Crop Protection In Unusual Weather

Onion Thrip

What is with the weather? After coming off an extremely mild winter in much of the country and in the midst of an unusually warm spring in some areas and cooler temperatures in others, growers will need to ramp up their scouting to stay on top of what is going on in their fields.

Insects are present earlier than usual in the Eastern U.S. as adults survived the mild winter. Weeds are already competing with crops, and in the area
of disease, it may be too early to tell, but one researcher predicts bacterial problems will — at the very least — be the same as in previous years.

“This type of weather scares me,” says Mike Orzolek, a professor of vegetable crops at Pennsylvania State University. “There will be similar or more disease problems this year because the winter was so mild that the inoculum survived and is out there. The warm temperatures in the Carolinas enhance the potential to bring the mildews and early blight and, if wet conditions occur, Phytophthora up the East Coast. The potential is there for more disease but will depend on the weather we get in the next two months.”

Weeds will also be an issue as weed seeds germinated in the soil about
a month ahead of time in the East. “In Pennsylvania, it is between May 15 and 20 when we see their first appearance,” explains Orzolek. Now, we are seeing them about one month early.

“Some growers are going to be caught off guard and will have to increase weed control costs,” he continues. “The weeds also will intercept fungicide and insecticide sprays. So basically, the weeds will be competing with the plants.”

Western Weather

The mild winter in California, which is typically the wet season in the Golden State, could present issues for growers in the coming months as well, adds
Joe Nunez, a vegetable/plant pathology advisor at the University of California Cooperative Extension. As a result of the atypical winter, the snow pack is down. Nunez says that could lead to a mild drought situation. The reduced snow pack also may mean a reduction in insect pressure, too.

“Insects usually build up in the foothills so they haven’t had as much of a chance to build up,” he says.

“The light rain has made for less grass and weeds in the foothills which is a major source of California insect pests,” Nunez continues. “As the hills dry in the late spring the insects (aphids, thrips, leafhoppers) move to the green fields in the valley.”

The warm, dry weather much of the area has been experiencing will also keep many diseases at bay. Unfortunately, though, he says dry conditions are conducive to the spread of powdery mildew, which may be an issue on tomatoes, depending on weather conditions.

On a positive note, Nunez says that diseases that rear their heads in wet years — late blight and downy mildew — will probably not be an issue for
California growers this season.

Too Many Insects In The East

Unlike the West Coast, growers in the East may need to ready themselves for battle against insects this season as many survived the winter. Orzolek predicts there will be an abundance of aphids, thrips, whiteflies, cucumber beetles, “and a bunch of other guys we don’t want to see.”

Stormy Sparks, a professor of entomology at the University of Georgia, says thrips arrived earlier than expected and in higher populations. In fact, he says a different species of thrips has been showing up in onion fields.
“In general, we do see a variety of species, but on onions we usually see tobacco thrips (Frankliniella fusca),” he explains. “This year, we are seeing a lot of onion thrips in our onion crops and we can’t really explain why this is happening. We are not sure if it is related to weather patterns.”

About six years ago, onion thrips were present in heavy populations in onion fields in the Southeast and the thought was that they were introduced from outside the U.S., explains Sparks. “This is pure speculation, but typically our populations are so low in onion thrips — we usually have less than 1% of thrips in some fields,” he says. “Now we are seeing 5% to 100% in some fields. The mild winter may well have resulted in more thrips and may have caused the shift in species in onions.”

The earlier and higher populations of thrips also are of concern as they might possibly result in more tomato spotted wilt virus in a variety of crops, he continues. “In the onion crop, the shift in species has resulted in a shift in the type of insecticide used, as the pyrethroids that provide good control of tobacco thrips provide little control of onion thrips.”

In the last month or so, Georgia growers also have seen low populations of spider mites on a variety of plants and have had reports of low populations of fall armyworm in corn. “It is very early in the year for both of these pests,” says Sparks. “If the trend continues this could be a bad year for insects in many of our crops. If we are lucky, it will just be an early year.”

Although a somewhat grim picture is being painted, Tom Kuhar, an associate professor in the department of entomology at Virginia Tech, says the abundance of insects should include higher numbers of beneficials that may come to the rescue.

“Warm winters do not always result in higher pest densities because the overwintering survival of natural enemy populations will also tend to be higher,” Kuhar explains. “In addition, the phenology of the insects with their respective host crops can be altered to the point that the pest populations suffer. Thus, it remains to be seen what pest outbreaks will occur in the 2012 season, but growers should certainly keep a watchful eye on the early spring crops that typically may not have much pest pressure.”
 
