Combining ability in maize for fall armyworm and southwestern corn borer resistance based on a laboratory bioassay for larval growth

The fall armyworm, Spodoptera frugiperda (J. E. Smith), and southwestern corn borer, Diatraea grandiosella Dyar, are major insect pests of maize, Zea mays L., in the southern USA. Both insects feed extensively on leaves of plants in the whorl stage of growth. A diallel cross of seven inbred lines with different levels of susceptibility to leaf feeding damage in the field was evaluated in a laboratory bioassay for fall armyworm and southwestern corn borer larval growth. Diets were prepared from lyophilized leaf tissue of field-grown plants of the inbred lines and their 21 F₁ hybrids. One inbred line, Tx601, exhibited heavy leaf damage in field tests but showed moderate resistance in the laboratory bioassay. Both general and specific combining ability were highly significant sources of variation in the inheritance of fall armyworm and south-western corn borer larval growth in the laboratory bioassay. Tx601 showed excellent general combining ability for reduced larval growth of both species.This article is a contribution of the United States Department of Agriculture, Agricultural Research Service, in cooperation with the Mississippi Agricultural and Forestry Experiment Station. Journal No. J-8525     

Parasitism of Western Corn Rootworm Larvae and Pupae by Steinernema carpocapsae

Virulence and development of the insect-parasitic nematode, Steinernema carpocapsae (Weiser) (Mexican strain), were evaluated for the immature stages of the western corn rootworm, Diabrotica virgifera virgifera LeConte. Third instar rootworm larvae were five times more susceptible to nematode infection than second instar larvae and 75 times more susceptible than first instar larvae and pupae, based on laboratory bioassays. Rootworm eggs were not susceptible. Nematode development was observed in all susceptible rootworm stages, but a complete life cycle was observed only in second and third instar larvae and pupae. Nematode size was affected by rootworm stage; the smallest infective-stage nematodes were recovered from second instar rootworm larvae. Results of this study suggest that S. carpocapsae should be applied when second and third instar rootworm larvae are predominant in the field.     

Rotations with Coastal Bermudagrass and Fallow for Management of Meloidogyne incognita and Soilborne Fungi on Vegetable Crops

The efficacy of fallow and coastal bermudagrass (Cynodon dactylon) as a rotation crop for control of root-knot nematode (Meloidogyne incognita race 1) and soilborne fungi in okra (Hibiscus esculentus cv. Emerald), squash (Cucurbita pepo cv. Dixie Hybrid), and sweet corn (Zea mays cv. Merit) was evaluated in a 3-year field trial. Numbers of M. incognita in the soil and root-gall indices were greater on okra and squash than sweet corn and declined over the years on vegetable crops following fallow and coastal bermudagrass sod. Fusarium oxysporum and Pythium spp. were isolated most frequently from soil and dying okra plants. Numbers of colony-forming units of soilborne fungi generally declined as the number of years in sod increased, but were not affected by coastal bermudagrass sod. Yields of okra following 2-year and 3-year sod and squash following 2-year sod were greater than those following fallow. Yield of sweet corn was not different following fallow and coastal bermudagrass sod.     

Effects of prococene II on the nutritional physiology of last instar Heliothis zea larvae

When precocene II was fed to last instar larvae of Heliothis zea, it caused significant reductions in the calculated rate of growth, rate of nutrient assimilation, and conversion of ingested and digested food to body mass. No change in the rate of food consumption occurred but respiration was significantly higher. Transport of the nutrient [1-¹⁴C] linoleic acid across midgut tissue was hindered when larvae were fed precocence II. There was also a precocene-induced change in the apical (luminal) morphology of midgut cells, including absence of the glycocalyx and loss of the microvillar absorptive surface. The influence of precocene II on the midgut physiology and metabolic processes in last instar larvae of H. zea may account for the observed reduced growth and delayed development. © 1992 wiley-Liss, Inc.     

Biological control of the western flower thrips,Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), in glasshouse sweet peppers with Orius spp. (Hemiptera: Anthocoridae). A comparative study between O. niger (Wolff) and O. insidiosus (Say)

In a comparative study for biocontrol of the western flower thrips (WFT) in commercial sweet peppers Orius spp. effectively controlled WFT. The introduced native Orius niger had replaced the introduced imported Orius insidiosus by the end of the growing season.     

Energy analysis of ethanol production from sweet sorghum

The Piedmont System is a collection of equipment for efficiently removing the juice from sweet sorghum stalks for the production of ethanol. The concept is to separate the whole stalks into pith and rind-leaf fractions, pass only the pith fraction through a screw press, and thus achieve an improvement in juice-expression efficiency and press capacity. An energy analysis was done for two options of this proposed harvesting/processing system: (Option 1) The juice is evaporated to syrup and used throughout the year to produce ethanol, and the by-products are used as cattle feed. (Option 2) The juice is fermented as it is harvested, and the by-products (along with other cellulosic materials) are used as feedstock for the remainder of the year. Energy ratios (energy output/energy input) of 0·9, 1·1 and 0·8 were found for sweet sorghum Option 1, sweet sorghum Option 2, and corn, respectively, as feedstocks for ethanol. If only liquid fuels are considered, the ratios are increased to 3·5, 7·9 and 4·5.     

玉米自交系间杂交种F1农艺性状的主成分分析

用Hótlling倡导的主成分分析法,(Principal comporient analysis),分析了玉米32个自交系间80个杂交组合的F_1世代.分析性状有株高、穗位高、雄穗分枝数、单株有效穗数、穗长、秃尖长、穗行数、行粒数、穗重、百粒重和单株产量.结果表明,前4个主成分贡献率占了总变异的大部分,因此就前4个主成分得分值对80个杂交组合进行了选择,为玉米组合的选择提供了直接依据.     

