Editor's note: This is the fourth in a series on getting back to the basics in cotton production. Subsequent articles will deal with in-season insect control and other production practices.
The fleahopper is the cat burglar of the cotton patch, making off with the good silver before you know he's in the house.
“We call them square thieves,” says Jim Leser, Extension entomologist with the Texas Research and Extension Center in Lubbock. “It's a small insect that attacks small squares, pinhead size.”
Leser says it's hard enough to detect a square that small, and identifying a tiny insect in it offers an even tougher challenge.
“Pinhead squares are hard to see,” he says. “They are barely visible and a field may be into the second week of squaring before the grower knows it. Potentially, three squares are vulnerable to fleahoppers before anyone knows the pests are around. If we get infestations early, fleahoppers can steal a lot of cotton before we know we've been robbed.”
Leser says the pests are constantly around in west Texas. “We always find a few fields with damaging populations and one year we estimated a 23 percent loss of yield potential to fleahoppers.”
He says the fleahopper used to be a more important pest than it has been for the past few seasons. “At one time, it superceded the boll weevil as the number one cotton pest in west Texas. As the boll weevil moved into the High Plains, however, overwinter applications to control emerging weevils also kept fleahopper numbers down.
“Some chemicals will take both pests out, but some do not. We often adjust rates to get the weevils.”
Leser says the Boll Weevil Eradication Program may elevate fleahoppers to a higher status as growers make fewer insecticide applications to take out overwintered weevils.
The problem goes beyond early damage, however. “In our worst fleahopper years, we treat early to control them, (eliminate a lot of beneficial insects) and then set the crop up for later insect pest problems.”
The key to control, Leser says, is identifying infestations early enough to prevent damage. “We have to know where to look,” he says.
Since fleahoppers feed only on small squares, Leser says growers should concentrate on pinhead squares, which are located just below leaves that have not unfolded.
“Our fleahopper scouting and identification system is the poorest one we have,” Leser says. He says the pests are extremely skittish and will “pop off the plant if disturbed. We have to walk stealthily through the field and keep from casting a shadow on the plant we intend to check.”
He also places one hand palm up at the bottom of the cotton stalk, with two fingers on each side of the stem, to catch nymphs that move down to escape into the soil.
“It's hard to train scouts to find and identify fleahoppers,” Leser says.
Detecting injury also poses problems. The pests suck juices out of the small squares and damage does not show up for hours.
Scouts must identify the pest, Leser says. “Misidentification can cause trouble.”
He says new scouting techniques may help. “A beat bucket may prove the best option,” he says. “We push the top of the plant into the bucket and shake it to get the pests off. It's a simple method that may replace visual inspection.”
He says ground cloth and sweep nets do not work as well. “We have to sample as quickly as possible to cover the acreage, but we also need a consistent reading of insect populations. We can cover more ground with a beat bucket.”
He says the fleahopper's preference for small squares provides a key for control. “Once cotton starts blooming, we rarely need to protect the crop from fleahoppers.”
He recommends monitoring the plant to determine if it's losing too many squares. “We look at the first position squares only to save time. During the first week of squaring, if we're retaining less than 90 percent of squares we want to find out why. In the second week of squaring, we want to hold 80 percent (cumulative) of squares, and we want to keep at least 75 percent (also cumulative) in the third week of squaring.”
Leser says he'd prefer square retention to be higher but conserving beneficial insects also plays an important role in season-long pest management.
“We may reduce insecticide rates to achieve adequate control and still allow beneficials to help control later pests.”
Leser says growers also may economize by banding insecticides to control fleahoppers. “But timing is important and nine times out of 10, fields will not all have fleahopper problems at the same time. Unfortunately, few growers know soon enough that they have trouble. They either need to learn to scout for these pests effectively or hire a consultant to do it.”
He says cotton farmers make two basic errors in fleahopper control: “They may over-react to fleahopper populations. Or they might not see heavy infestations coming and get taken by surprise. This is one of the hardest pests to manage in cotton, especially since a square can be damaged before it can be detected.”
At square set, treatment threshold for fleahoppers is 25 to 30 per 100 plants. “That's a range, and the lower end is a better trigger point,” Leser says.
Leser says farmers also should watch for weed hosts, including white weed, Lancelot sage and evening primrose. “If these weeds dry out when cotton begins squaring, fleahoppers may move into the cotton crop.”
Plant bugs (lygus) also pose problems for cotton farmers and are not as picky about square size as are fleahoppers.
“We rarely have enough lygus to treat,” Leser says, “and their populations are usually bundled with fleahoppers. They prefer small squares but can damage blooms and small bolls.”
Scouting for lygus is different. “We use a drop cloth to check a three-foot length of row instead of the visual inspection we employ for fleahoppers.”
Leser says lygus is bigger than fleahoppers and may cause more damage to the cotton, so thresholds vary as cotton begins fruiting. Leser says three fleahoppers equal one lygus. “After three weeks of squaring, we recommend treating if scouts detect two lygus per plant. That trigger remains as long as the crop is vulnerable. “We have no fleahopper threshold after the crop blooms.”
He says lygus infestations often involve only a few fields, usually near a preferred crop, such as peanuts, alfalfa or potatoes.
“In 1999, we had trouble with both fleahoppers and lygus.”
Leser says lygus control requires a higher rate of insecticide than is necessary for fleahoppers.
Recommended insecticides for fleahoppers include Bidrin, Orthene, a dimethoate material, or Vydate (which also controls weevils).
For Lygus, recommendations include Orthene “or one of the third generation pyrethroids. The pyrethroid is a good option because it provides immediate control and residual activity. The downside is impact on beneficials that may flare aphid infestations.
“Early, we can usually handle lygus with Orthene. Bidrin also has looked good in tests.”
Leser says good insecticides are available for both fleahoppers and lygus. “But we're cognizant of the resistance issue so we don't want farmers to over-react to infestations.”
Close observation of the crop and following other production recommendations also helps, he says.
“One important factor is following Roundup recommendations precisely. If mismanaged, Roundup injury can mimic insect damage. And some insect damage may be blamed on Roundup applied too late. Growers have to protect those early squares, Leser says.
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