Month: July 2020

Wayne County IPM Notes from July 5 – July 11

Vegetable Pests

            In sweet corn, the European corn borer (ECB) larvae are still doing damage. This week I started seeing some corn earworm (CEW) damage as well. The ECB trap counts dropped and showed little activity but the CEW traps started to increase in numbers. Even if the ECB activity seems to be slowing down, you need to be scouting your sweet corn for the CEW as well.

Squash bug egg mass on a zucchini leaf. F. Becker photo.

Squash Bugs have started to make their presence known. I have started seeing squash bug adults, primarily in summer squash plantings. I have also started to find squash bug egg masses. Large numbers of squash bugs feeding can cause leaves to yellow and eventually die which can significantly reduce yield.

Flea beetles are still very active and on a wide range of plants. Damage can be seen primarily on cole crops and potatoes.

Potato Leaf Hoppers (PLH) have high populations in several crops this year. PLH cause “hopper burn” on the leaves on which they are feeding. I have seen this damage to potatoes and green beans. Some of the PLH populations within green bean plantings have been incredibly high, in some cases, over 40 PLH per single leaf.

Potato leaf hoppers feeding on a green bean leaf. F. Becker photo.

Hopper burn from potato leaf hopper feeding on green beans. F. Becker photo

Vegetable Diseases

            Downy Mildew has been confirmed in Medina County. Cucumber growers should have started a spray program for the cucurbit downy mildew.

Powdery mildew is starting to show up on cucurbit crops around the state. I have not yet had any cases in Wayne County, but this disease should be watched for closely.

Cucurbit downy mildew on cucumber leaves. F. Becker photo.

Some field tomatoes are showing symptoms of early blight. Early blight is a common tomato disease which gets its start typically on the older, lower leaves. If not treated, early blight can cause significant defoliation of a plant.

In some melon patches, specifically in cantaloupe, there is some Alternaria leaf blight showing up. This disease primarily affects the foliage but if the infection is severe enough, it may also infect the fruit.

Fruit Pests

Spotted Wing Drosophila numbers are still increasing. The trap counts were up again this week, with all the traps being in blueberry patches.

Codling Moth and Oriental Fruit Moth trap counts were low again this week and showed very little activity.

I started to find red mites in apple orchards throughout the county. Feeding by large populations of red mites can cause leaves to “bronze” and when left uncontrolled, this heavy feeding could result in leaf drop and a reduced size and quality of the crop. This hot and dry weather has been ideal for the red mite populations to get established in orchards. Read more on Red Mite Management.

Mites feeding on an apple leaf. F. Becker photo.

Fruit Diseases

            Alternaria leaf blotch can be found on some apple trees right now. This can be made worse by red mite infestations. With high populations of mites and the leaf blotch, severe defoliation can occur.

Apple and peach growers should continue their spray programs to manage fruit rots and diseases such as flyspeck and sooty blotch. Managing Apple and Peach Summer Diseases

Grapes should be starting to get some color to them. At this point, most varieties of grapes should be resistant to black rot. Growers with varieties of grapes that are not resistant to downy mildew should consider a spray program.

Ready to manage spider mites?

With the current hot and dry weather conditions in Ohio, we expect to hear reports of spider mite outbreaks on specialty crops. Because mites are tiny, they are often overlooked or misdiagnosed as a disease. Infested leaves have fine webbing on the leaf undersides. Tomato leaves damaged by spider mites usually have yellow blotches, while bean leaves show white stipples or pin-prick markings from mite feeding. Pumpkins can tolerate moderate levels of mites, but watermelons are more sensitive to injury from mite feeding. A simple method of diagnosing spider mites is to shake leaves over a piece of paper and look for moving specks that are visible to the naked eye. A closer look with a magnifier can show the tiny mites that are white, marked with two large dark spots on the middle of the body.

Mites have many natural enemies that kill them, such as specialized predatory mites or generalist lacewings, ladybugs, and pirate bugs, but these helpful predators are often killed by pesticides. Mites can be suppressed by periodic overhead irrigation.

