The Hessian fly is present in wheat-growing areas throughout Indiana and often survives, although in lower numbers, in wheat stubble or grasses during the summer. Examination of three uniform nurseries located in the wheat growing regions of Indiana found no evidence of the fly in 2003. However, there is potential for rapid increase of fly populations as a result of weather conditions or cropping practices that favor survival of eggs and young larvae in the fall.
Much of the fall fly population can be avoided by planting after the fly-free date. This is key to avoiding subsequent infestation by the spring brood. Additionally, it has been shown that following the fly-free date will help reduce wheat disease problems and reduce winter kill from excessive growth. Crop rotation, where wheat following wheat is avoided, also is one of the key management strategies for reducing Hessian fly problems.
The Hessian fly passes the summer in the stubble of the current wheat crop. Plowing the stubble results in the destruction of the pest. Volunteer wheat germinates and begins growing just in time for the fall emergence of the Hessian fly. These plants are readily infested resulting in a rapid build-up of the population. Removal of volunteer wheat before the emergence of the fall brood greatly reduces the insect reservoir for a spring infestation.
INW9811, with the H13 gene for resistance to Biotype L was grown widely in mid-south regions of the eastern U.S. This cultivar, developed by the Purdue small grains breeding program in conjunction with USDA-ARS, was the first commercially available wheat with resistance to Biotype L. It is adapted to the wheat growing regions of southern Indiana and Illinois, southward to northern Alabama, Georgia and the Carolinas.
A new gene for resistance was identified by the USDA-ARS and Purdue University small grains group. The gene was moved from a tetraploid durum (Triticum turgidum Desf.), CI3984, which was obtained from the USDA-ARS National Plant Germplasm Laboratory in Aberdeen, Idaho, into a common wheat germplasm identified as P921696. The reference is cited below.
Theoretical and Applied Genetics
C. E. Williams1, C. C. Collier1, N. Sardesai2, H. W. Ohm3 and S. E. Cambron1
1 Crop Production and Pest Control Research Unit USDA-ARS-MWA and Department of Entomology, Purdue University, West Lafayette, IN 47907, USA
2 Department of Entomology, Purdue University, West Lafayette, IN 47907, USA
3 Department of Agronomy, Purdue University, West Lafayette, IN 47907, USA
The disease situation in soybean appears similar to that in 2002. As in 2002, the progress of planting soybeans this spring was delayed and sudden death syndrome is once again developing later than we normally expect to see it. The late planting, coupled with cool weather during June and July, slowed plant development. Blooming, pod set, and seed development lagged behind the 5-year average. Whereas the late appearing SDS symptoms would normally not cause concern about yield and quality of the crop, the later than normal plant development this year may make the soybean crop vulnerable to significant yield loss. Yields of plants affected after pods are well developed may still be reduced due to the production of only small seed.
Soybean.html#suddendeathsyndrome> or in Purdue extension publication BP-58 Sudden Death Syndrome in Soybeans.
The beginning of fall is the time for some soil-borne diseases to show. In soybean, one of the late season diseases is sudden death syndrome (SDS) (see companion article by Shaner and Westphal). Whereas SDS is strongly weather-dependent, other soil-borne problems are always present and oftentimes damage crops. Plant-parasitic nematodes are a constant threat. Some nematodes have a restricted host range, e.g., the soybean cyst nematode primarily infects soybean, but does not infect other crops widely grown in Indiana. In contrast, root knot nematodes have much wider host ranges and can infect several of Indiana’s agricultural and ornamental crops.
Drought conditions during August were a stress factor for many fields. In southern Indiana, plants were under drought stress on light soils because of the limited water holding capacity of these soils. In a drought, any debilitation of the root system can interfere with root functions and has potential to be detrimental to plant growth and reduce yield. Growers are well aware of the soybean cyst nematode that feeds on soybean roots and know that the selection of a variety resistant to the nematode population present in a particular field will mitigate yield loss. Root knot nematodes of the species Meloidogyne, have long been recognized as problem in soybean in southern states. Limited attention has been given to these nematodes in the North Central region, possibly because of the overwhelming importance of the soybean cyst nematode. Currently there is no indication that cyst nematode resistance has any correlation with root knot nematode resistance.
