May / June 2021
The Potential of Ultraviolet Light to Suppress Grapevine Powdery Mildew
Developing a Nitrogen Fertilizer Plan for Olive Orchards
Soil Health on Every Farm
Transitioning from Hand to Machine Harvesting of Blueberries
May/June 2021 VINEYARD REVIEW Pages 37-51
2021 DAY REGISTER NOW See Agenda on Pg. 16
Volume 6: Issue 3
Photo courtesy of David Gadoury, Cornell Agritech. Avocado Invasive Insect Pests Current, Potential and Recent Threats to Southern California’s Avocado Industry
By SONIA RIOS | UCCE Subtropical Horticulture Farm Advisor, Riverside and San Diego Counties AKIF ESKALEN | UCCE Specialist, Grapevine, Fruit Trees and Small Fruits Pathology MARK S. HODDLE | UCCE Specialist, Biological Control, UC Riverside
lobally, invasive insect pests for the most part, have been under ade- Diego region but has since spread to cause substantial damage to agri- quate levels of biological control (Hoddle Orange, Los Angeles, Ventura and Santa Gcultural crops and natural environ- 2005). However, due to the increase of Barbara counties. Presumably, PSHB and ments. In the U.S. alone, crop and forest international trade, illegal importation KSHB were introduced accidentally into production losses from invasive insects and the smuggling of foliage, branches Southern California via wooden products and pathogens have been estimated at with leaves, whole plants and budwood, and/or shipping material (e.g., pallets and almost $40 billion per year (Pimentel et invasive insect and mite pests have begun dunnage) from Southeast Asia. KSHB is al. 2005). On average, a new non-native to threaten the economic viability of morphologically indistinguishable from invertebrate is introduced into California avocado production in California. PSHB, but species can be separated using every 40 days. With respect to insects and molecular techniques. mites, about one-third of these become Polyphagous and Kuroshio pests (Dowell et al. 2016), and economic Shot Hole Borers The fungus gets into the woody tissue of losses in California are estimated at more Polyphagous Shot Hole Bore (PSHB) the tree when a female PSHB excavates a than $3 billion per year (Metcalf 1995). is an invasive ambrosia beetle from gallery and inoculates the gallery walls Southeast Asia that was first detected in with fungal spores that it carries in spe- Rapid growth of U.S. demand for fresh Los Angeles County in 2003 (Gomez et al. cial structures called mycangia (Beaver, avocados has increased the fruit’s promi- 2018, Rabaglia et al. 2006). PSHB is a pest 1989). The female PSHB and her offspring nence in retail sales and diets. California of great concern in Southern California feed exclusively on the fungal spores. is the largest producer of avocados grown as it can attack over 300 tree species and PSHB adults engage in sibling mating in the U.S. The value of U.S. avocado reproduce on a subset of these that are within the natal gallery. Offspring sex production measured at approximately capable of supporting beetle reproduc- ratios are female biased to maximize re- $392 million in 2017, (NASS, 2018). There tion and growing the fungi that cause productive output such that one male can are more than 3,000 avocado growers fusarium dieback. inseminate many of his female siblings. in the state farming on approximately Once fully developed and mated, female 50,000 acres of land, with Ventura Coun- PSHB has a strong symbiotic relationship PSHB exit their natal gallery to start a ty leading the state in most acres planted with several fungi, including Fusarium gallery of their own and repeat the cycle. and harvested in recent years (California euwallaceae and Fusarium kuroshium, Unlike their sisters, male PSHB do not Avocado Commission [CAC], 2020). the causal agent of Fusarium Dieback disperse since they are not capable of fly- (FD) disease (Eskalen et al. 2013). The ing and do not possess mycangia, which California avocados are particularly list of reproductive hosts includes several are specialized structures for fungus special because less than 1% of the state native oaks, maples, sycamores, willows storage. is suitable for growing them. A healthy, and avocado. The fungus disrupts the single ‘Hass’ avocado tree can produce vascular transport of water and nutrients Pesticide efficacy may be limited, and up to 