Grower Concerns

What are growers saying are their current pest concerns? How will the unusual weather this winter and spring impact their operations? A few from across the country provided feedback on their biggest pest worries and their plan of action.

Hundley Farms, Florida

Tom Perryman, farm manager of Top 100 Grower Hundley Farms, a producer of a variety of vegetables on about 11,000 acres, also is seeing fall armyworm and, like Sparks, is concerned about his sweet corn. In general, he says the pest is ramping up as the region is going through a drought.  

“We did have a little rain, but overall it has been very dry,” he explains. “Going into May, we could be looking at tremendous pressure.”
He also expects to see more silk flies targeting sweet corn. For this pest, however, he has a program in place, rotating products with different modes of action, such as malathion and lambda-cyhalothrin.

The drought-like conditions are also conducive to weed production, says Perryman, as the dry weather has caused herbicides not to react. In the end, he says “we will have everything under control, but I look for our [pest control] costs to go up.”

Perryman’s biggest issue, however, is when products he depends on — that work — are discontinued by the crop protection companies. This makes finding the best alternatives very difficult, he says.  

“I just wish the chemical companies would at least let us have some kind of say in discontinuing products,” he explains. “It is one thing if the chemical is regulated out; it is another if the product is going to be discontinued.”

Petrocco Farms, Colorado

The loss of crop protection tools also is an issue for Joe Petrocco, vice president of Top 100 Grower Petrocco Farms. The operation produces a variety of crops on 2,500 acres including leaf lettuce, spinach, cabbage, onions, spinach, beans, and more.

According to Petrocco, the loss of endosulfan, which had been used to control flea beetles on a variety of crops, has presented some difficulties. Imidacloprid was used in its place, but he says it doesn’t take too long for flea beetles to develop resistance. “The beetles hit the younger seedlings and sprouts, damaging plants, and that makes it difficult to raise those crops,” he says.  
Where the farm has met with more success is in controlling thrips, psyllids, and worms with the use of pyrethroids. “The thrips have become resistant to some of the pyrethroids so we have been using Lannate (DuPont Crop Protection) and spinosads to control the problems.”

The operation is no stranger to bacterial infections, either. A combination of rain and 80 to 85 degree days is a recipe for disease. Petrocco says applying copper preventively has been the best option. “We go heavy when plants are younger and back off as the plants get older so we don’t see that residue,” he adds.

Buurma Farms, Ohio

In the Northeast, Bruce Buurma of Buurma Farms, an operation producing numerous crops from sweet corn to carrots to cucurbits on about 1,500 acres, also says insects will be abundant this season.

An avid motorcycle rider, Buurma says in March he was seeing many insects on his windshield, making their debut way ahead of time. Thrips may be an issue in Georgia, but like Petrocco, Buurma expects a major assault from flea beetles.

“They really hammer our cruciferous crops,” he says. “Plus, they move from field to field which makes them hard to target with sprays. To lower the number of flea beetles, we needed the temperature to stay below 32° F for 90 days, and we didn’t have anything like that this winter.”
As a result of high populations of flea beetles vectoring Stewart’s wilt, the disease will be a problem in nonresistant sweet corn varieties. According to Buurma, the farm will monitor its sweet corn and spray pyrethroids on the nonresistant varieties to gain control of the pest and reduce the incidence of disease.   

Agreeing with Orzolek, he says weed control will be in full force. Most of the weeds that normally would have been winter killed survived.

“Barley, which is used as a cover crop, wasn’t winter killed this year for the first time in a long time and we had to go in and kill it,” he explains. “This winter it simply didn’t get cold enough to kill it.”

River Point Farms, Oregon

In the Northwest, Delbert Gehrke, vice president of Top 100 Grower River Point Farms, an operation producing 6,000 acres of onions, predicts that fungus issues will be rearing their collective heads as temperatures in the area have been cooler than usual. A cool late spring or early summer with humid conditions is conducive for the growth of fungus.

“We are assuming, at the moment, that we will need to be ahead of our fungicide sprays, especially on the coppers and preventative measures,” he says.

One fungus the farm battles on an annual basis is Rhizoctonia. Gehrke says the farm experimented with different fumigants to help control the disease but says “the more we experiment, the less we know.” Nothing has been a “cure all” for Rhizoctonia, he adds.

“We have been conducting trials with different products but our problem is that we can’t get consistency from year to year,” Gehrke continues. “That causes us to ask: Was it Rhizoctonia or was it something else? We may be treating other problems because the next year we do the same thing and don’t get the same results. It has been a real problem. We have gone back to the drawing board on our treatment trials and will be reevaluating our cause-and-effect assumptions in an attempt to generate repeatability.”

Click to page two for information on scouting in unusual weather

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