This time of year, two common leaf-spot diseases appear on tomato plants. Septoria leaf spot and early blight both appear as brown spots on tomato leaves.
Septoria leaf spot usually appears earlier in the season than early blight and produces small dark spots. Spots made by early blight are much larger and often have a distorted “target” pattern of concentric circles. Heavily infected leaves eventually turn yellow and drop. Older leaves are more susceptible than younger ones, so these diseases often start at the bottom of the plant and work up.
Mulching, caging, or staking keeps plants off the ground, making them less vulnerable. Better air circulation allows foliage to dry quicker than in plants allowed to sprawl. Mulching also helps prevent water from splashing and carrying disease spores to the plant.
If you know you have had one of these diseases in the past, rotation is a good strategy. It is too late for that now, but keep it in mind for next year. Actually, rotation is a good idea even if you have not had problems in the past. If you have room, rotate the location of the tomatoes each year to an area that has not had tomatoes or related crops (peppers, potatoes, eggplant) for several years.
If rotation is not feasible, fungicides are often helpful. Be sure to cover both upper and lower leaf surfaces, and reapply fungicide if rainfall removes it. Plants usually become susceptible when the tomato fruit is about the size of a walnut. Chlorothalonil is a good choice for fruiting plants because it has a 0-day waiting period, meaning that fruit can be harvested once the spray is dry. Chlorothalonil can be found in numerous products including Fertilome Broad-Spectrum Landscape and Garden Fungicide, Ortho Garden Disease Control, GardenTech Daconil and others. Be sure to start protecting plants when the disease is first seen. It is virtually impossible to control this disease on heavily infected plants.
If chlorothalonil doesn’t seem to be effective, try mancozeb (Bonide Mancozeb Flowable). Note that there is a five-day waiting period between application and when the fruit can be harvested. You may wish to pick some tomatoes green just before you spray if you use Mancozeb as the tomato fruit will ripen inside.
If you have vegetables that are blooming but not setting fruit, you may have a problem with flower pollination. There are several possible reasons for this that usually vary by species. One condition that can affect several species at the same time 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.
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.
Tomatoes are wind pollinated and therefore not dependent on pollinators. But they have another possible problem, which 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.
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. We are now seeing the nymphs of the first generation. 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 now 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, Pet and Livestock 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.
Have you ever been in your garden and found a mysterious insect, you weren’t sure what it was or how to control it? This program is for you! Our guest speaker will be State Extension leader for Entomology Dr. Raymond Cloyd. Dr. Cloyd will be talking about the top insects you might see this growing season. Join us Thursday, May 10th at 7:00pm, in the commercial building on the Cloud County Fairgrounds in Concordia, Kansas. This event is brought to you by K-State Research and Extension Horticulture Agents Cassie Homan from Post Rock District and Kelsey Hatesohl from River Valley District. Whether you have been gardening for years or are just getting started this program is open to all at no cost! Participants are asked to RSVP by May 7th to the Post Rock Extension Office at 785-738-3597 or by emailing Kelsey Hatesohl at email@example.com.
Sidedressing, also referred to as topdressing, is the practice of fertilizing your plants as they are actively growing. This is done using a fertilizer high in nitrogen and gives your plants an extra boost during the growing season. Done correctly, sidedressing can improve vegetable, fruit and flower production.
Use the chart linked below to learn the amount of fertilizer needed, and suggested time of application for your specific crop.
If you love cooking and gardening, then we have the perfect class for you. Healthy food choices don’t have to be boring and bland. Come learn how to cook with less salt but more flavor. We will demonstrate how to add herbs to your favorite recipes and grow them in your garden.