Plant Host Effect on the Development of <I>Heliothis virescens</I> F. (Lepidoptera: Noctuidae)

Abstract

Heliothis virescens F. is an important polyphagous pest that can develop on >100 plant species, including 20 economic crops. Populations of this insect are believed to be locally maintained on a few crops and weed hosts in Washington County, MS. To find the intrinsic value of these plants for the development of H. virescens populations, we fed different laboratory and wild colonies with fresh and lyophilized plant tissue under a constant temperature. Development time of this insect under laboratory conditions varied up to 10 d between plant hosts and was dependent on the type of plant tissue provided: fresh or lyophilized. Life table parameters such as net reproductive rate, finite rate of increase, and generation time indicated that Trifolium repens, a wild host growing around agricultural fields year round, could be one of the most suitable local plant hosts for the development of H. virescens. Two species of Geranium, previously reported as the source of the first H. virescens generation in the region, had lower intrinsic value as a food source than did T. repens. Gossyipium hirsutum, perhaps the most important crop source of H. virescens in the region, produced low net reproductive rate and finite rate of increase parameters. Sampling conducted in agricultural fields during 2006 and 2007 found no larvae on the above mentioned wild hosts as it was previously reported. Results indicated that H. virescens populations in this region were not supported by the wild plant species growing around agricultural fields during the time when the survey took place.

Heliothis virescens and Bt cotton in the United States

“…By this time, cotton would have a great influence producing this generation which is probably reflected (C.A.B., unpublished). These observations indicate that perhaps there is a physiological 77 or genetic [80][81][82] differentiation in TBW host races that may be responsible for these preferences, which will be addressed below.…”

“…Before the practice of controlling weeds and insects around fields was implemented, this area represented only ~3.5% of the agricultural landscape but harbored an estimated TBW density exceeding 90,000 larvae per hectare. 75 After arduous research efforts to document the benefits of the control of early generations in wild hosts, the area was reduced to ~2.4%, containing an average of only 62 heliothine larvae per hectare, 76 and 15 years later, for similar marginal areas surrounding agricultural fields, TBW was not present for a couple of years in these weeds, 77 which indicates that their populations were declining before the use of Bt-cotton in the area. But why this change is not evident in the pheromone trapping data?…”

“…It may also be difficult to reliably obtain them now from previously reported heavily-infested plant hosts such as Geranium spp, and velvetleaf (Abutilon theophrasti Medik.). [76][77][78] Contrastingly, a crop rarely planted in the southern US, garbanzo (Cicer arietinum L.), is where high numbers of TBW still can be reliably obtained. Year after year in Mississippi 53,79 and elsewhere where garbanzo beans were planted in small experimental plots, several hundred TBW larvae would be found devouring the plants to the point of complete defoliation.…”

“…Similarly, TBW colonies with dissimilar origin had different development when fed on an group of plant hosts. 77 The plant host where these colonies were obtained apparently made a difference on their capacity to develop or not on cotton. This can support the idea that certain host races are more suitable to perform on certain plants, possibly reflected by the constant male occurs between May to September in MS and LA, a similar time frame when cotton is also available in southern latitudes.…”

Lima bean–lady beetle interactions: spider mite mediates sublethal effects of its host plant on growth and development of its predator

“…Several 2.5-and 5.0-mg samples of frozen spider mites and predators were weighed, then placed into 1.5-ml plastic centrifuge tubes and returned to cold storage (-16°C), until chemical analysis. The protein content in predators (S. punctillum pupae) and prey (spider mites of all stages) reared on the two cultivars (Henderson, Fordhook) was determined using the DC protein assay (Product # 500-0116, Bio-Rad Laboratories, http://www.bio-rad.com) as described in more detail in Blanco et al (2008). Four 5.0-mg samples of frozen samples of predators (1-day-old pupae), and four 2.5-mg samples of frozen spider mites (eggs, nymphs, and adults as used to feed predator larvae) were individually weighed, then transferred into glass tubes (15 cm 9 1 cm).…”