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Insect Injury at Harvest: 2016

Apple maggot trapping using baited red spheres.

Apple maggot trapping using baited red spheres.

The Hudson Valley has a diverse and abundant pest complex in most of the food crops grown here. The regions orchards, both large and small, have wooded edge along the orchard perimeter that harbor migratory pests, which impact crops from beginning to end of the season. Yet each season can be dramatically different in injury levels to untreated fruit, with abandoned apple being a good indicator of yearly infestation levels of insect and disease.

In our research plots in which we conduct yearly efficacy studies, we maintain untreated plots randomly placed throughout the block to determine the yearly insect pressure. During early fruit harvest evaluations of UNTREATED Ginger Gold apple last week we found relatively low levels of leafroller, tarnish plant bug, European apple sawfly, rosy apple aphid and plum curculio injury this season. Injury from the native and invasive stink bug complex is almost nonexistent.

However, we observed a considerable amount of damage from three insects driving fruit injury this season in Ginger Gold, caused by internal lepidopteran, apple maggot and San Jose scale.

Plum Curculio (Red) and Apple Maggot  (Green) Tunneling.

Plum Curculio (Red) and Apple Maggot (Green) Tunneling.

This season injury from San Jose scale exceeded 75% from both 1st and 2nd generation, with generations emerging mid-June and early August this season respectively.

Internal lepidopteran comprised of oriental fruit moth, lesser fruit worm and codling moth causing surface stings, fruit and seed feeding from petal fall to harvest amounting to 34% injury. Seed feeding associated with codling moth is present in above 10% of our fruit.

At this point we are also seeing 27% injury caused by Apple Maggot with punctures with or without tunneling.

For varieties yet to be harvested, insects requiring management include apple maggot, codling moth and obliquebanded leafroller in orchards where this insect may be problematic.

2016 Adult Apple Maggot Fly Emergence

2016 Adult Apple Maggot Fly Emergence

The Apple Maggot (AM), Rhagoletis pomonella (Walsh), resides as an adult in the soil, emerging in June if soil conditions allow. Drought conditions in clay soils can delay emergence until rains and ample soil moisture is available. The first flies to emerge are very attracted to yellow sticky cards which mimic a large leaf.

Red spheres are very attractive to mature adult female AM flies, ready to oviposit. From work done by Chapman and Link, the apple maggot will first infest early apple varieties such as Ginger Gold, moving to later maturing varieties as the season progresses. Summer and early fall maturing varieties are particularly vulnerable, with thin skinned sweet and sub-acid varieties being most susceptible. These fruit should be protected upon trap threshold as they will be infested this week if emergence builds throughout the region from these recent and heavy rains.

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.

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 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 (neonicotinoids) to actually kill the AM fly. This was not the case when OP, Carbamate and Pyrethroid classes were used during the development of IPM thresholds for apple maggot.

Generally, the neonicotinoids prevent the fly from laying eggs into the fruit and as such work to reduce AM damage. 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 site in the apple. Thus, there is no tunneling of the fruit by the fly larva.

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, may not be the best tool for use to signal reapplications when some members of the neonicotinoid class of insecticides are used for control. HOwever, this is not true for the pre-mix group that contain a neonicotinoid and pyrethroid with high toxicity to the fly.

Apple Maggot presentation. Harvey Reissig 2010

Apple Maggot presentation. Harvey Reissig 2010

Yet, when older classes are employed for AM management (pyrethroids, carbamates, and organophosphates), spheres be ‘reset’ (cleaned) after 10-14 days with management and applications again initiated as AM flies again reach the 5 fly per trap threshold.

Instead, the use of the neonicotinoid Assail will need to be applied at a 10-14 day window (excessive rainfall aside), despite high trap captures immediately after orchard treatments, 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.

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.

2006 AM Field Screening Tests; HVRL

2006 AM Field Screening Tests; HVRL

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 the Jentsch Lab reinforce these findings, shown in 2006 field efficacy studies conduced at the Hudson Valley Lab research orchard.

Materials listed below are listed as having the greatest efficacy for management of the apple maggot.

Many will also be effective at controlling the codling moth (CM) as it continues to emerge this week.

Links for each treatment option will provide additional labeling and material information through the NYS PMEP portal.

AM Insecticide Efficacy

Neonicotinoid / 4
Assail 30SG

Pyrethroids / 3
Asana XL
Danitol 2.4EC
Baythroid XL 1E
Baythroid 2EC
Lambda-Cy 1CS
Warrior 1CS
Proaxis 0.5CS

Organophosphate/ 1
Diazinon 50WP
Imidan 70WP, WSP

PreMix Neonic & Pyrethroid/ 4&3
Leverage 360
Endigo ZC