Earlier this summer I talked about getting to know your weeds, so they’ll be easier to control. If you missed that article you can review it here “Why Can’t I Kill Weeds?”
Today we will look at the types of herbicides available so your selection will fit your situation.
Understand your herbicide options. Picking out the appropriate herbicide can be overwhelming. The options seem unlimited when you are standing in the store looking at aisles of containers. By preparing yourself before you shop you can save time and increase your chances of making the most effective selection. Here are some herbicide basics:
Label interpretation. The pesticide label is a multipage document that describes ingredients, how a pesticide works, application instructions, safety requirements, and other important information for the user. Before applying any pesticide (yes, herbicides are pesticides!) you should read the entire label. Pulling the label off the package in the store may be frowned upon and the print is very small. For this reason, I would recommend looking up a few options before you go shopping and reading the labels online. This allows you to take your time to be sure you understand if it is the appropriate product and you can make your shopping list for personal protective and application equipment before you leave the house. Three important things to look for when selecting your product are active ingredient, labeled site (site includes the location such as residential landscape vs. agricultural crops and the plants it is safe to use on), and targeted pest.
Non-selective, systemic herbicide damage on grass. Photo: J_McConnell, UF/IFAS
Pre-emergent herbicides. Pre-emergent herbicides provide control when applied BEFORE seed germination of your target weed. They do not prevent germination, rather they prevent emergence of shoots and roots essentially inhibiting normal plant growth which eventually results in plant death. It is important to have your product in place during the correct window of time. Typically, 1-2 weeks before germination of your target weed is ideal.
For warm season annual weeds (crabgrass, goosegrass, sandspur, and spurge are examples) apply pre-emergent herbicides when day temperatures in early spring reach 65-70°F for 4-5 consecutive days. This may be mid-February or as early as January.
For winter annual weeds (henbit, black medic, geranium, and chickweed are examples) watch for night temperatures in the Fall to reach 55-60°F for several nights in a row to indicate proper application timing.
Some products are selective to plant types such as grasses, sedges or broadleaf weeds. Other products are more broad-spectrum and are effective on multiple weed types.
Pre-emergent herbicide should not be used if you intend to plant seed – it will affect your desired plant in addition to the weed! There may also be effects on newly planted lawns or plants, so be sure to read the label closely to avoid damage to non-target plants.
Post-emergent herbicides. These products are used on weeds that have already emerged, regardless of life cycle (annual, perennial, biennial). This type of herbicide will be applied directly to the weed you are trying to kill. There are a few categories within this group.
Selective or non-selective.
Selective herbicides work on particular categories of plants: broadleaf, sedge, grass, or woody plant.
Non-selective herbicides can kill any type of plant regardless of category.
Contact or systemic. Contact herbicides kill the plant tissue it comes into contact with and does not translocate to the rest of the plant.
Systemic herbicides are translocated throughout the plant to affect more than just the place of absorption. These are ideal for perennial weeds that would regenerate from roots, bulbs, or tubers if the top is damaged or killed.
Effective weed management requires some preparation and research for the best outcome. For help with weed identification and control recommendations, contact your local UF/IFAS Extension Office.
Whitefly adults and eggs. Photo Credit: James Castner, University of Florida, IFAS.
Whiteflies are a pest we typically see in the fall but if you look around, you’ll notice high densities of them now. Despite their name, whiteflies are more closely related to an aphid or scale insect than a fly. They are 1/16 of an inch long (about the size of a gnat) and resemble small moths. They can be found on the undersides of host plant leaves and their behavior is easily recognizable as they scatter from the leaves when they are disturbed.
Silverleaf Whitefly. Photo by Lyle Buss, UF/IFAS
You’ll find whiteflies on a variety of plants ranging from ornamentals such as ficus, poinsettia, hibiscus, and ivy to vegetables like tomato, pepper, eggplant and okra. Some species feed on sweet potatoes, vegetables in the cabbage family, and citrus.
