What’s bugging your garden? – Buffalo Bur

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Farm Forum

Two comments I have been hearing a lot this summer is “the mosquitos are terrible” and “the weeds are really bad this year”. I would certainly have to agree on both counts and I think you would get the same response from our gardening crew, here at McCrory Gardens. The same applies to my garden at home, south of Aurora, SD. I have spent many evenings weeding and swatting mosquitos this summer. I would have to say that my most common weed is purslane, which seems to grow into these foot wide plants in just a few days with all the moisture. But I also have another weed, while not as numerous, I find it to be a real pain – buffalo bur. This spiny relative of tomatoes and potatoes is another annual that can also grow up quite quickly, but that is where the similarities stop. While purslane is low growing, has fleshy leaves and actually feels nice to touch, buffalo bur can grow to be a 2’ wide and tall ball of spiny leaves, stems and fruit. It makes up in ferocity for what it lacks in numbers.

Buffalo bur (Solanum rostratum) can be found in most of the northern Great Plains, except the northeastern corner of North Dakota. It can be found in areas where other plants are not growing abundantly, like roadsides, ditches, pastures, waste areas and in between vegetables in my garden. I didn’t know what it was when I first encountered it but I soon learned what it was from Leon Wrage, long-time Extension Weed Specialist at South Dakota State University. Since then I have learned, sometimes painfully, to get rid of it as soon as you can see it. The young seedlings are easy to identify by their narrow cotyledons followed by the development of the deeply lobed leaves and the yellow spines that soon start developing on the leaves, stems, and later the fruit. The flowers are bright yellow, and are actually quite pretty, looking very much like the flowers of tomato or potato. But soon the spine covered burs appear, which when ripe will contain numerous seeds, waiting to spill out and sow the crop of plants for next year. The seed can survive for several years in the soil so it is best to get rid of the plants before they can disperse seed.

Controlling young buffalo bur plants is fairly easy, just hoe, till or carefully pull them out. However, once they get some size to them, they are more difficult to control. Broadleaf and non-selective herbicides will also work well but you need to keep in mind when and where you are applying them so as not to damage desirable plants. If you are hand weeding, consider wearing gloves and maybe even collecting the plants to get them out of the garden. This will decrease the chance of any seed being released into the garden and also reduce the chances of grabbing or kneeling on a dry, dead plant that is still determined to give you a poke for good measure.

Plant Problems in Cool Wet Soil

By Mary Roduner, SDSU Extension Consumer Horticulture Field Specialist

This has been a hard garden year so far. First we had a long winter and late cool spring and now much of the state is too wet and cold or has flooded areas. Wet cool soils are prime conditions for many plant diseases to thrive.

Cool wet conditions promote fungal growth. Many types of fungal diseases require wet weather for the spores to germinate and survive. Dry soil and/or low humidity inhibit spore germination, reducing the chance of fungal diseases spreading.

Monitoring the garden closely will let you find these problems quickly and you can begin to treat the plants before the problems become serious or fatal.

The following are some of the most common cool, wet weather problems.

Nitrogen deficiency: Nitrogen is the nutrient most likely to leach out of the soil. When there is a large amount of precipitation in a short time, nitrogen is flushed out of the top soil layers into deeper layers that plant roots cannot reach. Continuous small amounts of precipitation will do the same thing but slightly slower.

Symptoms include a yellowing of the lower leaves and gradually moving to the upper leaves. If the leaves have dark green veins with yellow between them, this is an iron deficiency and nitrogen supplements will not help. To treat a nitrogen deficiency, add extra nitrogen according to package directions one time. If the weather continues to be rainy and the soil saturated, a second application may be needed a month later. Avoid over use of nitrogen as this will cause excessive green growth and reduced fruit set.

Verticillium wilt: Of all the tomato diseases, verticillium wilt ranks with fusarium wilt as one of the two most feared problems. Verticillium, Verticillium albo-atrum, requires cool weather and soil that is saturated for 24 hours to germinate and grow. This spring has had ideal conditions for the spread of verticillium.

While infection can happen early, symptoms are normally seen later in the season. Plants will start to wilt from the top down and watering will not perk them up, lower leaves will yellow; mimicking nitrogen deficiency, and the inside of the stem is discolored.

To diagnose the plant, cut a large low branch off and look for chocolate brown discoloration in the vascular tissue. This discoloration is a clogging of the vascular system, specifically the xylem tissue which pulls water from the soil and moves it into the plant tissues. Eventually the xylem becomes so clogged it can no longer carry water.

