Friday, April 20, 2018
University of Hawaii at Manoa
University of Hawaii System
College of Tropical Agriculture and Human Resources
 

Research Presentations at Scientific Conferences



Key On-Going and Recent Research Projects



Control of stem and leaf gall wasps on Chinese banyan

A new species of fig gall wasp was discovered on University of Hawaii at Manoa campus recently in 2012. This wasp attacks Chinese banyan (Ficus microcarpa), a common landscape tree species in Honolulu and other tropical regions of the world, and forms galls on stems. It appears to be in the same family and genus (Agaonidae, Josephiella spp.) as the Chinese banyan leaf galling wasp (Josephiella microcarpae). Wasp infestation results in progressive dieback of stems, causing canopy to thin out, thus may eventually cause tree mortality.

We conducted an applied research project to identify the effective means to control these two gall wasp species. Forty-five Chinese banyan trees on University of Hawaii at Manoa campus were included in this study. Nine trees (replications) were randomly assigned to each of the 4 treatments and the control. Trunk injection was used to deliver systemic pesticides. A peer-reviewed paper on this project was published in 2016. We are currently continuing research on these wasps with new treatment strategies.


               
Lobate lac scale control

Lobate lac scale (Paratachardina pseudolobata), was first discovered on Oahu at Moanalua Garden on weeping banyan (Ficus benjamina) recently in 2012. The resinous secretion of this insect makes sooty mold on leaves and stems and gives unhealthy appearance. The major effects on host plants are dieback of twigs and branches, thinning of foliages, and death of entire plant in some species. Our host survey indicates that over 110 plant species on Oahu are host plants of lobate lac scale, among which weeping banyan and Chinese banyan are heavily infested. We conducted an applied research project to test the effectiveness of imidacloprid delivered through trunk injection in controlling lobate lac scale using 45 Chinese banyans and 10 weeping banyans on UH Manoa campus. A manuscript on this project was recently accepted and is now in press. We are currently continuing research on this pest with new treatment strategies using 25 weeping banyans on UH Manoa campus and at a golf course.

Statewide survey of lobate lac scale and its host plants

Prior to our state-wide survey, lobate lac scale (LLS) is only confirmed on Oahu. But, given the frequency of inter-island, Hawaii-U.S. mainland, and international transports of travelers and goods, lobate lac scale is very likely to spread, and eventually disperse to neighbor islands in Hawaii, and even to U.S. mainland. Therefore, I recently secured funding from USDA and local source to survey LLS on all major islands in Hawaii (Big Island, Maui, Kauai, Molokai, and Lanai) focusing on urban landscapes where LLS infestation is the most severe on Oahu. When surveying LLS on Big Island on May 05, 2016, we confirmed lobate lac scale on several potted Junipers in the Garden Center of a big box store. This was the first incidence that lobate lac scale was confirmed on a neighbor island outside of Oahu. Later, LLS was confirmed by HDOA staff on Maui. Further in January 2017, we found lobate lac scale on several potted plants in the Garden Center of a big box store in Lihue, the first confirmed incidence of this pest on Kauai. A manuscript on this project was submitted and under review.


(image generated from Google maps)
                      
Suppressing Bermudagrass in seashore paspalum turf

An emerging management challenge of seashore paspalum turf installations and maintenance in Hawaii in recent years is the infestation of the bermudagrass cultivar that was replaced or common bermudagrass. PI Z. Cheng and Co-PI J. DeFrank continue to receive inquiries from golf courses that use seashore paspalum to develop new grassy weed control options that do not depend on salt applications. This project will address this immediate need of Hawaii's turf/golf industry. An M.S. student (A. J. Lindsey) who started in August 2016 is working on this 2-year project. Bench experiment and field trials are currently being conducted in UH Manoa Magoon research facility, West Loch Golf Course, and Hoakalei Country Club.

Biological and chemical control of coconut rhinoceros beetle

The coconut rhinoceros beetle (CRB;Oryctes rhinoceros) is a large scarab beetle native to southeast Asia and a damaging pest of palm species, most notably coconut palm (Cocos nucifera). Adult CRBs were first found at the Honolulu International Airport (HNL) and the adjacent Joint Base Pearl Harbor-Hickam in December 2013. CRB has been identified by USDA-APHIS as one of the most damaging invasive insect pests of coconut and other palm species whose introduction could result in significant economic losses to commercial coconut and palm nurseries, as well as Hawaii’s residents and tourists who value palm trees for their aesthetic value.

On-going CRB research in my lab focuses on biological and chemical control. Entomopathogenic nematodes and fungi were collected from Oahu and bio-assays against CRB larvae are being conducted. Low-risk systemic insecticides are also being tested in both lab assays and field trials against CRB adults.

  
Image by Dr. Arnold Hara (UH Manoa)
                     
Non-chemical light exclusion approach for turf renovation and weed/pest control

Turfgrass weed control in Hawaii is challenging. Many weed species traditionally classified as “annual” act as perennials in Hawaii, competing with turfgrass throughout the year for water, nutrients and light, and growing larger robust plants with succeeding years. As a result, sometimes turf renovation is necessary. Traditional turf renovation usually uses a non-selective herbicide (such as glyphosate) to kill the existing weeds and turf. However, in some sensitive turf areas such as high-profile golf courses, public school fields, public parks, and private residences, non-chemical means of turf renovation are gradually gaining attention.