There are several species of whiteflies in Florida but the three main species of agricultural and horticultural concern are the silverleaf whitefly (also known as the sweet potato whitefly), citrus whitefly, and the ficus whitefly. Whiteflies have piercing-sucking mouthparts with which they feed on plants. The top side of leaves on infested plants may become pale or spotted due to whiteflies feeding on the undersides of leaves. It’s not uncommon for an infestation of whiteflies to go unnoticed until leaves turn yellow or drop unexpectedly. Some whitefly species can cause greater damage by transmitting plant viruses.
Whiteflies, along with aphids, scales and mealybugs excrete a sugary substance known as honeydew. This honeydew coats the surface of the plant where the insect feeds and facilitates the growth of a black fungus called sooty mold. Ants and wasps also feed on the honeydew secreted by these insects and may serve as an indicator that a plant is infested with whiteflies or other honeydew secreting insects.
Adult female whiteflies can lay anywhere from 200-400 eggs in her lifetime. The eggs are laid on the undersides of leaves. These eggs hatch into nymphs (also known as crawlers) after 4-12 days. From there, the crawlers will insert their mouthparts into the leaves of host plants where they will molt, pupate and then become adult whiteflies. This process takes anywhere from four weeks to six months, depending on temperature and humidity.
Whiteflies are difficult to control due to their prolific reproductive cycle. It is difficult to get rid of whiteflies once there is an infestation. As with dealing with most insects, proper plant selection, irrigation, and fertilization are critical for managing whiteflies. Removing sources of infestation such as weeds around the garden or old plant debris around the yard can help prevent whitefly populations from carrying over to the next season. Natural predators such as lady beetles, lacewings and predatory mites can help keep whitefly populations in check.
Insecticides such as insecticidal soap or horticultural oil can be used to help reduce whitefly populations. Be sure to always read the label for instructions. For more information on whiteflies, please contact your local UF/IFAS Extension Office.
In late July, Larry Kinsolving, a Jackson County Master Gardener, noticed an insect pest in the beautiful, large azalea bushes that frame the front entrance to his home in Marianna, Florida. The azalea caterpillar is found in Florida from late summer to early fall on azaleas and other plants including blueberries. If left undetected, the caterpillars can defoliate (eat up the leaves) of much of a plant. In general, caterpillars seldom kill the plants they feed on, but the stress caused by defoliation can reduce flowering or fruiting the following spring, if it becomes a serious problem. Larry shows you how easy it is to find and remove this pest from your azalea bushes. While the caterpillar appears hairy, it is harmless to humans and can be handled without concern.
Remember last year’s vacation trip? You picked the perfect location, checked into the hotel and made sure to check every mattress corner for bedbugs. Bugs can hide in the strangest places. Now with COVID-19 those people insisting on still taking a vacation are flocking to Northwest Florida. While some are still utilizing hotels, the majority are pulling into the RV park or campground. They are bringing anything and everything anyone could possibly need for the week, from firewood to camp chairs. That way no one will have to go to the store. Somewhere on the vehicle or within all the stuff there may be some hitchhikers, insect stowaways. The problem is that these bugs may be staying even after the human beings head back north. Florida is notorious for invasive species. With 22 international airports and 15 international ports in the state, hundreds of foreign insects are intercepted each month. But, not all the problem creepy crawlers are coming from the south. Many have been introduced to northern states and work their way here.
One to keep an eye open for is spotted lanternfly (Lycorma delicatula). The Asian native was first detected in Pennsylvania in 2014. Since then it has spread to the east and south. While the insect can walk, jump, or fly short distances, the quickest way for the spotted lanternfly to relocate is to lay eggs on natural and man-made surfaces. Some of those egg masses may fall off and get left at the park. Next spring after the eggs hatch the nymphs will begin feeding on the sap of numerous plants, often changing species as they mature. Host plants include grape, maple, poplar, willow and many fruit tree species.
Nymphs in the early stages of development appear black with white spots and turn to bright red before becoming adults. At maturity spotted lanternflies are about 1 ½ inches wide with large colorful, spotted wings.
Photo from USDA APHIS
At rest their forewings are folded up giving the lanternfly a dull light brown appearance. But when it takes flight its beauty is revealed. The bright red hind wings and the yellow abdomen are very eye-catching. Remember, in nature bright colors are often a warning. Though spotted lanternflies are attractive, they pose a valid threat to native and food-producing plants. The adults feed by sucking sap from branches and leaves. What goes in must come out. Sugar in, sugar out. Spotted lanternflies excrete a sticky, sugar-rich fluid referred to as honeydew. Black sooty mold often develops on honeydew covered surfaces.
