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.
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.
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.
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)].
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).
Soil insect root injury to resistant sweet potato [Ipomoea batatas (L.) Lam.] cultivars ‘Regal’ and ‘Southern Delite’ was compared to injury to ‘Jewel’ and ‘Centennial’ in trials with the resistant-standard W-13 and the susceptible-standard SC 1149-19. Injury by three groups of insects was evaluated: the wirewoom-Diabrotica-Systena complex (WDS), which includes the southern potato wireworm (Conoderus falli Lane), the tobacco wireworm (C. vespertinus Fabricius), the banded cucumber beetle (Diabrotica balteata LeConte), the spotted cucumber beetle (D. undecimpunctata howardi Barber), the elongate flea beetle (Systena elongata Fabricius), the pale-striped flea beetle (S. blanda Melsheimer), and S. frontalis Fabricius (a flea beetle); the sweet potato flea beetle (Chaetocnema confinis Crotch.); and a white grub (Plectris aliena Chapin). Relative control estimates were obtained by comparison to the susceptible standard. ‘Regal’ and ‘Southern Delite’ provided good control of all three insect groups with control of all insect injuries of 79.2% and 81.0%, respectively. ‘Jewel’ and ‘Centennial’ were resistant to the sweet potato flea beetle and sustained less damage by WDS than the susceptible standard, but would still be classed as susceptible to WDS. ‘Centennial’ was as susceptible to the white grub as SC 1149-19. The levels of resistance demonstrated for ‘Regal’ and ‘Southern Delite’ would provide growers an alternative to insecticides for the control of these insects.
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.
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.
Correlation studies indicate visual and Hunter Lab Color and Color Difference Meter aL ratings are of comparable value for classifying flesh color of sweet potato [Ipomoea batatas (L.) Lam] roots. Dry matter content was correlated with flesh color, specific gravity, and dry matter yield and with sugar, starch, and sugar + starch (fermentables) contents. Dry matter yield, starch yield, and other responses of seedlings with light and with dark orange flesh color were as expected from correlation studies. Light flesh color and high specific gravity, in combination with high field yield, appear to be useful selection traits for expediting development of cultivars for industrial uses.