Weeds: Germination of many weed seeds is improved with alternating temperatures. With canopy losses the temperatures around trees will be more extreme between day and night and weed growth under trees may increase. The flooding will increase the breakdown of some herbicides (Mandate,Simazine, Pendimethalin and Oryzalin ) but it will not kill all weed seeds. Weeds such as milkweed vine, John songrass and yellow nutsedge are not affected by flooding and may be germinating. Soil moisture can be reduced by mowing if grass species dominate the row middles.
Herbicide Placement: If major portions of the root system are damaged, then serious consideration should be given to the placement of herbicides. Band widths of pre-emergent materials should be placed over the areas that will be actively growing in the next few months.
Herbicide Selection and Rates: With reduced root systems and significant translocation to new growth, the rates of herbicides used should be adjusted accordingly. For example on trees that normally received 4lbs of Simazine should be treated with 2lbs if topped and pruned. Select herbicides that will have minimal stress on the tree you can afford to lose any additional fruit. Trees that still have low hanging fruit should receive postemergence materials that do not increase the risk of fruit drop (apply Paraquat or glyphosate with enclosed booms). When weed species are treated soon after germination they typically are more susceptible to lower herbicide rates. Click on the slide show to see common weeds at growth stages susceptible to low herbicide rates. View Slide Show
There are several possible scenarios for what will happen next year or this late fall regarding new flush and flowering.