Watch for spider mites and thrips in late March and into April
Tom Dudek said greenhouse growers and scouts are seeing mites earlier than usual this year, with the most common problems being found on zonal and ivy geraniums, fuschia, New Guinea impatiens and spikes. Also, thrips activity is picking-up in some places.
Spider mites
Fortunately, we have some excellent miticides. When spider mites are
found, spray the infested plants and plants nearby with one of the
following products: Akari, Avid, Floramite, Hexygon, Judo, Kontos,
Ovation, ProMite, Pylon, Sanmite, Shuttle-O, Suffoil-X ( concentrations
> 1percent may be phytotoxic), Tetrasan, Kanemite.
Some of the miticides, like Hexygon, do not kill mites immediately, and
it may take three to four days to see a difference. All of these
products will reduce spider mite population for three to four weeks
after a single application with the exception of Suffoil-X, a
horticultural oil.
Thrips
Late March and April is when thrips become more active in greenhouses.
First, warmer temperatures and longer days give overwintering thrips the
green light to reproduce. Second, an ample supply of pollen and warmer
temperatures allow thrips to reproduce faster. Also, thrips present in
greenhouse crops since February have now completed a second generation,
turning 100 thrips into 30,000 thrips. This always comes as an
unwelcome surprise in late April.
The best way to avoid problems with thrips is to watch the scouting
reports carefully and begin your thrips management program when thrips
numbers begin to increase on yellow sticky cards. When the number of
thrips per yellow sticky card increases beyond your tolerance level (for
most growers the threshold is from 10 to 100 per card), spray the
infested greenhouse sections with one of the following products every
five days for four applications. Conventional sprayers usually give
better results than foggers. Obtaining good coverage of stems and the
undersides of leaves improves control. High spray pressure and good air
movement usually result in the best coverage.
Avid, Mesurol, NemaShield, Orthene 97, Overture, Pedestal, Pylon,
Safari, Sanmite, Tristar, and Conserve. Note: thrips may be resistant
to Conserve.