by Molly Jameson | May 7, 2020
Adult squash vine borer moths are easy to identify, as they are reddish orange and have black dots along their upper abdomen. Photo by Theresa Friday.
It’s been a few weeks, and your squash seedlings are really starting to take off. The days are blushing with summer warmth and the flicker of lightning bugs in the evening indicates the cool nip of spring is winding down. In your garden, this has culminated in lengthening cucurbit stems that now show off a beautiful bright shade of green. Squash blossoms appear overnight and begin to expand and take shape, nestling themselves under the backdrop of slightly darker green squash leaves.
Black beauty zucchini blossom in the morning sun. Photo by Molly Jameson.
A few more nights go by, giving you a chance to explore some recipes. Maybe it’s time to fire up the grill and make grilled summer squash, sprinkled with fresh mint or thyme. Perhaps you’ll make a summer squash pesto pizza. Afterall, your basil is ready for its first harvest. If you are ahead of the game, you might even have some vine-ripening tomatoes that would pair nicely with squash in a creamy pasta sauce.
Your culinary dreams are running wild when you start to notice the wilt. You panic, and think you’ve forgotten to water the garden. But no, you’ve given your garden a consistent dose of water every morning. Your basil looks fine. Your tomatoes look great. What is going on?
Squash vine borer adult in flight. Photo by Molly Jameson.
You have fallen prey to the dreaded squash vine borer (Melittia cucurbitae).
These garden pests rely strictly on plant species within the genus Cucurbita. If the squash vine borer didn’t wreak such havoc in your summer garden, you might find its striking red and black features fascinating. Unfortunately, if your squash plants are wilting unexpectedly, this daytime roaming moth may have already done its damage.
Adults lay single reddish-brown, millimeter-long eggs on the lower end of the main stem – or on leaves, leaf stalks, fruit buds, or in the soil near the squash plant. Within one to two weeks, larvae hatch, bore into the stem of healthy cucurbits, and begin to chew their way up. Multiple larvae can infect a single plant. This blocks the transport of water and nutrients, leading to the dreadful wilt that often signifies that it is too late.
A squash plant severely damaged by squash vine borer larvae. Photo by Molly Jameson.
So, what can be done? Once the wilting has begun, you may be able to reap a small harvest, depending on the timing of infestation. Adult females emerge from cocoons from May to October in Florida and have two generations per season. They prefer cucurbit varieties with large tubular stems, such as yellow squash, zucchini, and pumpkins, but can also infest watermelon and cucumbers.
If you have some cucurbits that do not show signs of infestation but others that are on the decline, it might be worth removing and destroying the infested plants. At the end of the season, cultivate your soil one to two inches deep, as this is where they overwinter in cocoons. Destroying infested plants and cultivation can help reduce the overwintering population.
Squash vine borer larvae inside a squash stem. Photo by Molly Jameson.
In North Florida, try seeding squash indoors in March and plant seedlings in the garden in early April. The earlier you plant, the better chance you have of beating the borers. Of course, you must balance the risk of borers with the risk of a late frost.
You may also want to install lightweight floating row covers that can prevent the female from depositing her eggs. But again, it’s a delicate balance, as you do not want to prevent beneficial insects from pollinating your squash once it is producing blossoms.
Scout your plants diligently each day and keep on the lookout for eggs and adults. Adults are attracted to the color yellow, so yellow sticky traps or yellow bowls of water may lure them in. Build up the soil around developing plants to act as a shield against egg laying and boring.
A healthy straightneck squash plant beginning to set fruit. Photo by Molly Jameson.
Once your plants slow their fruit production and you’ve had your fill of grilled squash, squash pizza, and creamy squash pasta, go ahead and remove the plants to prevent late infestations that can then overwinter. Lastly, rotate areas in which you plant cucurbits each year to break borer life cycles.
Vegetable gardening involves innovation and ingenuity. A clever gardener is always striving to balance weather, timing, insects, plants, soil, and everything in between. With a little planning and persistence, I know you can prevail against the tenacious squash vine borer.
