NEW HOLLAND, Pa. — When Extension entomologist Greg Krawczyk started experimenting with a certain kind of trap to catch stink bugs last year, he saw a ray of hope. A light at the end of the tunnel, literally.
A light trap placed in various orchards was catching hundreds of the little critters each night. These traps garnered a lot of press, and many saw it as a possible solution to finally dealing with the brown marmorated stink bug.
But as it turns out, Krawczyk’s hopes for a final solution slowly dimmed.
“We’re collecting a lot of stink bugs. But not all of them,” Krawczyk told a group of growers who gathered Monday at Yoder’s Restaurant for New Holland Vegetable Day.
Light traps are just the latest tool researchers have been looking into for controlling the brown marmorated stink bug, which feasts on everything from apples and peaches to corn and soybeans, and has become a major headache for the farming community.
“Even though the brown marmorated stink bug is found in every state, the problems are only caused in our region,” Krawczyk said.
The reason, he said, is that a lot of things grow here, giving the bug many options for feeding.
“For us, it really is a big problem,” he said.
Two classes of insecticides — pyrethroids and neonicotinoids — have proved effective at killing stink bugs on contact. They include products under the commercial names of Venom, Scorpion and Brigade.
But using these chemicals comes with a price.
“By constantly spraying, we are creating a problem with other insects,” he said, adding that some of these products may need emergency registration for 2013 or they can’t be used at all.
Insects such as scales, mites and the woolly apple aphid made a comeback last summer, even though they had been effectively controlled in the past by beneficial insects in integrated pest management systems.
Along with that, these sprays have little to no residual coverage, meaning growers have to constantly spray for stink bugs.
As a result, Krawczyk said, research has shifted to monitoring and trapping.
Light traps were something he got interested in this past growing season. He set up several of these light traps — essentially high beam lights on a pole with a trap underneath — in various commercial orchards to see their effectiveness.
The initial results were very good. The traps were catching 700 nymphs (young stink bugs) per week and between 10 and 90 adult stink bugs a night.
All told, between July and September of last year, Krawczyk said, nearly 5,000 stink bugs were caught using these light traps.
But whether the traps were catching a significant number of the bugs that were actually in each orchard was still unknown.
So, Krawczyk painted groups of stink bugs different colors, releasing them from various distances from the light trap on various nights before the lights were turned on.
About 900 stink bugs were released during the experiment, 180 a night.
The traps were still working effectively. But few of his bugs were being caught.
In fact, only 13 of the 900 that were set out were actually collected in the traps. Krawczyk said it tells him that even though the traps can catch stink bugs, they won’t catch all of them. In fact, the percentage being caught may be small, given the number of stink bugs in an orchard on a given night.
The traps are also ineffective when temperatures drop below 62 degrees, so their use is likely limited anyway.
“It shows me that the light traps are not an actual solution,” he said. “We think we are attracting stink bugs. But we are not actually controlling stink bugs.”
Monday’s vegetable meeting also featured several other speakers covering such topics as garlic production, pollination, blueberry establishment and fungicide resistance.
Steve Bogash, Penn State Extension regional horticulture educator, talked about fertigation in tomatoes.
He said the key to maximizing fertigation is to have a seasonlong plan, beginning with a preplant soil test to check for nutrients such as potassium, magnesium and calcium.
Testing the soil pH level is also crucial, he said, since tomatoes and peppers thrive in a soil pH of between 6.2 and 6.5. Even a small variation from that, he said, can limit nutrient uptake when fertilizer is applied.
Testing water pH, he said, is also critical.
“Adjusting irrigation water is the simplest method to lower pH. You should know exactly what the pH is in that drip line,” he said.
Once a plant goes into the ground, a grower should have a plan for applying fertilizer that can be adjusted throughout the season, Bogash said.
“Tomatoes go through several life stages that are crucial to consider,” he said.
Nitrogen is important, at first, to get a plant going. But the need for nitrogen decreases as the season progresses.
“At first flowering, you need that nitrogen level to come down,” he said.
By the second and third week of fruit set, phosphorus levels will crash, he said, so a high potassium, high phosphorus fertilizer is likely needed at this point.
Nitrogen levels that are too high, he said, can lead to fruit that is too soft and can even abort during blossom.
Plant tissue tests, he said, can be helpful during growing season — perhaps every two weeks — to check nutrient levels and see if any additional fertilization or adjustments are necessary.
“Put together a plan that is balanced,” he said. “I want you guys to all fertilize well.”