Have No Fear: The IR-4 Field Research Directors Are Here!

Authors – Kathryn Homa, Roger Batts, Marylee Ross, and Stephen Flanagan

avocado tree with man inserting injection equipment into lower trunk
David Ennes releasing the test substance into the injection system of the avocado tree

There’s no project too big or too small – IR-4 will handle them all!

There’s no doubt that IR-4 Field Research Directors (FRDs) work long, hard days to conduct difficult trials. Every year, there is that one (or two, or three or four) special study that tests the Field Research Directors and their personnel. Some years, the difficulty involves trial space planning. During a given year, IR-4 may conduct a large number of greenhouse or tropical fruit studies. These studies are difficult to conduct since there are only select locations where the trials can be placed. In other cases, the main issue revolves around the development of specialized equipment or plot design to conduct the trial. In other cases, the FRDs may be working with a new specialty crop for the first time. This is especially challenging since little may be known about the plant’s growth habit, preferred growing conditions or the crop’s natural enemies such as insects, diseases or birds.

However, as they say “what doesn’t kill you makes you stronger”. The challenges such as those above allow the FRDs to gain additional knowledge from doing these complicated studies. For many of the complicated studies, a number of IR-4 personnel become more deeply involved including Regional Coordinators, Study Directors, Project Clearance Requesters and other FRDs not directly involved in the study. Often, the researchers involved enjoy the challenge of coming up with novel study conduct strategies. This is one of the many examples that makes the IR-4 Project unique. By working together, FRDs are able to come up with the best plan forward and conduct the study successfully. The following are just a few examples of residue studies that have been successfully conducted by the IR-4 Project using a little creativity and a lot of hard work.

Greenhouse Studies
The 2018 Food Use Workshop resulted in 15 greenhouse residue studies for the 2019 season. This is difficult for some of the FRDs since not every research site contains greenhouses or enough space to conduct more than one or two greenhouse trials. To combat this issue, the FRDs are planning carefully and well in advance so that they are able to conduct the trials throughout the year without running out of space. Greenhouse trials are also tricky since at some sites, the trial can only be conducted during times of the year when there is not extreme heat, cold or light issues. For this reason, many IR-4 FRDs make test substance applications on weekends and major holidays including Christmas Day in order to complete the studies on time. Also, this year, there is an incredibly tight scheduling of trials. For example, at the Maryland field site, FRD Marylee Ross stated that once one trial is completed, the plants from that trial are quickly removed from the greenhouse, the greenhouse is cleaned, and new trials are started all within a couple of days. If a crop takes a bit longer to mature or there is a delay for any reason, it throws the whole schedule off for the rest of the year. To aid in correct timing of trials, FRDs are in the process of starting transplants to be ready when the previous trial(s) are concluded.

Strawberry Nursery Plant Study
In 2019, IR-4 will be conducting a fluazinam residue study (PR 11920) on strawberry nursery plants for control of diseases including anthracnose crown rot and fruit rot caused by Colletotrichum acutatum and Botrytis gray mold caused by Botrytis cinerea. The goal of the study is to obtain uses that can be exclusively used in strawberry plant nurseries in an effort to help mitigate fungicide resistance that is escalating due to use of the same products in strawberry fruit production fields and nursery production fields. The FRDs and Regional Coordinators have been working diligently with strawberry extension specialists to learn how to develop a “mock” strawberry plant nursery to conduct the trial. As can be imagined, this trial involves a lot of planning time. FRDs must determine when to plant the “mock” strawberry plant nursery, the correct commercial density of mother plants for the field trial location so that a sufficient number of daughter plants will be produced and a proper dormancy period that must be achieved before daughter plants are planted into the “mock” strawberry production field the following season. FRDs also have to research the proper chilling temperatures and chilling period needed for the specific variety of strawberry chosen for the field trial. Depending on the field trial location, this period may be achieved in the field. However, at other locations, the dormancy period may not be able to be properly achieved unless the plants are dug up and placed in cold storage for an extended period of time before they are planted into the “mock” grower production field in the spring. In addition to trial planning, IR-4 FRDs and personnel also have to constantly maintain the plots by removing flowers and berries from the mother plants to promote runner and daughter plant production, remove dead foliage from dormant daughter plants, and dig up enough daughter plants to achieve the correct commercial density for a “mock” strawberry production field the following season.

