Food Safety in Relation to Specialty Crops and Field Day

Get the most out of your high value crops

Friday, July 6, 2018   8:30 a.m.-1:30 p.m.
DSU Outreach & Research Center
884 Smyrna-Leipsic Road Smyrna, Delaware

Focus is on cage culture, blueberry; EQIP program and organic farming; farmer perspective.

Dr. Rohan Tikekar of the University of Maryland will speak on food safety measures to use while working with fruits and vegetables on farm.

Dr. Gary Pavlis of Rutgers University will speak on production and management of a blueberry farm.

Participants will tour the farm!

Please register by June 25, 2018 for this free field day/workshop by contacting Lekha Paudel at 302-857-7796 or

Guess the Pest! Week #13

Bill Cissel, Extension Agent – Integrated Pest Management;

Test your pest management knowledge by clicking on the GUESS THE PEST logo and submitting your best guess. For the 2018 season, we will have an “end of season” raffle for a $100.00 gift card. Each week, one lucky winner will also be selected for a prize and have their name entered not once but five times into the end of season raffle.

This week, one lucky participant will also win A Farmer’s Guide To Corn Diseases ($29.95 value).

You can’t win if you don’t play!

What is the damage on the potato leaves?

Guess the Pest! Week #12 Answer: Ground Beetle

Bill Cissel, Extension Agent – Integrated Pest Management;

Congratulations to Chris Williams for correctly identifying the insect in the photo as a ground beetle and for being selected to be entered into the end of season raffle for $100 not once but five times. Everyone else who guessed correctly will also have their name entered into the raffle. Click on the Guess the Pest logo to participate in this week’s Guess the Pest challenge!

Guess the Pest Week #12 Answer: Ground Beetle

There are many different species of Carabidae beetles, commonly referred to as ground beetles, which can be found in crop fields that are helping to keep pest populations in check. However, they aren’t all as attractive as this particular species of ground beetle. Ground beetles are considered “generalist predators” meaning they prey on many different kinds of pests. One pest that they are known to prey on is slugs. With very few natural enemies, gaining a better understanding of the predator-prey relationship between ground beetles and slugs can provide valuable insight into how we can take advantage of these natural enemies to help with slug control.

Curious about some of the current Delaware Soybean Board funded research being conducted at the University of Delaware?

Click on the link to watch a short (90 second) Youtube video to learn more about some of our research with ground beetles and slugs:

Fun Entomology Fact: In Europe, there is a species of ground beetle that is commonly referred to as the “Slug Killer”.

Managing Spider Mites in Soybeans and Vegetables

David Owens, Extension Entomologist, and Bill Cissel, Extension Agent – Integrated Pest Management;

We found our first two spotted spider mites in watermelon, cantaloupe, and soybean last week. Spider mites move into fields in 3 ways: hitching a ride on equipment or workers, crawling over soil, or by being transported by wind. When host quality declines, TSSM will move to high objects and stand on their ‘tip toes’, waving their first pairs of legs until a passing air current catches them.

Spider mites quickly reproduce with the warm weather that we have had. Mites can develop from egg to adult in as few as 8 days, and lay over 140 eggs during their 2 to 3-week life span. Eggs take about 6 days to hatch. Even with the wet weather we have had, it is possible that spider mites may need treating at some point in your fields later this season. Humid weather favors entomopathogenic fungi which can reduce mite numbers, but many fungicides slow down or prevent fungal growth.

Action thresholds for watermelon are 20 – 30% infested plants with 1 – 2 mites per leaf. For R-stage soybean, thresholds are 20-30 mites per leaflet and 10% of plants with one third of the leaf area stippled. For tomato, NCSU entomologist Dr. James Walgenbach recommends an action threshold of 2-4 mites per leaflet. On tomato, spider mites can also be a contributing cause of ‘gold-fleck.’

NCSU research indicates that two spotted spider mite resistance is unstable. If mites are resistant at the end of one season, that resistance will not be as strong at the beginning of the next. However, resistance is still present and can be rapidly selected for. There is limited population mixing from one farm operation to another. What this means is that a population of mites on one farm does not spread to others. This means that miticide rotation is extremely important. Miticides tend to be most active on certain demographic groups, meaning that there is likely a subset that will not be killed from the application. Given their life span (6 days as eggs, 8 as juveniles), if you need to spray, anticipate a second application.

The table below lists the miticide active ingredients and their mode of action group for watermelon. There are generic formulations of some of the chemicals, this list is not meant to serve as an endorsement.

Miticide Active ingredient MOA group Life stage active Applications/season
Agri-Mek Abamectin 6 Mobiles (translaminar) 3-5
Gladiator Zeta-cypermethrin + avermectin 3 + 6 Mobiles (translaminar) 3
Acramite Bifenazate 25 Mobiles, some ovicidal (contact) 1
Kanemite Acequinocyl 20B Mobiles, some ovicidal (translaminar) 2
Oberon Spiromesifen 23 Eggs and juveniles (contact) 3
Portal Fenpyroximate 21A Mobiles (contact) 2
Zeal Etoxazole 10B Ovicidal, juveniles (translaminar) 1

Please note that avermectin is in the same mode of action class as abamectin. Do not apply one right after the other. Also, some of these products will stop mite feeding quickly, but the mite will take a few days to die. If you have sprayed a field and see mites a couple of days later, wait another few days and resample. Also, many of these products have a long residual activity, meaning that if it is not active immediately on eggs, it should still be around once the eggs hatch. This year, we have plans to test these products at our research station.

