Category Archives: Entomology

Ambrosia Beetles: First Flight

Cook County Ag Agent, Tucker Price, called me this week to report seeing the first flight of ambrosia beetles. For us in deep South GA, the first flight is usually late February. UGA Extension Pecan Horticulturalist Dr. Lenny Wells has this information:

Ambrosia Beetle - Photo by Dr. Lenny Wells

Ambrosia Beetle – Photo by Dr. Lenny Wells

We’ve had reports of ambrosia beetles attacking young trees in south GA recently. This is no surprise with the very dry late summer/fall and very mild winter we’ve had.  The severe weather lately will likely make trees more vulnerable than usual where flooding rains and wind have really stressed some orchards. Trees that stand in water for long periods, especially when they are breaking bud and trying to leaf out, are very attractive to the beetles.  Growers should be checking young trees regularly for frass toothpicks that indicate ambrosia beetle attack. It is also a good idea to have some traps out around those young orchards so you will know when the beetles are active. Cold weather will slow or stop the beetle flight temporarily, but we can probably expect to see activity pick back up as soon as warmer temperatures return. See link here for description of management.

Anyone planning to plant trees this year should try to get the trees in the ground no later than mid-February to aid in recovery from transplant shock before budbreak and warm weather arrives. Trees planted late become more stressed and have a harder time recovering from transplant shock.

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Filed under Entomology, Pecans

More Bark Beetle Attacks?

With the persistence of this drought, we may see more bark beetle attacks. For the first time, I witnessed two Ips engraver attacks on the same property. The two attacks occurred four weeks apart. The scenario required for Ips attacks is not usually reoccurring. Because they attack only stressed trees, Ips usually leave the scene and are done. Could it be that stress from the drought is causing trees to release the stress pheromones that attracts the beetles?

Ips Engraver Beetle-UGA

Ips Engraver Beetle-UGA

There are a few species of beetles that cause problems in pine stands. The Southern Pine Beetle and Ips Engraver Beetle bore into trees and induce the blue stain fungus. This fungus clogs the vascular tissue of the tree and kills it. The difference in the two species is that Ips beetles rarely if ever attack a healthy tree. Pheromones (chemical signals) from a dying or distressed tree are picked up by Ips beetles. These are usually lightening struck trees. Once Ips beetles show up, they only attack a few trees and leave. Sometimes I see 3 trees in a stand killed and as many as 8 trees killed last week.

Symptoms/Signs

Other than a tree that suddenly dies,  the most common sign of an Ips attack is pitch tubes on the side of the tree. Once the adult beetle bore into the tree, the tree exudes sap to counter the beetle. The sap piles up and look like pieces of bubble gum attached to the tree. The center of the tube contains a hole through which the adult beetle enters the inner bark. If no hole is present in the pitch tube, the beetle attack was unsuccessful.

Boring dust and pitch from Ips attack

Boring dust and pitch from Ips attack

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Holes in pitch tubes where adult beetles entered the tree

An addition to the presence of pitch tubes, the adults construct egg galleries in the inner bark. These galleries are in certain shapes. Ips usually follow the wood grain, and have a “Y”- or “H”-shaped gallery patterns. I took my knife and scratched some outside bark away to find a few galleries.

Egg galleries of Ips beetle attack

Egg galleries of Ips beetle attack

Management

A common question is should we cut the trees down? Shortly  after the initial attack, needles at the crown turn yellow then brown. This happens quickly. Once we notice the trees are dead, the Ips beetles have already moved out. UGA Extension Forestry Specialist Dr. David Moorhead says in a pine stand, we actually do more damage cutting down a few dead trees than if they are left alone. The only time we would cut down trees is for 1) astetic reasons or 2) they pose a risk if fallen.

We can also use insecticides, but the issue is Ips attacks are difficult to predict and they enter the tree high up – you would have to cover the tree. The third beetle species is black turpentine beetles. They attack trees at the base and move about 5 feet high. However, their risk is minimal since they do no carry blue-stain fungus.

Cross section view of blue stain fungus

Cross section view of blue stain fungus

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Filed under Entomology, Forestry

Late Irrigation In Satsuma’s

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We are learning a lot this season as we experience abnormally dry weather this fall. It’s normal to be dry in October, but going into October dry is not normal. Once daylight shortens and temperatures drop, these plants move into a cold acclimation period as they prepare for dormancy. The water demand is lower. With 80 degree temperatures and no rain through October, you feel like you gotta run irrigation to get plants through the fall. When should we cut it off?

Last winter was not good for the southern peach crop, but good for citrus production. The satsumas had a great winter last year, with only a few nights getting into the mid 20s. The trees looked much better this season. These trees are between 3 and 4 years old now. They are producing satsumas but the taste is not ready.

