October is Farm to School Month and this year in Georgia we are celebrating with Oh My Squash!. Several of you have grown squash with success and several of you have grown it with less success. For future reference we have created this squash problem cheat sheet. As you plan for your next crop of squash, keep these techniques in mind:
The #1 crop grown in community gardens is tomatoes. I don’t remember visiting a community garden where I didn’t see tomatoes in the summer. I understand! There is not much better than a tomato from the vine warmed from the sun. BUT, growing tomatoes in the same space year after year creates disease and pest problems.
Over the next few weeks we will be exploring some food crops not typically grown in the community gardens. I am hoping that we can provide some options for that tomato garden space.
To get you ready to embrace new plant options, take a minute to view this video on tomato diseases!
To finish our series on “tiny topics” I want us to think about mulch. Most gardeners already know that mulching our plant is a MUST. It helps even out soil temperature and moisture and it holds down weeds. But we can improve how mulch works for us if we take a minute to look at it critically.
Choose your mulch type wisely. The first rule of thumb is that you want mulch to be inexpensive and easily available. However, you also want mulch that is free from weed seeds. I have purchased hay as mulch that ends up contributing more weed seed than it prevented.
If you are using the mulch in a seed bed you want the elements of the mulch not to be a hindrance to seed emergence. If a small seed is pushing against a wood mulch nugget that is a problem. Lightweight mulch is best.
Often communities will give free mulch made from old Christmas trees. Be cautious of receiving this type of mulch. It is often full of large tree chucks which will be problematic for small seeds and can damage plant stems.
Consider changing your mulch. Especially if you are growing food crops, consider changing your mulch each season. Disease-casuisng organisms and pest insects can often overwinter in mulch and plant debris. Replace old mulch with new disease-free mulch. Another piece of the integrated pest management puzzle!
I hope with this series you have had a change to realize how even small garden elements can have a big impact on your garden’s health. I have appreciated the feedback and emails about this series!
I hope everyone enjoyed a wonderful thanksgiving! Today we resume our series “tiny topics.” Our next tiny topic is watering. How we water our plants can make a huge difference in our plant health. There are three things every gardener needs to know about watering:
#1 Avoid watering overhead if possible. Many of our plant disease-causing pathogens thrive in wet conditions. By wetting the leaves and plant blossoms we are creating an ideal environment for the spread of disease. Most community gardeners do not have drip irrigation systems that add water at the soil line and that is okay. Just be mindful when you are watering to focus the water on the soil line and not the plant leaves.
#2 The best time to water is in the early morning. This allows the plant leaves to dry off as the sun comes up. Again, water spreads disease! For most community gardeners this is not possible. Many gardeners head to the garden in the evening after work. Just knowing that you don’t want plants going through the night with wet leaves will help you be a better waterer.
#3 Don’t work in the garden while it is wet. There is no better way to spread disease then by working in a wet garden. Not only is spreading disease a problem but walking on wet soil can create soil compaction.
You may have heard these best management practices before today. But hopefully by knowing why these practices are important will allow you to modify your habits and your garden will thank you!
Every year seems to bring a new set of challenges for the Georgia gardener. Some years the drought leaves our gardens in the dust and some years it never seems to dry out. Some years we break record heat waves and some years fall comes early. However, plant disease never seems to give us a break. As we try and coax healthy cool-season crops out of warm soil I thought it might be nice to take a look at some disease facts so we can come up with strategies to help ourselves.
Fact #1: Healthy plants can withstand disease better than stressed plants. Knowing what healthy plants look like (is that mottling part of the normal leaf or could it be a virus?), what your plants need in the way of fertility and water, and what conditions those plants need to thrive will go a long way in managing disease. If your plants need full sun, plant in full sun. Shade will stress your plants and open up the possibility for disease. Have your soil tested for fertility and use the results to meet the needs of your plants. Take away: Strive for healthy plants
Fact #2: Most of our disease-causing agents are fungi. We do battle some bacteria and some viral diseases but overwhelmingly fungi are our problem. Most fungi need a wet environment. You probably notice during rainy periods disease symptoms seem to magically appear. Community gardeners tend to plant our plots as full as possible limiting air circulation around the plants. Moisture stays on the leaves creating a perfect environment for pathogens. Take away: Limit overhead watering as much as possible. Make sure your plants have adequate air flow around them.
