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Maize Response to Corn Leafhopper (Homoptera: Cicadellidae) Infestation and Achaparramiento Disease
To determine the effect that the timing of infestation of Dalbulus maidis (DeLong &Wolcott), a vector of 3 maize pathogens, known collectively as "achaparramiento," has on stunt symptoms and maize yield, we conducted a field trial in the Sebaco Valley of Central Nicaragua. Achaparramiento has caused severe yield losses in maize throughout Central America. Six periods of D. maidis infestation were created using exclusion cages of finemesh screening. The treatments were natural infestations of D. maidis during 0-10, 10-20, 20-30, 30-40, 0-40 d after plant emergence, and no D. maidis infestation. The treatments were repeated on 3 planting dates. During the season, population densities of D. maidis varied from 4 to 8 per plant for the 1st planting date, from 1 to 3 per plant in the 2nd planting date, and from 2 to 8 per plant in the 3rd date. Planting date had a significant effect on plant height, the number of ears, and the yield per plant, but not on disease symptoms or the length of the ears. The timing and duration of D. maidis infestation affected disease symptoms, plant height, and yield: earlier periods of D. maidis infestation produced more pronounced disease symptoms, shorter plants, and lower yields than treatments with late D. maidis infestation. Plant infested 10-20 d after plant emergence had significantly lower yields than plants infested 30-40 d after plant emergence, and plants infested 30-40 d after plant emergence did not have Significantly different yields from plants that were not infested. The yield reduction was caused by smaller ears, not a reduction in the number of ears. The results demonstrate that a management program for reducing the effects of maize stunting diseases caused by the 3 pathogens should be focused on tactics that reduce D. maidis levels from seedling through midwhorl stage of maize growth.