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Apple Maggot: When Control Is No Longer Needed. August 14th.

Adult apple maggot flies. Female flies (R) are black, with a pointed abdomen with four white cross bands. The males (L) are smaller and have three cross bands on a rounded abdomen.

Adult apple maggot flies. Female flies (R) are black, with a pointed abdomen with four white cross bands. The males (L) are smaller and have three cross bands on a rounded abdomen.

During the growing season there are periods of uncertainty for starting and stopping management for specific pests. The beginning of management for most insects is straight forward. Early season timing is often based on tree phenology such as delayed dormant applications at 3% oil for San Jose scale, late tight cluster for obliquebanded leafroller emergence, pink for rosy apple aphid management with contact insecticides and petal fall, the trigger for European apple sawfly and plum curculio management. However, given the shift in chemistry from broad to narrow range spectrum, the use of insect growth regulators and mating disruption for lepidopteran pests, there comes greater reliance on pheromone trapping. These tools begin the developmental models for timing applications that, over the past few years, have become the standard for applications against summer generations of codling moth and obliquebanded leafroller.

Apple Maggot on Baited Red Sticky Sphere

Apple Maggot on Baited Red Sticky Sphere

Through the development of the red sticky sphere and attractive lures using ammonium acetate, butyl hexanoate (fruit odor) ammonium carbonate (food odor), or blends, the trigger for apple maggot management can be postponed until mature flies capable of laying viable eggs are captured in traps. When placed along wooded edges and abandoned blocks in commercial apple, traps can provide optimum timing for management of early maturing, highly attractive varieties such as Ginger Gold, using a threshold of 5 flies per trap.

P.J. Chapman and R. Dean found dramatic variability of AM emergence from season to season. There is considerable variability between farms with infestation levels differing between farms based on a number of variables. These include weather, soil moisture and site, with apple variety preference of early egg laying puncture of fruit coinciding with varietal maturity. Evaluations of apple maggot emergence from 1931 to 1969 in Hudson Valley Orchards showed that in 31% of the years monitored for emergence, AM emerged beyond the 20th of August. Yet there was little or no emergence of new flies after the 1st of September. This re-insured apple producers that applications beyond the 15th of August were not needed if effective reside was present up to the 1st of September. In 1969 the organophosphates such as Imidan and Guthion were the insecticides of choice.

AM emergence.R.W Dean and P.J. Chapman ‘Bionomics of the Apple maggot in Eastern N.Y.

AM emergence.R.W Dean and P.J. Chapman ‘Bionomics of the Apple maggot in Eastern N.Y.

AM seasonal ovipositional preference as per variety.

AM seasonal ovipositional preference as per variety.

One of the challenges we face today is the lack of residual efficacy of newer insecticides to actually kill the AM fly. This may not be as important as one might think. Generally, the neonicotinoids prevent the fly from laying eggs into the fruit, yet they produce lower levels of mortality of the fly, allowing adult AM to be present in the orchard late into the season. If there is significant rainfall there is often a reduction in residual activity that may lead to AM punctures with few or no eggs present in the sting or puncture of the apple.

The bottom line is that traditional IPM based use of the baited red sticky sphere, successful at monitoring the onset of AM emergence and treatment threshold, is not a good tool for use to signal reapplications once the spheres have been ‘reset’ (cleaned) and AM flies again reach the 5 fly per trap threshold. Instead, the use of neonicotinoids such as Calypso, Actara and to a lesser degree Assail, will need to be applied at a 10-14 day window despite high trap captures immediately after orchard treatments, and on into September. Assail is a very effective insecticide at managing the AM fly, with excellent efficacy against internal lepidopteran such as OFM late into the season.

Apple Maggot presentation. Harvey Reissig 2010

Apple Maggot presentation. Harvey Reissig 2010

To drive this point home, in page 9 of a presentation by Dr. H. Reissig in 2010, Harvey confirmed the ability of AM to ‘sting’ fruit yet produce very few eggs employing many old and new insecticides against the AM. In this comparative study, he demonstrated the efficacy of Assail and Guthion to be about equal in control of AM tunneling from larva. Additional studies by P. Jentsch reinforce these findings, shown in 2006 field efficacy studies conduced at the Hudson Valley Lab research orchard.

2006 AM Field Screening Tests; HVRL

2006 AM Field Screening Tests; HVRL