Blog Posts - K-State Research and Extension Horticulture Newsletter

Vegetables Produce Flowers But No Fruit

6/27/2022

This is the time of year that gardeners often have trouble with vegetables that are blooming but not setting fruit. There are several possible reasons for this. One condition that can affect several species is overfertilization. Too much nitrogen causes the plant to emphasize vegetative growth, often to the detriment of fruit production. Overfertilization can lead to a delay in flower production and a decrease in fruit set among the flowers produced. This is especially true of tomatoes. Overfertilized tomatoes will produce a large, apparently healthy plant with no flowers or with flowers that don’t set fruit.

Another possible problem with tomatoes setting fruit is temperature. Tomatoes normally won't set if the night temperature is below 50 due to sparse pollen production. They also won't set when nighttime temperatures are above 75 degrees F and daytime temperatures are above 95 degrees F with dry, hot winds. Under such conditions, fertilization is not completed and no fruit develops. However, cherry tomatoes may be more forgiving of high temperatures than the larger slicers and will often set fruit in the heat.

Squash, cucumbers, watermelon, and muskmelon can have a couple of other problems. First, the early flowers on these plants are usually all male. The production of both male and female flowers becomes more balanced as time passes. You can easily tell the difference between the two because only the female flower has a tiny fruit behind the blossom. If you have both, have not over-fertilized, and still have a problem, make sure you have pollinators.

Look for the presence of bees visiting the plants. If you don't see any, try hand-pollinating several flowers. Use a painter’s brush to transfer pollen from the anther of the male flower to the stigma of the female flower. If you get fruit on only those flowers you pollinated, you need more pollinators. Make sure you aren't killing them with overuse of insecticides. If you must use an insecticide, spray near dusk when the flowers have closed. (Ward Upham)

Brown Patch on Tall Fescue

6/27/2022

We have been receiving numerous reports of brown patch showing up on tall fescue. This disease is favored by warm night temperatures and extended periods of leaf wetness. If you go outside in the morning and the lawn is covered with dew and the temperature is in the high 60s or higher, it means that conditions are getting right for brown patch. The fungus is primarily a leaf pathogen and does not attack the roots. During severe outbreaks, the fungus may invade the lower leaf sheaths and crown and kill plants. But in most cases, the turfgrass can recover from brown patch. This recovery may take two to three weeks, depending on weather.

There is no way to eliminate brown patch from a lawn. It will persist indefinitely in the soil. Therefore, the disease is not carried from one lawn to another. In almost all cases, the limiting factor for brown patch development is the weather, not the amount of fungal inoculum. Although you can’t eliminate the fungus, cultural practices – especially irrigation – can help control it. Don't water in the evening; instead, water early in the morning. This will help decrease the number of hours the leaf tissue remains wet and susceptible to infection. The frequency of irrigation is not as important as the time of day you do it. Don't overfertilize and certainly don't fertilize when brown patch is active. Also, don't allow your seeding or overseeding rates to become too high.

Fungicides can be effective in preventing brown patch, but the two most commonly used products (Heritage and ProStar) are expensive and not available in small quantities to the general public. Homeowners do have access to some effective products including triadimefon (Green Light Fung-Away), propiconazole (BioAdvanced Fungus Control for Lawns, Fertilome Liquid Systemic Fungicide II) and myclobutanil (Immunox, F-Stop Lawn & Garden). Of the three, triadimefon may be the fungicide of choice because it protects the turf longer (3 to 5 weeks rather than 2 weeks). But my suggestion is not to use fungicides unless you want to maintain a blemish-free yard and are willing to pay for it. In those cases, you would need to be on a preventative spray program, which is very expensive, rather than waiting for symptoms and applying as a curative. These products do not cure an infection already present but are only effective as a preventative. Applications should begin in mid-June and continue through August. Often tall fescue lawns will recover from brown patch but infections this year seem more severe than usual and may require overseeding this fall. (Ward Upham)

Bermudagrass Control

6/27/2022

Bermudagrass can make a nice lawn if you don't mind its invasiveness and short growing season. But many people dislike both these characteristics. Warm-season grasses, such as bermudagrass, zoysiagrass and buffalograss, green up later than cool-season grasses such as tall fescue and Kentucky bluegrass. They also go dormant earlier in the fall, which can make a lawn unattractive.

Bermuda that invades a cool-season lawn will be brown during much of the spring and fall while the tall fescue portion of the lawn is green. Bermuda is much more drought and heat resistant than cool-season grasses, so it will take over a cool-season lawn during the summer months if it is in full sun.

