Things Peanut Growers Should Know About Three-Cornered Alfalfa Hoppers Steve L. Brown Extension Entomologist University of Georgia.

Things Peanut Growers Should Know About

Three-Cornered Alfalfa Hoppers

Steve L. BrownExtension Entomologist University of Georgia

First, THEY SUCK! They have piercing sucking mouthparts and feed on plant juices. Adults like the one shown have wings and are very mobile.

Nymphs look much like adults except they are spiny and do nothave functional wings. They feed in the same manner as adults.

They feed in a circular fashionaround stems…

and leaf petioles,and sometimes, pegs

They probe with their stylet and selectively feed from phloem tissue. Phloem is the tissue that transports sugars generated in the leaves.

Damaged phloem results in back up of sugars above the feeding site.Note the difference in stem diameter above and below the feedingsite, or girdle.

Under some conditions,the swollen stem mayeven split open.

Physiological changes sometimes cause the stem to turn purpleabove the feeding site(s).

Plants with multiple feedings sites can have severely restrictedsugar transport. Blooms, pegs and pods beyond a feeding sitemay be deprived of needed nutrients. Multiple feeding sites are often found on the same stem.

Plants react to damaged phloem in different ways and the reaction will worsen with time. Feeding sites will continue to swell and tissue will decay. The plant will try to bypassthe damaged area by developing aerial (adventitious) roots.

The damage on the right was probably caused by feeding thathappened weeks earlier.

Affects on yield are not well documented but extensive feedinglike this is likely to reduce yields.

There is some evidence that feeding sites close to the ground may lead to increased incidenceof white mold.

Scars in the stem above the feeding site are egg-laying (oviposition) sites. Eggs are laid in the plant tissue experiencingthe back up of sugars, apparently so young nymphs can easilyfind phloem tissue.

There is a varietal difference in the amount of feedingdamage and in the plant’s reaction to feeding damage.

In other words, the effect of 3CAH on yield depends upon the number of feeding sites and how the plant responds to that damage.

Variety 2003 # 2004 # 2005 # Avg. (Rank)

Hull 15.2a 2 19.2a 1 23.7a 1 19.4(1)

A Norden 17.0a 1 16.7ab 2 17.7a-c 3 17.1(2)

GaGreen 14.2a 3 14.0bc 3 19.2ab 2 15.8(3)

AndruII 7.7b-d 7 11.5b-d 5 15.2b-d 4 11.5(4)

C99R 11.0a-c 4 9.0c-e 8 12.2c-e 5 10.7(5)

DP1 9.7a-d 6 11.5b-d 4 10.2d-g 7 10.5(6)

Carver 11.0a-c 5 9.0c-e 9 11.2d-f 6 10.4(7)

GA01R 5.2cd 8 10.5cd 6 8.5e-g 9 8.1(8)

AP3 5.7cd 9 11.0cd 7 5.0g 8 7.2(9)

Avg. # Feeding Sites/3 ft. 2003-2005

Other Varieties

• GA02C – mid to good in 2 tests

• VA-98R – best among 14 in ’04

• Perry – slightly better than AP3 in 2 tests

• NCV11 – similar to AP3 in 1 test

• Gregory – mid to poor in 2 tests

• Tifrunner – middle of pack in ‘05

• 85A &81R – Similar to GG in 1test

“Low risk” varieties may not need any treatment at all in

most years. Higher risk varieties such as Georgia Green should be scouted and sprayed

as needed.

Scouting for 3CAH

• A sweep net is good for sampling adult populations, but not nymphs

• Flush counts can also be used – count adults flying away as you tap the foliage with a yard stick

• Nymphs can be dislodged from the foliage in the same manner as foliage feeding caterpillars

Insecticide timing is more important than selection, so scouting is critical

to controlling this insect!

Early generations are synchronized so nymph hatch out can be targeted. June and July hatch outsmust be controlled to prevent the heavy damageand high populations seen in August and September.

If you can’t scout, early July seems to be the key timefor control most years. But CAUTION, excessive spraying can lead to outbreaks of foliage feeders orspider mites.

Insecticides to Consider• Pyrtheroids such as Asana*, Karate and

Baythroid – mixed results, do not do well in high temperatures

• Orthene* – works well, but may flare mites under hot, dry conditions

• Sevin – works well, but may flare mites under hot, dry conditions

• Lannate* – works well but, little residual control

* 3CAH not listed on peanut label

A Case Where Spraying Didn’t HelpAvg. # Feeding Sites / 10 Plants

At Harvest – Randolph Co.

Total Within 3” of crown

Karate

1.3 oz X 2

27.0a 12.3a

Untreated 33.6a 14.3a

Komar,Duffie, Brown ‘03

A Case Where Spraying DID Help

Treatment Adults/10 sweeps

Girdles

/Plant

WM hits/

100’

Yield

UTC 9.7 a 6.3 a 5.0 a 5176 b

Karate

1.3oz.X2

3.8 a 2.0 b 2.7 b 5555 a

Komar, Duffie, BrownRandolph County

Proposed Treatment Thresholds

• Greater than 75 days to digging – 1 adult per 6 feet of row, or, any nymphs

• 25 –75 days to digging – 1 adult or nymph per 3 feet of row

• Less than 25 days to digging – do not spray