Dosage rates and application methods with PCNB for control of potato scab and rhizoctonia

American Journal of Potato Research - Pentachloronitrobenzene (PCNB) controlled potato scab in fine sandy loam of the Yakima Valley when applied at the rate of 50 pounds per acre broadcast before...     

Fertilizer application methods for Irish potatoes compared

This study was conducted in eastern Virginia on a Sassafras fine sandy loam soil to determine whether fertilizer for Irish potatoes could be broadcast before planting instead of band-placed at planting. Band placement is considered the most efficient method; however, use of the broadcast method involves less labor and speeds up the planting process. Two rates of fertilizer were used, 100 and 150 pounds per acre (112 and 169 Kg/Ha) of N, P₂O₅ and K₂O (43.7 and 65.6 pounds of P and 84.0 and 124.5 pounds of K) in a commercial material. The two rates were applied broadcast after plowing and disced in, on the rye cover before plowing, on the rye cover in January and band-placed at planting. Pungo and Superior varieties were compared, and responses varied from year to year and between varieties. The yields of Pungo potatoes were not significantly influenced by the two fertilizer rates or methods and time of application. Thus, for the Pungo variety, 100 pounds per acre (112 Kg/Ha) each of N, P₂O₅ (43.7 pounds P) and K₂O (83 pounds K) were adequate, either broadcast or band-placed. The Superior variety was less tolerant of adverse growing conditions than the Pungo and when stunted produced higher yields with band-placed fertilizer. The Superior variety under more optimum conditions (1968) produced higher yields with the broadcast fertilizer application.     

Comparison of methods for measuring dormancy of potatoes

Comparisons were made of different methods of measuring length of the dormant period of Russet Burbank potato tubers as affected by time of planting and harvest. The study resulted in the following conclusions: 1) when measured from planting or tuber initiation to sprouting, the dormant period of tubers harvested on the same date was longer from an early planted crop than from a late planted crop. 2) When measured from harvest to sprouting, the dormant period was shorter for tubers from an early compared to a late planting. 3) With the same planting date and different harvest dates, when measured from planting or tuber initiation to sprouting, the dormant period was shorter for tubers from an early compared to a late harvest. 4) On the other hand, with the same planting date, when measured from time of harvest to sprouting, the dormant period was longer for tubers from an early compared to a late harvest. Planting date to sprouting was considered the best practical field measure of dormancy since it closely correlated with tuber initiation to sprouting, a method which was more accurate but difficult to determine. Both methods were much better than harvest date to sprouting which is commonly used. In addition, larger tubers from earlier planting had shorter dormancy than smaller tubers regardless of method of measurement due to a probable earlier set. From later plantings, tuber size had no relationship to length of dormancy. Moisture stress significantly reduced dormancy of Lemhi, Russet Burbank, and Nooksack but the Butte cultivar was only slightly affected.     

Comparison of various weed control programs for potatoes

All weed control programs resulted in satisfactory weed control. Costs of controlling weeds ranged from $10 to $93/ha. Cultivation alone was the cheapest method of controlling weeds. Controlling weeds by using herbicides alone with no cultivation resulted in the highest weed control costs but tended to give the best weed control at harvest. Herbicides saved one to two cultivations. EPTC (S-ethyl dipropylthiocarbamate) gave slightly better control of green foxtail [Setaria viridis (L.) Beauv.] and slightly poorer control of broadleaf weeds than trifluralin (α,α,α,-trifluoro-2,6-dinitro-N, N-dipropyl-p-toluidine). Cultivation helped control weeds but had no other apparent beneficial or adverse effect on potatoes. The correlation coefficient between total tuber yield and dry weight of weeds was ?0.97 at Grand Forks, North Dakota and ?0.85 at Casselton, North Dakota.     

Terraclor (PCNB) for control ofRhizoctonia solani. II. PCNB residues in tubers

Terraclor (PCNB) applied to soils by broadcast and row slightly reduced the incidence ofRhizoctonia solani but did not increase yield or per cent of U. S. No. 1 tubers either by weight or numbers. Residues of PCNB in tubers grown in treated soils increased as the rate per acre of PCNB increased. Almost all of the residues were in the tuber peel.     