Chemical intervention can be needed to keep the crop alive if spider mites are abundant. In some fields, the mite infestation is worst on a field edge by a dusty road. When a mite infestation is limited to field edges, infested fields should be scouted, and a miticide applied as a spot treatment to isolated infestations. Mite control is better when higher volumes of water are used; 30 to 50 gallons of water per acre is better than 10 gal/A.

Several pesticides are registered for spider mite control; some are restricted use, and most are for general use. Some of these products kill only the motile mites (immatures and adults), while some kill eggs. Most do not have systemic activity but some do. These details are summarized in three attached tables. One table shows details about target life stages and mite species affected, as well as any insect target pests. Another table shows details about which products are registered for use on key vegetable crops, and another table for show similar registrations for hops and fruit crops.

At some locations, the old organophosphate Dimethoate is still effective for mite control. Dimethoate is an option for melons but is not allowed on squash or cucumbers; it has been a preferred product for mite control on soybeans. Dimethoate is prohibited from use on ornamental crops in high tunnels and greenhouses but is not prohibited from vegetable crops in high tunnels and greenhouses. Where Dimethoate is not effective, Agri-Mek (abamectin) is generally the most effective product for mite control but it is a restricted-use product, while Acramite (bifenazate) and Oberon (spiromesifen) are nearly as good but are not restricted-use products. Other options for some crops are Portal, Envidor, Zeal, Nealta, Onager, Savey, Apollo, and Kanemite, as well as a new product called Magister. Although Brigade (bifenthrin) and Danitol (fenpropathrin) are labeled for spider mite control when used at the high end of the rate range, they are generally not as effective as the true miticides. Vydate (oxamyl) is a Restricted Use product that is registered for use on eggplant for mite control. Several broad-spectrum products are available for use on organic farms to control mites as well as various insect pests: Grandevo, PFR-97, Sil-Matrix, SucraShield, as well as sulfur, oils, and insecticidal soap (such as M-Pede or Des-X). Soaps and oils can be used for mite control, but thorough coverage of the undersides of leaves is needed for good control because the action is by smothering of the mites. Soap can cause phytotoxicity if applied under sunny hot conditions. Soap is a good alternative in conventional fields that are too close to harvest to use a true miticide; insecticidal soap has a 12-hour re-entry interval and a 0-day pre-harvest interval.

-Celeste Welty, Extension Entomologist

Table 1: Details about miticide choices

Table 2: Miticides for key vegetable crops

Table 3: Miticides for key fruit crops and hops

Grafting, In-row Spacing, and Total Seasonal Nitrogen Effects on Watermelon Yield and Quality

Growers, seed, grafted plant, and fertilizer suppliers, extension-research personnel, and others are interested in identifying if, where, and how grafted plants may fit in vegetable production toolboxes. Those questions can be answered reliably only after the performance of grafted plants is documented under a range of management schemes because it is possible that standard production practices may need to be altered to account for the influence of rootstocks. Plant spacing (i.e., population density per acre) and fertilizer application rates (e.g., total seasonal nitrogen applied) are two variables likely to influence (grafted) plant performance; therefore, they have many peoples’ attention, including ours.

With USDA-SCRI program support, we began studying these variables at a preliminary level in 2018 and more thoroughly in 2019. Experiments started in 2019 are being repeated in 2020.

Data collection begins with tracking crop development and concludes with laboratory analyses of fruit quality. The experiments provide an opportunity to analyze fruit yield and quality as influenced by grafting, scion, spacing, and N level. In 2019, soilborne disease did not appear to be a factor and grand mean total cumulative fruit yield (ton/acre) values were: a) 32.5 (ungrafted ‘Fascination’), b) 25.0 (ungrafted ‘Jade Star’), c) 42.6 (grafted ‘Fascination’), and d) 47.7 (grafted ‘Jade Star’); these values include data for all density and N rate treatments. Analyzing data collected in both study years more thoroughly will provide a more reliable assessment of the influence of grafting, in-row spacing (4 or 5 ft), and total seasonal N application (100, 120, or 142 lb/acre) on watermelon fruit yield and quality.

