Denizens of El Paso and the American Southwest: the carpenter bee & the cuckoo wasp

I want to share with you a YouTube video that I filmed on May 7, 2015 in my patio of a carpenter bee (Xylocopa spp.) and its kleptoparasite (Family Chrysididae):

Pesticide efficacy trial on pecan aphid control

PECAN:

In 2013, Drs. Mark A. Muegge and Salvador Vitanza evaluated the efficacy of several insecticides for black-margined aphid (BMA) control.  This study was conducted in a commercial pecan orchard near Fabens, TX.  A single pecan tree constituted an experimental unit.  Each experimental unit was bordered by untreated pecan trees as buffers to help reduce potential drift contamination.  Experimental units were arranged in a randomized complete block design with 10 treatments replicated 4 times.  Insecticide applications were made using a high pressure sprayer calibrated to deliver 100 gallons per acre (gpa) at 100 pounds per square inch (psi).  From each experimental unit 3 randomly selected compound leaves were examined for BMA.  Adult and nymph aphids found were counted separately and recorded.  Treatments were applied on 11 Oct after pre-treatment samples had been collected.  Post treatment samples were taken at 10 and 25 days after treatment.  All data were subjected to analysis of variance (ANOVA).  Treatment mean separation was performed using Fisher's Protected LSD (P=0.05). 

Although total BMA densities were moderately high they never exceeded economically damaging population densities throughout the duration of this test.  Prior to treatment application, BMA adult and nymph population densities were statistically equal among untreated check and treated plots.  At 10DAT the Induce, Agriflex, Agrimek and Admire Pro treatments did not significantly reduce BMA adult population density.   All treatments except Agriflex and Admire Pro significantly reduced BMA nymph population densities.  At 25DAT only the Beleaf treated trees had significantly lower BMA adult population densities relative to the untreated check trees and BMA nymph populations were not significantly lower in any of the treated trees relative to the untreated check.  However, population densities of BMA nymphs were substantially lower in the Endigo, Voliam and Beleaf treated trees relative to the untreated check trees.  Interestingly, the NIS and Agriflex treated trees had significantly higher BMA nymph population densities relative to the untreated check trees.   Whether this result is a real cause and effect or a result of experimental and or sampling error requires further studies. 

		Mean BMA adults/3 Compound Leaves			Mean BMA nymphs/3 Compound Leaves
Treatment	Rate (oz/acre)	0 DAT	10 DAT	25 DAT	0 DAT	10 DAT	25 DAT
UTC	-	8.2	7.8ab	4.2bc	14.3	24.2a	11.3bcd
Induce	4.8	6.9	7.9a	9.2a	10.7	11.8bc	31.7a
Agriflex+NIS	5.5	4.6	5.7abc	6.4ab	11.7	15.6ab	30.6a
Agrimek+NIS	2.5	8.7	5.5abc	5.7bc	20.8	13.4b	17.9bc
Admire Pro	2	4.6	4.7bcd	4.8bc	7.6	14.7ab	15.0cb
Endigo	5	10.8	4.2cd	3.1cd	26.3	5.8bc	5.7cd
Water*	100g/a	10.1	3.9cd	4.8cb	17.8	10.7bc	19.7ab
Voliam Express	9	10.2	3.2cd	3.4cd	21.6	6.3bc	9.7bcd
Fulfill+NIS	4	8.7	2.7cd	4.7cb	9.8	2.5c	12.3bcd
Beleaf	2.8	8.4	2.4d	1.0d	21.3	2.2c	1.9d
LSD (P=0.05)		6.0	3.2	2.9	15.8	10.6	12.5
P>F		NS	0.0039	<0.0001	NS	0.0017	<0.0001

Is the Hickory Shuckworm becoming a more serious pest in El Paso County?

Mr. Kevin Giraud, Manager of Helena Chemical Company in Tornillo, placed two pheromone traps for hickory shuckworm (HSW) south of Fabens, near the Rio Grande, on June 3. Just three days later, he had collected 41 HSW moths. In previous years, I have found minimal amounts of HSW larvae and nut damage. This year, I did not set up HSW pheromone traps, but I have done so in the past with little success. Although in other regions HSW is considered a serious pest, pecan growers in El Paso generally do not monitor for HSW. This pecan pest has received little attention and might have been under the radar. Based on these recent captures, I am afraid that HSW populations might be increasing in El Paso region. It is hard to interpret what these captures mean in regards to affecting pecan nut yield and quality. When asked about this subject, Bill Ree commented: “HSW pheromone seems to catch adults early in the season, a few during the summer, then more in the late summer or fall”. He added “We (pecan entomologists) just don’t know what the trap catches are telling us so treatments are based on the fact that there was a problem last season and kernel development has reached the half shell stage.” It is not time to panic, but a good moment to monitor the development of this pest. If past events are good indicators of the future, we should find comfort in the fact that this pest has caused only a minor damage in pecan production during recent years. Fortunately, insecticide applications for second generation PNC, in case they are needed, may also reduce HSW population levels. I will be placing HSW pheromone traps in the field soon to monitor this pest more closely.

Boll Weevil and Pink Bollworm declared eradicated in El Paso County

The Texas Boll Weevil Eradication Foundation, Inc. (TBWEF) has placed the boll weevil and the pink bollworm in the status of ERADICATED. No cotton grower will shed a tear to see these major pests go. Last year (2012), a few pink bollworm moths captured in the traps had to be evaluated more closely, but finally were determined to be sterile. In 2012, TBWEF placed 1 trap every 10 acres in non-Bt fields, but this year they have reduced this rate in half (1 trap/20 acres). The rate for non-Bt fields continues to be 1 trap per field regardless its size. Last year, the program released almost 15 million sterile moths (14,833,784 to be exact). No releases of sterile pink bollworm moths are planned for this year.

