Utah Pests News Winter 2008-09

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Tree Fruit Monitoring Report for Summer 2008

Codling Moth

This season we saw a fairly typical pattern of moth flight, with two full generations and a partial third generation in most areas. The cool spring, however, lengthened the first generation flight period by 2 weeks compared to 2007. Another significant difference in flight pattern between 2008 and 2007 occurred during July to mid-August, when one codling moth generation occurred in 2008 and two in 2007.

  A=end of moth flight, 1st generation; B=end of moth flight, 2nd generation, C=end of moth flight (estimate), 3rd generation
We predicted that overall trap catch for 2008 would be greater than in 2007 because of the long hot summer. We felt that more moths were overwintering, and warned of a large first generation moth flight. Fortunately, the dips in temperature and intermittent moisture over the spring caused a herky-jerky first generation release, and probably reduced the population quite a bit. After the warm-up, however, many areas—both conventional and non-mating disrupted sites—saw a spike in moth numbers toward the middle of the first generation. If we combine moth trap catch for the entire summer, we found that there was a greater average number of moths per night for 2008 over 2007. In conventional sites, traps caught 2.5 moths/night in 2008, compared to 2.1 moths/night in 2007. In mating disrupted sites, traps caught 0.29 moths/night in 2008, compared to 0.12 moths/night in 2007.

Our prediction for 2009? Populations (i.e., moth catch per night) should go down. Many farms and homeowners saw a region-wide “off” year for alternate-bearing apple varieties. Growers fortunately maintained control methods on those trees, including mating disruption, preventing those few apples that formed from becoming infested. The lower fruit yield and fewer codling moth generations for 2008 should be good news for apple production in 2009.

Greater Peachtree Borer

This year, we placed three times more pheromone traps than last year in monitoring sites to get a better understanding of the moth flight pattern of this pest. We saw that start of trap catch depended on the site’s population size, where orchards with typically low populations did not see moths until July 8, and highly populated sites saw moths starting June 16. Peak moth flight occurred from late July through mid-August. Sites with heavy populations still had high numbers in mid-September. Flight ended in early October.

As far as numbers of moths, we caught a far greater number of moths across all sites in 2008 compared to 2007. Because there is only one generation, this phenomena is not easy to explain. Certainly 2007’s long season probably contributed to mating success and survivorship of larvae, especially those laid late in the season. Other contributing factors include changes in control methods of individual growers, changes in peach production acreage, and tree health.

Other Pests

In general, most other pests appeared as we typically expect. Because of the cooler summer, spider mite damage was low except in isolated areas. European red mite was nowhere to be seen, and leafrollers were easily controlled as a result of codling moth pesticides. Pear psylla incidence and damage was much lower than in 2007, and fire blight was not as severe as in 2007, although damage was sporadic throughout the apple and pear growing regions. Damage from white apple leafhopper was also minor.

Where established, woolly apple aphid populations continued to explode during the summer months, and should be monitored for further population increases over the years as growers continue to shift away from stronger codling moth control products, which in the past kept this pest at bay.

-Marion Murray, IPM Project Leader