University of Florida/IFAS Extension Director for Nassau County, Rebecca Jordi, provides expertise and tips about landscaping and gardening in northeast Florida.
QUESTION: I know the stuff growing on my tree trunk is lichen but there are different kinds. Which one is mine? SS
JORDI: I admire your curiosity. You have both types growing on your tree. Remember, lichen will attach to most anything, even plastic, and does not kill or damage the tree. It is not a parasite.
The flat one is called foliose lichen and the lichen which looks more like a beard is called fruticose. Seen above are two of my photos, so you can see the difference.
QUESTION: What is this weed growing in my lawn? SC
JORDI: Thank you for bringing in a sample which made it much easier to identify. The weed is purple deadnettle, Lamium purpureum. This winter annual is found throughout most of the United States and into Canada. The flowers and leaves are in a whorled pattern around the stem. Whorled means three or more leaves or flowers are attached at the same site around the stem. Most of the lightly purple flowers are clustered at the top of the stem with the lower third of the stem completely absent of foliage.
Purple deadnettle will tolerate most any light condition but does prefer moist, fertile soil. This plant is native to Eurasia. The nectar from the flower does provide food for native pollinators such as bumblebees. It is often mistaken for henbit, but henbit has a more sprawling growth habit. The leaves of henbit are sessile leaves which means they are directly attached to the stem whereas purple dead nettle has short petioles or leaf stems.
The name nettle often means prickly or stinging, but the purple deadnettle does not have the sharp structures to hurt. This is where it gets its name “deadnettle.” At this point, the weed is mature and producing flowers and seeds. The best management tool would be to hand pull purple deadnettle since it can only reproduce by seed. It would be best to do it sooner than later in the hopes of removing it before it drops its seeds.
Remember, we have a plant clinic the first and third Mondays of the month unless it is a holiday. The Yulee satellite office is open for plant and insect identification and diagnosis from 10am to 2pm.
QUESTION: What kind of caterpillar is this on my beet greens? JM
JORDI: You brought me the beet armyworm, Spodoptera exigua. Like so many other pests, this caterpillar is not native to Florida but originated in Southeast Asia. It was first discovered in Oregon around 1876, but in less than 50 years, it found its way to Florida.
It cannot tolerate frosts therefore beet armyworm is most often found during the winter in Arizona, Florida, or Texas. However, it can be found in the southern half of the United States (Maryland to Colorado to northern California, and south) annually. Except in greenhouses, it rarely is a pest except in southern states.
The female can lay as many as 600 eggs which are usually deposited on the lower surface of the beet leaf. The mature caterpillar is pale green with a stripe running the full length of the body. It looks like the Southern armyworm, but the placement of a large black spot is different. The spot is found on Southern armyworm on the first abdominal segment whereas, if present on the beet armyworm, it will be located on the mesothorax.
Remember, insects have three main body parts: head, thorax and abdomen. The mesothorax is the second or middle segment of the thorax. Aren’t you glad you asked? Beet armyworms usually feed on the leaves, but they can eat the fruit too. Plus, they are equal opportunity eaters meaning they can also feed on other vegetable greens, flowers and cotton plants.
If you over-use insecticides or broad spectrum (carbaryl or malathion) pesticides you can increase the caterpillar numbers, so please consider using neem, cotton or petroleum oil as an alternative. As always, follow the directions on the label because the leaves can be damaged if applied inappropriately. Pheromones, (chemicals used to disrupt mating) can be used and may reduce mating as much as 97%. For more complete information, read the UF/IFAS Featured Creatures article: http://entnemdept.ufl.edu/creatures/veg/leaf/beet_armyworm.htm
Rebecca L. Jordi
Nassau County Extension Director
UF/IFAS Environmental Horticulture
543350 U.S. Highway #1
Callahan, FL 32011