Performance of Certified Seed Lots of Dawson Alfalfa

Breeder, foundation, and certified seed lots of Dawson alfalfa, Medicago sativa L., were tested to determine stability in performance during three generations of seed increase under certification. Two field experiments were conducted, a seeded forage yield test and a space-planted test. Greenhouse experiments included separate tests for resistance to pea aphids, spotted alfalfa aphids, and bacterial wilt. Results obtained on certified Dawson alfalfa seed classes in field and greenhouse experiments were in agreement with the original variety description

The Biology and Ecology of the Bromegrass Seed Midge in Nebraska

These studies indicate that smooth bromegrass, Bromus inermis Leyss, is the only host of the bromegrass seed midge, Stenodiplosis bromicola Marikovskiy and Agafonova, in Nebraska. The midge did not infest two common annual brome species under field conditions. The midge has been collected from all counties surveyed in Nebraska and seems to be widely distributed throughout the midwestern states. An apparently undescribed species of Tetrastichus (Hymenoptera: Eulophiclae) was observed to parasitize all stages of the bromegrass seed midge. Parasitism rates greater than 90% were observed. The parasite larvae do not kill the midge until damage to the bromegrass floret has occurred. However, a high parasite population may help to reduce the population of the bromegrass seed midge in succeeding generations

EVALUATION OF FURADAN AND ORTHENE AGAINST A BLUESTEM SEED MIDGE, 1986 AND 1987:

The insecticides were applied to 2 fields, one in Saunders Co., Neb., (1986 and 1987) and the other in Cass Co., Neb. (1987 only). Both were seed production fields of\u27Pawnee\u27 big bluestem which were planted in rows spaced 3.5 ft apart and cultivated annually to maintain row spacing. The insecticides were single applications of Furadan 4 F (carbofuran) and Orthene (acephate) at the rate of 1.0 lb/A in 6 gal/acre water at early anthesis. The insecticides were applied with a C02 activated pressure, knapsack sprayer equipped with a 5 ft boom. Applications were made on either 16 or 17 Jul in both yr and at both locations. The experimental design was a RCB with 4 replications at each site. Each plot consisted of six 30 ft rows. The center 2 rows of each plot were harvested for seed by removing the upper portions of the raceme bearing culms with hand sickles during the last week of Sep. The harvested material was then threshed with a small plot thresher. The midge population was sampled by collecting 25 raceme bearing culms from each plot the first week of Aug and again during the first week of Sep at both locations in 1987. The culms were taken to the laboratory and placed in water-filled flasks, which were enclosed in dark insect rearing cages. Insects emerging from the florets were collected in glass vials (light traps) inserted in the sides of the cages

A seed midge pest of big bluestem

A Cecidomyiid midge reared from the panicles of big bluestem (Andropogon gerardii Vitman (var. gerardii) at Mead, Neb., was identified as Contrarinia wattsi Gagne. This midge was previously known only from panicles of little bluestem (Schizachyrium scoparium (Michx.) Nash) in New Mexico. In Nebraska, C. wattsi appears to have a minimum of 3 generations per season. Larvae of the earlier generations leave the florets after completing development, making it difficult to associate floret damage with the midge. Larvae of the last generation of a season remain in diapause, in the floret, throughout the winter. Evidence obtained in this study in 1985 indicates that, at harvest time, 7 and 15% of the florets in the 2 fields studied contained diapausing midges. However, when an estimate of seed loss by the earlier generations (as indicated by empty florets and small seed) was considered, the total loss was probably closer to 40%. An unidentified species of thrips (Thysanoptera: Thripidae) also was found in big bluestem florets during this study. However, evidence suggests that thrips do not damage big bluestem seed as seriously as the midge

Alfalfa Insect Management Studies 1971-77

Three tests in southwestern Nebraska during 1971 and 1972 evaluated insecticides against the army cutworm. Adult alfalfa weevils did not damage new second growth alfalfa in a small plot study during a 3-year period (1973-1975) at Gothenburg, NE. However, excellent control of larval alfalfa weevils was obtained. These results indicated a need to establish economic threshold levels for the alfalfa weevil in Nebraska to prevent unnecessary use of insecticides. Four tests to control the alfalfa weevil with registered insecticides verified the efficacy of these materials under Nebraska conditions. A series of tests conducted during 1975 at the Mead Field Laboratory were designed to evaluate plant resistance, cultural practices and insecticides. The use of alfalfa varieties with resistance to various insect pests of alfalfa appeared to be an ideal control method. During 1975-1977, a test was conducted each year at the Mead Field Laboratory to evaluate new experimental insecticides against the alfalfa weevil and other pest insects of alfalfa grown for forage. A number of the new insecticides showed promise against the alfalfa weevil and the pea aphid

