Using Dogs to Sniff Out the Bad Guys

Posted by: Alison O'Connor, Larimer County Extension

I wrote a previous post about our U.S. Customs and Border Patrol dogs, who are stationed at airports to sniff out contraband that enters from other countries. They are amazing and impressive...and of course, mostly beagles. Yay beagles!

A Master Gardener recently sent me an article about dogs that are employed to sniff out a devastating citrus disease that is threatening Florida's industry. The disease, Huanglongbing, abbreviated to HLB (thank goodness!) is a bacterium that prevents citrus fruit from ripening. It's also known as citrus greening. The bacteria is vectored by a psyllid, a very small insect related to aphids and mealy bugs.

Psyllids on citrus leaves (photo courtesy of californiacitrusthreat.org)

HLB has been confirmed in the United States in Florida, Louisiana, South Carolina, Georgia; and in Cuba, Belize, and the Eastern Yucatan of Mexico. Since its confirmation in 2005, agriculture authorities estimate that it's caused a 75% decline in Florida's $9 billion industry. Sadly, over 5,000 fruit growers have lost their businesses.

Symptoms of citrus greening (photo courtesy of USDA California)

The leaves of HLB-infected trees are blotchy, and the fruit is smaller in size, lopsided, poorly colored, and worst of all...very bitter. In short, the citrus fruit is of poor quality and no value. The worst part is there's no cure for the disease and it can move rapidly throughout orchards, since psyllids are mobile.

Back to the dogs! You've likely read that dogs have been used for sniffing out cancer, bed bugs, and even emerald ash borer (!!!!!!). In the case of sniffing out threats to our agriculture industry, the USDA has looked at using dogs to detect HLB for over 15 years. They've found our canine companions have a 99% accuracy in identifying the disease. Ninety-nine percent! And the dogs are super fast at their job. They can quickly detect HLB in just a couple seconds, quickly sniffing each tree within the row. The reward for a find? A favorite chew toy.

Jerry Bishop, a dog trainer and handler with Florida-based F1-K9, scouts a Ventura County, Calif., lemon grove for HLB-causing bacteria with Bello, a Springer spaniel. (Courtesy Farm Bureau of Ventura County)

As soon as the dog detects an infested tree (they sit by the culprit), the tree is marked and slated for removal. Dogs are much more accurate and quicker than visual inspections and lab analyses. Compared to dogs, the lab tests, using PCR, only had a 25% accuracy rate. Dogs rule.

Head's up to my two beagles, Maple and Hazel, you could be employed any day! Get your resumes up-to-date. And try to sell yourselves as experts in something other than sleeping.

Maple and Hazel doing what they do best.

Tomato Uh-oh!

Posted by Mary Small, State Master Gardener Coordinator
No, this isn’t a new game – the title comes from something my kids would say when they were little. It usually meant that something (usually not good) just happened.

Our tomatoes had some uh-ohs this season that produced (in addition to delicious fruit!) lively discussion and internet searches for information. We grew a few hybrid varieties and one heirloom that produces beefsteak tomatoes. Of course, I failed to write down the name and the writing on the tag has faded. I think it might be Black Krim, though. It was the variety with the most interesting symptoms.

Catfacing (Forestry Images.org)

  Catfacing – this is a cute name for distorted fruit that results from abnormal development of female flower parts. It can be caused by low temperatures during flowering (below 58 degrees F) and 2,4-D. In addition, beefsteak and some heirloom types are genetically more susceptible. At the front end of the season and now late in the season, cool temps at flowering certainly could have happened. But the only cause for this in mid- summer that makes sense is the cultivar and type of fruit.




Zippering

Zippering –This one is caused by the male flower parts (anthers) sticking to the developing fruit. Cool weather during fruit set and genetics can play a role.



