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Project description

Using Phenology Prediction to Improve Weed Management. (97DS035)
Program UC IPM competitive research grants program
J.S. Holt, Botany and Plant Sciences, UC Riverside
T.S. Prather, UC IPM, Kearney Agricultural Center
Host/habitat Unspecified
Pest Unspecified Weeds
Discipline Weed Science
Decision Support
Start year (duration)  1997 (Two Years)
Objectives Quantify phenology of common annual weeds in two different locations to identify functional weed groups defined by similar threshold temperatures and degree-day requirements.

Determine the effect of crop presence on weed phenology and phenology predictions.

Test phenology predictions for weed management in field experiments and growers' fields.

Seeds of annual weeds were collected at UC Riverside and Kearney Agricultural Center (KAC) for weed phenology experiments. Weeds studied at UC Riverside include Amaranthus albus, A. blitoides, A. palmeri, Chenopodium album, Conyza canadensis, Digitaria sanguinalis, Echinochloa crus-galli, Hirschfeldia incana, Portulaca oleracea, Setaria glauca, Solanum nigrum, and Sonchus oleraceus. Weeds studied at KAC include many of the above, plus Brassica geniculata, Conyza bonariensis, Euphorbia maculata, Malva neglecta, Physalis wrightii, Raphanus sativus, and Salsola kali. Field experiments were planted in spring of 1998 in both locations to quantify timing of weed emergence and development. Experiments were planted in randomized complete block designs with six blocks; weed species constitute the treatments. Parallel experiments were established in fields just planted to a crop to observe weed phenology in the presence of a crop canopy. Data were collected at two to three day intervals and included times to emergence, 1 to 10 leaves, 1 to 10 branches or tillers, flowering, and seed set. Using previously determined emergence and development thresholds, these data were converted to cumulative degree-days to each event for each species. In fall 1998, an experiment was planted at UC Riverside to test phenology predictions for their utility in choosing herbicide application timing. Additionally, during 1998 weed phenology in growers' fields near KAC is being monitored to validate degree-day models developed experimentally. Weed phenology predictions can be used to choose crop planting dates when weed germination is least likely; to improve timing of seedbed preparation, seedling management, and cultivation for weed control; and to plan postemergence herbicide applications to control the greatest number of weeds with the least amount of herbicide.

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