Horticulture 2020 Newsletter
Video of the Week: Common Tomato Problems; Part 1
https://kansashealthyyards.org/all-videos/video/common-tomato-problems-part-1
UPCOMING EVENTS
The 2020 Kansas Turfgrass Field Day is Canceled
The 2020 Kansas Turfgrass Field Day scheduled for Thursday, August 6 in Manhattan is canceled due to the complications arising from COVID-19.
The K-State campus is not allowing face-to-face contact through July 31. In addition, although turf research is continuing at Rocky Ford, the Olathe Horticulture Center, and the Pair Center, all centers are closed to the public and researchers must minimize their time at the facilities. We do plan to post written and video research updates through the remainder of the year on the Turf and Landscape Blog, accessible through our website, ksu.edu/turf. Next year’s Kansas Turfgrass Field Day will be at the Rocky Ford Turfgrass Research Center in Manhattan on August 5, 2021. We are looking forward to seeing you at the 70th Kansas Turfgrass Conference, December 8, 9, and 10, 2020 in Topeka, KS.
Reminders
- Renovate strawberry beds after last picking of fruit by cutting off leaves, fertilizing and narrowing row to 10 inches. https://tinyurl.com/y7mlwn3k
∙ Check for bagworms and spray if needed. https://tinyurl.com/yaoawohb
VEGETABLES
Hornworms on Tomatoes
Hornworms are the largest larval insect commonly seen in the garden. Though usually seen on tomato, they can also attack eggplant, pepper, and potato.
The larval stage of this insect is a 3 ½- to 4-inch long pale green caterpillar with five pair of prolegs and a horn on the last segment. The two most common hornworms are the tobacco hornworm (seven diagonal white stripes and, most commonly, a red horn) and the tomato hornworm (v-shaped markings with a horn that is often blue or black).
The adult of the tobacco hornworm is the Carolina sphinx moth. The five-spotted hawk moth is the adult of the tomato hornworm. Both moths are stout-bodied, grayish-colored insects with a wing spread of 4 to 5 inches. The larva is the damaging stage and feeds on the leaves and stems of the tomato plant, leaving behind dark green or black droppings.
Though initially quite small with a body about the same size as its horn, these insects pass through four or five larval stages to reach full size in about a month. The coloration of this larva causes it to blend in with its surroundings and is often difficult to see despite its large size. It eventually will burrow into the soil to pupate. There are two generations a year.
This insect is parasitized by a number of insects. One of the most common is a small braconid wasp. Larva that hatch from wasp eggs laid on the hornworm feed on the inside of the hornworm until the wasp is ready to pupate. The cocoons appear as white projections protruding from the hornworm’s body. If such projections are seen, leave the infected hornworms in the garden. The wasps will kill the hornworms when they emerge from the cocoons and will seek out other hornworms to parasitize.
Handpicking is an effective control in small gardens. Though large, these larvae are surprisingly difficult to see. Missing foliage is often the first clue that you have an interloper. Bt (Dipel, Thuricide), spinosad (Conserve; Colorado Potato Beetle Beater Conc; Captain Jack’s Dead Bug Brew, Monterey Garden Insect Spray), cyfluthrin (BioAdvanced Vegetable & Garden Insect Spray) and other insecticides may also be used to control hornworms. Pay attention to the harvest interval. The harvest interval is the number of days between when the spray is applied and when the fruit can be harvested. (Ward Upham)
Squash Bugs
Squash bugs are the grey, shield-shaped bugs that feed on squash and pumpkin plants. If you have had problems with these insects in the past, you know that they are almost impossible to control when mature. This is because the squash bugs have a hard body that an insecticide has difficulty penetrating. Thus, spraying when the insects are small is important. Look on the underside of the leaves for cluster of brick-red eggshttps://hnr.k-state.edu/extension/info-center/common-pest-problems/common-pest-problem-new/Squash%20Bug.pdf and small green insects with black legs. These nymphs will eventually become adults, which will lay eggs that will become the second generation. The second generation is often huge and devastating. Therefore, it is important to control as many squash bugs of the first generation as possible.
Because squash bugs feed by sucking juice from the plant, only insecticides that directly contact the insect will work. General use insecticides such as permethrin (Bug-B-Gon Multi-Purpose Garden Dust; Green Thumb Multipurpose Garden and Pet Dust; Bug-No-More Yard and Garden Insect Spray; Eight Vegetable, Fruit and Flower Concentrate; Garden and Farm Insect Control; Lawn & Garden Insect Killer), malathion, and methoxychlor provide control if a direct application is made to young, soft-bodied squash bugs. This means that you MUST spray or dust the underside of the leaves because this is where the insects live. (Ward Upham)
Physiological Leaf Curl in Tomatoes
Every year we have calls from gardeners who have tomato plants with leaves that curl up. When tomato plants grow vigorously in mild, spring weather the top growth often exceeds the root development. When the first few days of warm, dry summer weather hit, the plant ‘realizes’ that it has a problem and needs to increase its root development. The plant tries to reduce its leaf area by rolling leaves. The leaves curl along the length of the leaf (leaflet) in an upward fashion. It is often accompanied by a thickening of the leaf giving it a leathery texture. Interestingly, leaf roll is worse on some varieties than others.
Though rolling usually occurs during the spring to summer shift period, it may also occur after a heavy cultivating or hoeing, a hard rain, waterlogged soil or any sudden change in weather. This leaf roll is a temporary condition that goes away after a week or so when the plant has a chance to acclimate, recover from injury, or the soil has a chance to dry out. (Ward Upham)
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