So, how do you control bermudagrass that has invaded a cool-season lawn? Research conducted in 1996 showed that glyphosate (Round-up, Kleen-up, Killzall, Kleeraway) is the best herbicide for the job. Glyphosate is a nonselective herbicide and will kill everything— including tall fescue or Kentucky bluegrass. Therefore, you will need to reseed treated areas. In our study, we applied a 2% solution of glyphosate on July 15 and again on August 15 on a bermudagrass plot that was more than 15 years old. More than one year later, we saw no regrowth. Glyphosate works best if bermuda is growing well. The better the bermudagrass is growing, the more chemical is taken up and pushed into the roots. Water and fertilize if needed to get it going.

Spray about the middle of July (or when the bermuda is growing well). Use glyphosate (2% solution). Wait two weeks and scalp the lawn (mow as low as possible and remove clippings.) This will prevent dead grass from covering any bermuda that starts to recover. Wait another two weeks and spray again with glyphosate if there is any green. Wait two more weeks and reseed. (Ward Upham)

Carpenter Bees

6/27/2022

Although carpenter bees look much like bumblebees, they are easy to identify if you know what to look for. Bumblebees have hairy abdomens that are usually yellow and black. Carpenter bees’ abdomens are shiny blue-black. Carpenter bees are solitary (do not form colonies) and are nonaggressive unless provoked. Only the female possesses a stinger. The male may act aggressive but is harmless. Carpenter bees get their name from the ability of the female to bore into wood. Holes are about a half-inch in diameter and may be 6 inches deep. The female then builds six to eight cells off the main tunnel and lays an egg in each.

Developing larvae feed off of "bee bread" (pollen and nectar) regurgitated by the female bee. Larvae become adults by late August and September, but do not emerge until the following spring. Individual holes may not cause much damage, but cumulative effects of numbers of bees can weaken structures. Painting wood surfaces can make them less attractive to bees. Stains seem to have little effect.

Insecticides, such as Sevin, can be used to treat openings. Sprays and dusts are both effective but sprays may only last for 1 to 2 weeks and require retreatment. Dusts are most easily applied with a puffer duster. It is best to treat near sundown when the bees have returned to their tunnel. (Ward Upham)

Harvesting and Storing Onions

6/20/2022

Pulling Onions

6/20/2022

Onions are ready to harvest when about half the plants have tops that have fallen over. This is a sign that the onions are mature and need to be pulled out of the ground. Bulbs may sunburn without the foliage to protect them. The secret to onions keeping well is to allow the tops to dry completely before storage. This may take 2 to 3 weeks. Large-necked onions take more time to dry than small-necked onions such as Bermuda types. Move onions to a shaded, well-ventilated area after harvest and spread them out.

After tops are completely dry, remove the dry foliage and compost. Store the bulbs in a cool, dry location. Avoid storage in plastic bags because the lack of air circulation will shorten storage life. Use an open, mesh bag instead. (Ward Upham)

Squash Vine Borer

6/20/2022

If you have squash or related plants that suddenly wilt and die, you may have squash vine borer. This insect will bore into the stems of squash, zucchini, pumpkins and gourds. Zucchini squash are a favorite. Cucumbers and melons are usually not a target, although both can be affected by a disease that causes similar symptoms, known as bacterial wilt.

The adult of this insect is a clear-winged moth that resembles a wasp. The forewings are a dark metallic green but the rear wings are clear. The abdomen is orange with black spots. The larva is cream-colored and rather wrinkled. Adults emerge in the spring and lay eggs on or near susceptible plants. Eggs are deposited singly on the underside of the vines and are often concentrated at the base of the plants. Larva bore into the plant and feed for about a month as they move toward the base. Mature larva will exit the plant, burrow into the soil and pupate where they remain until the next year. Each plant can have numerous borers. If you suspect squash vine borer, split the stem of a collapsed plant near where it enters the ground. Infested plants will be hollowed out and mushy and may contain borers.

Unfortunately, there isn't much you can do at this late stage. Control measures should center on prevention.

