Submitted to: Journal of Economic Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/12/2005
Publication Date: 12/1/2005
Citation: Behle, R.W., Isbell, T. 2005. Evaluation of cuphea as a rotation crop for control of Western corn rootworm (Coleoptera: Chrysomelidae). Journal of Economic Entomology. 98(6):1984-1991. Interpretive Summary: Annual crop rotation between corn and soybeans no longer provides adequate control of the corn pest known as the Western corn rootworm because the rootworm has adapted its behavior such that it lays sufficient numbers of eggs in soybean fields to cause an economic infestation for the following year's corn crop. Cuphea is a new oil seed crop that could be planted in rotation with corn. This plant has a sticky surface and may help to prevent rootworm beetles from laying eggs in these fields. A 3-year crop-rotation study was conducted to measure the impact of rotation with Cuphea on the corn rootworm. In support of Cuphea as a rotation crop with corn, Cuphea plots generally had fewer adult beetles than plots planted to corn or soybeans indicating a lower potential for laying economic densities of eggs. Also, corn planted after Cuphea generally had faster early season growth, less rootworm damage, and higher yields than corn planted after corn or soybeans. In contradiction to planting Cuphea as a rotation crop, rootworm densities were sufficient to cause economic damage to corn planted after Cuphea, and adult emergence from plots planted to Cuphea indicate that this pest may be able to complete development by feeding on the roots of Cuphea. These results are important considerations for growers and for industry partners who wish to promote Cuphea production in corn growing regions of the United States. For academia, the report that rootworm larvae were able to complete development on roots of this broad-leaf plant is unique and will provide new basic research opportunities concerning this insect.
Technical Abstract: The ability to prevent significant root feeding damage to corn by the Western corn rootworm (Diabrotica virgifera virgifera LeConte) by crop rotation with soybeans has been lost as this pest has adapted to laying eggs in soybean fields. Cuphea spp. has been proposed as a new broadleaf crop that may provide an undesirable habitat for rootworm adults because of its sticky surface, and therefore may reduce or prevent ovipostion in these fields. A 4-year study (1 year to establish seven rotation programs followed by 3 years of evaluation) was conducted to determine if crop rotation with Cuphea would provide cultural control of corn rootworm. In support of Cuphea as a rotation crop, fewer beetles were captured by sticky traps in plots of Cuphea compared with traps in corn and soybeans suggesting that fewer eggs may be laid in plots planted to Cuphea. Also, corn grown after Cuphea was significantly taller during vegetative growth, had significantly lower root damage ratings for 2 of 3 years, and had significantly higher yields for 2 of 3 years when compared with continuous corn plots. In contrast to these benefits, growing Cuphea did not prevent economic damage to subsequent corn crops as indicated by root damage ratings >3.0 recorded for corn plants in plots rotated from Cuphea, and sticky trap catches that exceeded the threshold of five beetles trap**-1 day**-1. Beetle emergence from corn plots rotated from Cuphea was significantly lower, not different, and significantly higher when compared with beetle emergence from continuous corn plots for 2002, 2003, and 2004 growing seasons, respectively. A high number of beetles were captured by emergence cages in plots planted to Cuphea indicating that rootworm larvae may be capable of completing larval development by feeding on roots of Cuphea, although peak emergence lagged about 4 weeks behind peak emergence from corn. Crop rotation with Cuphea may provide benefits for cultural control of corn rootworms in situations where economically marginal infestation occur, but did not provide the level of control historically attributed to crop rotation before the development of the soybean adapted strain of the Western corn rootworm.