Entomology Notes

For insect management, it is all about scouting and getting the pest identified correctly.
As you prepare for 2018, use these entomology notes made by UGA Extension entomologist, Mark Abney, and your own field notes to plan next year’s crop management strategy.

Garden Fleahopper
It has been a while since anyone asked me about garden fleahopper in peanut. After a couple years with more fleahoppers than “normal,” populations in Georgia peanut fields in 2016 were low or nonexistent. This season, we saw increased numbers of adult and nymph garden fleahopper in our research plots around Tifton, so I figured now would be a good time to remind folks about the insect and the injury it causes.

Garden fleahoppers (GFH) are small insects that feed by sucking juices from plant leaves. The feeding results in stippling on the leaves that looks a lot like spider mite injury. The undersides of leaves that have been fed on by GFH will have tiny black “tar spots.” We want to be sure not to confuse spider mite injury, which can be a much more serious problem, with fleahopper injury.

Adult GFH come in three forms: short winged females, long winged females and long winged males. There is no published economic threshold for this insect in peanut, and populations have rarely been high enough to cause much concern. That said, we do not want to ignore GFHs. Some fields were treated in 2015 when defoliation was associated with very heavy infestations. In the past, pyrethroid efficacy against GFH in peanut has been only mediocre. Bryce Sutherland, a graduate student in the UGA Peanut Entomology program, is currently evaluating the activity of several insecticides on GFH in peanut.

Scouting For Caterpillars
Overlooking a field with an increasing infestation of Velvetbean caterpillar, which should be relatively easy to manage, can lead to rapid defoliation. For growers who may not have a professional crop consultant or scout, you need to check your fields for this and other insect pests so that decisions can be made on current pest activity.

We scouted a field this season that was at threshold with a mixed population of velvetbean caterpillar (70 percent) and soybean looper (30 percent). Most of the larvae were small, and there were a lot of VBC moths, which told me that feeding damage was likely to ramp up quickly in that field over the next 10 to 20 days if no treatment was applied. Not far away, we checked a different field that had virtually no caterpillar pressure or moth activity.

Folks who are not scouting on a regular basis should remember to check multiple locations (10 stops is a good number) within a field before making a management decision. Many times I have been called to look at a field that was “at threshold” for caterpillars only to find a hot spot in one area of the field and low numbers everywhere else.

Our caterpillar thresholds are calculated in number of larvae per row foot. If you check three feet of row, the number of larvae counted should be divided by three. A standard beat sheet is three feet long; 12 caterpillars on the beat sheet is only 4 caterpillars per row foot and is not threshold for healthy, actively growing vines that have lapped the row middles.

UGA county Extension agents can help with choosing the most cost effective and efficacious insecticides when caterpillar populations reach economic thresholds. Preserve profit potential by monitoring pests and making timely management decisions.

Hopper Burn
I received some hopper burn pictures on peanuts this season. The insect responsible for this damage is the potato leaf hopper (PLH). It is a tiny, bright yellow-green insect that feeds on the mid-vein of the leaf causing the characteristic “v” shaped yellowing at the tips of leaflets. Hopper burn is not caused by three cornered alfalfa hopper.

Potato leaf hopper is present in Georgia every year, but large populations and damage are usually sporadic. Because the insect is small, which is hard to see from the tractor or truck, and many of our acres are not routinely scouted, leaf hopper infestations are often overlooked until the field begins to yellow from hopper burn.

The decision to treat a PLH infestation should consider the extent of the hopper burn and the number of adult and immature leaf hoppers present. Because hopper burn will persist even after the insects are gone, you need to confirm that the pest is still present before applying an insecticide to a damaged field. If nymphs are present – nymphs do not have wings and cannot fly – we know that the insects are reproducing and are likely to be around for a while. Leaf hopper infestations often start near field borders, so scouts should not neglect these areas.

We tested the efficacy of several insecticides against PLH a couple years ago and found that they were easy to kill. The only problem is that most of the products we tested were broad-spectrum insecticides (pyrethroid, organophosphates and carbamate) that can increase the risk of secondary pest outbreaks.

If you have questions about potato leaf hopper or other pest management issues in peanut, contact your county Extension agent.