Suggested preventative controls would include crushing the dull red eggs before they hatch, excavating larvae from stems before they cause much damage or using insecticide applications. Applications should begin when the vines begin to run (too late for that) and reapplied every seven to 10 days through the end of June. Direct the spray at the crown of the plant and the base of runners. Chemicals used for borer control in gardens are permethrin (Eight Vegetable, Fruit & Flower Concentrate; Garden and Farm Insect Control; Lawn & Garden Insect Killer) or bifenthrin (Hi-Yield Bug Blaster II, Bug-B-Gon Insect Killer for Lawns & Gardens) applied as sprays or dusts. If plants wilt, look for the presence of holes and ooze. However, in extreme heat, these plants will temporarily wilt in the afternoon even if undamaged by this insect. (Ward Upham)

Raccoons and Sweet Corn

6/20/2022

It seems the official sweet corn inspector should be the raccoon as they seem to harvest the sweet corn the day before it is to be picked. The only effective control measure I have had success with is fencing; either electric or kennel fencing. First are some suggestions for electric fencing. Other designs may very well work but this is what has worked in my garden.

– Two or more wires must be used. Place the first about 5 inches above the ground and the second 4 inches above the first (or 9 inches above ground). Raccoons must not be able to crawl under, go between or go over the wires without being shocked.

– Fence posts used for electric fences work well for this application (go figure), as do the insulators used to support the electric wire.

– It is much easier to use the woven electric wire with strands of wire embedded than to use a solid metal wire. The woven wire is easier to bend around corners and to roll up when done for the year.

– Though both the plug-in and battery operated fencers work, the battery operated types allow more versatility in where corn is grown. One set of batteries is usually sufficient for the season.

– Start the charger before the corn is close to being ripe. Once raccoons get a taste of the corn, they are more difficult to discourage.

– Control weeds near the wire. Weeds can intercept the voltage if they touch a wire and allow raccoons entry beyond the weed.

– Check the wire occasionally to make sure you have current. This can be done easily (but unpleasantly) by touching the wire. There are also tools that will measure the voltage available for sale. They are worth the money.

As mentioned earlier, kennel fencing can also be used. Make sure that the panels are tied together well enough that raccoons can’t squeeze through corners. A covering over the top may be needed if the raccoons figure out how to climb the panels. Welded garden fence can work well for this. (Ward Upham)

Sweet Corn Earworm

6/20/2022

Corn earworm tends to be a problem every year on sweet corn in Kansas. The earworm moth lays eggs on developing silks at night. When the egg hatches, the larva crawls down the silk and into the ear. Feeding starts at the tip of the ear and works down. Though several earworms may hatch and attack a single ear, only one is usually present at harvest due to the cannibalistic nature of the insect. Control is challenging as silks continue to grow over a period of time. This means that even if silks are treated, new silk will appear that hasn't been protected. Applications every 2 to 3 days are needed for insecticides to be effective, especially in early July when peak flight of these moths usually appear.

There is a three-week period from silking to harvest, but there is only a two-week period from when the silks appear to when they begin to dry. Since moths prefer juicy silks and shun those that have started to dry, insecticides are only needed the first two weeks of silking.

Homeowners can use cyfluthrin (Baythroid) or spinosad (Captain Jack's Dead Bug Brew; Natural Guard Spinosad, Monterey Garden Insect Spray). Spinosad is an organic product. Commercial growers have additional choices including zeta-cypermethrin (Mustang Max), bifenthrin+zeta-cypermethrin (Hero), spinetoram (Radiant) and flubendiamide (Belt).

Though more time consuming, mineral or other light horticultural oils may also be used as an organic control. The oil is placed inside the silk end of the ear with a medicine dropper (½ to 3/4 of a dropper) when the tips of the silks begin to wilt and turn brown. This will coat the earworms already present and likely suffocate them and earworms that enter the ear after the mineral oil is applied will also be controlled. Applying the oil before the silk has begun to brown may interfere with pollination, leading to incompletely filled ears. (Ward Upham)

Why Tomatoes Don’t Set Fruit During Hot Weather

6/20/2022

Tomatoes will not produce fruit when the temperature rises above a certain point. Though there is some variation, a temperature of 95 degrees or above will stop fertilization and therefore fruit production. Fruit that has already formed is not affected.

So how does this work? For fertilization to take place, a pollen grain must land on the stigma of the flower. A pollen tube is then formed which grows from the stigma, down through the style to the ovule where fertilization take place. Excessive heat literally causes the pollen tube to explode, thereby preventing pollination. Even short bursts of temperatures above 95 degrees are enough to cause this reaction. Once temperatures cool, pollination can again take place.

I mentioned before that there is some variation among varieties in how susceptible they are to heat preventing fruit formation. There are "heat-set" slicing tomatoes such as Florida 91, Sun Leaper and Sun Master that will set fruit at higher temperatures, but that difference is normally only 2 to 3 degrees. Also, cherry tomatoes can be less susceptible. (Ward Upham)