For all parameters that were measured in the first set of bioassays using only susceptible colonies, the two negative controls moist filter paper and germinated oat seedlings were significantly different than all corn treatments Table 1 ; Fig. To account for any changes in the settings due to replacing the filter paper between bioassays, the detection variables were updated before the start of each trial. More recently, cross-resistance has been documented between Cry3Bb1 corn and corn that produces a different Bt toxin, mCry3A. Results from two years of on-farm research summarized patterns of root injury and rootworm abundance from across a range of farming practices. The other part of this work consists of conducting bioassays of rootworm populations to measure resistance. Each year US farmers suffer economic losses in excess of one billion dollars, as a result of yield losses and management costs associated with western corn rootworm.
Clair, C, Head, G. After ingestion, these dsRNA travel to other tissues and then are diced into short interfering RNA and interfere with gene expression causing larval mortality and stunting Baum et al. Bioassays Assays used in this study were modified from those developed by Strnad and Dunn Corn seedlings were used in bioassays when they reached 3—4 d old; oats were used at 4—5 d old. The opportunities for management of Bt-resistant western corn rootworm: Entomological Society of America.
By testing beetle gut contents for the presence of specific Cry proteins and comparing them to the Cry proteins expressed by plants at their collection site, recent movement could be detected.
Transgenic corn lines with genes from Bacillus thuringiensis Berliner Bt with resistance to WCR dkssertation are commonly used for rootworm management in the United States.
Additionally, the resistant larvae demonstrated a weaker host response to the isoline corn roots when compared to the susceptible larvae. We would like to thank Monsanto, Syngenta and Dow for the seeds used in this study, and Bill Moar and Tom Clark for their helpful comments. Interestingly, individual components by themselves did not elicit a major feeding response by the WCR larvae, but together, they did Bernklau and Bjostad The movement behavior and reproductive ecology of western corn rootworm beetles coleoptera: The larvae would presumably wander away from the plant and starve to death.
Getting Started About Contact Us. The resistant larvae moved farther from the origin after exposure to the isoline than the susceptible colonies Fig.
Item Statistics Statistics Report. Sequence of attack by northern corn rootworms on the crown roots of corn.
Olfactory response of larvae of Diabrotica virgifera virgifera to plant roots. Once the WCR larvae find potential host roots, contact cues are picked up by the maxillary palps that aid the larvae in making feeding decisions Branson and Ortman RNA interference directs innate immunity against viruses in adult Drosophila.
Genotyping results were inconclusive. Root damage caused by intense larval feeding can severely limit the ability of the plant to absorb nutrients and water and can weaken the plant base, making the plant vulnerable to lodging Kahler et al. Olfactory response cron larvae of Diabrotica virgifera virgifera to plant roots.
Zukoff 1 and Anthony L. Searching behaviour The behavioural ecology of finding resources.
Costs and benefits of controllin pest Diabrotica in maize in the United States. Although the rootworm larvae will feed briefly disseryation the oats, they will abandon them due to a feeding deterrent Branson and Ortman Western corn rootworm Coleoptera: The resistant larvae moved farther from the origin after exposure to the isoline than the susceptible colonies Fig.
Chrysomelidae larvae in corn roots.
Field-evolved resistance to Bt maize by western rooworm rootworm. Because the efficacy of the rootworm refuge strategy relies heavily on western corn rootworm movement and mating behavior, it is important to understand these behaviors in Bt cornfields.
Distribution and orientation of western corn rootworm Coleoptera: WCR eggs are laid in soil dissdrtation the base of the plant, and after hatching larvae use CO 2 a volatile given off by all plants as a long range attractant as they move through the soil in search of host roots BransonStrnad et al.
Structured refuges do not facilitate movement and mating patterns that favor production of heterozygous susceptible offspring.
Management of western corn rootworm and other insect pests of corn – IOWA STATE UNIVERSITY
Contact cues in the isoline root as perceived by the resistant larvae may not be as strongly perceived as the in the susceptible larvae or perhaps there is a slight difference in contact cue chemical composition. Thanks to Bruce Hibbard for his support in this research. RNA interference directs innate immunity against viruses in adult Drosophila. Diabrotica virgifera virgifera Coleoptera: The first set of bioassays consisted of a randomized complete block of nine treatments replicated 20 times.
Chrysomelidae larvae in corn roots. Corn seedlings were used in bioassays when they reached 3—4 d old; oats were used at 4—5 d old. For the mean meander, total distance moved, mean turn angle, maximum distance from origin and westfrn velocity, the linear statistical model contained the main plot effect of treatment.