I have gathered some more information after my first blog and here is an update on the maggot issue we are seeing in Santa Maria and parts of Oxnard.
Santa Barbara Co entomologist, Brian Cabrera and UC Davis entomologist, Frank Zalom both recovered larvae of the dark-winged fungus gnat (Family: Sciaridae) from the strawberry plants they received. These larvae primarily feed on fungus and decaying plant material, but they can also feed on plant roots. They are also known to mechanically vectoring plant pathogenic fungi.
Dark-winged fungus gnat larva from strawberry plants (Courtesy: Brian Cabrera)
A PCA had reported finding seedcorn maggot-like larvae in the strawberry fields near Oxnard. A few growers had also mentioned similar findings in Santa Maria. I too found similar maggots in fields I checked later on. So, we have two species infesting the strawberry plants at this time.
Seedcorn maggot flies are attracted to decaying plant material, but their maggots feed on living plant material. Dark-winged fungus gnats do not appear to be new in the strawberry fields. Brian Cabrera found them early this year in dead strawberry plant specimens. The probable reason for seeing more of them now is that there is more dead plant material from the other maggot damage. Is it possible that we have a primary invader, seedcorn maggot-like one and a secondary invader, the dark-winged fungus gnat larva? This is just a thought. High soil moisture from recent rains can also worsen their problem. Damage from both maggots can also increase vulnerability of plants to pathogens.
Organophosphates will control these maggots, but Frank Zalom mentioned that growth regulators like azadirachtin can also be effective. Neonicotinoids like imidacloprid are not known to have any effectiveness.
We need to continue close monitoring of this problem and share the information.