Cucumber Downy Mildew Confirmed in Medina County, OH

2020 cucurbit downy mildew outbreaks as of July 8. cdm.ipmpipe.org

Downy mildew was confirmed today in a 3 acre cucumber field in Medina County, OH. Given the outbreaks reported in Michigan in June and an outbreak confirmed in Kent County, Ontario this week, this was expected. Although recent weather has been hot and dry, there have been localized intermittent rainstorms that favor downy mildew spread, and nighttime temperatures are usually cool enough for infection.

Growers in northern Ohio should protect cucumbers and melons with fungicides. Recommendations can be found here.

Thanks to Frank Becker, OSU Extension Wayne County IPM Program Coordinator, for bringing us the sample.

Wayne County IPM Notes from 6-28 to 7-4

 

ECB damage to sweet corn tassel. F. Becker photo.

European Corn Borer has been doing damage in tasseling corn. The small ECB larva feed in the tassels as well as the developing ears. It is important to thoroughly inspect the plants as you are scouting, especially with early season corn as their damage will not always be detected in the tassel like in later planted sweet corn. The ECB moth traps were high again this week, which is consistent with the amount of damage being done in early planted sweet corn.

Japanese Beetles are also starting to increase in number. They are a pest on most any crop. They can be especially damaging to sweet corn. The beetles can defoliate the leaves, but they can also clip the silks which can prevent proper pollination from occurring.

Worm feeding on cole crops has really started to pick up. I am finding a lot of imported cabbageworms doing damage on all ages of cole crops such as cabbage and kale. The adult butterflies can be seen in large numbers in cole crop plantings laying eggs on the plants. Read more here on pests of crucifers. I saw an uptick in the population of the flea beetle as well. Keep in mind that especially on younger plants, the flea beetles can cause a lot of damage and may stunt the plant.

Imported Cabbageworm larva on cabbage. F. Becker photo.

This hot and dry weather has been perfect weather for onion thrips. The thrips population has been high already in some areas, so this weather is favorable for large populations of thrips to develop. The thrips feeding can open the plant up to diseases such as purple blotch, so early detection and management are crucial to maintaining the health of the plant.

Vegetable Diseases

            Downy Mildew has been confirmed, again, in southern Michigan. Considering the proximity to Ohio, it has been recommended that cucumber growers begin a downy mildew fungicide program immediately. “Managing Downy Mildew in Cucurbits”

Powdery mildew is starting to show up on cucurbit crops around the state. I have not yet had any cases in Wayne County, but this disease should be watched for closely.

Some of the field peppers I am scouting showed signs of damping off. Damping off is caused by soil borne fungi such as Rhizoctonia, Pythium, Fusarium and Phytophthora.

Angular leaf spot has started to show up on some cucurbit crops, however, the hot and dry weather has helped slow it down or stop its progression altogether. Angular leaf spot is a bacterial disease, meaning that fungicides are not effective for management of this disease.

Fruit Pests

SWD female with a serrated ovipositor. F. Becker photo.

Spotted Wing Drosophila are here. All the traps out in Wayne County were positive for SWD. These traps are out in blueberry and strawberry patches. Strawberries are winding down, but blueberries and raspberries getting ripe should be managed accordingly.

Codling Moth and Oriental Fruit Moth trap counts were down this week. Another week with our traps not over threshold.

Keep an eye out for aphids and mites in orchard crops. We are getting into the time of year where aphid and mite populations begin to increase and can do so rapidly. Leafhoppers are also a pest to be on the look out for, especially in grapes. More on Spider Mites

Fruit Diseases

            It is the right time to consider looking at managing summer diseases such as flyspeck, sooty blotch, and fruit rots. This can go for peaches as well with diseases such as brown rot and scab.

Peach “mummy” still present in a tree this spring. F Becker photo.