200 pounds of fresh fruit each on their host tree that eventually caus- this is attributed to the fact that PSHB year, which is ~500 pieces. In 2018 alone, es branch dieback. The most common feeds on fungi and not directly on wood California produced around 350 mil- symptoms of the disease include sugar tissue. This reduces exposure to active lion pounds. Avocados are considered a or gum exudates, dieback, wilt and ingredients when feeding (Eatough specialty crop and are not cheap to grow ultimately host tree mortality. Reports Jones et al. 2017). Cultural management because of water and land costs, and of dieback symptoms in El Cajon, San practices include: 1) removal of infected fruit therefore usually demands a high Diego County led to the discovery of branches to reduce local beetle numbers premium price. another species, the Kuroshio shot hole and fungal spread in the infested area; borer (KSHB) in 2013. 2) chipping (< 1 inch) and solarizing in- Traditionally, insecticide use in Califor- KSHB is also present in commercial fested wood; and 3) avoiding movement nia avocado orchards has been minimal avocado orchards in San Diego County. of infested materials to new areas (if due to relatively few pest species, which, KSHB was originally limited to the San
26 Progressive Crop Consultant May / June 2021 Beetle gallery formation in an avocado branch (photo by A female PSHB boring (photo by A. Eskalen.) A. Eskalen.)
transportation of materials is necessary, more information regarding PSHB, visit This beetle has been slowly spreading it must be covered(UC IPM 2017). ucanr.edu/sites/pshb/. across the southeastern U.S. and is currently found as far west as east Texas. These management strategies can perhaps Redbay Ambrosia Beetle Therefore, California growers need to abate the severity of local infestations. and Laurel Wilt Complex be aware that this pest-disease complex Also, limiting the spread of infected/in- An invasive ambrosia beetle, the redbay may spread to California avocados. What fested trees include minimizing firewood ambrosia beetle (RAB; Xyleborus glabra- makes this complex dangerous is that the transportation. Sterilizing pruning tus) is a serious pest currently spreading vector, RAB, has a symbiotic relation- tools with household bleach or another through the Florida avocado industry ship with the fungal pathogen Raffaelea cleaning solution can reduce the spread and has been responsible for significant lauricola that causes Laurel Wilt Disease of the FD pathogen. The PSHB was found yield reductions since its discovery in (LWD). Native to Southeast Asia, RAB in Israel in 2009 in commercial avocado 2005. The beetle was first detected in the has similarities to our current ambrosia orchards where it damages trees. To date, U.S. in Port Wentworth, Ga. in 2002 and pest, PSHB. However, the fungus as- there has been no avocado tree fatality was probably introduced via infested due to the PSHB or FD in California. For wooden packaging material (Crane 2011). Continued on Page 28
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May / June 2021 www.progressivecrop.com 27 Continued from Page 27 may mate with their male offspring or sociated with LWD is unlike the disease brothers to produce males and females. here in California. Trees become infected Females greatly outnumber males in when female beetles attack host trees and populations. In the Southeast U.S., introduce the pathogen into the xylem RAB’s lifecycle from egg to adult appears while boring their galleries. The infection to take 50 to 60 days, and there appear to restricts the flow of water in the tree, be multiple overlapping generations per induces a black discoloration in the outer year (Hanula et al. 2008). Female beetles sapwood and causes the leaves to wilt. emerging from galleries may reinfest the ® Tree mortality is so rapid that leaves do same tree or disperse in search of new not fall from dying branches. hosts. Host trees can remain standing Severe Laurel wilt vascular staining on avocado (photo by A. Eskalen.) for years and may continue to serve Symptoms of RAB beetle and LWD infes- as host material for beetles for several tations include (Carrillo et al. 2017): months after initial colonization. Flight activity peaks in the late afternoon and Zinc-Shotgun® is a fertilizer