NAVEL ORANGEWORM FOUND IN A PECAN NUT

On January 25, I received a pecan nut, with a hole in it, which a grower had found in his orchard and suspected to be infested with pecan weevil. I opened it, found a moth pupa, put the nut and its contents in a rearing cage, and completely forgot about it. Recently, I found 4 unfamiliar moths in that rearing cage. From the close-up photographs that I sent out, Bill Ree and Mark Muegge determine it to be the navel orangeworm. I mailed all the specimens to Kira Metz, Entomologist Identifier, USDA-APHIS in College Station, for confirmation. The navel orangeworm is a pest of citrus, walnut, almond, pistachio, macadamia, and figs in California, but I have not found a publication that deals with this pest in pecan. Bill Ree suspects that El Paso pecan growers should not be worried about this insect at the moment because the navel orangeworm cannot enter a pecan nut unless there is a crack in the shell. Potentially, this insect could become a stored product pest of pecan. The University of California IPM website mentions that the navel orangeworm does not damage sound walnuts, almonds, or pistachio, but nuts become susceptible when hulls begin to split.

COTTON THRIPS AND PLANT STAND DENSITIES

All cotton fields in our area have been planted and “capped off”. A majority of them have plants at the cotyledon stage. I have not seen much thrips damage yet. In the Texas high plains, thrips are considered a key pest in pre-squaring stage cotton (David Kerns et. al., Developing an action threshold for thrips in the Texas high plains, 2010). The currently accepted action threshold for thrips is 1 thrips per true leaf, but based on recent findings, these AgriLife Researchers suggest that it may be necessary to update thrips thresholds in cotton to the following levels: cotyledon stage = 0.5 thrips per plant, 1 true leaf = 1 thrips per plant, 2 true leaves = 1-1.5 thrips per plant, and 3-4 true leaves = 2 thrips per plant. Cotton plants are most susceptible to thrips damage at the cotyledon stage and this susceptibility decreases as the cotton plant grows. Another caveat is that whole-plant samples placed into jars containing alcohol have been shown to be a more accurate sampling technique than simple visual inspections. Usually, warm weather allows cotton seedlings growth to compensate for thrips damage. The weather forecast calls for the next couple of days below average temperature and then return to warm conditions. I do not expect thrips to be a problem in El Paso and Hudspeth Counties this year, but it is wise to monitor the crop for thrips levels. There are some plants showing sandblast damage; especially in sections of fields with soils high in sand content.

            In recent years, I have observed that cotton fields in our region have an average plant stand density around 55,000 plants/acre, with fields planted as low as 30,000 plants/acre and as high as 63,000 plants/acre. Yesterday, I obtained four samples per farm from 4 cotton farms. For each sample I counted the number of plants in 11 feet of row. The first 3 farms had plant stand densities falling within expectations: 41,818; 59,459; and 63,828 plants/acre. However, the last farm sampled now holds the highest plant stand density that I have observed so far: 105,981 plants/acre. It is generally accepted that 2-4 plants/foot of row maximizes yields. This is equivalent to 26,136 - 52,272 plants/acre in fields with 40 inches between rows. Most cotton fields that I have visited this season have been planted at 40 inches between rows and a few at 38 inches. It seems to me that some growers could gain substantial savings in seed costs by planting at recommended densities.

LEAFMINER DAMAGE IN ALFALFA

A 14-acre alfalfa field south of Fabens has been affected by an undetermined leafminer, possibly the American Serpentine Leafminer (ASL), Liriomyza trifolii. This field had areas with severely damaged plants next to areas with plants that had little damage. Approximately 30% of the field was affected. I recommended an early harvest and immediate removal of the alfalfa to reduce both the pest and susceptible host. Additionally, that field could also benefit from prompt irrigation. A sample of adult leafminers was submitted for species identification. Dr. Scott Armstrong, a research entomologist with ARS-USDA in Weslaco, TX, reports that this species has been a problem in cotton and vegetables in southeast Texas this year.  ASL is one of the most widespread and economically-important leafminers in the world. It is a very polyphagous leafminer species that feeds on a wide variety of row crops, ornamentals, weeds, and native plants. Therefore it can maintain continuous populations even when crops are not in cultivation (C. E. Stegmaier Jr., The Florida Entomologist, Vol. 49, No. 2). In general, leafminers can become key pests in crops where insecticides are used excessively.  Usually, leafminers are kept in check by natural enemies, especially small wasps that parasitize eggs, larvae, and pupae stages. They are called “parasitoids”. Parasitoid is defined as an organism that, during its development, lives in or on the body of a single host individual, eventually killing that individual. Sometimes there are also “hyperparasitoids”, which are parasitoids that develop in other parasitoids. The leafminers are very tiny insects so you can imagine the size of its associated hyperparasitoids. When insecticides are applied too frequently, the populations of natural enemies may crash and this results in leafminer outbreaks. Interestingly, alfalfa fields in our region receive very little insecticide applications, if any. The good news is that we are definitely not dealing with the Alfalfa Blotch Leafminer, a major alfalfa pest in other parts of the country; especially the Midwest.