There is no cure for verticillium wilt. The spores are able to survive in soil for 4-10 years, making plant rotation very important. If your plants are diagnosed with verticillium wilt, pull them out and either put them in the trash or burn them. Do not compost diseased plants.

Over 300 plants can harbor verticillium wilt. This website from the Missouri Botanical Gardens has several lists of susceptible plants.

http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/diseases/cankers/verticillium-wilt.aspx

Septoria leaf spot: An airborne fungus, Septoria leaf spot, Septoria lycopersici, is most active in wet years when the temperatures are between 59 F and 80 F. The spores need a film of moisture on leaves to germinate. Frequent rain, high humidity and watering late in the day all provide the needed moisture.

The infection first shows up as brown spots ringed by yellow, on the lower leaves. As it progresses the spots will join into larger spots and stem develops lesions. Control is best done by watering in the morning so plants dry out before dark and using drip hoses or watering just the base of the plant will prevent foliage from getting wet. While this is not a soil borne fungus, spores do fall to the ground. Mulch will prevent any spores on the ground splashing up onto the plants.

If plants are frequently infected begin spraying a fungicide two weeks before you normally see the infection, and continue spraying weekly through the growing season. Copper soap is an organically approved fungicide providing good control. Plants with a heavy infestation should be removed and put in the trash.

Powdery mildew, (multiple species), looks like it sounds, a white powdery coating on leaves. Like septoria and verticillium, powdery mildew spores germinate in wet conditions. The initial infection looks like a slightly whitish/yellowing area on leaves. White spores develop on the undersides of leaves first and then move to the upper side. Plants that are too close together have reduced air flow which enhances the spread of the mildew. Spores blow on the wind and will infect nearby plants.

Control measures include using a fungicide as soon as the first symptoms are present. Do not wait because this fungus spreads very rapidly and is capable of covering a plant in one week. Copper and sulfur based fungicides work well. If a chemical fungicide is used, check the label to be sure that powdery mildew is one of the fungi controlled. Water plants only in the morning so leaves dry off, thin crowded plants and remove infected leaves, throwing them away. Also look for varieties that list resistance to powdery mildew.

Stem, root and seed rot: Cool wet soils cause a number of stem and root rots. Roots need to breathe oxygen and will drown just like humans. Soil that stays wet and does not drain has all the air spaces filled with water. Adding organic matter to soil, especially clay soils will loosen it and allow water to drain. Seeds planted deeply like corn, beans, peas and cucurbits will rot if the soil is saturated for more than a day or two.

Phytopthera fungi will attack seedling stems at the ground level, entering the plant in areas where there is environmental or insect damage. Stems will turn dark in color, become thin and stringy and the plant top tips over. Roots will become soft and mushy.

Drenching the soil with fungicide is not a cost effective method to control soil borne fungi in large areas and will also kill the beneficial fungi in the soil necessary for plant health. If cool wet conditions are anticipated, seeds treated with a fungicide can be planted. Be sure to wear gloves and wash your hands after handling the seeds.

The best way to control stem, root and seed rot is to plant in an area with good drainage and no low areas that puddle. If good drainage is not possible, then using raised beds or containers will elevate the growing surface, allow for faster drainage and soil warming, and reduce the chances of fungal infections.

While we can’t stop all fungal infections and nutrient deficiency problems in cool wet weather, careful planning and monitoring of the garden will help to reduce them.

Come to Our Party!

The Annual McCrory Garden Party is being held on August 1st this year. The gardens are beautiful so we hope you will join us for this wonderful event that is free and open to the public. It will be the perfect opportunity to meet old friends and exchange news and gardening ideas while listening to some great music by a local jazz band “Murph and Friends”. For the folks who had not been to the new Education and Visitor Center, it is a perfect evening to wander through the new facility enjoying an SDSU ice cream cone. This year we are also starting something new, the Garden Party Flower Show. Entries will be accepted from 3 to 5 p.m., followed by closed judging from 5 to 7 p.m. with a short program at 7 p.m. announcing the winners and open viewing until 8:30 p.m.

The Flower Show categories: Zinnia (small, medium, & large) – 3 stems;

Petunias (single & double) – 3 stems; rose – 1 stem; garden phlox – 1 stem.

Please bring each entry in a clear glass canning jar. Ribbons will be awarded for each category. There is no entry fee.

Contact us at 605-688-6707; mccrorygardens@gmail.com or go to our website www.mccrorygardens.com for more information.