Recent damage surveys of soybean diseases did not associate extensive damage with root knot nematodes. However, in isolated regions of Indiana the situation might be different. Westphal and Egel observed root knot nematodes in a southern Indiana field. The field is in a cucurbit-field crops rotation and root knot nematode damage was detected on watermelon roots in 2002. In 2003, this field had the typical wavy appearance (Fig. 1) often seen with soil-borne problems. Nematode damaged plants are stunted and lack vigor compared to healthy plants. Above-ground symptoms can be confused with other soil-borne problems. Examination of the roots of symptomatic plants revealed several root knots. Roots of symptomless plants were devoid of nematode-induced galls, and had copious nodulation (Fig. 2). Nematode-induced galling can be distinguished from the beneficial Rhizobium nodules. Nodules, typically 1/8-1/4 of an inch in diameter, develop on the surface of the root. Root knot nematode galls are integrated into the root structure and can result in pronounced deformation. Soybean cyst nematodes were also present in this field. Thus plant damage was probably not solely associated with root knot nematodes, but the root knot nematode likely contributed to plant stress and damage.
Seed might also be saved from the previous season if it is high quality and not contaminated with seed borne diseases like smut. Seed should be professionally cleaned to remove light, shriveled, low quality kernels. A seed treatment can also be applied. Good quality seed should have at least 85 to 95% germination.
The seeding rate for soft red winter wheat should be adjusted for seed size. Seed size can vary from less than 12,000 seeds per pound to more than 16,000 seeds per pound. Accordingly seeding rates can also vary from as little as 90 lb./acre for very small seeded varieties to as much as 165 lb./acre for large seeded varieties (see table). Optimum plant population is around 1.3 to 1.5 million plants/acre. The higher rates should be used for late-planted wheat (i.e., more than 3 weeks after the Hessian fly free date).
Seed should be sown 3/4 to 1 1/2 inches deep. This becomes especially important in no-till situations with heavy residue. It is important to get the seed through the residue and into the soil to assure good seed to soil contact and subsequent uniform germination and emergence. Wheat will be more winter hardy and less susceptible to winter heaving if well established by proper seeding in a timely manner. Adequate nitrogen and phosphate fertilizer is also important for seedling establishment in the fall. Apply approximately 20 to 25 lb. N/acre and phosphate fertilizer according to soil test. Potash is important for later growth and development and should also be applied according to soil test.
Wheat should be sown in a timely manner, but not before the Hessian fly-free date. The optimum planting window for wheat is the two-week period following the Hessian fly-free date. The fly-free date ranges from September 22 across the northern tier of Indiana counties to October 9 in the southwestern corner of the state. In addition to dodging the Hessian fly, planting in this window reduces the risk of several diseases. For example, wheat that is planted early is more susceptible to take-all and may also be exposed to high aphid populations that can transmit Barley Yellow Dwarf virus. Early planted wheat could also succumb to winter kill if it gets too much fall growth prior to dormancy. Late planted wheat (more than 3 weeks after the fly-free date) is often predisposed to winter die back and increased susceptibility to heaving.
Fields of corn around Indiana, especially early-planted ones, are in the process of shutting down for the season. While only 3% of the state’s crop was estimated to be mature (i.e., kernel black layer) as of the week ending 31 Aug, 41% of the crop was estimated to be at dent stage or beyond (Indiana Ag Stats Service, 2 Sep 2003).
Identifying the cause(s) of premature “shutdown” this year may help you identify management decisions for future years. For example, if leaf disease(s) is the primary culprit this year, then be sure to include disease tolerance/resistance as one of your primary hybrid decision factors next year.