For more information about squash vine borers, check out the UF/IFAS EDIS publication, Squash Vine Borer Melittia cucurbitae (https://edis.ifas.ufl.edu/in1068).
by Mark Tancig | Apr 30, 2020
Symptoms of oak leaf blister on swamp chestnut oak. Credit: Gordon Magill.
Even during global pandemics, it’s a joy to be outside during the great north Florida spring we’ve been experiencing lately. As cold fronts come through with their rain bands, some packing a punch, they leave behind the most pleasant mornings, clear blue daytime skies, and crisp evenings. Unfortunately, we’re not the only organism that also enjoys those cool days. Many species of fungi are quite active this type of year as the rains, followed by warmer, yet not too hot temperatures, create the perfect conditions for fungal growth. Some of these fungi grow right on or in the plants we’d like to be enjoying for ourselves, stealing nutrients and causing plant decline or merely causing aesthetic damage. As this is an active time for certain species of fungi, local extension offices are getting more calls and questions regarding lawn and landscape damage due to fungal pathogens. A recent call was a new one for me and an example of a native fungi-plant interaction that looks bad but requires no intervention from us. It also highlights how correctly identifying a disease leads to the best action and can often save time and money and prevent unnecessary pesticides (in this case a fungicide) from entering the environment.
Close up of oak leaf blister on swamp chestnut oak. Credit: Gordon Magill.
The fungi and plant involved here was the oak leaf blister (Taphrina caerulescens) on a swamp chestnut oak (Quercus michauxii). It forms, you guessed it, blisters on the leaves of any of the oaks, though live oak (Quercus virginiana), laurel oak (Quercus laurifolia), and water oak (Quercus nigra) seem to be preferred hosts. The spores of the fungi, dormant since the previous summer/fall and which happen to get lodged in bud scales through wind and rain, germinate in cool, wet weather. The fungus then infects young leaves as they flush and its growth causes a disruption in the leaves’ development. This leads to the blistered look of the leaf tissue and, during extended periods of cool, wet weather, the entire leaf sort of shrivels, browns, and eventually falls off. Spores are eventually released from the fallen leaves to start the process over the next spring.
Severe oak leaf blister on swamp chestnut oak. Credit: Gordon Magill.
Though the leaves look pretty terrible, this fungal disease rarely causes plant health issues and the tree recovers just fine. Specimen trees that experience it year to year may be treated with a fungicide, but most homeowners can just let it go. Raking up and disposing of the leaves may help prevent further infections by reducing the number of spores released in the area.
As you enjoy another cool morning after an evening rainstorm, remember that the fungi all around you are also having a great day. You may want to look at your landscape plants and see if there’s anything abnormal going on. If so, take a photo and send it to your local extension office for help with identification and best methods of control, or, like in this case, just leaving it alone.
p.s. As I said this was a new one for me and I want to thank Stan Rosenthal, Extension Agent emeritus, for assisting with identification.
by Larry Williams | Apr 29, 2020
In times like these, it seems that our own perceived “problems” pale in comparison to the “big picture.” In my day-to-day work, I have the opportunity to help people solve problems with their landscapes, lawns and gardens. I enjoy the problem solving part of my job as an extension agent.
Winter annual weeds in lawn in early spring. Photo credit: Larry Williams
You’d be surprised how upset some people can be about a few weeds, a dying petunia or a tomato with a crack in it. They’ll let small things like this upset their entire world. It’s as if they think we live in a perfect world when it comes to expectations for the plants in their own landscape.
It has become apparent to me that too many people spend too much time letting too many small things bother them too much.
When my twin sister, Linda, and I were growing up in a small town in middle Georgia, an elderly couple (Mr. and Mrs. Hunt) would crack pecans and give the shelled halves to us to eat. They’d hand the shelled pecans to us over the fence that separated our yards. At five or six years old this was a treat for my sister and me.
