Iowa State University Extension specialists offer tips for taking care of your lawn, annuals and garden in hot weather. To have additional questions answered, contact the experts at hortline@iastate.edu or call 515-294-3108.

Is it necessary to water an established lawn during hot, dry weather?

Gardeners have two basic options when confronted with hot, dry weather. One option is to do nothing and allow the grass to go dormant. The alternative is to water the turfgrass during dry weather to maintain a green, actively growing lawn.

Cool-season grasses, such as Kentucky bluegrass, can survive long periods of dry weather. In dry weather, the shoots of the turfgrass plants stop growing and the plants go dormant. Dormancy is a natural survival mechanism for turfgrass. While the leaves have turned brown and died, the turfgrass roots and crowns remain alive. Generally, Kentucky bluegrass can remain dormant for four to six weeks without suffering significant damage.

Cool-season grasses are at risk of dying if dormant for more than six weeks. To ensure survival of dormant grass, it's best to water lawns that have been dormant for six weeks. Apply 1 to 1 ½ inches of water in a single application. Water again seven days later. The grass should begin to green up after the second application.

When is the best time to water a lawn?

Early morning (5 to 9 a.m.) is the best time to water a lawn. A morning application allows the water to soak deeply into the soil with little water lost to evaporation. When watering is completed, the turfgrass foliage dries quickly. Watering at mid-day is less efficient because of rapid evaporation; in addition, strong winds may cause uneven water distribution. Strong, mid-day winds also may carry water onto driveways, sidewalks or streets, wasting considerable amounts of water. Watering lawns in late afternoon or evening may increase disease problems.

How frequently should I water my lawn? How much water should be applied per week?

Most cool-season lawns in Iowa require approximately 1 to 1 ½ inches of water per week. When watering the lawn, apply this amount in a single application or possibly two applications three or four days apart. Avoid frequent, light applications of water, which promote shallow rooting and lush growth. Lush, shallow-rooted turfgrass is less drought tolerant. It also is more susceptible to pest problems. To determine the amount of water applied by a sprinkler, place two or three rain gauges within the spray pattern.

How frequently should I water annuals in containers?

The frequency of watering may vary considerably from container to container. Watering frequency depends on the size and type of container, composition of the potting mix, plant species and weather conditions. Some plants, such as impatiens, like an evenly moist soil. Others, such as vinca, possess good drought tolerance.

Annuals growing in containers should be checked daily (especially in summer) to determine whether they need to be watered. A few plants, such as New Guinea impatiens and fuchsia, should be checked twice a day (morning and late afternoon or evening), as they dry out quickly on hot, windy days.

When watering annuals in containers, continue to apply water until water begins to flow out the drainage holes in the bottom of the container.

How often should I water my garden?

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AMES, Iowa - In past years, sudden death syndrome (SDS) has appeared during the last week of July or the first week of August in Iowa. Therefore, researchers at Iowa State University (ISU) anticipate symptoms of SDS will begin appearing in the state with the next couple of weeks. Although researchers do not expect SDS to be as widespread or as severe as the 2010 growing season, there have been some counties within the state that have received higher-than-normal precipitation. Scientists expect the risk of SDS in these counties to be higher since disease development is favored by wet conditions.

Begin scouting for SDS soon
The first symptoms of the disease are usually found on more compacted and low areas of the field. First symptoms are seen on the leaves of infected plants as scattered, yellow spots between leaf veins. Large sections of leaf tissue between veins turn yellow as spots grow together. These yellow blotches soon turn brown, but the veins remain green. Eventually, the leaves die and drop, but the petioles remain on the stem. Infected plants are also easily pulled from the soil because the roots are rotted. When split lengthwise with a knife, the internal tissue of the main or tap root will be gray to reddish brown, not healthy white.
ISU researchers emphasize that, while there are no in-season management options for SDS, scouting is still important for several reasons. 

• First, this is a good time to evaluate soybean varieties for resistance to SDS. Growing resistant varieties, or avoiding very susceptible varieties, is the most effective way to reduce losses to SDS.
• Also, identifying fields or parts of fields with SDS can help with future management practices. These management tactics include reducing soil compaction since the disease has been associated with compacted soil; planting fields with a history of SDS towards the end of a planting schedule when soils may be warmer and drier; and testing for the presence of soybean cyst nematodes.
• Soybean cyst nematode (SCN) is usually, but not always, associated with SDS and may increase its severity, especially in varieties that are SCN-susceptible. Therefore, management practices to reduce SCN populations, including SCN-resistant variety selection and preventing the spread of soil from field to field, may delay onset and spread of SDS.