Comparison of methods for measuring leaf and tuber water potentials in potatoes

Comparative methods for measuring water potential in leaves and tubers of potatoes (Solarium tuberosum L., var. Russet Burbank) are described. For leaves drier than -3 bars, the pressure chamber gave estimates of water potential which were zero to three bars drier than potentials measured using thermocouple psychrometers. Pressure chamber readings ranged ±2.5 bars from psychrometer value for leaves wetter than -3 bars; the psychrometer measurement usually was drier than the pressure chamber when leaves were sampled in the evening. With tubers, water potential measurements usingin situ psychrometers and the pressure chamber agreed to within one bar,except in tubers drier than -7 bars, where there were discrepancies of± 2.5 bars. However, if the interval between psychrometer insertion and water potential measurement were longer than 24 hours, serious errors arose in the psychrometer measurements, apparently from suberization of tissues surrounding the psychrometers which prevented vapor equilibrium. Pressure chamber measurements of tubers also were compared with tuber water potentials determined from the weight changes of tuber samples immersed in graded sucrose osmotica. For tubers wetter than -5 bars, the osmotica method gave drier estimates than the pressure chamber; for tubers drier than -5 bars the reverse occurred. Causes for these discrepancies are discussed.     

Rhizoctonia disease of potatoes (Rhizoctonia solani): Fungicidal efficacy and cultivar susceptibility

Rhizoctonia stem canker and black scurf is an economically important disease of potatoes in Alberta and around the world. It reduces the quality and yield of potatoes and has become an important impediment for export of seed potatoes, especially to Mexico. Seed treatment using fungicides, presently registered in Canada, are not effective in controlling the disease to growers’ satisfaction. Field experiments conducted to evaluate the efficacy of various fungicides showed that captan (Captan), iprodione (Rovral), mancozeb (Tuberseal), and fludioxonil (Maxim) provide effective control of the disease. Of these fungicides, fludioxonil consistently provided superior protection. Based on the results of this study, Maxim was registered in 2000 for control of this disease in Canada. Potato cultivars/breeding selections showed a range of susceptibility reactions toR. solani but none of these was completely resistant to the disease. The information on comparative susceptibility of potato cultivars will help the growers make informed decisions regarding the management of this disease. Of six plant species (Beta vulgaris,Brassica compestris, Hordeum vulgare, Pisum sativum,Triticum aestivum, Zea mays) most commonly used in rotation with potatoes in Alberta, none was infected by potato isolates ofR. solani. The results suggested that use of these plant species as rotation crops with potatoes in Alberta will help in reducing the development of rhizoctonia disease in potatoes.     

Comparison of inoculation methods on ring rot development in potatoes

Symptoms of bacterial ring rot (Corynebacterium sepedonicum) developed earlier and were more severe in root-inoculated potato plants grown from stem cuttings treated with indole-3-butyric acid (IBA) than in those grown from stem cuttings not so treated or from tuber seed pieces. Disease expression was more rapid and severe in root-inoculated plants than in plants from inoculated seed pieces. The use of IBA-treated stem cuttings provided uniform plant material for ring-rot studies.     

The effect of crop rotations on Rhizoctonia disease of potatoes

Since 1964, replicated rotation plots in Presque Isle, Maine have continually been planted and evaluated to determine the effect of various rotation crops on tuber appearance, quality, and yield. In 1974 and 1975, the saprophytic activity ofRhizoctonia solani in the soils of each rotation combination was determined, and the tubers harvested were scored forRhizoctonia damage. Soils with a two-year rotation of oat-potato had the lowest amount of saprophytic activity byRhizoctonia and provided the lowest incidence of disease on the stems, roots, and tubers of the cultivars Kennebec and Katahdin. With the cultivar Russet Burbank, the three-year rotations generally provided the lowest incidence of disease; however, this cultivar is more susceptible to the pathogen. The plots of potatoes that were not rotated had the highest pathogen activity and the greatest disease incidence.     

Relative efficiency of three methods for chemical control of Pacific coast wireworms in potatoes

Data from six experiments with registered, nonpersistent chemical compounds for control of Pacific coast wireworm (Limonius canus Le-Conte) were combined to elucidate the relative efficiency of three types of treatments. The treatments were soil fumigation and band or broadcast applications of granular organophosphorus insecticides. Band treatments gave less effective and more variable control than broadcast treatments. Fumigation treatments were more effective than, and about equally as variable as, broadcast treatments. All treatments became progressively less effective and less dependable as the population of wireworms increased. It was not economical to treat infestations of less than 0.12 wireworms/ft². Band treatments were usually adequate for populations up to 0.4/ft² and broadcast treatments for populations up to 1.6/ft². However, it was considered most economical to broadcast for infestations between 0.15 and 0.7/ft². For heavier infestations, either fumigation or a combination of treatments appeared prudent. Because all treatments performed rather inconsistently, precautions to avoid underestimating an infestation are justified.     

