Florida beggarweed is native to the Western Hemisphere but is naturalized around the world. During the last century, the mechanization of agriculture has transitioned Florida beggarweed from an important forage component to a weed of significance in the coastal plain of the southeast United States. This herbaceous annual is naturalized and found in fields and disturbed areas throughout the southern United States. The characteristics that made Florida beggarweed a good forage crop also make it a formidable weed. This review describes the importance of Florida beggarweed as a weed in the southern United States and the taxonomy of this species and details the distribution throughout the world and within the United States. The ecology of Florida beggarweed and its interactions with crop plants, insects, nematodes, and plant pathogens also are summarized. Finally, management of Florida beggarweed in agricultural systems using cultural practices and herbicides is reviewed.

Desmodium tortuosum (Sw) DC (Papilionaceae) is a preferred wild host of Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae) which is an important pest of cotton in Tolima, Colombia. From November 1976 until March 1979, cotton and D. tortuosum were compared and contrasted in the field as hosts of the pest. A very high infestation level of H. virescens in cotton in 1977 was preceded by an extremely low infestation level of the insect in D. tortuosum previous to the cotton-growing season. In 1978 and 1979 moderate infestation levels in cotton were preceded by moderately low infestation levels of H. virescens in D. tortuosum previous to the cotton growing season in both years.

Progressively less eggs were laid on cotton versus D. tortuosum as the cotton plants aged. Peak numbers of H. virescens occurred during the latter part of the cropping season and immediately after. A mean of 13% of first-instar larvae of H. virescens on D. tortuosum were found stuck by the glandular trichomes of the plant. On cotton significantly more eggs were found during the week of full moon than new moon or first quarter. Apparent sterility and pre-hatch mortality of eggs of H. virescens varied between 1–5 and 0 and 7%, respectively, for both hosts combined.

Egg parasitism by Trichogramma sp. (Hymenoptera: Trichogrammatidae) in cotton was 1.5% in 1977, presumably due to excess use of pesticides, and 23.5% in 1978 when pesticides were not used much. Parasitism of eggs on D. tortuosum by the same parasite averaged 1%; the glandular trichomes of D. tortuosum trapped and killed adult Trichogramma.

The fact that infestation levels of H. virescens in cotton were very high in the year that they were very low in D. tortuosum previous to the cotton-growing season, and moderate in cotton during 2 years that they were not as low previously in D. tortuosum suggests that the continued presence of the pest many aid its natural regulation, perhaps by providing a source of hosts to H. virescens specific parasites.

If relative levels of oviposition in cotton could be predicted by lunar cycles this would aid in planning control strategies, such as massive liberations of egg parasites and more intensive monitoring of infestation levels during predicted peak periods.

Field data of counts of eggs and larvae of Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae) in 12 uncultivated plants in Tolima, Colombia, were used to conduct analyses of variance of the relative importance of the 12 for the insect. Analyses were based on the number of eggs and larvae found per terminal and per 5 g of terminal material of each host.

Regardless of the analysis, more eggs and larvae of H. virescens were found on Desmodium tortuosum (Sw) DC (Papilionaceae) than on the other 11 hosts. In general, more eggs were found on pubescent plants, especially those with glandular trichomes.

A relatively high ratio of larvae:eggs for Ipomea triloba L. (Convolvulaceae) was interpreted to mean that larvae of H. virescens migrated to this plant from eggs laid on other hosts.

The removal rate of eggs from seven hosts due to unknown reasons was estimated to differ between the seven.