Alfalfa Insect Management Studies 1971-77

Three tests in southwestern Nebraska during 1971 and 1972 evaluated insecticides against the army cutworm. Adult alfalfa weevils did not damage new second growth alfalfa in a small plot study during a 3-year period (1973-1975) at Gothenburg, NE. However, excellent control of larval alfalfa weevils was obtained. These results indicated a need to establish economic threshold levels for the alfalfa weevil in Nebraska to prevent unnecessary use of insecticides. Four tests to control the alfalfa weevil with registered insecticides verified the efficacy of these materials under Nebraska conditions. A series of tests conducted during 1975 at the Mead Field Laboratory were designed to evaluate plant resistance, cultural practices and insecticides. The use of alfalfa varieties with resistance to various insect pests of alfalfa appeared to be an ideal control method. During 1975-1977, a test was conducted each year at the Mead Field Laboratory to evaluate new experimental insecticides against the alfalfa weevil and other pest insects of alfalfa grown for forage. A number of the new insecticides showed promise against the alfalfa weevil and the pea aphid

Seasonal Population Fluctuations and Natural Control of the Sweetclover Aphid

Because the potential of the sweetclover aphid for damaging sweetclover is well documented, yet damage occurs only occasionally under field conditions, it would appear that natural factors which depress midsummer populations are important in preventing greater damage and worthy of detailed study. Thus, this study was begun early in 1959 to investigate the natural factors which generally keep populations of this aphid below levels causing economic damage

Bluestem Seed Midge Influence on Sexual Reproduction of Big Bluestem: A Review

A Cecidomyiid midge (Contarinia wattsi Gagne\u27) has been identified as a significant parasite of big bluestem [Andropogon gerardii Vitman var. gerardii] by adversely affecting the production of viable seeds. The midge was first identified from specimens collected from big bluestem racemes in 1983 in eastern Nebraska. Subsequent collections and studies have shown that it is widespread in the Great Plains, and that it can reduce seed yields of big bluestem by over 40%. The midges apparently over winter as diapausing larvae in disarticulated spikelets, emerge as adults at the time of early panicle emergence, and lay their eggs near developing caryopses. The larvae feed on the developing caryopses, pupate, and develop into adults within the florets. The adults emerge without leaving a trace. Up to three generations may occur per year with generation intervals of 13 to 16 days. The bluestem midge, in tum, is parasitized by a wasp that remains unidentified

EVALUATION OF FURADAN AND ORTHENE AGAINST A BLUESTEM SEED MIDGE, 1986 AND 1987:

The insecticides were applied to 2 fields, one in Saunders Co., Neb., (1986 and 1987) and the other in Cass Co., Neb. (1987 only). Both were seed production fields of\u27Pawnee\u27 big bluestem which were planted in rows spaced 3.5 ft apart and cultivated annually to maintain row spacing. The insecticides were single applications of Furadan 4 F (carbofuran) and Orthene (acephate) at the rate of 1.0 lb/A in 6 gal/acre water at early anthesis. The insecticides were applied with a C02 activated pressure, knapsack sprayer equipped with a 5 ft boom. Applications were made on either 16 or 17 Jul in both yr and at both locations. The experimental design was a RCB with 4 replications at each site. Each plot consisted of six 30 ft rows. The center 2 rows of each plot were harvested for seed by removing the upper portions of the raceme bearing culms with hand sickles during the last week of Sep. The harvested material was then threshed with a small plot thresher. The midge population was sampled by collecting 25 raceme bearing culms from each plot the first week of Aug and again during the first week of Sep at both locations in 1987. The culms were taken to the laboratory and placed in water-filled flasks, which were enclosed in dark insect rearing cages. Insects emerging from the florets were collected in glass vials (light traps) inserted in the sides of the cages

Resistance of Red Clover to the Clover Leaf Weevil

Red clover (Trifolium pretense L.) varieties in the third season of growth, that had been exposed to a heavy infestation of larvae of the clover leaf weevil [Hypera punctata (Fabricius)], differed significantly in percentage defoliation, feeding injury score, plant height, and forage production. Based on these four characters, \u27Mammoth,\u27 \u27Lakeland,\u27 \u27Dollard,\u27 and \u27LaSalle\u27 were highly resistant to larval feeding; \u27Kenland,\u27 \u27Common,\u27 and \u27Pennscott\u27 were highly susceptible. Long term second-season yield tests including six of these varieties indicated no con• sistent superiority of any of the varieties in the absence of weevil feeding