Avocado Injection/Infusion Studies
A number of avocado studies have been conducted throughout the years at IR-4 field sites in California, Puerto Rico and Florida. However, there are few avocado studies that “warm the hearts” of the FRDs as the injection/infusion studies on propiconazole and tebuconazole (PR 11053 and 11160) that were conducted over the past several years. These studies were conducted for the control of Laurel Wilt caused by Raffaelea lauricola that is introduced into host trees by a non-native insect, the redbay ambrosia beetle (Xyleborus glabratus). These residue studies are important, as all avocado cultivars are vulnerable to the pathogen. Because the most effective method to deliver the test substance is via direct delivery to the xylem, researcher and IR-4 Project Clearance Requester, Dr. Jonathan Crane, conducted several studies to determine a workable use pattern and method for delivering the test substance into the tree. For these studies, FRDs had to plan and purchase the supplies needed for the trial in order to develop the unique test substance delivery system. In addition, Dr. Crane visited field sites to aid in conducting the trials.

Quinoa has gained popularity in the U.S. over the past several years. Because of this, many growers are producing quinoa throughout the Western Region of the US. However, as many know, establishing a new specialty crop isn’t always easy because there are little or no chemical tools available for control of diseases, insects and weeds. For this reason, IR-4 conducted some residue studies to support quinoa production. However, these studies were met with some challenges. For example, in one study, FRDs learned the hard way that quinoa plants do not produce seed in some trial locations because of hot summer temperatures. However, it was discovered that if quinoa is planted as early as possible, a crop can be successfully produced. In another example, FRDs in eastern Washington learned that Lygus bugs can serve as a real challenge to growing quinoa, as substantial feeding injury can result. The FRDs found out that alfalfa is the preferred host for Lygus and when alfalfa fields are cut, large numbers of adult Lygus fly out of these fields and invade the adjacent quinoa plots. None of the three registered insecticides on quinoa had any activity on Lygus. Therefore, it was a major challenge to obtain proper samples from the residue plots to complete the study. A 2019 sulfoxaflor, quinoa residue study (PR 12526) is being conducted to target Lygus bugs in quinoa. Weeds and birds also continue to be a challenge to producing a quinoa seed crop.

Stevia, a fairly new specialty crop in the US, has been encountering similar pest issues in the U.S., including stem and root rot of stevia caused by Sclerotium rolfsii, Septoria leaf spot caused by Septoria steviae and many species of weeds including yellow and purple nutsedge.

Similar to quinoa, as IR-4 FRDs began conducting residue studies on stevia, they learned the hard way that growing this crop can result in many challenges in the field. For example, FRDs Marylee Ross of Maryland and Roger Batts of North Carolina discovered after conducting one year of a two-year s-metolachlor herbicide study (PR 09872) that stevia does not overwinter well in locations that may experience extremely harsh winters. Although it appeared that the roots showed signs of life in the early spring, several late freezes and snowfall eventually killed the crop. Since there was limited information on growing stevia in cooler climates, the FRDs and IR-4 Project Clearance Requester talked with each other to come up with possible solutions for re-conducting the trials such as the options of planting the crowns deeper into the soil when transplanting the initial crop or covering the rows for winter. The average temperatures for the Northeast that year were 42 / 25°F in January, 37 / 18°F in February, 51 / 31°F in March and 66 / 45°F in April, with some evenings near freezing.

Another issue that was encountered with stevia trials involved the growth habits of the stevia plants. The herbicide protocol instructed the FRD to make drop nozzle applications. Since plants were extremely bushy, they fell across the row middles. To correct this issue, plants in the plots were staked before making the applications.

In 2019, IR-4 will continue to conduct stevia residue studies, including PR 12532 azoxystrobin + benzovindiflupyr, PR 12538 benzovindiflupyr + difenoconazole, and PR 12535 fluxapyroxad + pyraclostrobin for control of stevia leaf spot.

Wasabi is a specialty crop that is mainly grown in Japan in stream beds in cool, shady climates. Therefore, when the IR-4 Project received a request to conduct a residue study for control of Pythium, the IR-4 Western Region knew they had to brush up on their wasabi knowledge. They learned that since wasabi does not grow well in a number of climates or in soil production, a special production system had to be developed to be able grow the wasabi to conduct the trials. Over the course of several months of visiting wasabi growers in Washington, the IR-4 Western Region FRDs and Regional Coordinators developed a specialized system in the greenhouse on gravel with frequent misting to simulate the stream bed conditions. The application of the test substance was made through the mist system, since this was the way a grower would apply the chemical. This use was recently granted a tolerance and will be labelled soon (PR 10375).

While residue studies continue to become more complex, it is great to know that the IR-4 Project has a team of Field Research Directors, Regional Field Coordinators and other personnel that remain dedicated to learning new ways to fulfill the needs of specialty crop growers. Thank you for your service!