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Brower, L.P., Taylor, O.R., Williams, E.H., Slayback, D.A., Zubieta, R.R., and Ramirez, M.I., “Decline of monarch butterflies overwintering in mexico: Is the migratory phenomenon at risk?,” Insect Conservation and Diversity, 5 (2): 95-100, 2012.

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Decline in Milkweed (Asclepias syriaca) Populations in Central New Jersey over a One Year Period

1The Lawrenceville School, Lawrenceville, New Jersey, USA

2Science Department, Montgomery Township Schools, Skillman, New Jersey, USA

World Journal of Agricultural Research. 2015, Vol. 3 No. 4, 119-122
DOI: 10.12691/wjar-3-4-1
Copyright © 2015 Science and Education Publishing

Cite this paper:
Nikhil Gopal, Jamie Witsen. Decline in Milkweed (Asclepias syriaca) Populations in Central New Jersey over a One Year Period. World Journal of Agricultural Research. 2015; 3(4):119-122. doi: 10.12691/wjar-3-4-1.

Correspondence to: Nikhil  Gopal, The Lawrenceville School, Lawrenceville, New Jersey, USA. Email:


Milkweed (Asclepias syriaca) is the primary food source of the eastern North American Monarch butterfly (Danaus plexippus), and numbers have been steadily declining. Between 2012 to 2013 we conducted a survey measure to milkweed numbers in Montgomery Township New Jersey. The purpose of this survey was to examine and measure the change in milkweed numbers after a 1 year period. In October 2012, publicly accessible areas of Montgomery Township were surveyed. This same survey was repeated in 2013, and the change in mean number of milkweed plants per plot recorded. Global positioning satellite data were collected using GPS tracker 1.0 for iPhone. All plots from publicly accessible areas were measured except one plot that was intentionally cultivated. Apart from the single intentionally cultivated plot, only 2 plots remained from the original 30 in the 2012 survey (6%). From the original 302 stalks, only 87 remained one year later (a decrease of 71.9 %). A total of 3 new plots were found, indicating new growth. There was a notable decrease in the mean number of milkweed stalks per plot from 2012 (10.4 ± 2.3) to 2013 (4.3 ± 2.4). This decrease was statistically significant at the 5% level (P = 0.03958). Over a one year period, a statistically significant decline in milkweed plants was observed in central New Jersey. More should be done to conserve milkweed populations.