Fruit and Vegetable Pest Monitoring in Summer 2014
For the last 3 years in Utah County, codling moths have had just 2 full generations. Over this time period, the moth population has been increasing in non-mating disrupted sites.
In Utah, apple maggot flight peaks before apples mature. Research has shown that maggots feeding in non-mature apples are killed by the pressure of the expanding apple, which may explain why we have not yet found them there.
Obliquebanded leafroller has always been the dominant leafroller species, and numbers have declined since 2012.
The tobacco flea beetle was found in very high numbers on potato plants in northern Utah. It is a reddish, yellow brown, with a brown patch across the width of the wing covers.
Many tomato plants in the vegetable monitoring sites showed symptoms of curly top virus, including the classic symptom of curled, yellow leaves with purple veins.
Every summer, the Utah IPM Program monitors for pests in fruits and vegetables in northern Utah and uses that information for research and to produce pest activity reports. In 2014, we hung over 80 pheromone traps for 12 fruit pests in 9 sites, and conducted vegetable pest monitoring in 8 community and commercial vegetable sites.
Codling moth is the primary pest of apples in Utah, so it is important to provide timely information to growers. Despite the warmer early spring temperatures, biofix (first flight) was about average across all sites, occurring from late April to early May in northern Utah. We saw a fairly typical pattern of moth flight, with two full generations and a partial third generation in most areas.
The last very hot season in this region was in 2007. Several years of cooler springs and summers since then have not helped in reducing codling moth populations. In fact, in Utah County orchards that are not using mating disruption, our trap catch numbers have increased over the last 3 years (see graph). In 2012, the average number of moths per night for these monitored sites was 1.5, in 2013 it was 1.7, and in 2014, it was 4.0. This change may be due to a change in predator populations, milder winters, or individual farm practices.
During the 2013 season, we heard several reports of apple maggots infesting apples and plums. We were able to confirm maggots in plums, and although we found suspicious symptoms in apples, we were not able to find any apples with maggots inside them. During 2014, we hung 12 traps in 3 sites in the Cottonwood Heights area near Salt Lake City. All of these sites grew apples, and we inspected apples throughout the growing season for possible infestation. Although trap catches were very high (see graph) and we found maggots in plums, we again did not find any maggots in apples.
The IPM Program normally monitors for several leafroller species, but through a USDA Specialty Crop Block Grant, USU researchers have been looking at a greater number of species in more sites. We will report on that project in detail in a future issue of Utah Pests News, but for the most part, we have observed that the obliquebanded leafroller is the most commonly trapped species in Utah fruit orchards. In the past, this pest had always been trapped in high numbers, but the larvae that cause the damage were almost non-existent, controlled by Guthion, a commonly used insecticide for codling moth and other pests. When Guthion was cancelled, leafrollers were not controlled by the alternate products and in 2011 and 2012, the larvae started causing problems, primarily for tart cherry growers. Now that growers are aware of the problem and have targeted the leafroller larvae, the adult moth and larval population of this species have declined significantly (see graph on previous page). In 2014, we did not see any economic injury from leafrollers.
Other Fruit Pests
Thankfully, growers dodged the fire blight bullet this spring due to the drier conditions and moderate temperatures during bloom. Those conditions also seemed to dampen the effects of coryneum blight. Woolly apple aphid, which was becoming an issue in 2011-13, seems to be more under control, mostly due to growers’ diligence. Other pests were present in typical numbers, including aphids, spider mites, powdery mildew, and peachtree borer. Boxelder bugs on ripening peaches have become an increasing nuisance over the last 5 years, with very high numbers this year. And finally, we had no reports of brown rot on peaches, unlike in 2013.
In 2014, we monitored for vegetable pests more intensely than in past years, thanks to the addition of Bonnie Bunn, the new Vegetable IPM Associate. The monitoring sites were located in Box Elder, Cache, Salt Lake, and Utah counties, and consisted of backyard and community gardens, including 3 locations within the Wasatch Community Gardens program.
Flea beetles and squash bugs and the injury they cause were found in high numbers throughout the season in almost every site we monitored. Three species of flea beetles were identified: the pale striped flea beetle, tobacco flea beetle, and the western flea beetle. These insects cause “shot hole” damage from feeding adults, and are particularly harmful to young plants and seedlings. Squash bug feeding can cause plants to suddenly wilt, mimicking a disease problem. We predict that squash bug and flea beetle populations will continue to be high in 2015. They overwinter as adults, so it will be important to watch for them next spring.
We also saw a widespread problem of stunted tomato plants with yellow, curled leaves. Many of these affected plants also had the classic symptoms of curly top disease: purple venation on the leaves and premature fruit ripening. However, despite testing more than 20 symptomatic plants, none were positive for curly top disease. The cause of the symptoms remains a mystery that we will investigate further next season.
- Marion Murray, IPM Project Leader and Bonnie Bunn, Vegetable IPM Associate