摘要:

The movement of first-instar western corn rootworms,Diabrotica virgifera virgiferaLeConte, was studied in relation to soil porosity. Movement toward corn roots was restricted to0.30 mm. The distance moved did not increase with time. Movement decreased significantly with distance in continuous artificial pores with a diameter of 0.15 mm. Pores approximating the larvae head-capsule size and larger did not limit larval movement out to 30 cm. Movement toward a host depends on continuity of soil pores.

ISSN:1754-5692    

DOI:10.1093/ee/18.3.343

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

A 2-yr study investigated the relationship between heat units and nymphal and adult development of meadow spittlebug,Philaenus spumarius(L.), on strawberries. Heat units (HU) were accumulated after the first observed hatch using an upper developmental threshold of 26.7°C and a lower threshold of 2.8°C. First appearance and mean residence time (heat unit accumulation required for development of an individual to the successive instar or stage) of the various instars and adults, and the duration of occurrence (heat unit accumulation over which individuals of a specific instar were observed in the field) of the nymphal stadia were estimated. The first through fifth instars and adults began appearing in the field at 2, 154, 262, 364, 472, and 660 HU accumulations, respectively. The mean residence time of the five instars was 154, 103, 101, 113, and 181 HUs, respectively. The duration of occurrence in the field was approximately 190 HU accumulations for all nymphal instars. A heat unit model is proposed for use in control application timing and population sampling studies and for incorporation into pest management programs.

ISSN:1754-5692    

DOI:10.1093/ee/18.3.347

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Pitfall traps were used in field tests to evaluate the relative attractiveness of red pine,Pinus resinosaAiton, volatiles, turpentine, ethanol, and combinations thereof to adultHylobius radicisBuchanan andPachylobius picivorus(Germar). Traps baited with a combination of ethanol and turpentine caught significantly more of both species of weevils than any other bait tested. Only overwinteredH. radiciswere attracted to the baits. The sex ratio for weevils captured in all traps was 9.1:1 females/males forH. radicisand 1.7:1 forP. picivorus. A significant relationship was observed between numbers ofH. radiciscaptured in pitfall traps placed in plots of Scotch pine,Pinus sylvestrisL., and percentage incidence of foliar symptoms.

ISSN:1754-5692    

DOI:10.1093/ee/18.3.351

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

To investigate whether the pH of maize,Zea mays(L.), silks could serve as a useful screening criterion for resistance to the corn earworm,Heliothis zea(Boddie), the relationship between silk pH of six maize genotypes and damage resulting from artificial infestation of ears with corn earworm larvae was determined. Higher mean pH values generally corresponded to reduced corn earworm damage. Silk pH of all entries increased as silks matured. When silk pH and corn earworm damage were determined in four cycles of selection of a maize population which had undergone recurrent selection for corn earworm resistance, a significant linear relationship between pH and cycle of selection was observed. Significant correlations were observed between silk pH and corn earworm damage and between the percentage of plants with nonbrowning silks and corn earworm damage. There appears to be only limited potential for using silk pH or the nonbrowning silk trait as the sole screening criterion for corn earworm resistance, but when combined with other criteria, they will contribute to increased corn earworm resistance screening sensitivity.

ISSN:1754-5692    

DOI:10.1093/ee/18.3.356

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Gypsy moth instars four through six move down trees at dawn and climb back up at dusk. This daily migration appears to be influenced by environmental conditions, including abiotic factors. In this study, gypsy moth caterpillars were given choices of abiotic conditions to see what their preferences are. Different gypsy moth instars responded similarly in a temperature gradient, were indifferent to direct infrared radiation, and moved upward in a uniformly illuminated tube. All instars tended to accumulate at the lower of two relative humidities when given a choice. Small larvae, but not large ones, were strongly attracted to light. Under a laboratory photoperiod of 16 h light per day, fifth instars migrated away from a food source during the lighted period and toward the food when it was dark. I conclude that sunlight is probably responsible for stimulating large caterpillars to migrate up and down trees.

ISSN:1754-5692    

DOI:10.1093/ee/18.3.361

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

When the dosage of the primary pheromone component (Z)-ll-hexedecenal (Zll-16:AI) of the cranberry girdler,Chrysoteuchia topiaria(Zeller), was varied from 0.03 to 10 mg in field tests, maximum catch was obtained at a dosage of less than 1 mg. When (Z)-9-hexadecenal (Z9-16:AI)was present at 0.3, 1, or 3% of Zll-16:AI, trap catch was proportional to the logarithm of the dosage over the same concentration range. The amount of Z9-16:Althat produced maximum trap catches within calculated confidence limits of each dosage ranged from 0.2 to 2.1% when the dosages of Zll-16:Al were 0.3, 1,3, and 10 mg. Z9-16:AI at 1% always was included within the confidence limits of these dosages. The two higher dosages captured significantly more males than the two lower dosages, but trap catches were not significantly different between dosages of 0.3–1 and 3–10 mg. The reduced trap catch by Zll-16:AI alone for dosages above 1 mg was the result of the absence of an important pheromone component. In flight tunnel studies, Zll-16:AI induced limited plume-oriented flight (19% of tested males) at a dosage of 0.03 mg only, and males did not reach the source. The percentage of males exhibiting upwind flight in the plume increased dramatically when Z9-16:AI was present. At a dosage of 0.3 mg, upwind flight in the plume was 0% for the single component and 90% for the two components. Maximum upwind flight occurred at dosages from 0.03 to 3 mg and, as occurred in field tests, the Z9-16:AI at 1% of Zll-16:AI always was included within the calculated confidence limits for these dosages. The 3-mg dosage of Zll-16:AI reduced the number of males landing on the septa.

