Sep 26, 2018 | Silverleaf whitefly populations have increased in many areas in the last few weeks and will likely continue to increase as we stay above average temperatures. When we start to cool off at night, the population increases should slow down. We have been fortunate that we have not seen population explosions like we had last year. Part of this is likely the impact of a fungus that attacks whitefly. We saw a lot of it last year after the hurricane and are seeing impacts in many areas this year. When present, you will see fuzzy, white, dead adults stuck to the leaves. High humidity (which we have had even without rain) helps fungal attack on whitefly and other pests (unfortunately it also helps fungi attack plants). Hopefully we will experience cooler weather with some rain in the near future and help suppress the whitefly population growth.
Insecticide trials have mostly shown good efficacy with most of the products we usually use. We have seen reduced performance with imidacloprid (Admire Pro) and thiamethozam (Actara) – these two neonicotinoids are very similar and resistance has historically been worse with these as compared to other neonicotinoids. Coragen has also shown less efficacy than expected but is still providing some control. Insecticide resistance is always a threat and rotation of modes-of-actions is highly encouraged.
