Sugar is Death to Aphids

A treat for humans, sugar can be deadly to aphids.


Agricultural researchers are now exploiting this vulnerability as an insecticide-free way to control insect pests.

"There is an urgent need for new strategies for insect control, because insects are developing resistance to traditional broad spectrum insecticides," says professor Angela Douglas of Cornell University.

Douglas and fellow scientist Georg Jander are genetically engineering plants to protect themselves by increasing the sugar in their sap.

continued Out There

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Drought Causing Nutrient Deficiencies

Dry conditions persisting across much of the Midwest U.S. are causing nutrient deficiency problems. Unfortunately, only rainfall will fix some of these problems.

Foliar or soil application of nutrients is not recommended, according to University of Illinois assistant professor of crop sciences Fabián Fernández.

Many corn fields show potassium deficiency even though adequate fertility is present in the soil. Why is potassium deficiency showing up in corn more often than any other nutrient deficiency?

“The most likely reason is that, early in development, corn takes up larger amounts of potassium than of nitrogen and phosphorous,” Fernández explains. “Soon after the V12 development stage, corn has already taken up half of all the potassium it will need.”

In contrast, nitrogen and phosphorus are taken up until sometime after the dent stage (R5). Unlike nitrogen, which moves freely over large distances in the soil solution, phosphorous and potassium can move only a few millimeters at most; thus, when the soil dries out, their position makes them unavailable to the crop.

The reason this happens is that pore space in the soil contains water and air. Plant-available potassium ions are dissolved in the soil water or attached to soil particles ready to come into solution as the plant needs them. When there is sufficient water in the soil, the potassium ions dissolved in water have to travel (by diffusion) only a short distance to be taken up by the crop.

As the soil dries out, the pore space fills with air. The potassium ion has to travel across a larger distance to reach the root because it cannot diffuse through air. Increased diffusion time can cause important reductions in potassium availability to corn during vegetative stages when potassium demands are large.

“Under dry conditions, the soil is unable to keep up with the crop demand even though there might be sufficient potassium in the soil,” Fernández explained.

While there is nothing that can be done to solve the current drought problems, this year has taught producers a number of important lessons.

“For the future, I recommend that we minimize the effect of drought by ensuring that any water in the soil is protected to be used by the crop,” Fernández said. “This year, some farmers have seen firsthand how much water weeds can take up when not treated early in the season.”

Similarly, too much tillage in some situations has caused unnecessary water evaporation from the soil and those fields are running out of water sooner than those that were managed more carefully.
       
Source: University of Illinois

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Plant Roots: Growth, Function and Interactions with the Soil
Artwork: Corn Field

Ragweed Season Grows and Grows

Studies by USDA a scientist have confirmed that because of climate changes ragweed season now lasts longer and ends later across much of North America.

Ragweed pollen in some parts of the northern United States and Canada now lingers almost a month longer than it did in 1995, and these increases are correlated to seasonal warming shifts linked to climate change, according to report published in the Proceedings of the National Academy of
Sciences.

"One of the biggest challenges in studying climate change is finding out how the plant kingdom is adapting to increases in air temperature and other meteorological phenomena," says Agricultural Research Service (ARS) Administrator Edward B. Knipling. "Studies like this also show us that these
ecological shifts don't stop at crop production. They can also have a significant impact on public health."

Assessments by the Intergovernmental Panel on Climate Change suggest that current and future increases in land-surface temperatures are more likely to occur at higher elevations and at higher latitudes.

Source: Agricultural Research Service

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Avoid Planting Wheat After Corn

Growers following wheat planting after corn harvest should be mindful of the potential for head scab development in their crop.

Wheat and corn are both members of the grass family, and as such, are affected by some of the same pests and diseases, one of which being head scab.

Head scab, a major disease of wheat that affects the crop during the flowering stage, is caused by the same fungus (Fusarium graminearum) that causes ear and stalk rot in corn.

Even if the cornfield into which wheat is planted did not have a major ear rot or stalk rot problem this year, the fungus still is present in the corn stubble left in the field after harvest. Wheat planted into this stubble is more likely to have a head scab and vomitoxin problem next year, especially if conditions are favorable.

Advice: plant wheat after soybeans, not after corn.

If it's essential to plant wheat following corn, plant a scab resistant variety.

In addition, plow under the corn stubble before planting wheat and be prepared to apply a fungicide next year at flowering if the weather becomes favorable. These approaches will minimize, but will not eliminate the risk of head scab in wheat planted after corn.

Source: Pierce Paul, Ohio State University Extension
330-263-3842

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• Artwork: Wheat by Jerianne Van Dijk

Controlling Weeds After Harvest

Winter annual species can create dense mats of vegetation prior to spring planting if not controlled before the onset of winter. Applying a herbicide in the fall to control these weeds and prevent them from producing seeds are important objectives of fall herbicide applications.

But before rushing into fall herbicide applications, University of Illinois Extension weed specialist Aaron Hager offers a few suggestions:

"Scout fields before making any application to determine what weeds are present and if their densities are high enough to warrant treatment this fall."

Many herbicides are not labeled for fall application so check labels first. For example, Atrazine is widely used before and after corn emergence, but is not labeled for fall application. Some herbicides approved for fall application have application timing and geographical restrictions. Before applying a treatment that does not possess much soil-residual activity (for example, 2,4-D or glyphosate), schedule the application to occur after the majority of winter annual species have emerged.

