Garden Talk

with Rebecca Jordi


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Q: How do I control whiteflies on my leafy green vegetables?

 

Whiteflies

Whiteflies

 A:  Whiteflies feed exclusively on leaves, nearly always occurring on the undersurface. They suck juices from the plants and also excrete large quantities of honeydew in which sooty mold grows. Leaves will be sticky if there are many whiteflies feeding on the leaves above them and may turn black with sooty mold which grows on the honeydew. The most common whitefly found on Florida vegetables is called the silverleaf whitefly (http://edis.ifas.ufl.edu/in286) because of the effect its feeding has on squash leaves. Feeding by the immature stages or nymphs can also result in white areas in tomato fruits, streaking of pepper fruits, and blanching of broccoli stems. Whiteflies are not flies but are distant relatives of aphids and leafhoppers and, like them, feed on plant sap with piercing- sucking mouthparts. Whiteflies can spread some plant viruses, such as tomato yellow leaf curl virus and bean golden mosaic virus. The adult is a very small (less than 1/16 inch long) and has white wings dusted with a waxy substance. It holds its wings like a tent over its yellow body (Figure 26). It lays its eggs on the lower surface of leaves of many plants, including tomatoes, eggplant, melons, cucumbers, squash, okra, beans, cabbage, and broccoli. Except for a very brief time after hatching, the nymphs cannot move on the plant and look like clear or pale yellow scales. Regular applications of insecticidal soap may help keep whiteflies under control. Tiny wasps also attack the whiteflies. Flowers planted around and in the garden may help these wasps and other beneficial insects survive by providing a source of nectar. Other general purpose garden insecticides that kill on contact may also be helpful but will harm the beneficial insects. Because the insects are found on the lower leaf surface, sprays must be directed there in order to be effective.

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Q: Formosan termites have been in the news lately – what can you tell me about them?

 

Formosan subterranean termite

Formosan subterranean termite

A:  The Formosan subterranean termite, Coptotermes formosanus, is the most widely distributed and most economically important of the termite species. The Formosan subterranean termite (FST) acquired its name because it was first described in Taiwan in the early 1900s, but Coptotermes formosanus is probably endemic to southern China. This destructive species was apparently transported to Japan prior to the 1600s and to Hawaii in the late 1800s.  By the 1950s, it was reported in South Africa. During the 1960s, it was found in Texas, Louisiana, and South Carolina. In 1980, a well-established colony was thriving in a condominium in Hallandale, Florida. Just recently, they have been identified in Duval County. A single colony of FST may contain several million termites (versus several hundred thousand termites for native subterranean termite species) which can forage up to 300 feet in soil. Because of its population size and foraging range, the presence of FST colonies poses serious threats to nearby structures. The scariest part – once established, FST has never been eradicated from an area. There are more soldiers (10 to 15%) in an FST colony than the native subterranean species in Florida which generally contain only 1 to 2% of the total colony. Because the FST colony contains a larger soldier proportion than native subterranean termites, infestations with many soldiers is a clue to its presence. The FST attacks structural lumbers and living plants because they are sources of cellulose. However, this termite is also known to attack non-cellulose materials such as plaster, plastic, asphalt, and thin sheets of soft metal (lead or copper) in search of food and moisture. Their highly publicized ability to penetrate solid concrete is a fallacy. However, the FST is persistent in finding small cracks in concrete, which they enlarge and use as foraging routes. Leaky plumbing, air conditioning condensate, and any portion of the building collecting excessive amounts of moisture should be corrected to maintain an environment less attractive to FST. The conventional method for control of subterranean termites, including the FST is to place a chemical barrier between termites and the structure to be protected. In recent years, baits have become available to control Formosan subterranean termite populations near a structure. When termites are found in the station, the monitoring device is replaced with a tube containing chitin synthesis inhibitor (CSI) laced bait with the active ingredient hexaflumuron. Termites feeding in the stations then carry baits to other members of a colony, leading to the demise of entire colony population.  For more complete information, please read the following University of Florida publication:  http://edis.ifas.ufl.edu/in278


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Q: Can you identify this caterpillar? I found it under my redbud tree.

Tolype velleda larva

Tolype velleda larva

Tolype velleda moth

Tolype velleda moth

A:  I have not seen this large caterpillar before, so I called an entomologist at the University of Florida who identified it as the caterpillar of the Large Tolype moth.  The two – three inch caterpillar can be found feeding on the leaves of apple, ash, birch, elm, oak, plum, and several other trees.  The first thing you will notice about the Large Tolype adult moth is the white to grey hairy body. The moth grows from 1 – 2.5 inches long. The Large Tolype moth is a very striking moth with variations of color from white to black and grey – love to have one in my collection.  The Large Tolype moth can commonly be found from as far north as Nova Scotia south to central Florida, and westward to Minnesota, Nebraska, and Texas.


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Q: What is the name of the insect and what does it do? It looks like it has a long stinger at the end of the abdomen.

Broadnecked Root Borer

Broadnecked Root Borer

A: I believe the insect you brought in to the office is a Broad-neck root borer, possibly Prionus laticollis.  The female is much larger than the male, growing to two inches or more. The structure you see at the end of the abdomen is actually called an ovipositor, not a stinger. Ovipositors are structures on female insects in which they deposit eggs. This particular insect deposits eggs into the ground around trees and shrubs. The yellow eggs are about 1/8 inch long developing into larvae which then feed on the living roots of trees and shrubs. One female may lay as many as 100 eggs in clusters. The larvae may be as long as 3 ½ inches with black mandibles (very scary).  Broad-neck root borers prefer deciduous trees of the forest but have been known to feed on fruit trees and shrubs such as peach, pear, apple, blueberries and even grapes. The complete life cycle takes about three years. Adults emerge from the ground between June and August eating the foliage of trees and, on some occasions, even damaging the fruit.  Generally, the adults feed at night but stay hidden during the day. The smaller males are seen more often as they are attracted to light. Broad-necked root borer’s range is from Quebec and Ontario to Minnesota and as far south as Florida.  Because the larva of this insect feeds exclusively on the roots of trees, the only visible symptoms are limb die-back and the yellowing and/or thinning of foliage. Borers can completely destroy young trees and make older trees more susceptible to being blown over.  Prevention is the best way to deal with a borer. Keep grass, leaves, mulch, bark and other litter cleared away from the bases of trees. This prevents the borer from having a place to hide and makes it more visible to predatory birds. In addition, avoid over pruning, over fertilizing and over watering trees – all of these can cause additional stresses. 