Fact #3: Often pathogens overwinter in garden debris. Many times fungal survival structures, like spores and mycelia, will last for months(years) in organic matter, leaves, and garden debris creating an environment for a reinfection during the next planting cycle. Take away: Clean your garden plots after every season.
Fact #4: Most fungicides are used as preventatives and not as a cure for disease. Once a plant has been infected it is hard to cure that plant. The pathogen is already present, has done damage and gardeners cannot rely on fungicides to fix the problem. Take away: Plan ahead for disease management.
Fact #5: Some pathogens will infect many types of plants but many pathogens have a narrow plant host range. Rusts (Uromyeces spp.) are common among bean plants and powdery mildew (Oidium spp.) always seems to find all types of squash. Take away: Know what diseases normally affect the plants you have in your garden. Learn to recognize the pathogen signs and symptoms. Use your local Extension office to help identify the diseases that plague you. Your agent can also help you devise a plan of disease management.
This important information is shared with us by Robert R Westerfield, College of Agricultural and Environmental Sciences, Extension Horticulturist. He is our vegetable guru.
The tomato is the most commonly-grown vegetable in America. Unfortunately, producing big, red, juicy tomatoes requires considerable effort in preventing and controlling diseases.
Select tomato varieties that are disease resistant. This is very important! This may be your only chance to control certain diseases. The letters behind a variety’s name tell what diseases it is resistant to: T-Tobacco Mosaic Virus, V-Verticillium Wilt, F-Fusarium wilt and N-Nematodes, some good possibilities are Celebrity and Better bush but there are many others. Resistance does not mean the plants are immune to these diseases.
Move tomatoes away from where they or potatoes, eggplant or peppers were planted last year. Soils in these areas may harbor leftover diseases. Bury all plant debris when tilling and keep mulches pulled back an inch or two from the stem.
You can plant tomatoes in a traditional vegetable garden, a raised bed or put a few plants in a flower garden. I would avoid potted tomatoes because they require extra care in watering. If you grow potted tomatoes-use 5 gallon or larger pots. Water until water runs out the drain holes and then let the soil dry slightly before watering again.
The number one tomato disease now is Tomato Spotted Wilt Virus (TSWV). It is spread by thrips. Usually the top of the plant looks stunted or wilted. The young leaves may turn yellow and often have brown or black discoloration in them. The veins on the underside of leaves may thicken and turn purple. Fruit can have raised or flat rings or circles on them. Ripe fruit will have yellow circles or semicircles. The stem can have long brown lesions.
Once tomatoes get the disease, there is no control. There are two varieties of tomato that are resistant to TSWV. I have not yet seen them yet in stores. Spraying for thrips is also not effective.
Destroy infected plants as quickly as possible early in the season to prevent spread. Seal them up in a plastic bag. Even after the plant is pulled up thrips can leave it to spread the virus. Late in the season you may just want to let the infected plants finish ripening the fruit they have. Late season infection is less of a concern.
A fungus causes Fusarium wilt. It blocks the water conducting tissues in the plant. The leaves yellow and wilt, often starting at the bottom of the plant. This disease can affect just one side or one to several branches of the plant. The plant can die early producing no fruit. If you cut into the plant, the vascular system (just under the bark) will be brown. Control Fusarium wilt by planting resistant varieties. The ‘F’ after the name, like Celebrity VFN identifies these. Fusarium wilt can survive in the soil. Do not plant tomatoes in infected areas more than once every four years.
Bacterial wilt causes a rapid wilting and death of the plant. The plant dies so quickly it does not have time to yellow. To identify Bacterial wilt, cut through the stem. Bacterial wilt browns the pith or middle of the stem. On bad infections, the pith may be hollow. Cut a short section of the stem and suspend it in a clear glass of water. You can often see a milky ooze streaming out of the bottom of the cut stem. There are no controls or resistant varieties for bacterial wilt. It also attacks peppers, potatoes and eggplant. Carefully dig out infected plants and soil and discard. Do not plant any of these vegetables in this area for at least four years.
Southern blight is a white mold that rots the stem at or near the soil line. The plant then wilts or dies. Look for the cottony fungus growth and the light brown BB-sized fruiting structures of the fungus. The fungus may be slightly above or below the soil line. You may not see the fungus growing on infected plants when the weather is dry.
Bury all plant residues before planting, plant vegetables farther apart, and treat with Terraclor at planting if you have a problem with Southern blight. Some people wrap the stem near the soil line with foil to slow this disease and to control cutworms. The foil must extend two inches above and below the soil line.