that focuses on • Wilting of leaves and young stems. early evening. micronutrients to satisfy needs of customers You can usually see dead leaves hanging on branches. It is known that ambrosia beetles are seeking high zinc with manganese, iron and notoriously difficult to control with copper. The micronutrients are completely • Color change in leaves from light insecticides because they are protected We Are Here to Help chelated with natural organic acids, amino green to dark purplish green or from residues by living inside the tree greenish brown. most of their life versus being outside Call: 209.720.8040 acids, and carbohydrates that are readily the tree. RAB can fly short distances, Visit: WRTAG.COM bio-degradable and supply energy to the • Stem and limb dieback. but LW fungus spreads more quickly through the movement of insect-infest- plant and soil microflora. Many soils are low • Trunk and major limbs that ed plant material, such as firewood. Laurel wilt branch die back on avocado (photo by in zinc and also require other micronutrients show dried sap which has a white S. Rios.) for the growth of good crops. appearance and is a crystalline, Additionally, the pathogen also spreads powder-like material. to other ambrosia beetle vectors. This happens when beetles feed on diseased • Dark streaks in the sapwood. trees and become contaminated with Normally sapwood should be white spores of R. lauricola. Spread can also to yellowish white in coloration occur through root grafting between Organically complexed with plant with no dark staining or streaking. trees. Sanitation is the most effective way based amino acids, organic acids, To check for this symptom simply to manage this problem. Scouting for Zn and complexed polysaccharides. remove a section of the bark to wilted branches and quickly removing check for discoloration, which, them has been key to successful early if present, may indicate fungal intervention and eradication. infection. It has been suggested to remove symp- • Small, dark holes in the sapwood tomatic trees immediately upon their Mn and what looks like loose wood identification. However, once the RAB entry holes in avocado (photo by S. Rios.) dust and frass indicate wood boring appearance of frass and streaks start to Fe beetles are present. show in the wood, this is a sign that the tree has already been infected and has LWD affects redbay Persea( borbonia) been for some time. As soon as a grower and other tree species of the Laurel sees the wilt in the branches, it’s time family (Lauraceae), including avocado. to move quickly. Verticillium wilt and R. lauricola is introduced into host trees Phytophthora root rot can be mistaken Cu when adult RAB colonizes a tree. Adult for LW, so avocado growers should check RAB are very small (~1/16-inch-long), for these diseases before removing trees. dark brown to black in color and spend most of their life within the tree. Larvae The Florida avocado industry has are white, legless grubs with an amber implemented a universal detection and colored head capsule and are found with- suppression program with the goal of in galleries throughout infected trees. Fe- preventing or limiting the incidence of Complete, organically complexed Designed to be applied both by male beetles can produce flightless male The present of frass indicates the presents of RAB micronutrient package containing foliar application and fertigation offspring without mating, but females Continued on Page 30 (photo by A. Eskalen.) essential elements to improve plant The nutrients are readily absorbed practices and is also eective health and growth. by the plant for a faster response. when applied directly to the soil. 28 Progressive Crop Consultant May / June 2021 ®
Zinc-Shotgun® is a fertilizer that focuses on micronutrients to satisfy needs of customers seeking high zinc with manganese, iron and copper. The micronutrients are completely We Are Here to Help chelated with natural organic acids, amino Call: 209.720.8040 acids, and carbohydrates that are readily Visit: WRTAG.COM bio-degradable and supply energy to the plant and soil microflora. Many soils are low in zinc and also require other micronutrients for the growth of good crops.
Organically complexed with plant based amino acids, organic acids, Zn and complexed polysaccharides.