This week, we noticed lots of suckers growing from limbs. It being November, this is really the time when these trees need to be shutting down, sending more sugars to the roots to prepare for the winter. We believe our watering through October has kept these trees producing shoots. UGA Extension Pecan Specialist Dr. Lenny Wells reminds us not to run too much irrigation on young pecans trees as they need to go dormant.

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Suckers on the limb of Brown Select

When we looked at the soil around these satsumas, we found plenty of moisture. This was inside the row between the trees. It’s actually safe to turn off irrigation when moisture is present between the trees 6 inches down. These roots still have plenty of moisture.

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Filed under Citrus, Entomology

Screwworms Back In Florida

It’s literally been a few generations ago that we last dealt with screwworms. There has been a reinvasion in South Florida, and an eradication program is underway. UGA Extension Livestock Entomologist Dr. Nancy Hinkle has good information on the current situation.

In late September the USDA’s National Veterinary Services confirmed that New World Screwworms had been found in deer on Big Pine Key in south Florida. Additional screwworm-infested animals have been located in the same area since.

Lifecycle

Screwworms will lay their eggs on any wound in an animal–even an area as small as a tick bite. They are unusual in that the maggots feed only on living flesh (while other types of maggots consume necrotic tissue). Once the maggots have gotten as big as they are going to get, they crawl out of the wound, fall to the ground, burrow into the soil and pupate. A few days later the adult fly will emerge from the pupal case, seek a mate, and start the life cycle all over again.

History

Screwworms were a scourge of the Southeast from the 1930s to the 1960s. Cattlemen funded an eradication program to eliminate screwworms using the sterile insect technique, successfully eliminating screwworms from the Southeast in 1959. They were eradicated from the rest of the U.S. in the 1970s, and by the mid-80s screwworms had been eradicated from all areas north of Panama, where they have been maintained since. South American countries still have thriving screwworm populations, so risk of reintroduction persists.

This is a reportable disease, so veterinarians are being particularly vigilant. Cattlemen can watch their animals to ensure that screwworms do not develop in their herd. Other livestock such as goats, horses, swine, etc. can also be infested by screwworms, so should be checked regularly.

Back in the 1950s screwworms killed over 60% of white-tailed deer fawns born every year. Hunters may want to keep a ziploc bag with them in the field to scoop maggots out of wounds on deer they kill, so they can be submitted for identification.

Identification

Pet-owners should keep an eye on their animals to avoid screwworms infesting their pets. Contact your veterinarian to have any suspicious maggots checked out.

Any suspect maggots should be put into a container of alcohol and submitted to the County Extension office. Don’t just scrape the maggots off on the ground and let them crawl away! We want to eliminate these pests before they have a chance to re-establish in Georgia.

Screwworms can be treated and the animals will recover fully, if the infestation is caught in time.

Again, other types of maggots can be found in wounds, but screwworms are the only maggots that feed on the living tissue and enlarge the wound. Screwworms cannot live in dead animals. The University of Georgia will be glad to identify any maggots of concern.

Current Situation

We have several factors working in our favor. (1) Fortunately the screwworm infestation is hundreds of miles south of Georgia, so the risk is small. However, we realize that thousands of vehicles move from Florida through Georgia every day, including many with pets or other animals. When these stop at service stations, restaurants, or welcome centers there is the risk that any hitch-hiking maggots could disembark and try to make a home in Georgia. (2) We’re moving into winter, so it will soon be too cold for screwworm flies to survive in Georgia. (3) And we have a very vigilant network of veterinarians who are attentively watching to ensure none of their patients have screwworms. We can anticipate that Florida will eradicate screwworms this fall and by the time spring begins to warm Georgia, there will be no risk of screwworms moving north to our state.

Additional Information

If you want to know more about screwworms (and how much we don’t want them back in the Southeast), talk with someone whose family had cattle back in the 1950s. They can tell you about digging maggots out of calves’ navels and smearing insecticides in dehorning and branding wounds. Florida has lots of good information about screwworms on their website at http://www.freshfromflorida.com/Divisions-Offices/Animal-Industry/Consumer-Resources/Reportable-Animal-Diseases/New-World-Screwworm.

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Filed under Entomology, Livestock

Grub Damage In Pastures

General decline of forages in pastures or hayfields can be attributed to many things. Fertility is generally our first thought. Secondary factors are then assessed to see how they might have played a leading role in the reduction of productivity. These secondary factors include drought, diseases, weed pressure, herbicide injury, soil compaction, or insect damage. Producers that have areas declining in the late summer into fall can suspect insect damage from a soil borne insect complex we call grubs.

