Managing Late Season Black Aphids

Pecans (5)Pecans are still the nut sizing period and will likely be through mid-August. Aphids have been strong with dry weather, and sprays have also led to increase in mite populations. Our late season aphid generations have a lower threshold we need to watch for. Here is an update from UGA Extension Pecan Specialist Dr. Lenny Wells:

“Black aphids can be one of the most difficult pecan pests to manage because they often slip in, do their damage, and are gone before you know they are there. For this reason, they require pretty intensive scouting on susceptible varieties like Schley, Sumner, Oconee, and Gloria Grande. Anyone growing these varieties probably needs to check for black aphids at least twice a week from July through August. PecanAphid2There is normally a flight of black aphids that comes through sometime in early June. These are usually winged adults that come through to feed, damage a few leaves and condition the foliage for the later generations (black aphids reproduce more and develop more rapidly on damaged foliage).

The late season generations, seen now, can develop into a problem quickly. These cause the characteristic yellow spotting, developing necrosis, and eventual loss of leaves. Tolerance for black aphids at this time of year should be very low because August is a critical month for both the current season’s crop and the crop potential for next year. Thus, trees should be kept as stress free as possible at this time. For this reason, it is recommended that pecan trees are sprayed when only 15% of the terminals sampled have more than one black aphid adult with nymphs present on a compound leaf.”

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Chinch Bugs In St. Augustine

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In between checking fields, I look at many lawn related issues in Thomasville. Shortly after our drought spell, we were seeing cetipedegrass die out in some areas. This was the result of heat and drought. Soon after this, I was asked to look at some St. Augustinegrass that appeared to have the same problem. Lawn symptoms looked similar to drought stress, but we looked down in the thatch and confirmed chinch bugs. They are very small and hard to catch. You have to look toward the boarders of the infected area, and then look down in the thatch.

Chinch Bug

Chinch Bug

Chinch bugs are in the Hemiptera or “true bug” insect order which means they have piercing/sucking mouthparts. They cause damage by feeding on the lower blades of the grass. They affect St. Augustine primarily but can also infect all other warm season grasses. Their damage is first noticed during hot, dry periods in sunny areas of the lawn. This is why they thought this was likely result of drought. In the case of chinch bugs, dry spells are an indirect cause.

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Armyworms In Hayfields

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Armyworms026Fall armyworms are in our hayfields now. This is a Bermuda hayfield that is down to the stems. You can see the damage has caused the pasture to look dry with a silver tint. The foliage feeding caterpillars are also feeding on other grasses like this vasseygrass. Just last week, this field was getting close to being cut. The caterpillars move very fast and can do the damage in just a few days. Here is a link to the 2014 UGA Pest Control Handbook Pasture Section.

 

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Leaf Spots Found In Cotton

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We’ve been seeing some spots on lower cotton leaves that resemble target spot. The spots I am seeing are very sporadic. A few times I have seen spots on only one lower leaf. Many growers have sprayed fungicides early bloom to protect from target spot already. The spots we are seeing right now appear to be Ascochyta (wet weather) blight. Ascochyta blight was seen also last year with abundant rainfall. UGA Extension Pathologist Dr. Bob Kemerait says this about Ashchochyta blight:

“It is a disease of sporadic importance in GA, especially during periods of cool weather with abundant rainfall early in the season. Hence, young plants are most often affected. The spots in the field can be tentatively diagnosed by presence of tan lesions bordered by a dark ring; embedded in the lesion are dark fungal structures that appear like pepper grains (below). Though use of fungicides for effective management has been reported, such is generally considered unnecessary in GA. This disease tends to become of little significance as conditions become drier.”