Mn Fe
Cu
Complete, organically complexed Designed to be applied both by micronutrient package containing foliar application and fertigation essential elements to improve plant The nutrients are readily absorbed practices and is also eective health and growth. by the plant for a faster response. when applied directly to the soil. Continued from Page 28 commercial formulations of insecticides leaves. Through feeding, leaf cells and LW in commercial groves and depressing can be effective in controlling the beetle. pierced cell contents are extracted and ambrosia beetle populations (Carrillo et. For more information regarding LW and ingested, preventing photosynthesis. al 2017). Surveying for the symptoms of RAB, please visit sfyl.ifas.ufl.edu/mi- LW is a key component to limiting the ami-dade/agriculture/laurel-wilt---a-dis- Adult avocado lace bugs are small, spread of the disease. Growers and their ease-impacting-avocados/. winged insects, about 2 mm in length workers should survey groves weekly or (slightly longer than 1/16 in), with black more often if an infestation is detected Avocado Lacebug bodies, yellow legs and antennae, and are in an adjacent grove. Early detection, The avocado lacebug (ALB), Pseudacysta visible to the naked eye (UC IPM 2021). removal and destruction of LW affected perseae (Hemiptera: Tingidae), was first ALB live in colonies on the lower surfaces trees is the most important practice for detected in California on backyard avo- of mature leaves, often adults, eggs and controlling LW. cado trees in Chula Vista and National nymphs are found together. Eggs are City, San Diego County in 2004. This laid in an irregular pattern, sometimes Contact insecticides are ineffective pest was first described in Florida in 1908 in loose rows, attached to the lower leaf because the pathogen vectors (i.e., the and has since been reported from Mexico, surface and are covered with irregular ambrosia beetles) are primarily inside the Guatemala, Puerto Rico, Jamaica, the globules of a black, sticky, tar-like sub- tree. The first goal is to avoid infestation Dominican Republic and parts of north- stance excreted by adults. To the naked with the beetles by maintaining a healthy eastern South America. The native range eye, eggs will appear like grains of black tree as stressed trees are more attractive of ALB is uncertain. Molecular studies pepper or dirt. to colonizing beetles. Beetles prefer trees suggest that the western areas of Mexico in orchards that have dense canopies may be the evolutionary center of origin Eggs hatch into wingless nymphs that are with overlapping leaves and branches. for this pest and it was spread uninten- capable of walking. Nymphs go through tionally from this area, probably on av- a gradual metamorphosis, shedding their Chipping infected trees is effective in re- ocado trees into eastern Mexico, Florida exoskeleton several times as they grow in ducing the spread of the disease. Howev- and the Caribbean (Rugman-Jones et al. size, finally developing wings and becom- er, chips must be as small as possible (one 2012). ing flying adults. Nymphs are dark red- square inch or smaller) and dried quickly brown to black and covered with spines. so that the wood is not conducive to fun- After a lull of approximately 13 years, They feed for approximately two to three gal growth. A potential drawback to this reports started coming of ALB damage weeks before maturing into adult males method is that the aroma of the chipped to avocados outside of San Diego. In Oc- and females which mate, and females wood can attract other wood boring tober 2017, well established, reproducing then lay eggs, starting the cycle over. In insects. Research in Florida is currently populations of lace bugs were confirmed California, ALB populations tend to peak being conducted to determine if different in commercial Hass avocado groves in over early summer, around June, then Oceanside and De Luz in San decline in fall, sometime around Septem- Diego County and in Temecula ber (Humeres et al. 2009). in Riverside County (CAC, 2017). Around this time, infestations ALB restrict their feeding to the under- were reported from backyard sides of leaves. Feeding initially causes avocados in Culver City in Los small white or yellow spots on the Angeles County. Genetic analysis surface of the leaves as individual cells suggested that these new, more dry out. These necrotic areas look like damaging populations of ALB tip-burn caused by excessive salts, but in were different to those originally this case, the necrotic areas are islands detected in San Diego in 2004, and of dead tissue in the interior of the leaf it’s likely that a second introduc- surrounded by living tissue. It is sus- tion of ALB into California has pected that feeding damage can provide occurred, possibly from Florida entrance for pathogenic fungi, in particu- (Rugman-Jones and Stouthamer lar Colletotrichum spp., which are leaf unpublished molecular data). anthracnose fungi. As lace bug colonies grow, brown necrotic areas develop ALB has been recorded feeding where there has been heavy feeding dam- on avocado, red bay and camphor, age. Heavy feeding can cause striking leaf which are all in the Lauraceae discoloration and early leaf drop (Hoddle family. 2004; Hoddle et al. 2005). Avocado lace Avocado lace bug is a true bug bug nymphs and adults do not feed on with sucking mouth parts. Lace fruit. However, heavy feeding damage to Avocado lace bug adult and eggs (photo by M. Hoddle.) bugs use these needle-like mouth- leaves will likely have a detrimental effect parts to feed on the undersides of on yield, which may result from the loss