The effect of forty years of continuous corn cropping on soil organic matter characteristics

Changes in humus and some of the major extractable components of soil organic matter were examined, following forty years of conventionally tilled continuous corn cropping compared with those of an adjacent untilled native grassland soil. Results indicate that long-term continuous cropping caused a significant reduction in the content of alkali extractable and water soluble carbon, as well as in the phenolic and chloroform extractable compounds, while no differences in volatile acids and n-hexane extractable substances were found. On the basis of organic C, corn cropping led to a relative enrichement of phenolic compounds, volatile acids and substances extractable by Na₄P₂O₇, but it did not affect the substances extractable by water. Except for the humification ratio (HR), the humification parameters, such as humification degree (HD), the extracted humic and fulvic acids, the C_HA/C_FA ratio and the humification index (HI) revealed a higher degree of humification of the organic matter in native grassland than in the continuous corn cropping system. IR spectra of n-hexane, chloroform, alkaline and water extracts failed to show significant differences between sites under native grassland and sites under continuous corn.     

In vivo effect of mixtures of allelochemicals on the life cycle of the European corn borer, Ostrinia nubilalis

The phenylpropanoid, dillapiol, a compound capable of inhibiting the activity of cytochrome P-450 epoxidase in microsomal preparations of midguts of the European corn borer (ECB), Ostrinia nubilalis Hubner (Lepidoptera), did not enhance the toxicity of two insecticidal allelochemicals from the Asteraceae: the sesquiterpene lactone, tenulin or the phenylacetylene, phenylheptatriyne, when ingested simultaneously. Dillapiol alone was toxic to ECB larvae, and inhibited their growth. Possible reasons for the lack of synergism or potentiation by dillapiol of the insecticidal activity of the other allelochemicals are considered.

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Résumé Le dillapiole, un phénylpropanoide monomère d'un lignan et contenant un groupement méthylènedioxyhphényl (MDP), a la capacité d'inhiber in vitro les enzymes d'oxydations multiples à cytochrome P-450 (PSMO) utilisées par la pyrale du maïs (ECB), Ostrinia nubilalis, pour detoxifier les substances allélochimiques. Les composés contenant un groupe MDP comptent parmi les plus nombreux et puissants synergistes d'insecticides. Cependant, aucun synergisme n'est observé lorsque le dillapiole est ingéré par la pyrale en association avec l'une ou l'autre ou les deux substances secondaires insecticides des Astéraceae, la lactone sesquiterpène ténuline ou/et le polyacétylène phénylheptatriyne (PHT). Plutôt, le dillapiole est une toxine qui diminue la prise de poids des larves et retarde leur développement. Les effets toxiques sont plus importants avec le dillapiole seul que lorsque celui-ci est associé à la ténuline ou/et au PHT. Les expications possibles de ces résultats sont discutées.

     

Influence of adult diet on the reproductive biology and survival of the western corn rootworm,Diabrotica virgifera virgifera

Adult corn rootworm beetles,Diabrotica virgifera virgifera LeConte, were maintained on three dietary regimes which mimicked the progression of corn tissues that would be available in the field for beetles eclosing when corn was in the following growth stages: (A) after tassels had emerged but prior to silking and pollen shed; (B) while plants were silking and shedding pollen; and (C) after pollination was complete and silks had turned brown. A fourth regime (D) was established in which green corn silks, pollen, and leaves were provided throughout the study. The mean number of eggs laid per female over the 12-week duration of the study was 125, 235, 179, and 441 for regimes A, B, C, and D, respectively. Median length of life was 7.2, 7.2, 6.7, and 8.8 weeks for regimes A, B, C, and D respectively. Beetles in regime A laid a greater proportion of their eggs at an older age than did beetles from regimes B and C. To further investigate the influences on survival of changes in food quality of corn as plants and beetles aged, newly-eclosed beetles and beetles that had been maintained in caged plots of corn growing in a greenhouse for various lengths of time were caged on corn at different stages of growth, and the proportion of beetles surviving for 48 h was determined. Survival decreased as plants aged for both groups of beetles, but decreased at a faster rate for old than for young beetles.

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Influence de l'alimenation sur la reproduction et la survíe deDiabrotica virgifera virgifera

Résumé D. virgifera virgifera LeConte a été placé sur des régimes nutritifs mimant l'évolution des tissus du maïs disponsibles dans le champ lorsque les insectes éclosent est aux stades suivants du maïs: 1) après émergence de l'épi mâle, mais avant l'apparition des barbes et l'émission du pollen; 2) lors de la présence de barbes et de l'émission de pollen; 3) après la pollinisation et quand les barbes ont bruni. Un quatrième régime a été fourni pendant toute l'expérience comprenant des barbes vertes, du pollen et des feuilles. Les pontes moyennes des femelles pendant les 12 semaines de l'étude on été 125, 235, 179 et 441 pour les régimes 1, 2, 3 et 4. Les dates de mort de la moitié des adultes a été 7,2, 7,2, 6,7 et 8,8 semaines pour respectivement les mêmes régimes. Les femelles du régime 1 pondent à un âge plus avancé que les femelles des régimes 2 et 3. L'influence des changements de la qualité alimentaire du maïs au fur et à mesure du vieillissement des plantes et deDiabrotica, a été déterminée par la survie au bout de 48 heures d'insectes éclos depuis peu et d'autres maintenus en cage sur des lots de maïs à différents stades poussant en serre depuis des temps plus ou moins longs. Plus les plantes sont âgées, plus la survie des 2 groupes deDiabrotica diminue, mais plus vite chez les lots d'insectes âgés.