AGNET - The Palm Tree Whodunnit, Part 1

By Laurie Sheldon
Based loosely on Robert Northrop's presentation at the 2012 FNPS Conference.

(Please start by playing the following video)

This is the city: Ruskin, Florida. Located in Hillsborough County on the south shore of Tampa Bay, it has all of the charm you’d expect from a town with a population of about 17,000. Founded on the shores of the Little Manatee River, its pristine estuarine preserves, untouched natural areas, and mild winters combine to make Ruskin ideal for quiet, peaceful living… so when I get a phone call from a hysterical woman screaming about a killer on the loose, that's when I go to work.

Ruskin, a sleepy little town on Florida's west coast.

"My tree is dead and someone just
mistook me for Barbara Billingsley!"

Friday, November 24, 2006, 65°
I was on field patrol, Department of Agriculture’s Plant Industry Division, with my partner, Phil Shannon. Our boss, Captain Crunch, was out fishing. My name is Sunday - Moe Sunday - I carry a badge.

8:45 A.M.
Our day got started in a hurry. "Lady, calm down," I said, "did you see the perpetrator?" "No - only the victims," she replied, “they’re all around my neighborhood and one of them is in my front yard.” "Can you describe it to me?" "Yes,” she responded, “it’s 20' tall and looks like it had a run-in with a hairdresser who was bad at highlighting.” I took down her address, instructed her to stay put, and headed out the door with Shannon.

9:15 A.M.

When we got to her house she was standing in the driveway, dabbing at her teary eyes. Her Phoenix canariensis was not looking good, and she thought she was to blame. I told her it was not her fault, and tried consoling her. "Our palms aren’t living on easy street. Lethal yellowing moved into the Keys from the Caribbean, wiped out 75% of the coconut palms in Key West by the mid 1960s. It hit the east coast of mainland Florida around 1970, took out 100,000 palms in just over 10 years, made its way to the Gulf coast and Mexico in the '80s, then turned south towards Honduras. They already had native pests and diseases to contend with, including Palm Weevil, Phytophthora bud/root rot, and Ganoderma basal stem rot.” She blew her nose, and, still sobbing, asked, "so what’s wrong with my palm?” “Ma’am, I’m afraid it has Fusarium wilt, a lethal disease caused by a fungus that blocks water-conducting tissue. It rolled into Florida halfway through the 1990's. Its primary targets are Date Palms."

(left) Phoenix canariensis with Fusarium wilt. (right) Close-up of unilateral leaf damage.

She began blubbering again, “my palm has a fungus? Like athlete's foot? That's so gross!" "Lady," I said, "your palm doesn't have athlete's foot. Where do you women come up with this stuff - soap operas? Tell me something, do you use the same company to trim the old leaves off your palm as they do?” I pointed at the house catty-corner to hers, then another a few doors down. Both had Canary Island Date Palms that were in equally sorry health. She nodded. Shannon called her attention to her palm’s fronds, which had dead leaflets on only one side of the rachis, and said, “Is this what you described as ‘bad highlighting’?” She nodded again. He followed up with, “It’s definitely Fusarium. Your tree maintenance people must have spread it around your neighborhood on their pruning equipment. If you’ll give me their number, I’ll tell them what’s going on and give them some information about how to sterilize their equipment before they do any more damage.” A look of relief spread across the woman’s face. “Thank you,” she said. “Just doing our jobs,” I replied, then tipped my hat and headed for our vehicle.

"Mmm... donuts."

10:30 A.M.
We heard a voice coming from the radio in the squad car. “Crunch to Sunday and Shannon. Do you copy?” I grabbed the handset. “10-4, Captain. What’s up?” He told us about a sick Phoenix dactylifera (date palm) he saw on his way back from fishing that morning. “I have a hunch it’s Ganoderma,” he said, “but I was driving and didn’t get a very good look at it. It’s on the southeast corner at the intersection of SE 14th Avenue and SW 1st Street, just off the Tamiami Trail. Please check it out before you return to headquarters. Also, bring me a donut - something with sprinkles.” “10-4. Over and out,” I responded.