30 Progressive Crop Consultant May / June 2021 of photosynthetic capacity in damaged leaves.
Relatively little is known about biology and ecology of ALB in California. In Florida, the most important biological control agents are two egg parasitoids including Oligosita sp. (a Trichogramma- tid wasp) and an unidentified mymarid wasp. Green lace wing larvae and other generalist predators are also thought to Severe feeding damage to avocado leaves caused by avocado lace bug (photo by M. be important natural enemies. A preda- Hoddle.) tory thrips, Franklinothrips vespiformis,
is reported to be the most important Hughes, M.A., Smith, J.A., Ploetz, R.C., Kendra, P.E., Mayfield, A.B., Hanula, J., Hulcr, natural enemy of the avocado lace bug in Ideally, finding a new pest species in the J., Stelinski, L.L., Cameron, S., Riggins, J.J. and Carrillo, D. 2015. Recovery plan for lau- rel wilt on redbay and other forest species caused by Raffaelea lauricola and the Dominican Republic and is similarly early stages of the invasion and quickly disseminated by Xyleborus glabratus. Plant Health Progress, 16(4), pp.174-210. abundant on ALB-infested avocados in containing and treating the new in- Humeres, E. C., Morse, J. G., Stouthamer, R., Roltsch, W., & Hoddle, M. S. 2009a. Escuintla Guatemala. festation may reduce costly long-term Detection surveys and population monitoring for Pseudacysta perseae on management, especially if eradication is avocados in southern California. Florida Entomologist 92(2): 382-385.
Insecticide treatments for other sucking possible. Rapid and decisive containment Humeres, E. C., Morse, J. G., Stouthamer, R., Roltsch, W., & Hoddle, M. S. 2009b. pests currently registered for use on actions are an important consideration as Evaluation of natural enemies and insecticides for control of Pseudacysta perseae (Hemiptera: Tingidae) on avocados in Southern California. Florida avocado in California will likely provide controlling invasive pests, especially fruit Entomologist, 92(1), 35-42. control of avocado lace bugs (Hoddle et feeders, in California avocado orchards Lu, M., Hulcr, J., and Sun, J. 2016. The role of symbiotic microbes in insect inva- al. 2005). In a trial reported in 1998, J. E. will always be a challenge and expensive sions. Annual Review of Ecology, Evolution, and Systematics, 47, 487-505. Peña, University of Florida (UF), showed should they establish widely. Mayfield, A.E. III, Barnard, E.L., Smith, J.A., Bernick, S.C. , Eickwort, J.M., and T.J. that citrus oil, M-Pede (insecticidal Dreaden. 2008. Effect of propiconazole on laurel wilt disease development in red- soap) and Mycotrol (a Beauveria fungal References bay trees and on the pathogen in vitro. Arboriculture & Urban Forestry 35: 317-324
species) all controlled lace bug, but it was Mayorquin, J. S., Carrillo, J. D., Twizeyimana, M., Peacock, B. B., Sugino, K. Y., Na, Byrne, F. J., Almanzor, J., Tellez, I., Eskalen, A., Grosman, D. M., & Morse, J. G. 2020. F., and Eskalen, A. 2018. Chemical management of invasive shot hole borer and not indicated how long the effect lasted. Evaluation of trunk-injected emamectin benzoate as a potential management Fusarium dieback in California sycamore (Platanus racemosa) in southern strategy for Kuroshio shot hole borer in avocado trees. Crop Protection, 132, 105136. Researchers at UF have shown that citrus California. Plant disease, 102(7), 1307-1315. oil and M-Pede provided short-term lace Byrne, F. J., Humeres, E. C., Urena, A. A., Hoddle, M. S., and Morse, J. G. 2010. Field Mead, F. W., and Peña, J. E. 2016. Avocado lace bug, Pseudacysta perseae evaluation of systemic imidacloprid for the management of avocado thrips and bug control. Results of small tree trials (Heidemann)(Insecta: Hemiptera: Tingidae). Entomol. Circ, (346). avocado lace bug in California avocado groves. Pest management science, 66(10), or weathered residue tests have indicated 1129-1136. Metcalf, R. L. 1995. Invasion of California by exotic insects. California Agriculture that carbaryl, imidicloprid, cyfluthrin, 49(1): 2. Carrillo, D., J. Crane, R. Ploetz, E. Evans, and J. Wasielewski. 