AshchochytaBlight

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Aphids Down, Plant Bugs Still Around

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Cotton is looking good in the county. This morning I looked at fields anywhere form 3 weeks to 6 week bloom. Older

Aphid Fungus

Aphid Fungus

cotton is producing heavy boll load. Aside from applying PGR’s, we’re still looking for insects. Many fields have been sprayed for stink bugs. Brown and Southern Green stinkbugs are present. Most checks are showing 10% – 20% boll damage. The aphid fungus has set in, and aphids are pretty much gone. Many cast skins are seen under the leaves, and some of them have a green to brown wooly fungal mass. This is not the fungus that killed the aphid, but is a secondary fungus that grows on the dead ones (above).

Something we are still aware of is immature tarnished plant bugs in some fields which is rarely observed. We’ve sprayed more for them this year also. Below is an update from UGA Extension Cotton Entomologist, Dr. Phillip Roberts:

“Our primary method for scouting plant bugs is square retention.  Our goal is to retain 80 percent of all first positions as we enter bloom.  The square retention technique works well in pre-bloom cotton but is not as a reliable technique in blooming cotton as physiological shed confounds counts.

Effective use of the sweep net becomes difficult after bloom due in part to plant size and more emphasis should be placed on use of a drop cloth.  Also be observant for both adult and immature plant bugs when making visual plant inspections; examine terminals and inside the bracts of squares, blooms, and small bolls.  Also be observant for “dirty blooms”, blooms in which many of the anthers are dried and brown.  Dirty blooms are an indication that plant bug (especially nymphs) are feeding on larger squares which the plant did not shed.”

Clouded Plant Bug Nymph - Photo by Andrew Taylor

Clouded Plant Bug Nymph – Photo by Andrew Taylor

We have also seen clouded plant bugs in addition to tarnished plant bugs. Clouded plant bugs will feed on squares similar to tarnished plant bugs but will also more readily feed on small bolls. To the left is an immature clouded plant bug taken by scout, Andrew Taylor. The antennae of immature clouded plant bug nymphs are horizontally striped with red and white.  A dark-colored spot on the dorsal surface of the abdomen is visible in larger nymphs.

“We do not have recommended thresholds for use of drop cloths, visual inspections, or sweep nets in Georgia.  However, entomologist in the Mid-South have developed solid workable thresholds when using these sampling techniques which should be applicable to Georgia cotton:

Mid-South Plant Bug Thresholds: Tarnished plant bug thresholds can be used for clouded plant bugs, but clouded plant bugs should be counted 1.5 times when using a sweep net. Note that the threshold is higher during the third week squaring and bloom compared with the first two weeks of squaring.

Third week of squaring through bloom: Drop Cloth: 3 plant bugs/6 row feet, Visual: 10 plant bugs/100 plants, Sweep Net: 15 plant bugs/100 sweeps

First 2 weeks of squaring: Drop Cloth: 1 plant bug/6 row feet, Visual: 5 plant bugs/100 terminals, Sweep Net: 8 plant bugs/100 sweeps.”

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Pyricularia Leaf Spot

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We were looking at some pearl millet on a plantation that has some leaf spots. Its planted next to soybeans which they thought may have been some spray drift. The browntop millet on the left is not affected. It’s actually a leaf spot disease. I once saw this in rice on a plantation a few miles away. The lesions on the leaves are elliptical or diamond shaped. Pyricularia leaf spot is also called rice blast on rice and is the same as grey leaf spot in turfgrasses. This is actually just grown for cover crop. The armyworms are causing more damage in other areas on the plantation than the leaf spot will do in this situation. Here is a link to Fungal Diseases of Pearl Millet.

PyriculariaLeafSpot004

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Pecan Leaves Dropping

We’ve had lots of leaves dropping off pecan trees. This is brought in many residential calls associated with this also. Its an environmental effect of rain following a period of dry weather. We started out this season much like last season in terms of rain, and it shut off around June and through the Fourth of July. Recent rains have saturated the soils essentially drowning some of the pecan roots. In residential situations, leaves dropping is also a result of scab disease pressure. There is nothing that can be done about either.

 

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