Lack of Good Sanitation Leads to High Navel Orangeworm Numbers
By Jessica Theisman, Associate Editor
It could be another heavy year for Navel Orangeworm (NOW). David Haviland, UC Cooperative Extension farm advisor for Kern County and entomologist told California Ag Today that sanitation in almond orchards over the winter was not as good as it could have been.
“Everything right now is about trying to prevent a repeat from last year, and it is a little tricky so we know that sanitation wasn’t as good this winter as it generally should be,” he said. “The best time to shake NOW mummy nuts from an almond tree is after a rain when the nuts are heavier.”
However, rains came late this season, and by the time the rains left, there was only a few weeks before spring.
“This left a very short window to get any shaking done, and some people did an excellent job during that window to sanitize and other people just couldn’t get around all their acreage,” Haviland said. “On average across the whole industry, sanitation was not up to where it should have been, and it gave growers a difficult start to the season.”
NOW could be early this year, but the crop is on time.
“With all of this prolonged hot temperatures, particularly high night-time temperatures, the trees are shutting down a little bit at night compared to what they would do if the nighttime temperatures were cooler,” Haviland explained.
As a result, harvest is not coming as quickly as people would like.
“The problem is that the longer the nuts are in the orchard, the greater chance there will be NOW damage,” he said.
Orchard Sanitation to Push Back on NOW Underscored
By Mike Stevens, Associate Editor
We are completing our coverage of the importance of orchard sanitation to push back on Navel Orangeworm (NOW) pressure for 2018.
We recently spoke with David Haviland, UC Cooperative Extension entomologist and farm advisor for Kern County. He spoke about how sanitation is the most important practice that needs to be implemented.
“Yes, 2017 was a really interesting year on NOW. It was a bad year overall. Several things led up to that. The first one was sanitation was an issue,” Haviland explained. “There is not much of an excuse in the southern half of the almond industry, but with all the rain up north and the flooded orchards, yes, it was very difficult to get in and do sanitation, and we know that that is the absolute backbone of navel orange worm programs.”
Pistachios were also a concern when it comes to NOW.
NOW was right on schedule in pistachios. The pistachio crop was a little behind and so it was common to do a normal monitoring, normal spray program, and set up for a normal harvest. But then the crops sat out there for another 10 days or two weeks, which, of course, makes it very vulnerable to NOW worm damage.
“The longer you get away from your insecticide sprays, the more damage that’s going to occur, and a lot of the crop was harvested after the fourth flight occurred,” Haviland said. “When you put in the concerns with sanitation this year, and with the increased degree day accumulation, there were plenty of moths and then the crop got delayed. The overall effect was that this was a worse than normal year.”
At the same time, the industry is full of examples of growers that had very acceptable damage.
“Growers that did follow in greater pest management practices … did get their sanitation done. They documented that those things are really important, they are very effective, and the growers that weren’t able to get that sanitation done hopefully got a case study, personal experience in the value of sanitation,” Haviland said.
Every grower needs to do their part by incorporating sanitation, noted Haviland. “Obviously, if you’re the only one sanitizing amidst a bunch of growers that aren’t, that’s a concern,” he said.
Gill’s Mealybug May Appear in Orchards Over the Next Few Weeks
By Patrick Cavanaugh, Editor
As Gill’s Mealybug overwinters, a new generation will appear in May, and growers should treat the first generation around June 1.
Gill’s mealybug is a relatively new pest of pistachios in California. “It was first recognized in the late 1990s in a an orchard near Tulare. It has now spread up to Colusa County and has move down to Kern County,” said David Haviland, UC Cooperative Extension Kern County, who organized the field day with Elizabeth Fichtner, UC Cooperative Extension Tulare County.
Tulare County is a hot spot with most pistachio orchards having the bug, which has three generations per year. “Right about harvest time there are a whole bunch of mealybug crawlers hatching, and then they overwinter and become adults in May. These adults will produce an enormous amount of new crawlers the first week of June, which is an important treatment time, right when those crawlers come out,” said Haviland. “The ones that are born the first week of June will become adults in about mid-to-late July, which is the second generation. The mealybugs that are in the tree now are the start of the third generation when they become adults then hatch more young bugs at harvest.”
“Population-wise, growers will get millions of crawlers at harvest, but if you come back to the tree in the spring, you will see maybe one or two per pistachio cluster, so there is a huge winter mortality,” said Haviland.
Haviland stood by a tree that had only about one mealybug per 10 clusters in the May, but now the untreated trees in the trial have clusters that are covered with honeydew, and now blackened with sooty mold, with 30 or 40 adults on the clusters. The lower leaves on the trees were turning black from the sooty mold.
“Typically growers go out in their orchards April and May and see about one mealybug for every 10 clusters. In fact they might not even notice it. But that mealy bug produces about 20 live young, which increases the count to about one per cluster, but now those adults give rise to 15 or 20 crawlers per cluster which causes clusters to be moist and black,” said Haviland. “So the point is that one or two per cluster can cause many more per cluster near harvest time, so May is the time to be thinking about spraying the first of June.”
Haviland looked back at the tree he was standing next to, and said: “If you have tree that looks like this, with a lot of mealybugs and sooty mold, let it go; you can’t do anything about it. Come back the first week of June 2014 and treat it with an insecticide and you should be clean at harvest next year. It’s really that simple.
Insecticide timing is important, but there is a widow. Of all the products registered, they are most effective on crawlers. “So you really want to get them the first week of June when the crawlers are out regardless of which product your using,” Haviland said.
During the upcoming harvest season, Haviland warn growers to ask the harvest crew to wash down the harvesting equipment and make sure no tree debris from another orchard is on the equipment. “And if growers have an orchard with mealybug, please inform the harvest crews so that they clean the equipment before moving to another site, which may not have mealybug.
“The harvest crew should blow off all leaf trash and hose the equipment down before it goes from property to property. Growers should insist upon this,” Haviland said.