One of the non-chemical ways to control weeds is through light exclusion. This method works the best in areas with warm temperatures, making it a feasible approach in Hawaii. This method also has potential to suppress some turf pathogens and insect pests. This project provided research-based data to evaluate the application of this turf renovation and weed/pest control approach. This was Jennifer's M.S. thesis project at UH Manoa. Dr. Joe DeFrank (TPSS) was the Co-PI of this project. A manuscript on this project was submitted and under invited revision.

Management of take-all patch of turfgrass in Hawaii

Take-all patch, or take-all root rot, is a root fungal disease of turfgrass. When the host turfgrass is Bermudagrass, this disease is also commonly called Bermudagrass decline or Bermudagrass winter decline. In 2015 and 2016, I confirmed this disease at multiple golf courses on Oahu, Big Island, and Maui. The causal pathogen is commonly considered to be Gaeumannomyces graminis var. graminis. Its major hosts are warm-season turfgrasses, including Bermudagrass, seashore paspalum, zoysiagrass, St. Augustinegrass, and centipede grass. It most occurs on stressed, closely mowed turfgrass, such as golf greens. In Hawaii, this disease most occurs on bermudagrass and seashore paspalum, two turfgrass species mainly used for golf course greens.

Through meetings and discussions with golf course superintendents, chemical and technical sales representatives, and a brief turf pest management survey in Hawaii, it became clear that more research and education were needed to manage take-all patch of turfgrass in Hawaii’s tropical environment. Therefore, in collaboration with several golf courses on Big Island, Oahu, and Maui, and two major chemical companies, I conducted applied research trials on both Bermudagrass and seashore paspalum to evaluate various fungicide programs against this disease in 2015 to 2016.




                     


Management of leaf and sheath spot (mini ring) of turfgrass in Hawaii


Leaf and sheath spot, a turfgrass fungal disease, is a relatively less studied turfgrass disease in Hawaii, mainly because it is uncommon in occurrence. It is sometimes also called leaf and sheath blight, or simply mini ring. The causal pathogen is commonly considered to be Waitea circinata var. zeae, more commonly known as Rhizoctonia Zeae. In Hawaii, the common turfgrass hosts of this pathogen are bermudagrass and seashore paspalum. Through meetings and discussions with golf course superintendents, chemical and technical sales representatives, and a brief turf pest management survey in Hawaii, it became clear that more research and education were needed to manage this turfgrass disease. Therefore, in collaboration with a golf course on Maui and with industry support, I conducted an applied research project to evaluate various fungicide programs against this disease from June to October 2015. Seven treatments and an untreated control with four replications each were included in this field research.

 

Management of Rover ant, a nuisance pest of Hawaii's golf courses

Rover ant (Brachymyrmex sp.) alate (winged forms of the ant) swarms have been a seasonal nuisance at some of Hawaii’s golf courses (and home lawns) for the past some years. Colonies of this ant species form mainly in soil underneath turfgrass, bases of trees, and in leaf litter, etc. Attracted to light colored objects such as white/yellow shirts/caps/etc., alate swarms drive golfers off the course from May through August. We focused on control strategy by testing some granular ant baits in the lab, and then conducted a field trial at Four Seasons-Hualalai Resort Golf Course on the Big Island using several promising baits based on our lab assay results. We are currently working with the manufacturer of one ant bait to continue this research effort.

 

 

 
                     

Management of hala scale


In Hawaii, hala scale (Thysanococcus pandani Stickney) was originally detected in Hana, Maui in 1995. It is currently wide spread on Maui and Molokai, and was also confirmed at limited locations on Oahu since 2013. Hala scale can cause leaf deformities, discoloration, stunting, twisting, yellowing, and leaf blade length can be greatly reduced. It also attacks the tree’s fruit, can cause entire crowns of the plant to fall off, and premature death of the tree. At the request from Hawaii Department of Agriculture, we conducted this hala scale control research on Chaminade University campus, where hala scale has been confirmed. We started this project in December 2016 with several systemic insecticides delivered via either injection or soil drench. We monitored the effects of treatments monthly post treatment till July 2017. Our results indicated that imidacloprid delivered via either soil drench or injection was effective against hala scale.   

Foliar nematode control and ornamental plant safety

Foliar nematode (Aphelenchoides sp.) is an increasingly widespread pathogen of ornamental plants with a wide host range, attacking more than 250 plant species in 47 families. This nematode species tends to feed inside tender leaves of plants, and negatively impact plant growth in greenhouses, nurseries and in the landscape. In this study, we are testing several new formulations of nematicides (both synthetic and microbial based) against foliar nematode on Hibiscus and fern. We are also testing if there is any phytotoxicity effect of a new nematicide on some popular ornamental/landscape plants in Hawaii, i.e. Hibiscus, orchid, plumeria, Anthurium, and Indian Hawthorn.
    

New Research Project(s) coming up in the near future:


Frit fly control in golf courses



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