Monthly Archives: July 2014

July 31, 2014 · 3:28 PM

Managing Late Season Black Aphids

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. There 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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Filed under Entomology, Pecans

July 30, 2014 · 8:21 PM

Chinch Bugs In St. Augustine

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 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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Filed under Entomology, Turf

July 29, 2014 · 4:38 PM

Armyworms In Hayfields

Fall 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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Filed under Entomology, Forages, Pasture

July 25, 2014 · 8:17 PM

Aphids Down, Plant Bugs Still Around

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

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

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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Filed under Cotton, Entomology

July 25, 2014 · 4:51 PM

Pyricularia Leaf Spot

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.

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Filed under Disease, Forages

July 23, 2014 · 7:45 PM

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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Filed under Pecans

July 22, 2014 · 8:00 PM

Nematodes In Centipede

Last week, we checked into some centipedegrass sod that was showing some odd symptoms. The patches of dying grass were shaped irregular and could see obvious wilting signs on the boarder. We checked for disease under the microscope and did find some however, with these symptoms, we decided to check nematodes. Here is the report below:

UGA Extension Pathologist, Dr. Alfredo Martinez, said centipedegrass can easily be colonized by nematodes compared to other species. The report showed both Ring and Sting nematodes being above thresholds. UGA Extension Turf Agronomist Dr. Clint Waltz says at this stage it would be best to increase irrigation and fertility. When ready, harvest this grass then consider a nematode treatment prior to reestablishment.

Also, the soil test showed pH to be 4.9. Centipedegrass can take a lower pH than bermudagrass, but below 5.5 is pushing it. Research shows a pH of closer to 6.0 is better for centipede establishment. The liming will raise the pH and take effect next year. This will help increase overall fertility. Dr. Martinez also suggested using an all purpose systemic fungicides (fungicides containing thiophanate methyl, propiconazole or an strobilurin). This might help to control any facultative pathogen/saprophyte that might be lingering.

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Filed under Disease, Turf

July 21, 2014 · 12:19 PM

Peanut Disease Update

Over the weekend, Thomasville and most of Thomas County had more than half an inch of rain. We were checking peanuts last week, looking at 06G’s. We were seeing a little bit of tomato spotted wilt virus (above). The picture above shows the some of the classic, chlorotic ring characteristics of TSWV. It is not bad in the field, but we can expect to see some on even resistant varieties. No variety is immune.

The initial appearance of soilborne diseases such as white mold (below) is related to soil temperature, the growth of crop and rainfall/irrigation. White mold was seen less than TSWV in this field. Most peanuts have hit the 60 day mark where we generally begin spraying for soilborne diseases. Below is an update form UGA Extension Pathologist, Dr. Bob Kemerait:

Very warm weather and scattered thunder storms will increase risk of several important diseaes.

1. White mold: warm soils, increased growth of peanut crop, and rainfall have created ideal conditions for development and spread of this disease and fungicide programs should be implemented accordingly.

2. My graduate student Abraham Fulmer is finding development of early and late leaf spot in his unsprayed peanut plots. A further indication that it is time to spray.

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Filed under Disease, Peanuts

July 17, 2014 · 8:04 PM

Peanut Insects On The Rise

Dryland and irrigated peanuts are looking good throughout the county where we have received as much as 4 inches of rain on the east side over the past week and a half. This morning, we were checking for insects and disease. We started off looking at caterpillars. Our caterpillar threshold is 4 – 8 per row foot. We use the lower numbers for peanuts that may already be stressed. This is an irrigated where field is about 75% lapped and plants are growing well and healthy. We saw soybean loopers, armyworms and corn earworms at 6 – 7 worms per row foot. Since we are at high end of threshold, it is going to be sprayed.

The main insect issue we are watching for is lesser cornstalk borers. With the dryer weather, these caterpillars become a problem. The problem is more likely to be observed in non-irraged fields first. If you see a plant that is wilting serverely, slice into the shoot and try to locate the worm. Mitchell County Ag Agent, Andy Shirley, has a picture of LCB he took this week. You can see his blog post here: Lesser Cornstalk Borers.

Lesser Cornstalk Borer – Photo by Andy Shirley

Here is what UGA Extension Peanut Entomologist, Dr. Mark Abney, has to say:

Lesser cornstalk borer (LCB) is probably the most serious (insect) pest of peanuts in Georgia. LCB thrives in hot, dry conditions and light sandy soils. Fields need to be scouted to determine if LCB is present. When scouting for LCB, several locations should be checked in each field. The caterpillars are most easily found if you pull up the plant. Pull a few plants at each location. You will be looking for larvae, feeding damage, and silken tubes covered with soil. The larvae can be difficult to find as they will often be inside the silk tubes or inside the stems of the plant. You may also see LCB moths flushing from the peanut foliage as you walk through fields.

Granular chlorpyrifos (Lorsban 15G) is currently the only material recommended for LCB control in the UGA Pest Management Handbook. This product CANNOT be applied by airplane to peanut. Liquid formulations of chlorpyrifos are NOT REGISTERED for foliar application in peanut. Granular chlorpyrifos must have rainfall or irrigation to be effective. Chlorpyrifos will kill beneficial insects, so we should be made aware that using this product increases the risk of outbreaks of foliage feeding caterpillars and more importantly spider mites.

Additionally, previous work at UGA found foliar insecticides to be ineffective at controlling this pest. While there are several products available for use in peanut that would probably kill LCB larvae, getting the insecticide to the target will be nearly impossible. We are currently testing a variety of foliar insecticides against LCB and will provide updates if/when any new information is available.

Rainfall and cooler temperatures will slow LCB populations, but once we get into an outbreak situation, we should not expect rainfall to alleviate the problem.

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Filed under Disease, Entomology, Peanuts

July 17, 2014 · 1:28 PM

Pond Weeds – Torpedograss & Southern Water Grass

Torpedograss

We looked at a pond yesterday which was about 1.5 acres, spring fed and covered in some weeds. Weeds in ponds are placed in one of three categories: submersed, emersed, or floating. These weeds were coming from the bottom of the pond and sticking out, which are emersed. UGA Extension Aquaculture Specialist, Dr. Gary Burtle, helped us ID the weeds. The short weed is southern water grass which has some emergent parts and some submerged parts. The other plant is torpedograss. It is the tall grass with the panic-grass seed head.

Southern Water Grass

Both weeds respond to glyphosate if enough of it is emergent in order to obtain a good treatment. Dr. Burtle says one problem is that glyphosate does not seem to translocate into the underwater portion of plants as well. If the weed is submerged more than 25%, the herbicides have less effect. For this reason, tt is recommended to use a sticker/spreader adjuvant, like a crop oil. Also, stocking 10 grass carp triploids per acre after the weeds have decomposed would help.

This pond does have bass which is very risky to treat during hot time of the year. As the plants decay, fish can die from result of oxygen depletion. Instead of treating the entire pond at one time, it is best to treat 1/3 or 1/4 sections at a time.

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Filed under Aquatic Environments