Guess the pest – Page 2 – Maryland Agronomy News

Guess the Pest! Week #20

Bill Cissel, Extension Agent – Integrated Pest Management, University of Delaware; bcissel@udel.edu

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 this insect?

Guess the Pest! Week #19 Answer: Hole Puncher

Bill Cissel, Extension Agent – Integrated Pest Management, University of Delaware; bcissel@udel.edu

Congratulations Bob Leiby for correctly identifying the damage as mechanical 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 #19 Answer: Hole Puncher
By David Owens, Extension Entomologist

Photo by Joe Deidesheimer, defoliator is Kevin Troyer

This week’s guess the pest was a bit of a trick question, the answer is hole puncher operated by a hard-working student. Soybean canopy defoliation can be a little tricky to estimate, defoliation often appears more severe than it really is because our eyes focus on differences. We are simulating bean leaf beetle feeding injury to R-2 stage soybean by removing approximately 25% of the foliage canopy-wide.

Although this looks really severe, soybeans can compensate for this level of defoliation. Our threshold for defoliation at this soybean stage is 20% CANOPY and FIELD wide. Our most common defoliators right now feed primarily in the upper canopy. So if 25% of the upper canopy of R-stage soybean is defoliated, but only 5% of the lower canopy, total defoliation could be lower than 15% and the plants will not suffer a yield impact. If there is little to no defoliation in the lower canopy, the upper canopy can take a severe beating before canopy-wide defoliation hits 20%. We may start seeing soybean looper later in the season, this species often defoliates from the bottom up.

Vegetative stage soybean can compensate even greater defoliation. Recent work out of Mississippi indicates that 66% of the canopy of VEGETATIVE beans can be lost without a significant yield loss. In the Mississippi study they also defoliated beans during vegetative growth, at R3, and constantly during the season to simulate the impact of multiple sub-threshold ‘dingers’, and found that a constant 17% defoliation did not significantly reduce yields.

Two other important factors that reduce soybean’s compensatory ability are drought and planting date. Late planted beans have less time to recover from severe defoliation and may (but not always) loose yield. Drought stress may also reduce this compensatory ability. The Mississippi defoliation experiments involved a small army of students around the clock picking leaves off of over 100 10-ft plots.

Guess the Pest! Week #19

Bill Cissel, Extension Agent – Integrated Pest Management, University of Delaware; bcissel@udel.edu

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 caused this damage?

Guess the Pest! Week #18 Answer: Western Bean Cutworm

Bill Cissel, Extension Agent – Integrated Pest Management, University of Delaware; bcissel@udel.edu

Congratulations Bob Leiby for correctly identifying the moth as a western bean cutworm 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 #18 Answer: Western Bean Cutworm
by Bill Cissel, Extension Agent, Integrated Pest Management and David Owens, Extension Entomologist

The western bean cutworm (WBC) is native to the western United States where it is considered a pest of corn and dry beans. Despite the name, they actually do not “cut” plants. Western bean cutworm are univoltine, meaning they have a single generation per year and overwinter as pre-pupa. In the spring, they pupate and adult moths emerge in early June. Female moths will lay eggs throughout July and August on both wild and cultivated plants. Field corn in the whorl stage prior to pollination is a preferred oviposition site. Eggs are typically laid on the upper leaf surface near the whorl in masses of 20-200 eggs which take approximatley 7 days to hatch. Larvae undergoe six instars before burrowing into the soil to pupate. Since the early 2000s, WBC has spread, causing economic damage as far east as NY, MI, OH, WI, and Ontario. Studies conducted in Nebraska and Iowa suggest an infestation averaging one larva per ear can cause yield losses reaching as high as 4 bu/A. Larvae bore through the side of the ear and open the ear up to mycotoxin-causing fungal colonization. Most Bt traits do not adequatley control this pest.

We first detected WBC in Delware in 2011 after capturing a few moths in a pheromone trap in New Castle Coutny. We captured 14 moths in 2012 and have not trapped for this pest since 2012 until 2018. This year, we have been monitoring 10 pheromone traps located throughout the state and have captured four moths to date. We will continue to monitor for this pest throughout the growing season but at this point, it appears that WBC populations remain low for us in Delaware. By comparison, states where western bean cutworm causes signficant injury to corn catch dozens of moths per week in a single trap.

2012 Western Bean Cutworm Trap Summary: http://s3.amazonaws.com/udextension/ag/files/2012/06/2011WesternBeanCutwormTrapSummary.pdf

2013 Western Bean Cutworm Trap Summary: http://s3.amazonaws.com/udextension/ag/files/2012/06/2012-Western-Bean-Cutworm-Trap-Summary2.pdf

Here is a link to a Fact Sheet from Purdue University with more detailed information on the identification, biology, and damage of the Western Bean Cutworm: https://extension.entm.purdue.edu/fieldcropsipm/insects/western-bean-cutworm.php

Fun Entomology Fact: It is not unusual to find an ear infested with multiple western bean cutworm larvae because they are not canabalistic like corn earworms.

Guess the Pest! Week #18

Bill Cissel, Extension Agent – Integrated Pest Management, University of Delaware; bcissel@udel.edu

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 this moth?