"Instead of applying such a treatment in early-October, a mid- to late-October application might provide better results. On the other hand, if your fall application will include a herbicide with soil-residual activity, then the application could be made sooner."

Combinations of one or more herbicides can broaden the weed control spectrum which can become quite valuable if winter annuals have emerged before the application is made. Combining 2,4-D and/or glyphosate with soil-residual products can improve control of emerged species and help control biennial or perennial species. Include the appropriate spray additives with all applications.

"Fall applications that include soil-residual herbicides may not always result in a clean field by planting time next spring. Delays in spring field work may allow the fields to green up before the crop can be planted. Additionally, we have found that if we successfully control the suite of winter annual weed species,
the emergence of summer annual weed species (such as common lambsquarters and smartweed) sometimes occurs sooner than if the winter annuals were still present."

Hager does not recommend using a fall herbicide application as an avenue to provide residual control of summer annual weed species. Control of summer annual species, such as waterhemp, is improved when applications of soil-residual herbicides are made closer to planting compared with several weeks (or months) prior to planting.
Thus, he recommends selecting an application rate of a soil-residual herbicide that will provide control of winter annuals throughout the remainder of 2010, and do not increase the application rate in hopes of obtaining control of summer annual species next spring.

"With the increasing prevalence of horseweed, including glyphosate-resistant populations, fall herbicide applications may prove more efficacious than spring applications. Glyphosate alone may not provide adequate control when applied in either fall or spring, but a fall application timing provides an opportunity to utilize higher application rates of products (such as 2,4-D) than are feasible to use in spring."

Source: Aaron Hager, 217-333-4424

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Artwork: After the Corn Harvest in Minnesota

No-till Seeding a Good Way to Improve Pastures

"One of the primary concerns in establishing new forage stands in a well-tilled seedbed is the threat of soil erosion during the establishment period. In addition to reducing soil erosion, no-till seedings conserve moisture already present in the seedbed," says John Hobbs, an agriculture and rural development specialist with University of Missouri Extension.

Moisture conservation, along with a dramatic reduction in water run-off, improves the water supply for the new seedlings.

No-till seeding methods also require less time and fuel than traditional methods because rocks remain below the soil surface.

No-till seeding can also improve the forage quality of existing pastures and hay fields.

"No-till seeding practices can be used to completely reseed forage stands that have become unproductive," said Hobbs.

Forage stands can be improved using no- till methods to add legumes to pure grass stands and to strengthen weak grass stands through the introduction of both legumes and/or grasses.

There are several rules that must be followed for no-till seeding to be successful.

The five most important are: proper soil testing, minimizing competition fromexisting sod, seeding on the proper date, using high quality seed, and controlling the depth of seeding.

"It is a waste of time and money to try to establish or improve stands when the soil fertility and/or pH are too low to support productive plants," said Hobbs. "You have to fertilize and lime according to soil test recommendations prior to seeding."

Landowners also need to graze fields, cut them for hay or apply herbicides to reduce competition from existing sod or cover. After seeding into an existing pasture, periodically graze or mow the growth of existing pasture or hay plants to favor growth of the newly established seedlings.

"No-till seeding can be successfully done in late winter, spring or early fall, but it is important to make plans and preparations in advance so the seeding can be made on time," said Hobbs.

The use of seeds with a high germination percentage is also important for success. Cheap, low quality seed is often the most
costly item in no-till seeding because it results in low productivity stands or thin, weak plant density.

Making sure seeds are planted at the right depth is the final step toward success. Hobbs recommends adjusting seed equipment to place the seed at a shallow depth of one-quarter to one-half inch.

"Placing the seed too deep is the most common single reason for failure to get a stand. If you see a few seeds on the soil surface after seeding, then your seeding depth is about right," said Hobbs.

Source: John Hobbs, (417) 223-4775

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Bee Pastures Help Pollinators Prosper

Beautiful wildflowers are being planted in "bee pastures" -- floral havens created as an efficient, practical, environmentally friendly, and economically sound way to produce successive generations of healthy young bees.

Pesticide-free pastures are simple to establish, and -- at just a half-acre each -- easy to tend, according to U.S. Department of Agriculture (USDA) entomologist James H. Cane at the Pollinating Insects Biology, Management, and Systematics Research Unit in Logan, Utah.

Bee pasturing isn't a new idea, but studies by Cane and his collaborators in a research greenhouse and at outdoor sites in Utah and California are the most extensive to date.

The research indicates that one of the best species of pastured pollinators is the blue orchard bee, Osmia lignaria, a gentle bee that helps with pollination tasks handled primarily by the nation's premier pollinator, the European honey bee, Apis mellifera. Cane estimates that, under good conditions, blue orchard bee populations could increase by as much as four- to fivefold a year in a well-designed, well-managed bee pasture.

Cane and colleagues have studied wildflowers that might be ideal for planting at bee pastures in California. In particular, the team was interested in early-flowering annuals that could help bolster populations of blue orchard bees needed to pollinate California's vast almond orchards.

Five top-choice, bee-friendly wildflowers for bee pastures in almond-growing regions:
Chinese Houses (Collinsia heterophylla)
California Five-Spot (Nemophila maculata)
Baby Blue Eyes (N. menziesii)
Lacy or Tansy Phacelia (Phacelia tanacetifolia)
California Bluebell (P. campanularia)

Source: USDA - Agricultural Research Service

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