Altrevin Almond Article

Altrevin Almond Article

Posted by Teresa Frediani | June 21 2019

Introduction

Managing ants and the damage they cause continues to be a difficult problem for almond farmers.  Historical experience with ant populations can be a good indicator for growers to determine if they are likely to have a problem species in the orchard. In California the fire ant species (Imported and Native) are considered the most damaging to nut crops.  In addition to fire ants, pavement ant can also cause significant damage, especially in the northern San Joaquin Valley.  Fire ants can also be a safety issue for workers and PCAs in the field, as the ant will aggressively bite and sting.

Fire ants are more prevalent in drip- or sprinkler-irrigated orchards than flood-irrigated orchards.  Also, damaging species will often be found with weeds growing within the nest and are easily excited by disturbing the soil near their nests.  Good weed management is an important factor in managing ants.  In order to maximize bait acceptance, it is best if weeds are well controlled.  Lack of weeds makes bait easier to find and some weed seeds may be a more attractive food source for ants than baits.

Damage

Damage on almonds occurs when the nuts are on the ground, after being shaken from the tree.  In only a few instances will ants climb into trees to feed on nuts.  This usually occurs with limbs that touch the ground giving ants easy access to hullsplit nuts. The primary factors that influence damage include the population of ants in the orchard and the length of time the nuts are left on the ground to dry.  The ants can completely hollow out nutmeats leaving only the pellicle. Damage is lower on varieties that have nuts with tight shell seal, as the seal limits an access to the nut. Shell seal can vary greatly from year to year depending on variety, crop size, and horticultural practices. A heavy crop of small(er) nuts will likely have fewer open shells and thus less potential for ant damage.

Management

Ant baits, like Altrevin® Fire Ant Bait Insecticide, have been very effective in controlling ants and reducing damage, when applied at the correct time.  To make the best managing decisions, survey your orchard for ants from April to June to determine if treatment is necessary.  Treatments can be made any time of year but should be made prior to harvest to manage potentially damaging populations.  As demonstrated in the table below, removal of nuts from the orchard floor as soon as possible after shaking is the most certain way to limit losses.  A harvest sample should be evaluated for damage to determine if your management program was effective. 

According to UCIPM the following should be considered to make the best ant management decisions. 

1. Survey the orchard floor for ant colonies 2 to 3 days after irrigation. 
2. Choose five survey areas per block of the orchard, each about 1000 square feet, including the soil area from mid-alley to mid-alley beneath trees.
3. Count the number of active pest-ant colonies in each area, sampling five different areas of the orchard.
4. Total the ant colonies to get the number in a 5000 square foot area and compare it to the table below which gives an indication of the amount of damage you can expect at harvest.  

Percent Damage by Southern Fire Ants to Almonds on the Ground in an Almond Orchard

 

Number of colony entrances per 5,000 sq. ft. in April to May

Days nuts are on the ground

 

4

7

10

14

21

 

15

0.9%

1.6%

2.1%

3.1%

4.9%

 

45

1.4%

2.3%

3.2%

4.7%

7.0%

 

185

2.0%

3.6%

5.0%

7.0%

11.1%

 

 

Baits are only effective when foraging ants collect the bait and take it back to the colony. The bait works by killing or sterilizing the queen and as a result the developing larvae fail to mature.

Altrevin® Fire Ant Bait Insecticide, works very quickly (within days), and has a residual of 30 to 45 days depending on conditions. For the best results, apply Altrevin® Fire Ant Bait Insecticide approximately 2 weeks before shaking begins.  Do not use baits within 24 hours after an irrigation or 48 hours before an irrigation with sprinklers or microsprinklers. The soil surface should be dry so that moisture is not absorbed by the bait, reducing its attractiveness to the ants.

Altrevin® Fire Ant Bait Insecticide should be used within 60 days after opening.  Bags of the bait that have been stored for a few weeks or more should be turned over so that the soybean oil attractant remains evenly dispersed throughout the corn meal carrier. Product must be used soon after opening the bag so that the soybean oil does not turn rancid.  Do not purchase more bait than can be used in the current season.

In the trial below, Altrevin® Fire Ant Bait Insecticide was tested for fire ant control in a non-bearing orchard in Newman, CA.  The study evaluated the knockdown and residual activity of Altrevin® Fire Ant Bait Insecticide.  The number of foraging ants was evaluated prior to and after treatment at the location of a food source of corn chips and hot dogs.  Altrevin® Fire Ant Bait Insecticide significantly reduced ant populations by 7 days after treatment. 

A trial conducted in Famosa, CA shows the residual control of fire ants with Altrevin® Fire Ant Bait Insecticide.  In this trial, active mounts were flagged 24 hrs prior to treatment.  Treatment was applied on June 23, 2012, and ratings were taken after approximately 7, 14, and 30 days after treatment.  The graph below shows the average number of mounds 27 days after treatment. 

Resistance

The IRAC resistance database only cites two cases of ant colony resistance to an insecticide, neither in North America.  Ants are social insects, sharing resources like shelter, defense, and food.  Furthermore, ants reproduce cooperatively.  Only the queen reproduces and determines offspring sex; female workers do not contribute to egg production.  Most ants only produce on generation per year, and very small percentage of the population can pass heritable traits, such as resistance genes.  Altrevin® Fire Ant Bait Insecticide is not metabolized by ants, so populations are less prone to develop resistance.  The IRAC website states, “Metabolic resistance is the most common mechanism of resistance and often presents the greatest challenge.”

Best Use Practices

At 1.5 lbs/A Altrevin® Fire Ant Bait Insecticide can control populations and allow you the flexibility to treat in as little as 5 days prior to harvest.  As seen above, Altrevin® Fire Ant Bait Insecticide provides the control you need, where you need it, when you need it.  Talk to your Pest Control Advisor about using Altrevin® Fire Ant Bait Insecticide for control of troublesome ants in your orchard.