Miller County Agent Brock Ward wrote a good description of these beetles, and how to deal with them:

Grubs are the larval stage of beetles that feed on decaying organic matter and some of those species also feed on roots as well. Pastures and hayfields that have had chicken litter or other manure applied as a fertilizer are typically the areas where these grubs are the most severe. It is important to also identify the grubs that are causing the damage as control and management of them can be different. Perhaps the most troublesome is the May/June beetle (MJB). The grubs of the MJB have a characteristic “zipper” pattern in the hair on the underside of their “tail-end”. This helps you to distinguish it from other grubs like the Green June Beetle (GJB) or chafer beetles. When faced with the MJB complex of beetles, the larvae burrows deep into the soil for much of its yearlong lifecycle (as many as three years in Northern states), so treatment isn’t an option, because we can’t expose the grubs to an insecticide treatment with any repetitive certainty. In the case that you have grubs from the MJB complex, renovation or replanting after the emergence of the beetles is likely the best management strategy. Chafer beetles are much like the MJB complex of beetles but require many more of them to reduce a stand of pasture grasses. Typically the source of the forage decline in a pasture is linked to other causal agents when chafer beetles are found in heavy numbers.

may-junebeetle

If the Green June Beetle (GJB) is the source of your damaged forage, treatment can be managed with insecticide use. The GJB has a one year lifecycle and feeds up through the soil surface before burrowing down again. This feeding habit makes it easier to target the pest. Many pyrethroids are labeled for use on the GJB adults, however the larvae have fewer insecticides labeled for their control. It is unlikely that GJB alone is reducing the stand of forage. As with most secondary factors, it is likely a combination of stressors that begin to reduce the stand. An example, I have seen recently is where drought stress, soil compaction, and grubs were leading to stunted areas in a pasture.

greenjunebeetle

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Filed under Entomology, Pasture

Tip Moths In Loblolly

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This week, we looked 2-year-old loblolly showing dieback in the tips of branches. This turned out to be damage from tip moths, Rhycacionia genera. There are different species. Loblolly’s are susceptible to tip moths, especially young, less than 5 -6 feet tall. The damage is similar: the tips of terminals and laterals are killed as result of larval boring into base of the needles or buds, and then into the shoot itself.  They can also kill small trees.

Lifecycle

Eggs are laid on the base of needles. When the eggs hatch, larvae bore into the needle sheaths and mine needles near their base. By midwummer, larvae move to buds and burrow in them. They stop feeding in August. They overwinter in the wound area. On the terminal of branches, we observed resin-coated webs, frass from worms, brown needles, and where worms were still present, you can see the tunnel in the branch. We also found a few caterpillars inside the stem. This is something we probably need to think about treating, though we are past effective treatments now. Here is a table from the book “Insects That Feed On Shrubs & Trees” showing species and hosts.

tipmoths-specieshosts

Control

When it comes to treating, UGA Extension Forestry Specialist Dr. David Moorhead has a detailed guide to spray control. See the weather station locations in Table 4 to choose a site closest to your site for the spray date times.  There are numerous insecticides in the 2016 UGA Pest Control Handbook that are effective for control. These can be applied by fixed wing crop dusters or by ground rigs.

10 Bainbridge March 12-16 May 21-25 July 10-14 Aug 19-23

Identification

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Resin soaked web from tip moth attack

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Stem bored by tip moth

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Tip moth larvae

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Loblolly pine attacked by tip moth

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Filed under Entomology, Forestry

Effectiveness Of Bt

J.Whitaker-ThomasCounty

It’s been easy for me to take for granted not having to count bollworms in cotton with Bt technology. UGA Entomologist Dr. Phillip Roberts discusses Bt traits at meetings, but don’t have to get in depth because of how effective the technology is for us. After our cotton field day yesterday, UGA Agronomist Dr. Jared Whitaker and I looked at plots for a while. It was a great learning experience for me as he was showing me to how to actually scout for bollworms and make seeing some damage.

Tobacco budworm and corn earworm make up the Heliothine complex. Though they are different insects, they appear similar in the egg and larval stage. Three generations of tobacco budworm infest cotton each year and two generations of corn earworm occur each year. ID is important since TBW are resistant to pyrethroid class of insecticides. But susceptibility of CEW to pyrethroids has declined in recent years.

We have Bollguard II, Widestrike, Twinlink, and Widestrike III technologies of Bt. The difference between technologies is how much they are expressed throughout the plant. Bt is not immune from economic damage from caterpillars and don’t have actually on regular bugs (Stink bugs & plant bugs). TBW are actually more susceptible to Bt than CEW (and other worms).

Scouting

Dr. Whitaker showed me how to look for caterpillars. Since the flower has the least expression of Bt, if the moth lays an egg in the flower, it can hatch and feed. Once it feeds outside this, Bt should kill the caterpillar. We were seeing some larger bollworms and bollworms moving from one boll to another.

Since it takes the eggs three days to hatch, it’s best to look in pink flowers. Pull the petals back and look for a very tiny black-headed worm, OR you may see a black dot where the worm “hit” the edge of the boll. You can also look for a flared square. Here are some pictures of all of this we saw yesterday.

Hit from bollworm

Hit from bollworm

Bollworm Hatchout

Bollworm Hatchout

Flared square

Flared square

Bollworm 018

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Filed under Cotton, Entomology