Blossom-end rot (BER) appears as a dry leathery spot on the blossom end of tomatoes. It can also affect peppers and watermelons. The spot is usually on the blossom end, is tough and leathery and slightly sunken. Other rots may infect this spot. These fruits may turn red first.
BER is caused by lack of calcium in the blossom end of the fruit. By the time the tomato reaches the size of a nickel it has most of the calcium that it will ever have. This is why we need to prevent blossom end rot early. Inadequate water supply, low pH or low soil calcium levels can cause this problem. Find and correct these problems.
Once a plant has BER, it is hard to control. Calcium is best taken up by the roots so sprays are not very effective. Control and prevent BER by:
Water the plants well and let the soil dry between waterings. A sample watering schedule is three-quarter inch twice a week if there is no rain.
Apply a two to three inch mulch around the plant. Do not heavily prune the plant.
Soil sample and lime and fertilize as needed. Avoid large applications of high nitrogen fertilizers when fruit are small.
Add gypsum (calcium sulfate) or lime to the soil at planting. Mix a cup in each planting hole or use one pound per 100 square feet. You can apply this once you see the problem but these treatments work slowly. Plants often appear to grow out of the problem as conditions improve.
For further information. Tomatoes flowers will not set fruit if temperatures are not right, if the plant is water stressed or if it already has enough fruit. Night temperatures should be 55o to 75o F. for best fruiting. Night temperatures above 90o will especially cause problems. Water twice a week (3/4 inch each time) and mulch plants. There is a blossom set chemical you can spray if you can locate it in the garden centers.
Leaf Rolling occurs when the plant has set a heavy load of fruit and the light intensity is high. It can be caused by wet soils. The condition is harmless and should not hurt final production. Prune less heavily and plant in a well-drained area.
Uneven ripening occurs as grey or white spots inside the fruit. Several factors can be involved including improper nutrition, high temperature and disease. The only thing we can correct is nutrition. Do not use too much nitrogen and/or too little potassium. Soil sample and fertilize accordingly. Use high potassium fertilizers, 5-10-15, 15-0-15 especially as fruits begin to get larger than a quarter.
Fruit cracking is due to rapid growth after periods of slow growth. Rain after drought and heavy fertilization can cause fruit cracking. Harvest fruits after they begin to turn red but before they crack. Follow the watering practices we have discussed and look for cracking resistant varieties.
Catfacing is caused by cool temperatures at time of pollination. The fruit is deformed with ‘zippers’ on the skin. The fruit can have lobes, tear drops or several blossom scars. Plant resistant varieties, plant later, or use row covers to increase the temperature on cool days and nights. The large beefsteak varieties appear to be more susceptible. The fruit is still edible.
Sun scald appears as a white blistered area on the top of the tomato. Do not prune heavily and maintain nutrition and pest control so as to provide a good leafy cover for the fruits. Be careful not to confuse this with Blossom End Rot.
You probably have seen them and not given them much notice, growing among your blueberry fruits. They look like something just went wrong in fruit development. These are mummy berries and they are actually part of a fungal pathogen, Monilinia vaccine-corymobosi. This is a blueberry disease!
Mummy berries are caused by a pathogen
Over the season mummies fall off of the plant and oversummer and overwinter on the ground. When conditions are just right in the spring, these bodies will germinate and can produce 650,000 disease-causing ascospores. The ascospores can re-infect your plants creating a disease cycle.
Control is not difficult for hobby blueberry growers
This disease affects leaves and affects the fruits when the pathogen is spread to the flower bloom, by wind or by insects. For commercial growers this can be a serious problem. For the casual blueberry grower it is much easier. Simply remove the mummies and throw them away. Also, check the ground to remove those mummies that have fallen.
For those of you interested in pathology, Jade Florence has an excellent article, Mummy Berry, in The Plant Health Instructor. If you are unsure if mummy berry is your problem, contact your local UGA Extension office for assistance. If you don’t have blueberries in your community garden, they are a great addition and easy to plant.
Crop rotation is a huge part of integrated pest management (IPM) in Georgia vegetable production. It is an inexpensive tool in disease and nematode management. Correctly using crop rotation can cut down on pesticide use and result in healthier plants. Growing Vegetables Organically has some great information on this type of IPM.
As we are all planning our warm-season gardens crop rotation is something to consider. However, it is a whole lot easier to rotate crops around a 3 acre farm than it is to move them around a 32 square foot garden plot. How do we practice crop rotation in the community garden? It is even necessary?