Spotted lanternflies are most active at night, steadily migrating up and down the trunk of trees. During the day they tend to gather together at the base of the plants under a canopy of leaves. So, you may need your lantern (or head lamp) to locate them. If you find an insect that you suspect is a spotted lanternfly, please contact your local Extension office of the Florida Department of Agriculture and Consumer Services Division of Plant Industries.
August is awful. Its heat makes one miss the relative cool of July. Its rain is so sporadic that it invokes nostalgia for the rainy afternoons of early summer. But if there is a silver lining in August for gardeners, it is the simplicity that it brings. The weaker spring crops, tomatoes, squash and the rest, are all gone now, destroyed or rendered fruitless by insects, disease, and heat. This leaves only the hardened, usually pest and disease-free survivors Okra, Pepper, Sweet Potato and Eggplant. I say usually because, this year, my eggplant bed is under attack by a new-to-me pest, the False Potato Beetle!
I’ve dealt with Colorado Potato Beetles (CPB) before. Those orangish, black-striped terrors often attack my spring potato crops and occasionally bother early tomatoes. However, I’ve never seen them in late summer on Eggplant. This raised suspicion. Also, I spotted unusual, round, whitish purple creatures munching on leaves from the same plants; these appeared to be the larval stage of the unidentified beetle. A little digging led me to identify these garden pests as the lesser known, lookalike cousin of CPB, the False Potato Beetle.
False Potato Beetle munching on an Eggplant leaf in the author’s garden.
False Potato Beetle (FPB) looks nearly identical to its cousin in the adult stage. They are similarly shaped and colored, though a close look reveals subtle differences between species. While both have yellowish-orange heads and pale-yellow backs with dark stripes, the FPB’s back is slightly lighter hued, more of a whitish, cream color. Also, the CPB’s underside and legs are a very dark orange to brown, with the False Potato Beetle having lighter colored legs and underside. If you’re saying, “These old eyes will never be able to tell the difference, County Agent. Cream and light-yellow look the same to me.”, I get it. Fortunately for those of us with poor vision, the larval stage (babies) of the two beetles looks very different and is the key to correct ID! FPB larvae are larger and have a whitish coloration. CPB larvae, in contrast, are a similar burnt orange color to the adult beetle. I promise, the difference is very distinguishable!
False Potato Beetle is considered a minor garden and agronomic pest as they typically only bother Eggplant, and they don’t usually destroy entire plants. However, if you get a FPB outbreak in your Eggplant garden, they can still be pretty destructive. These beetles feed in the same manner as caterpillar pests, chewing away entire sections of leaves and stems. Unchecked infestations can defoliate entire sections of plants. So, if you find these little beetles eating away at your eggplant garden, what can you do?
False Potato Beetle larvae. Photo courtesy of the author.
First, if you scout regularly, you’ll notice the beetles and their larvae in relatively small numbers before outbreaks become widespread. I had pretty good success this year just catching infestations early and picking off the beetles I saw and squishing them. Continue scouting and squishing for a few days and pretty soon, the population is reduced to a manageable level. However, if squishing makes you squeamish, you also have some common pesticide options at your disposal. I normally encourage clients to start their chemical pest control strategy with “softer” products like Pyganic, a pyrethrin make from an extract from the Chrysanthemum plant. Pyganic works great but is a little harder to find; you may have to order online or ask your local retailer if they can get it for you. If you are unable to find Pyganic or it doesn’t perform for you, the old standby products with carbaryl or pyrethroids (Sevin, Ortho Bug-B-Gone, and others) also work well.
False Potato Beetle can be a late summer garden pain, but with regular scouting, proper insect ID, lots of squishing, and maybe a timely pesticide application or two, you should be able to continue to harvest eggplant deep into fall! If you have FPB in your garden or have another horticultural question, give your local UF/IFAS County Extension office a call! Happy Gardening!
Earlier this summer I talked about getting to know your weeds, so they’ll be easier to control. If you missed that article you can review it here “Why Can’t I Kill Weeds?”
