As we get through the stonefruit season and start the early-apple harvest, sprays for some pests has finished. However…
However, in many growing regions we now have a longer seasonal problem with Carpophilus Beetle; and an increasing threat from Queensland Fruit Fly (Qfly)—more now than in previous years and before Qfly was declared endemic in Victoria and NSW.
Management needed for longer
These two pests are old problems, but the change in chemistry for controlling them has extended our spray season right through the harvest period.
Previously, Carpophilus was generally an early to mid-season problem; and we had Qfly Exclusion zones to protect stonefruit growing areas. Now—with the loss of residual products for Carpophilus, and the need to actively control Qfly in orchards—we have to manage these pests for the whole season.
Pyrethroid use a backward step for IPM
Whether from economics or effectiveness, these pests have increased the widespread use of synthetic pyrethroids in our orchards, especially over the last two years—a giant backward step for our IPM system.
Extreme heat affects predators
Coincidentally, the extreme heat events in January and February these last two years (successive days over 40C) have been hard on beneficial predators and parasites that help manage another major pest, Two Spotted Mite; and the secondary pests, San Jose Scale, Mealy Bug and Woolly Apple Aphid.
We have seen increasing flare and outbreaks of San Jose Scale in recent years, Woolly Apple Aphid at times, and Mealy Bug is a consistent problem.
Pyrethroids & secondary pest flare-ups
Pyrethroids were always a bad word in IPM programs.
They adversely affect the biological control of secondary pests; and predators and parasites that help keep minor pests in control are devastated with this chemistry.
We see the consequences of pyrethroid use in the orchards as mite flare and secondary pest outbreaks.
These secondary pests, flare-up later in the season as a result of the early season sprays for Carpophilus Beetle and Qfly.
With few beneficials as a result of these spray programs, and with severe weather also having a significant impact, beneficials have provided little or no guard to keep pest populations in check.
Return of broad spectrum insecticides
Carpophilus Beetle and Qfly have brought the return of the harsh broad spectrum carbamate and synthetic pyrethroid insecticides.
We haven’t used these since the days before mating disruption for Oriental Fruit moth was the main pest of concern in many stonefruit orchards.
Our biological control agents seem to tolerate some of the new products, or we’ve learned to use them at times when they do not affect beneficials such as the parasitic wasp that helps control San Jose Scale and Woolly Apple Aphid.
Two Spotted Mite flare-ups
For growers that had to give up on their IPM programs and use harsh pesticides to control Carpophilus and Qfly, the severe mite problems resulting from these sprays are explained below.
Two Spotted Mite flare-ups come from either the loss of predator mites such as T. Occidentalis, P. Persimilis, and the lady bird Stethorus; or a growth hormone-like stimulatory effect on Two Spotted Mite from some pyrethroids and neonicotinoid insecticides called hormolygosis.
Hormolygosis
Hormolygosis is a strange phenomenon, but an extremely important result of your spray program.
This process can cause pest mites to have more generations in a year and more importantly—with late-season Carpophilus and Qfly sprays—may cause the mite females to lay many more overwintering mite eggs than normal in the autumn.
When these mite eggs hatch next spring, even if predatory mites have survived the sprays, the predator population can’t increase fast enough to keep up with all the pest mites.
Some of the new products that are very effective on Oriental Fruit Moth, Western Flower Thrip and Codling Moth are very toxic to the Stethorus ladybird.
Stethorus are very effective in fruit varieties where some mite injury can be tolerated, as it takes some time to arrive in the orchard and then build up a population that can control Two Spotted Mite.
Hormolygosis will be expanded in the next article, and strategies for Woolly Apple Aphid and San Jose Scale will be discussed in the following editions of Tree Fruit.
Contact Russell
See this article in Tree Fruit January 2015