Comparison of inoculation methods for field studies on varietal response to verticillium wilt of potatoes

Verticillium albo-atrum, cultured on potato dextrose agar plates or on sterilized wheat kernels, was used to incite disease in field studies. Immediately prior to planting, seed potatoes were dipped in a spore/mycelium suspension that was prepared from agar plate cultures. A second inoculation treatment involved placing infested wheat kernels under the potato seed at planting time. Both inoculation methods resulted in verticillium wilt development. However, the inoculum suspension dip method resulted in slightly greater incidences of verticillium wilt than did the infested wheat method. Inoculation by means of a suspension dip immediately after cutting the seed resulted in more wilted plants than when seed was inoculated 24 hours or 7 days after cutting. The spore/mycelium suspension dip method is now routinely used for field studies on disease susceptibility or resistance in potato cultivars.     

Evaluation of on-farm irrigation scheduling methods for potatoes

The neutron probe, infrared thermometry and crop water stress index (CWSI), and a computer-assisted irrigation scheduling method were evaluated in terms of their effect on tuber yield, tuber quality, and water use. The experiment was conducted during 1990 and 1991 near Othello, central Washington, using Russet Burbank potatoes grown in a silt loam soil. Irrigation treatments did not commence until after tuber initiation. In general, no differences in total number of tubers and total tuber yield resulted from the different scheduling methods. However, the canopy temperature method showed reduction in the yield of number one tubers in 1990. The least total irrigation water was applied during the growing season with the neutron probe method. Using CWSI values above 0.5 to 1.0 (scale 0 to 10) for two consecutive days as a threshold to schedule irrigations appeared to be adequate for potatoes grown in silt loam soils. However, shortcomings of infrared thermometry suggested that this method may not be practical for scheduling irrigation of potatoes.     

Selection for resistance to potato leafhopper in potatoes: III. Comparison of two selection procedures

A comparison was made of two breeding procedures for recurrently selecting potato,Solanum tuberosum L., for resistance to infestation by potato leafhopper,Empoasca fabae (Harris). On the basis of selection advance per year, the more efficient procedure involved randomly intermating a group of clones, planting seedling tubers in a field test to measure resistance to infestation, and then bulking the seed from the most resistant clones to complete the selection cycle in one year. A population developed by five cycles of selection (five years) for resistance to infestation using this procedure resulted in a decrease of 57% in the level of infestation from the original population.     

Postemergence directed application of bentazon + metribuzin for broadleaf weed control in Russet Burbank potatoes

Field studies were conducted to evaluate potato (cv. Russet Burbank) injury and weed control with mid- or late-postemergence directed applications of bentazon at 0.56, 0.84, or 1.12 kg ha^?1 + metribuzin at 0.28 kg ha^?1 + petroleum oil concentrate (POC) at 2.3 L ha^?1. Potato injury was 5% or less when bentazon + metribuzin + POC was applied as a postemergence directed spray. Hairy nightshade, redroot pigweed, and common lambsquarters control were excellent with all rates of the bentazon + metribuzin + POC mixture tested at either application time. In weed-free trials, neither U.S. No. 1 nor total tuber yield was reduced compared to the untreated control by any rate of the bentazon + metribuzin + POC mixture applied as a directed spray. Thus, postemergence directed applications of bentazon + metribuzin + POC show excellent potential for broadleaf weed control in Russet Burbank potatoes.     

Comparison of aircraft,ground-rig and center pivot irrigation systems for application of pesticides to potatoes

Studies were conducted from 1979 to 1983 in central Wisconsin to investigate the utilization of center pivot irrigation systems for the application of pesticides to potatoes. Fungicides, herbicides and insecticides were applied with a conventional tractor-mounted boom sprayer, a boom mounted beneath the center pivot (underslung boom), direct injection into the center pivot irrigation water and by aircraft. In comparisons between irrigation system application and tractor-mounted boom application, materials through both the underslung boom and center pivot system provided comparable pest control to the tractor-mounted boom, with the exception of water soluble insecticides which were ineffective when applied through the irrigation system. In addition, under intense disease pressure a somewhat reduced efficacy was associated with fungicides applied through the center pivot system compared to tractor-mounted boom applications. Comparison of center pivot pesticide applications with aerial and tractor-mounted boom applications in 65 ha commercial fields in 1982 and 1983, showed that all application methods provided acceptable levels of pest control, and comparable tuber yields.     

Comparison of application methods for aphicides on sugar beet and swedes

Different designs of electrostatic sprayer (based on hydraulic, rotary atomizer or electrodynamic principles) were compared with uncharged hydraulic sprayers for application of aphicides to sugar beet and swedes. On small plants, the underleaf cover given by low-volume electrostatic systems, ‘APE 80’ and ‘Electrodyn’, enabled effective use of contact-active pyrethroid insecticides. On large plants, electrostatic systems gave no advantage over hydraulic systems and all the systems required the use of aphicides with systemic or fumigant properties to give effective control.