 Concentric growth cracks – this happens when the insides of the tomato grow faster than the skin. The skin can’t keep up with the interior tissue expansion so it cracks or splits. It can be caused by extreme fluctuations in water and temperature as well as genetic susceptibility. Any of these three causes could have figured in this season – but only the heirloom has the problem. 

Concentric growth cracks

Green or yellow shoulder

Green (or yellow) shoulder – the tomato "shoulders" (the stem end of the fruit) stay green or yellow and hard. Adverse tomato growing weather, soil nutrition and genetics (again!) are possible causes – but the exact reason hasn’t been determined.  Only one hybrid variety had this symptom.

Psyllid nymphs

  Psyllids –These were thankfully NIMG – not in my garden - although I have dealt with them other years. The insects feed on sap and inject toxic saliva into the plant. This stops growth, stunts leaves and causes them to turn yellow and/or purple. Tomato fruit is abundant – but tasteless. The little stinkers aren’t easy to find until you a) check the undersides of leaves for the nymphs or b) find what looks like sugar or salt accumulating on leaves, stems or the soil underneath plants. While there are insecticides available– and sulfur works well – it may be too late depending on when you discover the problem.

This has been one of the most entertaining, educational and delicious tomato years we’ve had in a long time. Can’t wait for next years’ adventures!

Hackberry Nipple Gall (the name alone describes it best)

Posted by: Alison O'Connor, Larimer County Extension

When I first learned about hackberry nipple gall during my undergraduate degree at Iowa State University, I snickered. How could you not? We were in our woodies class (ha!) [woody plant materials for those of you who are more mature than me] and I'm fairly certain it was at the point in the semester where we were all looking for a good laugh.

Hackberry nipple gall in all its glory.

But good ol' hackberry. And its nipple gall. This year, I have never received so many calls and emails about, "This weird thing plaguing the leaves on my tree" and "What are the warts on my tree leaves?" It often seems that we have a "great year" for certain things...and it's the Year of the Hackberry Nipple Gall. We do see it every year, but this year it seems to be more common or more obvious.

Look at those galls!

Psyllids (sill-ids) are the cause. This insect is teeny-tiny and so small it can easily fit through the screen grids on your windows. Fortunately, the hackberry psyllid is only interested in hackberry. If you could zoom in on the insect, it would look like a miniature locust/cicada.

Adult hackberry psyllid on the tip of a pencil. Photo by B. Ogg.

Adult psyllids tend to overwinter in cracks of trees to survive cold winter temperatures, but they also snuggle in other crevices, like around windows and siding. If they wander indoors, they meet their fate, since our homes are not very accommodating to the insects.

In spring, the adults will lay eggs on emerging hackberry leaves and the young nymphs will feed on the leaf tissues. The tree responds by creating a gall, which is simply abnormal growth. The nymphs spend the rest of the summer sucking plant juices in the comfort of the gall until they pupate in the fall as an adult and emerge to overwinter and start the cycle again.

The gall is a comfortable cocoon for the hackberry psyllids to spend their summer.

I can see why people are concerned...not only by the leaf appearance, but also by premature shedding of the leaves on the ground. Fortunately, hackberry is one of the toughest trees we have in the landscape and it seems to be unaffected by the galls and early leaf drop--so there is no need to worry, apply insecticides or cut the tree down. (To me, what's even more fun is walking on the gall-ridden leaves--they "pop" under your feet!)

A hackberry tree that has shed many of the afflicted leaves in late August.

Interestingly, if you can prevent raking/destroying the leaves in the fall, a beneficial wasp overwinters in the galls that will parasitize the new nymphs the next spring. Nature does its best to help control pest populations.

Nipple gall would not be a reason to stop planting hackberry--this tree has so many benefits. As my co-worker Eric Hammond described: it's reliable...like your friend with a truck. It's drought tolerant, has good yellow fall color and is tolerant of many soil types and urban conditions. The nipple gall just provides a great conversation starter when you have friends for dinner. "Hey Joe! Let me show you the nipple gall on my tree!"