Crop rotation has been around for centuries. Simply it is changing what is planted in a particular area each year. Planting the same crop year after year in the same location causes disease pathogens to build up and become a real problem. Rotating crops helps break this disease cycle. Also, since different crops use varying amounts of plant nutrients, crop rotation is a wise use of the nutrition in your soil.
Plants can be divided into families. Learn those plant groupings because many pathogens infect crops in the same families. The basic rule of crop rotation is:
Don’t plant crops from the same plant family in the same place every year.
Onion family (Alliaceae): chives, onions, garlic
Cole family (Brassicaceae): lettuce, collards, cabbage, broccoli, spinach
Squash family (Cucurbitaceae): pumpkins, watermelon, squash, cantaloupe
Bean family (Fabaceae): beans, peas
Tomato family (Solanaceae): tomatoes, peppers, eggplant
Since tomatoes and peppers are in the same family (Solanaceae), don’t plant tomatoes where you have been growing peppers. And, don’t follow squash with pumpkins (same Cucurbitaceae family). Many farmers follow a four year or even longer rotation plan. Their lettuce won’t see the same piece of soil for several years. This helps lower disease pressure and cuts down on fungicide use. Many Master Gardeners usually try for a three year rotation for a large garden area.
We know that crop rotation works to help create healthier plants but how does that translate in a Georgia community garden plot?
The best way is for the community gardener to choose plants from different families each year. This isn’t always practical. A gardener wants to grow what his/her family likes to eat. That may mean beans every year. The #1 vegetable grown in community gardens is tomatoes – year after year!
So, maybe you work with your fellow community gardeners and rotate who grows tomatoes and you all agree to share the tomato harvest. This may not always work, either. Some gardeners want lots of tomatoes every year.
Move your pole beans to the other side of the plot this year. Buy your tomatoes from the farmers market this year and try growing squash. Better yet, try growing and eating something entirely new.
At the very least Bob Westerfield, UGA vegetable specialist, recommends turning your soil over. Dig deeply bringing up soil that hasn’t been exposed to the sun. Go as deep as you are able. In a small way you are not rotating your plants but rotating your soil. Your UGA Extension agent can help you come up with a plan for crop rotation that will work for your situation.
You may have heard about integrated pest management (IPM) and wondered if it is something only farmers use. Actually IPM has a real place in any type of gardening, including your community garden plot. According to the UGA Integrated Pest Management website this is the definition of IPM:
It is a science-based decision making process that employs biological, mechanical, cultural, and chemical control methods in such a way as to minimize economic, environmental, and public health risks associated with pests and pest management practices.
Notice it is science-based decision making. This is important.
In practice, the gardener employs many different strategies to combat an insect pest or disease instead of just reaching for the chemical spray. For a very basic example a gardener wants to grow tomatoes knowing that Fusarium wilt can be a problem. (Fusarium wilt is a fungus that lives in the soil and infects plants through their root systems.) This gardener will employ IPM by:
making sure his/her soil is healthy
growing healthy plants using recommended fertilization and watering practices
learning about the Fusarium wilt fungus and its biology
choosing tomato cultivars that show resistance to Fusarium wilt – these will have the letter “F” after the cultivar name
caring for garden equipment by proper disinfection and not using equipment from another gardener that has not been disinfected
being aware of the hot, dry weather that favors Fusarium wilt and looking for wilting especially during these conditions
destroying any infected plants
practicing crop rotation
With IPM, actions are taken to prevent diseases and pests from becoming a problem. Rather than simply eliminating the pests that are found right now, using IPM means the gardener will look at environmental factors that affect the pest and its ability to do damage. Armed with this information, the gardener can create conditions that are unfavorable for the pest. Know your enemy!
Your local UGA Extension agent can help you make a positive disease or insect identification so that you can make a plan to deter the problem.
Learning when and where an insect pest lays her eggs can help you find those eggs and remove them. Determining what weather conditions favor a disease can help you adjust your planting date to avoid the peak of the disease. Finding out how a disease is spread can also help you combat it. Is it soil-borne or are fungal spores spread with wind? Also, what beneficial insects prey on your insect pest and how can you attract those helpful insects?
Subscribing to this blog and other researched based information sources can help you know what diseases or pests are problematic in your area and what you can do about them.
If you haven’t visited the Upcoming Classes page of this blog, please do so. There are many classes and workshops coming up. Many are free and some are offered online.