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- Author or Editor: J. M. Schalk x
A greenhouse study was conducted to confirm the availability of resistance in pepper (Capsicum annuum L.) to western flower thrips [Frankliniella occidentalis Pergande)]. Host plant resistance ratings confirmed earlier observations that there is a considerable amount of variability within pepper germplasm for reaction to F. doccidentalis. Plants of `California Wonder', `Keystone Resistant Giant', `Mississippi Nemaheart', `Sweet Banana' and `Yolo Wonder L' were resistant to the insect and exhibited only mild injury. Plants of `Bohemian Chili', `Carolina Cayenne', and `Santaka', however, exhibited the symptoms of severe thrips injury, i.e., poorly expanded, deformed and distorted leaves, greatly shortened internodes, and severe chlorosis. The resistance in pepper to F. occidentalis appears to be due to tolerance mechanisms, not nonpreference or antibiosis mechanisms. The levels of resistance identified in this study are sufficiently high to justify the initiation of breeding efforts to transfer F. doccidentalis resistance into susceptible pepper cultivars.
There were no differences in mortality, plant preference, or plant damage when diamondback moth (DBM) (Plutella xylostella L.) larvae were tested in no-choice and free-choice tests using leaf disks of resistant (`Green Glaze') or susceptible (`Vates', standard commercial cultivar) collards (Brassica oleracea Acephala group). No residuals of the pyrethrin insecticide Asana-XL (esfenvalerate) were detected 6 days after its application when DBM larvae were exposed to excised foliage for 72 hours. In a field test, more imported cabbage worm (ICW) (Pieris rapae L.) eggs were found on `Vates' treated with the insecticide than on nontreated Vates' or nontreated or treated `Green Glaze'. The fewest ICW, cabbage looper (CL) (Trichoplusia ni Hubner), and DBM larvae were found on the insecticide-treated cultivars. Fewer caterpillars were found on `Green Glaze' than Yates'. An additive effect of plant resistance and insecticide application lowered counts of DBM, ICW, and CL larvae. Percent parasitism of DBM by Diadegma insulare Cresson (Hymenoptera: Ichneumonidae) was lower on cultivars treated with the insecticide. Field plant damage ratings were higher for nontreated `Vates' and lowest for treated cultivars, but nontreated `Green Glaze' had a significantly lower feeding damage rating than nontreated `Vates'. Chemical name used: (S)-cyano (3-phenoxy phenyl) methyl-(S)-4 chloro-alpha (1-methylethyl) benzeneacetate [esfenvalerate (Asana-XL)].
Aluminum mulches lowered soil temperatures and reduced heat stress for young tomato transplants, increasing their survival and height. Yields were improved in all mulch treatments. Greatest yields of large and extra-large fruits were obtained from plants grown on aluminum alone, on aluminum in combination with black plastic, and on black plastic alone. Aphids were repelled by the aluminum mulches, while fruit injury increased due to tomato pinworm and tomato fruit worm feeding in these plots.
A two year study was conducted to evaluate the efficacy of insect resistance in sweetpotato cultivars from our breeding program in combination with an insecticide (fonofos) and/or a parasitic nematode (Steinernema carpocapsae). In the laboratory, use of the parasitic nematode resulted in 99% mortality of Diabrotica larvae. In both years, much higher control of damage by all insect classes was achieved by the use of resistant cultivars in combination with a nematode and/or fonofos treatment. Analysis of the first year's field data showed the parasitic nematode treatment gave good damage protection against the WDS (Wireworm, Diabrotica, Systena), sweetpotato flea beetle, but not grubs. In this same year, fonofos only gave good protection against WDS. In the second test year, fonofos gave good protection against WDS, but the nematode did not. High moisture conditions may have affected the efficacy of the parasitic nematode. Host plant resistance by sweetpotato cultivars appears to be less affected by variable field conditions and accounted for 64% of the total crop protection (compared to the check susceptible line).
Twenty-two sweet potato (Ipomoea batatas (L.) Lam.) breeding lines and 19 open-pollinated offspring from each were used to estimate the heritabilities of 7 measures of soil insect injury. Four measures of injury by the wireworm, Diabrotica spp., and Systena spp. (WDS) complex and h2 (± SE) were: percentage of roots injured, 0.45 ± 0.12; holes per root, 0.32 ± 0.09; severity index, 0.37 ±0.11; and damage score, 0.39 ± 0.17. Two measures of injury by the sweetpotato flea beetle, Chaetocnema confinis Crotch, and h2 were: percentage of roots injured, 0.40 ± 0.07, and tunnels per root, 0.25 ± 0.08. The h2 of percentage of roots injured by all insects was 0.51 ± 0.12. The percentage measures were more easily obtained and were as effective as the other measures under the conditions of natural infestation that occurred in this test. Further advances in selection for high levels of resistance to soil insects are possible within the breeding materials tested.
Root injury of sweet potato (Ipomoea batatas (L.) Lam) was significantly increased when eggs of banded cucumber beetles (Diabrotica balteata (LeConte)) in a agar-water mixture were applied at preroot enlargement. This technique should prove useful in screening sweet-potato lines or cultivars for insect resistance.
Plants of Lycopersicon hirsutum Humb. & Bonpl., which were resistant to the Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), and plants of susceptible Lycopersicon esculentum Mill, were grown in controlled environment chambers with 8- or 16-hour daylengths. Rates of feeding by CPB on lower leaves from these plants were measured at 3 stages of plant development and tomatine contents of the leaves were determined. Leaves from young plants were more susceptible to CPB feeding than leaves from flowering or mature plants, and tomatine content was lower in the young leaves. The daylength also had significant effects on tomatine content, feeding rate, and the resistance expressed by L. hirsutum plants. For all plants in the experiment, tomatine content and feeding rate were negatively correlated (r = −0.643, p = 1%). Feeding was inhibited 20–80% when tomatine was infiltrated into tomato leaf disks at concentrations between 65 and 165 mg/100 g fresh weight. The results suggest that a high tomatine content in leaves of L. hirsutum or L. esculentum inhibits CPB feeding.
‘Sumor’, a multi-use sweet potato [Ipomoea batatas (L.) Lam.], was developed jointly by the Agricultural Research Service, U.S. Department of Agriculture, U.S. Vegetable Laboratory, and Clemson Univ., South Carolina Agricultural Experiment Station, Edisto Research and Education Center. This cultivar has potential as a high dry matter type for ethanol production and as a white-fleshed garden potato.
‘HiDry’ is a high dry matter (DM) yielding sweet potato cultivar with high DM content developed jointly by Clemson Univ. and the USDA for industrial uses. It possesses high levels of multiple disease and insect resistances.