I remember their landscape. I remember Mrs. Hunt sweeping their dirt driveway lined with coconut sized rocks. She used handmade brooms. I remember their pink flowering dogwoods in spring. I remember their old-fashioned yellow and orange daylilies during summer. I remember the fascination of seeing red spider lilies seemingly come from nowhere in the fall underneath deciduous trees as they displayed their autumn colors. I remember Mrs. Hunt letting me smell a flower from a sweetshrub plant, which reminded me of sweet apples. The deep red blooms and dark green leaves of this shrub complemented the white wooden wall on the east side of their home.
Mulberry tree with fruit. Photo credit: Larry Williams
I remember climbing a large mulberry tree in their backyard and picking and eating the berries. I remember watching Mr. Hunt prune grapevines growing on an overhead trellis. I remember learning about the history of a ginkgo tree planted just outside a chicken pin in their side yard. I remember watching hummingbirds flying in and out of the reddish orange funnel-shaped blooms of a large trumpet vine growing on an old metal frame of a water tank.
I don’t remember the weeds, even though I know there must have been weeds in the Hunt’s landscape. I know there was the occasional pecan that didn’t fill out or that was worm infested. And I’m sure an occasional plant had to be replaced. But these are not the things that made lasting impressions for me.
The big picture is not the weeds, the dying petunia plant or the pecan with a worm in it. Sure you will have weeds in your yard and certain plants that don’t survive. Just don’t let these things become the source of worry. In my opinion, a landscape should be a source of pleasure, a place to learn and a place to pass along lasting memories. Besides, with all the things there are to worry about in this world (as recent days have revealed), why let your own backyard be one of them?
by Larry Williams | Apr 23, 2020
One of the things to do while stuck at home due to COVID-19 restrictions, is to look for caterpillars and butterflies in your landscape. I’ve noticed giant swallowtail butterflies (Papilio cresphontes) a little early this year. The giant swallowtail is one of the largest and most beautiful butterflies in our area. Its larval stage is known as the orangedog caterpillar. This unusual name comes from the fact that it feeds on young foliage of citrus trees.
Orangedog caterpillar. Photo credit: Donald Hall, University of Florida
The orangedog caterpillar is mostly brown with some white blotches, resembling bird droppings more than a caterpillar. When disturbed, it may try to scare you off by extruding two orange horns that produce a pungent odor hard to wash off.
I’ve had some minor feeding on citrus trees in my landscape from orangedog caterpillars. But I tolerate them. I’m not growing the citrus to sell. Sure the caterpillars eat a few leaves but my citrus trees have thousands of leaves. New leaves eventually replace the eaten ones. I leave the caterpillars alone. They eat a few leaves, develop into chrysalises and then emerge as beautiful giant swallowtail butterflies. The whole experience is a great life lesson for my two teenagers. And, we get to enjoy beautiful giant swallowtail butterflies flying around in our landscape and still get plenty of fruit from the citrus trees. It is a win, win, win.
In some cases, the caterpillars can cause widespread defoliation of citrus. A few orangedog caterpillars can defoliate small, potted citrus trees. Where you cannot tolerate their feeding habits, remove them from the plant. But consider relocating the caterpillars to another area. In addition to citrus, the orangedog caterpillars will use the herb fennel (Foeniculum vulgare) and rue (Ruta graveolens) as a food source. Some butterfly gardens plant citrus trees to provide food for orangedog caterpillars so that they will have giant swallowtail butterflies. So you could plan ahead and grow some fennel, rue or find a butterfly garden in your area for the purpose of relocating the larvae.
Yellow giant swallowtail butterfly on pink garden phlox flowers. Photo credit: Larry Williams
The adult butterflies feed on nectar from many flowers, including azalea, bougainvillea, Japanese honeysuckle, goldenrod, dame’s rocket, bouncing Bet and swamp milkweed. Some plants in this list might be invasive.
Keep in mind that mature citrus trees can easily withstand the loss of a few leaves. If you find and allow a few orangedog caterpillars to feed on a few leaves of a mature citrus tree in your landscape, you and your neighbors might get to enjoy the spectacular giant swallowtail butterfly.
More information on the giant swallowtail butterfly is available online at http://edis.ifas.ufl.edu/in134.