For soybean, three materials have been previously recommended: bifenthrin (a pyrethroid), Agri-Mek 0.7SC, and Zeal 2.88SC. Generally speaking, pyrethroid resistance can be an issue with spider mites. This class will also remove beneficial predatory insects.

As always, read the label thoroughly for further guidance. Some products have restrictions on reapplication interval, and restrictions on consecutive applications. There are also requirements on some for spray adjuvants to avoid illegal residues. Good coverage is key for miticide efficacy, even on those that are translaminar.

Growing Degree Days (GDD) and Rainfall Through June 19

Jarrod O. Miller, Extension Agronomist,

With dry weather the last week we have finally seen steady field work and replanting going on. If you look at the graph of statewide accumulation, the last week has been the longest period without rain for most of the state this planting season. Ground has dried out fast, or it may appear that way once we got used to constant saturation. So be sure to check your soil moisture and irrigate if you need to. With minimal root development under saturation, field crops may not reach soil moisture even if it is just six inches down.

As long as it wasn’t drowned out, any corn planted between April 22 and June 3 should have had plenty of GDD to emerge. Here are some general guidelines to GDD to monitor your corn fields and see if they are growing normally.

V6: 475 GDD

V12: 870 GDD

VT: 1135 GDD

R1: 1400 GDD

Table 1: Growing degree days accumulated through June 19th from the beginning of each week.

Soybean Insect Scouting Update

David Owens, Extension Entomologist, and Bill Cissel, Extension Agent – Integrated Pest Management;

Low populations of bean leaf beetles, grasshoppers, green cloverworm, bean leaf rollers and soybean leafminer, and thrips are being observed in soybeans. We are also seeing spider mite hotspots in a couple of the oldest fields. Levels are not yet of concern, but with warm temperatures, keep an eye on their populations. Interestingly, we have been seeing thrips hotspots in Kent County. In the experience of other university entomologists, 95% of the time, thrips do not cause yield reductions. There is a general guideline where if most of the leaves are injured, and there are more than 8 thrips per leaflet and the field is stressed, they can be significant. That is, are the plants being ‘held back’? Are they not growing? Soybean that is growing can tolerate a great deal of feeding.

SNAP Electronic Benefit Transfer (EBT) Equipment Options for Farmers’ Markets

Nancy Mears, Extension Agent – Family and Consumer Science;

Did you know that Approximately $17.6 million of SNAP Benefits issued each month in Delaware? The USDA Food and Nutrition Service places a high priority on expanding SNAP participants’ access to fresh and healthy food through farmers markets and direct marketing farmers, encouraging participants to spend their benefits on healthy foods.

FNS’ EBT Equipment Program offers low-cost, wireless EBT point-of-sale (POS) equipment to eligible markets and farmers. The program pays for the equipment and service fees for up to 3 years, including set-up costs, monthly statement fees, and wireless plan fees. The market or farmer is responsible for paying transaction costs, the costs of scrip systems (paper, ink, tokens, etc.), and fees to terminate an existing contract. The program will be available very soon to eligible farmers and farmers’ markets. To be contacted when the program resumes operations, please email 

Watch for Thrips in Vegetables

Jerry Brust, IPM Vegetable Specialist, University of Maryland;

I have gotten reports from flower growers of an inundation of thrips into their flower crop in the last week or so. I know, I know flowers are not vegetables, but many of the Flower thrips species that get into flowers will get into and on vegetables. Thrips are tiny, thin yellowish-orange insects the size of metal filings with fringed wings. They feed by puncturing the outer layer of plant tissue and sucking out the cell contents, which results in stippling, discolored flecking, or silvering of the leaf surface (Fig.1). Thrips feeding is usually accompanied by black flecks of frass (thrips poop) (Fig. 1). Pest thrips are plant feeders that discolor and scar leaf, flower, and fruit surfaces, and distort plant parts or vector plant pathogens. There are several species of vegetable thrips with the most common being the Eastern flower thrips, Frankliniella tritici, Tobacco thrips Frankliniella fusca, Western flower thrips, F. occidentalis and Onion thrips Thrips tabaci. The last three species are the ones most likely to transmit tomato spotted wilt virus, TSWV. Feeding results in various tissue responses, including scar formation and distorted growth (Fig. 2). Thrips hatch from an egg and develop into two larval stages and then the ‘prepupa and pupa’ stages, before becoming an adult. Females of most plant-feeding species lay their kidney-shaped eggs on or into plant tissue. The prepupae and pupae of most species drop to the soil or leaf litter to pupate. Thrips have several generations (up to eight) a year. When the weather is warm, the life cycle may be as short as 2 weeks.

It is difficult to identify thrips to species in the field. Thrips color, size, markings will not separate the different species found in our vegetable fields from one another to any great extent. Thresholds for vegetables are: flowers of tomato, pepper or watermelon can tolerate 5 thrips/flower with no fruit developmental problems. Squash and pumpkin flowers can tolerate 5-10 thrips/flower with no effect on fruit quality. One or two applications of a pyrethroid or neonic or spinosad (see 2018 Mid-Atlantic Commercial Vegetable Production Recommendation Guide) applied with enough water (80-100 gal/a) should control most thrips infestations. Spraying more than 4-5 times for thrips in a 4-5-week period will usually lead to an even worse thrips problem. This is because the sprays will reduce eastern flower thrips and other thrips species, but usually not western flower thrips that are often resistant to many insecticides. Once the thrips population consists mostly or entirely of western flower thrips it may not be possible to get the population under reasonable control.

Figure 1. Early thrips feeding on tomato leaf, black specks are thrips feces (A) and later feeding damage (B)

Figure 2. Pepper leaf distortions due to thrips feeding