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Q: What are these growths on my pignut hickory leaves? I think they are insects and they are chewing my leaves

 

Hickory midge gall

Hickory midge gall

A:  I appreciate you bringing in samples of the growths as this helped me identify the problem more easily. Actually, these growths are most likely an insect gall.  Galls are formed when the female insect places an egg in the leaf tissue and then the plant forms a protective coating around the egg.  The egg then goes through its normal growth stage from egg to larvae then pupae exits out of the gall as an adult. Generally, these galls cause few problems for the plant and in some instances, the galls support beneficial insects. I believe the chewing you are seeing on the leaf edges is caused instead by a caterpillar such as the eastern tent caterpillar. Eastern tent caterpillars can be seen in of our area in April – right now!  Just poke holes in the caterpillar webbing and the birds and wasps will take care of the caterpillars for you.


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Q: My sister says cicadas are the same as locusts. Are they? I’m keeping my fingers crossed as I have a dinner bet on this.

Cicada

Cicada

A:  Well, get your fork and knife ready because you are correct, cicadas and locusts are different species with very distinct characteristics. The fame of locusts is of Biblical proportions because of their tendency to swarm in large numbers. However, it should be noted, cicadas have been known to show a similar behavior but they are not nearly as destructive.   Locusts belong to the family of family Acrididae (grasshoppers) and Tettigoniidae (katydids) whereas cicadas belong to the family Cicadidae. Locusts are found on every continent outside of North America and Antarctica, so they really have an impact all over the world, but not here. The U.S. did have a serious locust species around the late 1800s called the Rocky Mountain locust, and it caused numerous problems for settlers in the region, but then it quietly became extinct around 1900. When food supplies are high, the locusts will produce large numbers of offspring.  The large number of offspring causes the locusts to swarm to other outlying areas seeking other food supplies and better habitat sites.  So the locusts start migrating from their original birth site in bands or swarms.  There may be millions at one time eating every green thing in sight.  The area of atmosphere the locusts cover may be as much as 500 square kilometers.  The largest recorded swarm has covered more than 1,000 square kilometers. Typically agricultural crops are highly nutritional and are grown in large patches or plots providing the perfect place for locusts.  Once the location is found there can be severe damage the crops, making the locust a serious pest to farmers. Cicadas have large, membranous forewings which easily extend beyond their abdomen. These wings are important for flying. Cicadas have distinctive, large eyes located far apart in their head.  The noise we hear in our oak trees is often caused by the male cicada.  The sound of cicadas is distinctive, and species can be differentiated by their calls. Only males can make sounds, most of which are calling songs to attract female mates. Periodical cicadas are species with synchronized development so they mature into adults in the same year, usually on 13 or 17 year life cycles. News reports and interest pieces are popular around the time the cicadas emerge. Florida, however, does not have periodical populations of cicadas, and adults emerge every year from late spring through the fall. Cicadas are not considered to be a pest of any significance in Florida. They do not require treatment and are best left alone, since any damage they cause is negligible. Cicadas do not bite or sting and do not carry harmful diseases. They are a food source for wildlife and can even be a food source for people – but I will let you try them first!


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Q: Is this the “kissing bug” recently described on television?

Kissing Bug

Kissing Bug

Leaffooted Bug

Leaffooted Bug

A:  You are the second person to bring me one of these insects asking if it was the “kissing bug” seen on a recent television program.  In both instances, the insect was a leaffooted bug, Leptoglossus phyllopus. This insect is a minor pest of various crops, including fruits, vegetables, grains, nuts and ornamentals landscape plants as well as citrus. Most of the problem on citrus involves early and mid-season oranges, tangerines, and satsumas, with injury usually occurring between early September and late November.  Since we are well into the fall season, most of you have been finding these insects on your citrus fruit.  Pecan is one of the other crops attacked causing a black pit and kernel spot of pecan. Nuts with black pit can drop prematurely.  The “kissing bug” is actually known as the eastern bloodsucking conenose, Triatoma sanguisuga. The eastern bloodsucking conenose looks quite different from the leaffooted bug and it is not a plant pest at all. Kissing bugs are members of a larger group known as assassin bugs. Assassin bugs are named for their habit of attacking and voraciously feeding on insects with their piercing-sucking mouthparts. In this way, assassin bugs can reduce pest insect populations, and are considered beneficial. What makes kissing bugs unusual is they require blood meals to survive and reproduce. These particular insects can also harbor Triatoma sanguisuga which is a vector of American trypanosomiasis (or Chagas Disease) in South America, a debilitating illness caused by the parasite Trypanosoma cruzi. This parasite has a complex life cycle, relying on both invertebrate vectors (such as the eastern bloodsucking conenose) and mammal hosts (such as humans, livestock and rats) to reproduce and spread. This disease is a problem in South and Central America and has been detected in the United States, but has not been found in Florida. For more complete information on both insects, look over the following University of Florida publications:  http://edis.ifas.ufl.edu/in1018; http://edis.ifas.ufl.edu/in229