Necrotic leaf blotch and Alternaria leaf blotch can be found on some apple trees right now. Alternaria leaf blotch can be made worse by red mite infestations. With high populations of mites and the leaf blotch, severe defoliation can occur. More on foliar apple diseases: Leaf Spots

Another note on apples, although not a disease, the effect of freeze/cold damage can appear unsightly and may be confused for a disease. This scabby looking ring or spots on the fruit are known as “frost rings”. This is a result of the tissues being damaged in cold or freezing temperatures.

Grapes are now around the “shatter” stage where the unfertilized berries fall off the clusters. It is important to be considering proactive treatments for grape downy mildew especially if you have a variety of grapes that are susceptible to downy mildew.

Water Needs and Supplies, and Delivered during Typical Drip Irrigation Events

Warm, dry weather can lessen some production challenges, but it clearly increases the need to irrigate. Not surprisingly, growers are currently working overtime to meet crop water demands. Some forecasts call for high water demand conditions to continue, important because many crops are entering particularly “thirsty” stages uniquely sensitive to water deficits. Therefore, as one step in overall crop water management, consider taking stock of how much water is delivered during typical irrigation events. Doing so helps compare water supplies to expected irrigation demands and prioritize irrigation across plantings if rationing becomes necessary, in addition to providing other benefits. Of course, in the big picture, crops differ in their sensitivity to even temporary periods of sub-optimal soil moisture. Just as relevant, the production cycle for each crop includes stages in which sub-optimal soil moisture has a greater or lesser impact on yield and quality. The June 28, 2016 VegNet article (https://vegnet.osu.edu/sites/vegnet/files/imce/newsletters/VegNet/6-28-16%20VegNet%20Vol%2023%20Issue%2011_0.pdf) outlined this issue briefly for cabbage. In addition to the yield and head size differences shown there, laboratory and taste panel tests revealed: (a) that irrigation program (timing) influenced cabbage flesh chemical properties and (b) that panelists could differentiate cabbage samples from different treatments by taste.

Installing and recording information provided by a flow meter is a simple, relatively inexpensive, and, importantly, direct method of measuring system flow. Using charts, tables, and other references such as the one below also helps. They remind us that irrigation system factors, especially bed or row spacing and emitter flow rate, typically set the baseline system flow rate, although actual flow rate is impacted by leaks and plugs. Leaks, plugs, etc are another reason to both include a meter in the line and check the system frequently. Ultimately, keeping and reviewing irrigation and crop records can be useful in optimizing irrigation practices as a major step in maximizing yield and quality.


Source: Knott’s Handbook for Vegetable Growers (5th ed.; D.N. Maynard and G.J. Hockmuth)

Another Cucumber Downy Mildew Outbreak in MI – and Closer to Home

Downy mildew sporulation on underside of a cucumber leaf.

Outbreaks of cucumber downy mildew on two commercial farms in Monroe County, MI were detected on June 29. Monroe County is in southeast Michigan and borders Ohio’s Lucas County. In addition, spores of the downy mildew pathogen have been captured in spore traps in four Michigan counties, so downy mildew is ramping up and very likely to be in cucumbers in northern Ohio at this time. Although the sunny, dry, warm conditions of the past 5 days or so do not favor downy mildew epidemics, growers in northern Ohio should protect cucumbers, melons and giant pumpkins with appropriate fungicides as outlined here.  Squash and pumpkins are generally much less susceptible than cucumbers, melons and giant pumpkins to the group of isolates of the downy mildew pathogen that circulates early in the Great Lakes Region.  The second group affects all cucurbits and usually migrates from the southeastern states to Ohio in late July or August.

Although daytime temperatures are expected to be > 90°F for the next two weeks, cooler nighttime temperatures, high humidity and intermittent rainstorms may allow initiation and spread of downy mildew disease foci.

There are a number of downy mildew lookalikes, especially angular leaf spot, a bacterial disease, and anthracnose. If you aren’t sure and would like a lab confirmation, send leaf samples to the OSU Vegetable Pathology Lab for diagnosis. The diagnostic service is free for Ohio growers. Doing so will also help us track downy mildew on cucurbit crops across the state of Ohio.

Angular leaf spot of squash.

Anthracnose on cucumber – photo by M. Netz.