2017. Brief Update to carbaryl, fenpropathrin and malathion Laurel Wilt Recommendations – Ambrosia Beetles. Univ. of Florida, IFAS Extension Pimentel D, Zuniga R, and Morrison D. 2005.Update on the environmental and Notice. provide excellent control of avocado lace economic costs associated with alien-invasive species in the United States. Ecol Econ 52(3):273–288. bug nymphs. Spinosad, abamectin and Crane, J. (2011) Laurel Wilt and the Redbay Ambrosia Beetle threaten Florida’s avocado and native trees in the Laurel Family. Univ. of Florida, IFAS Extension mineral oil are much less effective at Ploetz, R. C., Pérez‐Martínez, J. M., Smith, J. A., Hughes, M., Dreaden, T. J., Inch, S. A., Homeowner informational brochure. providing control (Humeres et al. 2009b; and Fu, Y. 2012. Responses of avocado to laurel wilt, caused by Raffaelea lauricola. Plant Pathology, 61(4), 801-808. Byrne et al. 2010). For more information Coleman, T. W., Poloni, A. L., Chen, Y., Thu, P. Q., Li, Q., Sun, J., and Seybold, S. J. 2019. Hardwood injury and mortality associated with two shot hole borers, Euwalla- Rios, S., B. Faber, P. Mauk, A. Eskalen, and M.L. Arpaia. 2018. Redbay Ambrosia Bee- on lace bugs, please visit biocontrol.ucr. cea spp., in the invaded region of southern California, USA, and the native region tle Poses Potential Threat to California’s Avocado Industry. California Association of of Southeast Asia. Annals of Forest Science, 76(3), 1-18. edu/avocado-lace-bug. Pest Control Advisors. February 2018. 22(1):36-38, Pp 36-38. Dowell, R. V., R. J. Gill, D. R. Jeske, and M. S. Hoddle. 2016. Exotic macro-inverte- Rivera, M. J., Martini, X., Conover, D., Mafra-Neto, A., Carrillo, D., & Stelinski, L. brate invaders in California from 1700 to 2015: An analysis of records. Proceedings Proactive Management L. 2020. Evaluation of semiochemical based push-pull strategy for population of the California Academy of Sciences Series 4 63(3): 63-157. and Early Detection suppression of ambrosia beetle vectors of laurel wilt disease in avocado. Scientific reports, 10(1), 1-12. The concept of early detection and rapid Hanula, J.L, Mayfield, A.E. III, Fraedrich, S.W., and Rabaglia, R.J. 2008. Biology and host associations of the redbay ambrosia beetle, (Coleoptera: Curculionidae: Rugman-Jones, P. F., M. S. Hoddle, P. A. Phillips, G. Jeong, & R. Stouthamer. 2012. response is fundamental to effective in- Scolytinae), exotic vector of laurel wilt killing redbay trees in the southeastern Strong genetic structure among populations of the invasive avocado pest United States. Journal of Economic Entomology 101: pp. 1276-1286. vasive species management. Developing Pseudacysta perseae (Heidemann) (Hemiptera: Tingidae) reveals the source of introduced populations. Biological Invasions 14: 1079-1100. collaborative relationships with avocado Hoddle, M. S. 2004. Invasions of leaf feeding arthropods: why are so many new pests attacking California-grown avocados? California Avocado Society research colleagues in different countries University of California Integrated Pest Management Guidelines for Avocado Yearbook, 87, 65-81. can provide insight into new potential
May / June 2021 www.progressivecrop.com 31