"Several Iowa State University pathologists and agronomists continue research to improve our understanding the biology of the fungus that causes SDS and develop improved management options for the disease," said Alison Robertson, ISU Extension plant pathologist. "The ISU soybean breeding program continues to develop and release germplasm with improved resistance to SDS that is available to all private soybean breeding companies. ISU scientists collaborate with scientists at other universities."

Most of the SDS research at ISU is funded by soybean checkoff dollars from state, regional and national organizations, namely the Iowa Soybean Association, the North Central Soybean Research Program and the United Soybean Board.

ISU Research

Key advances from the last five years of research on SDS at Iowa State include :

• Development and release of soybean breeding lines with improved resistance to SDS that can be used by seed companies to develop resistant varieties adapted to Iowa;
• Discovery, identification and molecular characterization of a toxin produced by the SDS fungus that causes the disease and that the toxin needs to be exposed to light to cause the disease on the leaves;
• Discovery that the fungus needs to colonize the central part (or vascular system) of the roots so the toxin can be moved up from the roots to the leaves in the cells that carry water up the plant;
• Discovery that soybean seedlings are most vulnerable to root infection in the first few days after planting, and in cold soils the seedlings are vulnerable to infection for a longer period of time than when planting occurs in warmer soil;
• Discovery that the SDS fungus can survive in corn residue, including corn kernels dropped in field, and this may be a way the fungus overwinters from season to season.

Several other ongoing projects include :

• Sequencing of the entire genetic composition (genome) of the SDS pathogen, which will allow scientists to identify the genes involved in the ability of the fungus to cause disease on soybeans;
• Identifying the mechanisms behind the interaction between the SCN and the SDS pathogen;
• Identifying soybean genes involved in resistance to SDS using molecular approaches;
• Continuing to screen soybean breeding populations adapted to Iowa for improved resistance to SDS;
• Evaluating the impact of crop rotation, planting date and seed treatment for SDS management in Iowa.

Partially funded by the soybean checkoff.

Iowa Master Gardeners (MG) find many ways to volunteer in their communities, from answering horticulture questions that come into county offices to helping manage farmers' markets and community gardens. Public plantings in many Iowa communities are visual signs of the many volunteer hours Master Gardeners provide.

Master Gardener training has been offered in Iowa by Iowa State University Extension since 1979. Over the years, more than 10,000 Iowans have received instruction on a wide range of horticulture and related topics and in return provided a specified number of hours doing volunteer outreach through ISU Extension.

However, there are Iowans that would like to have the training, without the commitment of providing community service. To better serve this group of people, ISU Extension Scott County is offering the ProHort Certification for the first time this year. The ProHort Certification program will be delivered through the Iowa State University Master Gardener training program this fall in three locations. It is different from the Master Gardener program because it is a fee in-lieu-of volunteer service version of the program.

"ProHort participants will train alongside Iowa Master Gardeners," said Jennifer Bousselot, Iowa MG coordinator. "However, without the volunteer commitment, participants do not become Iowa Master Gardeners."

The Iowa Master Gardener (MG) training includes sessions on animal ecology, botany, entomology, fruit culture, herbaceous ornamentals, home landscape design, houseplants, integrated pest management/pesticides, landscape plants, plant pathology, soils, turf grass management, vegetables and weed management.

Upon completion of the program requirements, ProHort participants receive an official ProHort Certificate of training from Iowa State University, which may be displayed in a place of business.

To find out more about the ProHort Certification program being offered in Scott County this fall, contact Duane Gissel, ISU Scott County Extension 563-359-7577.

Pasture improvement and rotational grazing are key topics for many beef and dairy producers, but one of the big challenges becomes subdivision, fencing, and watering systems over rolling or rough terrain. These topics will be discussed at a pasture walk at the farm of Bret DeLarm on Wednesday, August 3, at 1:00 pm.

DeLarm has subdivided a pasture that was previously in CRP, and installed a pipeline watering system. Dr. Ken Holscher, ISU entomologist, will attend the pasture walk to discuss fly control in cattle operations. NRCS staff will also be on hand to discuss cost share programs to assist in pasture improvement. The DeLarm pasture is located just to the east of their home at 2835 Hwy 64, between Wyoming and Mommouth.

Pasture walks are informal educational programs designed to demonstrate one or two key areas of interest, as well as answer any questions you might have. Each has a slightly different focus and producers are invited to attend any that are of interest to improving their own pasture management.

All producers who are dependent on forage production are invited to attend. If you have questions, or need detailed directions to the farm location, contact Denise Schwab in the Benton County Extension office at 319-472-4739.

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