Buried seeds of witchgrass (Panicum capillare L., # PANCA) exposed to natural seasonal temperature changes in Lexington, KY, for 0 to 35 months exhibited annual dormancy/nondormancy cycles. Seeds were dormant at maturity in early October. During burial in late autumn and winter, fresh seeds and those that had been buried for 1 and 2 years became nondormant. Nondormant seeds germinated from 76 to 100% in light at daily thermoperiods of 15/6, 20/10, 25/15, 30/15, and 35/20 C, while in darkness they germinated from 1 to 24%. In late spring, seeds lost the ability to germinate in darkness, and by late summer 63 to 100% of them had lost the ability to germinate in light. As seeds became nondormant, they germinated (in light) at high (35/20, 30/15 C) and then at lower (25/15, 20/10, and 15/6 C) temperatures. As seeds reentered dormancy, they lost the ability to germinate (in light) at 15/6 C and at higher thermoperiods 2 to 3 months later.

Corn and soybean farmers across Indiana were surveyed in 2003 to determine the perceived importance of weeds at the state and district levels. Weeds were considered the primary crop pest by 69 to 84% of farmers, depending on district. Diseases or insects were ranked first by no more than 14% of farmers and nematodes were ranked first by no more than 11%. Giant ragweed, Canada thistle, common lambsquarters, common cocklebur, and velvetleaf were considered the most problematic summer annual and perennial weeds statewide. Chickweed, horseweed, dandelion, and henbit were considered the most problematic winter annual weeds statewide. However, no weed species was listed by more than 41% of farmers statewide suggesting that relatively unique weed management problems may exist on many farms. Also, the perceived importance of most weed species varied substantially among Indiana's nine districts. For example, velvetleaf was not listed as a problematic weed by any farmers in three districts. Burcucumber was not considered a statewide problem but was listed among the top three weeds by 14 and 16% of farmers in two southern districts. This survey supports the idea that educational programs focused on weed management should be tailored to geographic regions within Indiana.

Common purslane is a widely distributed summer annual weed. It can reproduce vegetatively from stem cuttings by forming adventitious roots from the cut end of the stem. Apart from large stem cuttings, it is unclear whether purslane cuttings of various plant tissues differ in their ability to reproduce asexually. The objective of the study was to determine the survival and asexual reproductive capacity of purslane cuttings. A greenhouse study evaluated three cuttings from two stem locations and a leaf from one stem location for their survival and new leaf growth after 21 d. Cuttings included a stem node with either leaves attached or removed and a stem internode, all from proximal and distal stem locations relative to the root crown, and a leaf from a proximal stem node. Stem node cuttings had ≥ 70% survival, whereas internodes had 0% survival. Nodes with leaves attached further increased survival by > 20%. The location of the cutting on the main stem did not affect survival. Only noded cuttings produced new leaves, and cuttings with leaves attached produced the most new leaves. For purslane to vegetatively reproduce, nodes on stem cuttings are required, and the presence of leaves on the cutting improves the survival and new leaf growth of cuttings. Therefore, mechanical methods of weed control that chop and spread purslane leaves and stems might not be effective and could ultimately increase weed populations.

Corn and soybean growers across Indiana were surveyed in 2003 to determine their perceptions of the importance of weed problems in various crop rotations. Growers were asked to list the three most problematic weeds in the following rotation systems: soybean and corn planted in alternate years (SC) and corn (CC) or soybean (SS) planted to the same field for 2 or more years. Although some summer annuals and perennials (common lambsquarters, Canada thistle, and common cocklebur) and winter annuals (chickweed and henbit) were considered problematic by at least 10% of growers in all three systems, there were differences among systems in the relative importance of weed species. Giant ragweed was considered problematic by at least 30% of SC and CC growers but by less than 10% of SS growers. Horseweed was listed as a problematic summer annual by 13% of SS growers but by only 3% of CC growers. Purple deadnettle was listed by 15% of CC growers but by less than 6% of SC and SS growers. Perennial dicots were more problematic in SS than in CC. Annual and perennial grasses were more problematic in CC than in SC or SS. Despite these differences, the results of this survey suggest that the cumulative effect of weed management practices in corn and soybean rotation systems in Indiana has been the promotion of larger seeded, broadleaf, summer annual species.