Ganoderma basidiocarp (a.k.a. "conk")

11 A.M.

We located the palm and I gave it the once over, noting that an unusually high percentage of its leaves were desiccated and had turned a brownish-gray. The stems upon which its fruit should be were largely barren. I started walking in a slow circle around the tree, staring at its base. Phil looked at me curiously, then asked if I lost something. I kept moving until he stood in my path, at which point I rammed into him with my head. When I stood up straight he could see the puzzled look on my face. "I don’t think it’s Ganoderma," I asserted, "there's no conk." "I don't see what sea critters have to do with this tree, Moe," he chuckled. "Not c-o-n-c-h, it's c-o-n-k,” I explained, “they look like stemless mushrooms growing laterally from the base of the palm. Conks and Ganoderma usually go hand in hand." "Thanks, Captain Obvious. Ever hear of a joke?” I rolled my eyes. “I think it might be lethal yellowing,” I replied, “but I can’t be sure without getting a tissue sample and sending it to a lab for testing.”

11:10 A.M.

P. dactylifera with fruit drop

Shannon and I agreed that we should get permission from the homeowner before testing the tree, so we walked over and rang the doorbell. An older man opened the door, wearing nothing but an undershirt, boxer shorts, socks, and sock suspenders. He did not look happy about having visitors. “Whaddaya want? If you’re one of them religious nuts, I aint interested!” “Good morning, sir,” Shannon responded. “We're here from the Department of Agriculture’s Plant Industry Division. We noticed your palm tree out there doesn’t look particularly healthy.” “That piece of junk?” he huffed and pointed to the specimen in question. “All I wanted was a low-maintenance tree. Not like them damn oaks that drop leaves all over the place. That crook at the nursery told me to get this one. Got more brown leaves than green. Last week almost all the fruit fell off in two days - unripe. Some of it hit me on my head! Low maintenance my foot!” “I’m sorry to hear that, sir,” I countered. “Would you mind if we took a sample from your tree to try to determine what’s wrong with it?” “Go right ahead. It already looks dead - guess y’all can’t make it deader.” We both thanked the man. Shannon told him we’d send him the lab results when we got them back, and took down his name and phone number.

Flame sterilization of drill bit

Meanwhile, I walked to our vehicle and opened the trunk. I took out a cordless drill, an enormous drill bit, a squirt bottle of distilled water, a golf tee, a hammer, a butane torch, a permanent marker and a ziploc bag. "Look at you getting all MacGyver on us," Phil joked. I pretended not to hear him. I flame-sterilized the drill bit, gave it a squirt of water to cool it off, then bored into the trunk, holding the ziploc below the drill to catch any shavings. I sealed the bag, wrote the date, location and palm type on it with a marker, then stuck it in my lunch cooler. Afterwards, I re-sterilized and rinsed the bit and plugged the hole in the tree with the golf tee and hammer. I returned the tools to our vehicle, where Phil was waiting in the driver’s seat, playing Sudoku. “Where to, partner?” “FedEx - to overnight this sample,“ I answered. “Then I suppose we had better hit Dunkin Donuts."

Monday, December 11, 2006, 8:30 A.M.

Neighbor-joining phylogenetic tree of
phytoplasma 16S rRNA gene sequences

I had just arrived at headquarters when my phone rang. "Inspector Sunday?" “That’s right,” I answered, “how can I help you?” It was the lab. “We’ve got the DNA analysis of that palm sample you sent in. We ran it twice, as we were confounded by the first set of results we got, but it turns out they were right.” “Oh, great,” I said, “does is it have lethal yellowing?” “Actually, Sunday, it has Candidatus Phytoplasma palmae. It’s similar to lethal yellowing in that they are both phytoplasmas, but lethal yellowing is strain ‘A’. The sample you sent us was strain ‘D’ - an identical match with isolates from southern coastal Texas. We’ve never seen it in Florida before.” I took a moment to process this, then I replied, “wait a minute - are you telling me what I think you’re telling me?” “If you think I’m telling you that the sample you sent us has Texas Phoenix Palm Decline, then yes.” I thanked the man and hung up, then immediately dialed Shannon. I cut straight to the chase when he picked up, “you aren’t going to believe this…”

TO BE CONTINUED---
(Click Here for Part 2) 

Image Sources 

Ruskin
Woman on phone
Fusarium (left)
Fusarum (right)
Homer Simpson
Ganoderma
Date palm
Bit sterilization and phylogenic tree