Historically, our Areawide Pheromone and Sticky Trap monitoring for insects was terminated around the first of April as the produce season ended. Beginning 2 years ago however, we continued our Areawide Trapping Network throughout the summer to collect trapping data from all 16 areawide trap locations year-round.  So why is this additional trapping data useful? For several reasons. First, understanding the activity of some of our key pests when produce is not grown during the summer may give us an indication of what to expect as the fall produce season begins. This may be particularly helpful for predicting moth flights and whitefly flights in August-September coinciding with early transplanting and direct seeded crops.  Another example is keeping track of corn earworm which can unexpectedly show up near the beginning of fall harvests. Secondly, trapping for pests during the summer has shown us that 2 of our more important produce pests are not caught in traps during the summer. We presume this is due to the absence of brassica crops and weeds for diamondback moth, and high daytime/nighttime temperatures lethal to aphids. The fact that trap catches resume in the fall supports our conclusion that these pests are absent in the summer, only to reenter the desert via winds and/or transplants in the fall. And finally, it gives me something to do in the summer.  So, visit the Areawide Summer Trap Network if you’re curious what our key pests are up to. We also continue to monitor thrips activity during the summer. This involves plant sampling using a dislodgement sampling method (beat pan) to determine the relative abundance of thrips adults and larvae on alfalfa, cotton, melons, wheat, Sudan grass, and weeds.  This is being conducted to supplement our yellow sticky trap data that only indicates thrips adult flight movement an area. With this plant sampling we should be able to determine the primary host plants thrips are colonizing in the cropping season during the long hot summer. We are also trying to determine whether these crops allow for the reproduction of thrips. So far, all the crops and weeds we have sampled have shown that thrips will reproduce and complete their life cycle on them. This is important, particularly for weeds, as we are trying to determine whether INSV can be survive the summer in the absence of lettuce. It is also important because it allows us to determine potential exposure of thrips to key insecticides like Radiant and Lannate for resistance management purposes. These crops essentially serve as untreated refugia that likely sustains insecticide susceptibility and is the reason these products are still effective against thrips.  We will be conducting this work throughout the summer, as well as through next produce season. We will periodically provide updates of these thrips monitoring results throughout the summer.  As my dad used to say, “to solve the problem, you must first understand the problem”.

This study was conducted at the Yuma Valley Agricultural Center. The soil was a silty clay loam (7-56-37 sand-silt-clay, pH 7.2, O.M. 0.7%). Variety: Deluxe (HMX2595) was seeded, then sprinkler-irrigated to germinate seed on March 20, 2024on 84 inches between bed centers. All other water was supplied by furrow irrigation or rainfall. Treatments were replicated five times in a randomized complete block design. Each replicate plot consisted of 25 ft of bed. Treatment beds were separated by single nontreated beds. Treatments were applied with a tractor-mounted boom sprayer that delivered 50 gal/acre at 100 psi to flat-fan nozzles spaced 12 in apart. 

Spray treatments were done on 05-21-2024, 05-31-2024, 06-07-2024 and 06-14-24. Powdery mildew was first seen on 06-05-24. Please see excel file for additional details.  

Disease severity of powdery mildew (caused by Sphaerotheca fuliginea and S. fusca) severity was determined 6-17-2024 by rating 10 plants within each of the four replicate plots per treatment using the following rating system: 0 = no powdery mildew present; 1 = one to two mildew colonies on leaves  ;2 = powdery mildew present on one quarter of leaves; 3 = powdery mildew present on half of the leaves; 4 = powdery mildew present on more than half of leaf surface area ; 5 = powdery mildew present on entire leaf. These ratings were transformed to percentage of leaves infected values before being statistically analyzed.

The data in the table illustrate the degree of disease control obtained by application of the various treatments in this trial. Most treatments significantly reduced the final severity of powdery mildew compared to nontreated plants. Quintec, Merivon, Tesaris, Luna Sensation, and V6M-5-14 V gave the best disease control. Phytotoxicity symptoms were not noted for any treatments in this trial.

ANR Webinar 10/17 click link for details.

Foliar applied herbicides almost always have more uniform activity on plants than do soil applied herbicides. This is largely because the conditions that affect their activity are more uniform above the soil than they are below ground. It is not uncommon to see inconsistent activity with soil applied herbicides. It is also difficult to predict where and for how long the effects of these herbicides will occur. Many factors affect soil applied herbicides.

In this desert region where crops are intensively irrigated and the soils are low in organic matter, the most important variables affecting soil applied herbicides are adsorption and volatility. Adsorption is the process whereby herbicides are bound to soil particles. All herbicides have electrical charges that cause them to bind to the positive or negative charges in soil or organic matter. This is similar to how metal is bound to a magnet. It is reported as the absorptivity coefficient (K) and is generally more important than water solubility in determining how herbicides move in the soil. Many factors can affect adsorption. These include soil texture, pH, organic matter and soil moisture. Although the soils here are generally low in organic matter, crop residues from crops grown previously in rotation can temporarily tie up many herbicides. Soil moisture can also have a significant effect. Herbicides compete with water for binding sites on the soil and bind stronger to dry rather that wet soils.

Absorptivity and water solubility are usually inversely related. As solubility increases, binding to the soil decreases. There are some exceptions to this. Notable among these are Gramoxone (Paraquat) and Glyphosate. Both of these herbicides are highly water soluble but they bind tightly to the soil.

Herbicide volatility occurs when a herbicide changes from a liquid or solid form to a vapor. This is affected primarily by vapor pressure and varies considerably for various herbicides. The higher the vapor pressure, the higher the volatility. Some of the most volatile herbicides used here are Eptam, Banvel, MCPA and 2,4-D. Some of the least volatile are Glyphosate, Gramoxone, Karmex and Pursuit.

Area wide Insect Trapping Network   VegIPM Update, Vol. 12, No. 11, Jun 2,  2021
Results of pheromone and sticky trap catches can be viewed here.
 
Corn earworm:             
We saw a slight peak of activity in early May consistent with last season, but numbers appear to be trending down now. 
 
Beet armyworm:         
Trap counts have been highest in May so far consistent with last summer.
 
Cabbage looper:          
Adults reached their highest levels of the year in early April, but have declined to low levels since.
 
Whitefly:                      
Adult movement beginning to increase slowly, particularly in the Yuma Valley. Can anticipate higher numbers with melon harvest ending.
 
Thrips:                          
Thrips adult movement reached the highest point in the season during May, again consistent with last summer.
 
Aphids:                        
Seasonal aphid counts peaked in January, and have been absent for the past 2 weeks with high temperatures. 
 
Leafminers:                   
Adult activity has been high during April and May consistent with maturation of melons and alfalfa cuttings.
 
Diamondback moth:      
DBM counts are slowly decreasing with a few adults be captured in areas where seed crops were recently harvested.