery represents the first Hawaii and U.S. record of any Asterococcus species, as well as the first species of the Cerococcidae family to be established in Hawaii. The common name is ornate pit scale. Adult females produce a protective waxy test that shields their body. They hatch in the spring and emerge through a small hole at the back. These first instars are ambulatory and disperse around the host plant. Second instars appear early in the summer and adults towards the end of summer, with egg-laying taking place in the autumn. Males occur in most species.

Sooty mold developing from the scale honeydew on Rhaphiolepis

indica

Magnified mature female scales in alcohol Immature scales Scale on woody stem of

Rhaphiolepis indica

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Boxwood Blight in Washington State

In the Fall 2012 Newsletter, pages 2 -3, the fungal disease, boxwood blight was featured. The disease is caused by the fungus Cylindrocladium pseudonaviculatum. There are several informative links in the article. Washington State University Cooperative Extension reports that boxwood blight is now in the Seattle area. On the West Coast it is in British Columbia, Oregon, and now in Washington. It is very important, especially for commercial nurseries, to understand the disease.

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Western Plant Diagnostic Network News

Ditylenchus dipsaci, stem and bulb nematode, discovered on Garlic in the Rio Grande Valley of New Mexico

Jason M. French, Jacki Beacham, Amanda Garcia, Natalie P. Goldberg, Stephen H. Thomas, and Stephen F. Hanson – New Mexico State University

Ditylenchus dipsaci, called the stem and bulb nematode, is a serious temperate-climate nematode pest of over 500 plant species in over 40 plant families, including alfalfa, onions, and garlic. Among plant-parasitic nematodes, it ranks fifth in economic importance and is a quarantine pest of international concern. In 2015, New Mexico harvested 190,000 acres of alfalfa hay with a value of over $188M and is the eighth largest producer of onions in the U.S. cultivating 5,200 acres in that year with a crop value of $91M. These two crops rank number 1 and number 3, respectively, for highest grossing crops in NM in 2015. New Mexico also has a vibrant small farm garlic industry that supplies local markets with fresh garlic and seed for producers. New Mexico has never reported an infestation of D. dipsaci and its presence could have serious ramifications for NM’s alfalfa, onion, and garlic, and producers.

In May of 2015 garlic plants (Allium sativum) from a home garden in were submitted to the Plant Diagnostic Clinic at New Mexico State University. The grower reported poor growth in ~30% of 1,200 plants originating from seed purchased in southern New Mexico. Early symptoms included chlorosis, wilting, and poor root and bulb development. As the disease progressed, roots turned brown, were easily separated from the bulb, and older foliage had collapsed and turned straw colored (Figure 1). Microscopic examination showed large numbers of nematodes present in symptomatic garlic plants. Based morphological characteristics of the nematode and the DNA sequence of the ITS-1 region, the nematodes were identified as D. dipsaci.

This discovery is highly significant as this nematode has the potential to cause significant economic losses on agriculturally important hosts grown in the state and in the region. The longevity of this pest in the soil and international trade issues are major concerns for producers. Based on information from the grower it appears that this is an isolated introduction from infested plant material which can potentially be contained as the presence of D. dipsaci was discovered before any material was harvested or distributed. Monitoring of production areas in the state will be performed to determine if this was an isolated and contained introduction or if this important pest has become established in NM.

Figure 1. Left: From left to right,

two garlic plants exhibiting severe

symptoms of Ditylenchus dipsaci

infection compared to healthy plant

on the right. The plants exhibit leaf

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progressive loss of functioning

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Western Plant Diagnostic Network News

Fig.1 Fusarium oxysporum (C) and Fusarium solani (D) were detected from marijuana plants

(Cannabis sativa). Infected plants generally show wilting symptom and poor uptake of

nutrients from soil. Internal reddish brown streaks occur typically at the base of stem and are

visible by breaking the stem (A) or by longitudinal or cross sectioning (B-right).

A C

B D

Fusarium Wilt of Cannabis Plants Jennifer Schoener and Shouhua Wang

Nevada Department of Agriculture Plant Pathology Laboratory (NDA-PPL)

Fusarium is a genus of fungal pathogen that kills diverse crops. Fusarium oxysporum is a species complex that has

many formae speciales (f. sp.), each of which only infects specific plant species, causing vascular wilt, rot or

damping-off diseases. F. oxysporum f. sp. cannabis has been reported to be specific to Cannabis species, so it has

been suggested as a biocontrol agent for unwanted cannabis plants.

We recently detected both Fusarium oxysporum and Fusarium solani from submitted cannabis plant samples.

Infected plants showed symptoms of chlorosis, wilting, and the lack of response to nutrients in soil. Lab analysis

using culture morphology and DNA sequencing of ITS region confirmed the infection of F oxysporum (Fig. C) and

F. solani (Fig D) on two different varieties, respectively.

Cannabis species are very susceptible to Fusarium infection. Infected plants become systemically wilted and may

eventually die. The pathogen survives in soil, infected plant materials, or mother plants. Early diagnosis and

timely eradication is the key to keep the growing facility free from this disease.