Guess the Pest! Week #17 Answer: Soybean Leafminer

Bill Cissel, Extension Agent – Integrated Pest Management, University of Delaware; bcissel@udel.edu

Congratulations Julie Knudson for correctly identifying the damage in the photo as soybean leafminer damage 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 #17 Answer: Soybean Leafminer
By David Owens, Extension Entomologist, owensd@udel.edu

This week’s Guess the Pest is an interesting but rather unimportant member of the defoliating insect complex. The soybean leafminer (Odontota horni) adult is a beautiful red, flattened, rectangular beetle with red wings and prothorax and black head, antennae, legs, and a black stripe down the middle of the back. The black stripe doesn’t reach all the way to the end of the wings. Adults are active beginning around early to mid-June. They lay eggs on the underside of leaves, and the larvae immediately mine into the leaf. Larvae spend their entire lives between the upper and lower leaf surface, leaving a quarter sized brown blotch. When larvae complete development, they pupate in the mine. Immatures require 30 – 40 days to fully develop into adults. There is only one generation per year. Beetles will continue to lightly skeletonize leaves and over the course of their adult life might feed on the equivalent of one leaflet until they migrate out of fields to find overwintering shelter in late summer. Beetles and larvae are never present in any significant populations.

There are a couple of other beetle leafminers that you may see this summer. The most obvious and abundant is the locust leafminer, Odontota dorsalis. It pretty much stays confined to locust and can cause a large amount of locust defoliation by August. So, as you drive along the highway and notice trees with a brown cast to them, you may be seeing locust leafminer. Locust trees can handle the defoliation and leaf back out.

Guess the Pest! Week #17

Bill Cissel, Extension Agent – Integrated Pest Management, University of Delaware; bcissel@udel.edu

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 caused this damage?

Guess the Pest! Week #16 Answer: Spider Mite

Bill Cissel, Extension Agent – Integrated Pest Management, University of Delaware; bcissel@udel.edu

Congratulations Jeffrey O’Hara for correctly identifying the damage in the photo as spider mite damage 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 #16 Answer: Spider Mite

The damage in the photo is from two-spotted spider mite (TSM) feeding on soybean. Hot, dry weather favors TSM and drought can trigger outbreaks. TSM populations are held in balance by natural enemies and the weather. Under high temperatures, the amount of time required for TSM to complete its lifecycle is shortened, allowing more generations to be completed in a shorter period of time. A female TSM can produce 300 offspring in her lifetime (~30 days) and most of the individuals in the population are female. Dry conditions also diminish the activity of fungal diseases that often play a key role in keeping outbreaks from occurring.

So, if it rains, does it mean we don’t need to worry about TSM? Precipitation not only favors spore formation and mite infection but also reduces plant stress. This however isn’t always a silver bullet and TSM populations can continue to increase even after rain events, especially if the weather returns to being hot and dry. Cool nights and humid conditions promote the fungal disease that infects TSM.

Below is a graph showing rain events and observed TSM populations in the untreated check from a TSM field trial conducted in Georgetown, DE in 2017:

Observed Influence of Precipitation on Two-Spotted Spider Mite Populations, 2017

Weather data obtained from the Delaware Environmental Observing System (DEOS): http://www.deos.udel.edu/data/agirrigation_retrieval.php

As you can see in the graph, TSM populations continued to increase and remained high despite rain events occurring on 7/22, 7/23, 7/25, and 7/28.

To scout for TSM, examine the underside of 5 leaflets in 10 locations for mites, noting the presence of mite eggs and the amount of leaf damage. The threshold for TSM during bloom to podfill is 20-30 mites per leaflet and 10% of plants with 1/3 or more leaf area damaged.

Concentrate scouting efforts on field edges for initial detection, especially edges bordered by grass and road ditches (it’s not unusual to also find hot spots in the interior portions of the field). TSM typically develop on grasses and other plants on field borders before ballooning into fields. Once TSM are detected, scout the interior portions of the field to determine if they have spread throughout the entire field. If only concentrated on field edges, spot treating may be an option. If spot treating on field edges, extend the treated area about 100 feet further into the field from the damaged area.

Here is a link to our Soybean Insecticide Recommendations for chemical control options if your field is at threshold for TSM: https://cdn.extension.udel.edu/wp-content/uploads/2018/05/02102500/Insect-Control-in-Soybeans-2018.pdf

Guess the Pest! Week #16

Bill Cissel, Extension Agent – Integrated Pest Management, University of Delaware; bcissel@udel.edu

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 caused this damage?

Guess the Pest! Week #15 Answer: Stink Bug

Bill Cissel, Extension Agent – Integrated Pest Management, University of Delaware; bcissel@udel.edu

Congratulations Chris Leon for correctly identifying the damage in the photo as stink bug damage 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 #15 Answer: Stink Bug

The damage on the corn stalk is stink bug feeding injury. Stink bugs will use their piercing-sucking mouthparts to probe into the stalk of the plant, removing plant fluids. If the stink bug hits the ear at this stage, the ear will often fail to develop kernels at the feeding site. This causes the ear to develop into the classic “C”-shaped or boomerang-shaped ear. This is why the greatest damage and yield loss potential due to stink bug feeding is prior to pollination. This is also why waiting until after tasseling (pollination), to control a stink bug infestation in field corn is too late. Here is a link to last week’s article discussing stink bug management in field corn: http://extension.udel.edu/weeklycropupdate/?p=12194

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