Using LI 700 in chemigation applications
Most adjuvant labels are written on a per-gallon of spray solution basis and NOT a per acre basis. Our recommendation is to use 1-4 pt/A of NIS for chemigation. Although LI 700 works a little differently than NIS, the recommendation is still the same!
We have been hearing from some growers that they are using as little as 4 oz/A of LI 700. This is a rate on the label based 100 gallons of water. This is not enough to be effective for chemigation!!! When we apply by chemigation, the spray solution is between 400-600 gallons of water per acre.
There is a wide range of rates on the LI 700 label for different uses (with herbicides, as a replacement for crop oil, with insecticides, etc.). I talked to the adjuvant expert at Loveland to ask about chemigation rates for LI 700. He agreed that sticking with the 1-4 pts/A adjuvants for chemigation in cranberry is reasonable.
Marty stands by 1 pt/A for chemigation of insecticides. It’s what we’ve been using and it seems to work. It is needed especially with Altacor, Intrepid/Invertid, and Delegate. Avaunt, Actara and Fanfare also likely are improved with the addition of an NIS/LI 700 adjuvant.
For herbicides, a higher rate of adjuvant may be beneficial - especially with herbicides like Intensity One that really needs an adjuvant to be effective, and QuinStar (use postemergence) where we are substituting NIS/LI 700 for crop oil.
Insects.
The second peak of cranberry fruitwom moth flight, and thus egglaying, will likely happen next week (historically, it occurs in the last week of July). This late season fruitworm activity only occurs on 1 in 10 bogs but if you were planning a final Delegate spray, now (or next week) would be the time to use it. Sparganothis larvae typically start showing up now as well. Weevil numbers should be dropping as the adults leave the bog to overwinter in the woods. Unless you detect very high numbers (30+), it is not economically reasonable to treat for them. Flea beetle may start showing up as we move into August, and again, unless very high numbers are found or significant damage is seen, the cost (and trauma) of a Diazinon spray, the only management option, may not be justified. They generally feed on the overgrowth areas, but very high numbers could damage next year’s developing bud.
Disease.
Red fruit with scaring caused by the viruses Tobacco Streak Virus and Blueberry Shock Virus are now very visible on infected uprights. There is no management strategy for these viruses. Infected plants do not necessarily show symptoms every year. In the years after the initial infection, uprights can produce healthy-looking berries but the vines may continue to test positive for the virus
Weeds.
Beds with dodder problems are very visible now. Some growers with dense patches have raked off the mats to allow light and air to better reach the cranberry canopy. Raking does not remove the imbedded dodder attached to the host plant, and where the dodder flowers are present there will still be some seed production. Some growers are applying Callisto (either as a spot treatment or broadcast by chemigation) to try to control the dodder.
Fireweed is now a few inches above the cranberry canopy in some places. In another week or two, it will suddenly be very visible! We have had one grower report that Stinger was effective for fireweed. Callisto is more effective when fireweed plants are small, and now that the weeds are getting larger it may not work well.
We applied QuinStar to State Bog last week, and are seeing the effects on some weed species. This herbicide can act as a growth regulator on some weeds, and causes twisting and irregular growth. This hypericum turned bright red, and narrow leaf goldenrod and horseweed are showing twisting stems after one QuinStar application.