ISSN:1754-5692    

DOI:10.1093/ee/18.3.368

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

In an unsprayed cotton field in east Texas, orb weavers were one of the numerically dominant groups of spiders, constituting 10% of all spiders collected by D-vac during the summer of 1985 (range, 0.04 individuals/m2in June to 0.72 individuals/m2in August). Direct counts, conducted during peak orb-weaver density in August, showed that 0.86 individuals/m2were found. More than two-thirds of all orb weavers collected by D-vac in cotton consisted of the five speciesAcanthepeira stellata(Walckenaer),Neoscona arabesca(Walckenaer),Gea heptagon(Hentz),Tetragnatha laboriosaHentz, andUloborus glomosus(Walckenaer). Their prey consisted of insects (>99%) and spiders90% of the prey of the orbweaving spiders, which are characterized as generalist predators. Differences among the five spider species indicate that prey selection was occurring; this seems to be determined by web location, web inclination, and web strength. Of the orb weavers occurring in cotton, 99% were small-sized spiders (primarilyG. heptagon) that intercept small prey with their delicate (about 4 cm diameter) webs. These orb weavers are predators primarily of smallsized pests such as the cotton aphid,Aphis gossypiiGlover, and the cotton fleahopper,Pseudatomoscelis seriatus(Reuter).

ISSN:1754-5692    

DOI:10.1093/ee/18.3.373

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

A guild composed of bark beetles (Coleoptera: Scolytidae) and the southern pine sawyer,Monochamus titillator(F.) (Coleoptera: Cerambycidae), occurring in pine phloem was studied. The goal of this study was to examine interactions between bark beetles andM. titillatorthat may be involved in maintaining guild structure.M. titillatorpotentially can cause significant bark beetle mortality. Mortality to the bark beetles was low because the bark beetles had little direct contact withM. titillator. Dendroctonus frontalisZimmermann larvae avoidedM. titillatorby migrating to the outer bark, whereasIps avulsus(Eichhoff) andI. calligraphus(Germar) developed rapidly and emerged from the tree before the phloem was foraged heavily byM. titillator. The fact that the bark beetles have little direct contact withM. titillatoris enough to maintain the bark beetles' presence in this guild. In contrast, commensalism, through the expansion ofM. titillator'sresource base caused by bark beetle activity, seems to be important in maintainingM. titillator'splace.

ISSN:1754-5692    

DOI:10.1093/ee/18.3.381

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Interactions among the English grain aphid,Macrosiphum (Sitobion) avenae(F.), and three wheat (Triticum aestivumL.) cultivars infected with two isolates of barley yellow dwarf virus (BYDV) were investigated under laboratory conditions by caging individual aphids on leaves of healthy ‘Caldwell,’ ‘Abe,’ and ‘Talento’ wheat plants or plants infected with BYDV (P-PAV and RPV-NY isolates).M. avenaefeeding on infected wheat had a significantly shorter (P ≤ 0.05) developmental time, a greater fecundity, and a greater intrinsic rate of natural increase (rm) than aphids feeding on noninfected plants. These results suggest that BYDV andM. avenaeinteract for their mutual benefit, resulting in a higher potential for population growth of the virus and the vector. The wheat cultivar ‘Caldwell’ was found in this and previous studies to have a degree of tolerance to BYDV as indicated by milder symptoms. Resistance to virus production also was detected for the P-PA V-infected ‘Caldwell’ wheat, which had significantly lower ELISA values (i.e., lower virus concentration) than ‘Abe’ wheat.M. avenaealso had a significantly reduced fecundity on ‘Caldwell’ compared with that on ‘Abe’ and ‘Talento’ wheats infected with BYDV. No significant differences were observed inM. avenaefecundity on BYDV-free cultivars. The results suggest that infection with BYDV might improve the nutritional quality of wheat toM. avenae, resulting in changes in the fecundity of the vector. These changes were greater with the BYDV-sensitive ‘Abe’ and ‘Talento’ cultivars than with the tolerant ‘Caldwell’ wheat cultivar.

ISSN:1754-5692    

DOI:10.1093/ee/18.3.388

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

The effects of parasitism byCampoletis sonorensis(Cameron) and silk-feeding resistance ofZea maysL. cv. Zapalote Chico were evaluated for their effect on growth and development of the fall armyworm,Spodoptera frugiperda(J. E. Smith). Individually, parasitism or a meridic diet containing silks from ‘Zapalote Chico’ resulted in a significant reduction in larval growth of fall armyworm. The combining of these two factors was found to be additive in their ability to reduce larval growth. Progeny ofC. sonorensisfrom fall armyworm fed a meridic diet containing silks of ‘Zapalote Chico’ had prolonged times to pupation and adult eclosion compared with parasitoids from fall armyworm fed a diet without resistant silks.

ISSN:1754-5692    

DOI:10.1093/ee/18.3.394

出版商:Oxford University Press    

年代:1989

数据来源: OUP