What To Look For This Summer

Summer is usually the time of more intense insect and mite pest pressure, simply because temperatures are warmer and many major pests develop faster – or in some cases, just develop, which they do not do outdoors in a northern winter.

Mites and insects are “cold-blooded” animals that are affected by temperatures.

Feeding, reproduction, development time and survival are mostly dependent on temperature, but moisture, humidity, plant health, nitrogen level, and soil/potting mix contribute as well. Following are a few examples of greenhouse and nursery insect and mite pests that do best when temperatures warm.

Two-spotted spider mites

Two-spotted spider mites are warm-season mites, doing best when temperature are higher. It takes about 28 days to develop from egg to adult at a cool temperature range of 50°–68°F, but only about 8 days at a warmer temperature range of 77°–95°F. You can easily see that more spider mite generations in a given amount of time will occur at high rather than low temperatures.

Fortunately (or not, depending on your point of view), plant injury caused by two-spotted spider mites appears quickly on most plants and can be detected using a good scouting and monitoring program. Applications of effective miticides can then be made to stop the infestation’s spread.

Western flower thrips

Western flower thrips, or WFT, generally cause more problems on greenhouse-grown plants, but can also affect plants grown outdoors. WFT are warm – but not too hot – weather pests. The ideal temperature for development and reproduction is about 80°F. WFT development takes place between about 50 to 90°F. Thrips can survive temperatures lower than 50°F, but there is no development. Above about 95°F development again stops. With a warm temperature range of 65–95°F the egg to adult cycle is about 10 to 14 days.

At cooler temperature ranges, the egg-to-adult cycle extends to as long as 30 to 40 days. Growers have reported thrips infestations that seemed to appear overnight. Unless you believe in spontaneous generation, this seems unlikely. The probable causes for these “overnight” infestations are:
1. Movement into the crop from adjacent areas;
2. Favorable environmental conditions allowing the thrips – which were already there at low numbers – to increase rapidly.

Have I mentioned having a good scouting and monitoring program?

Leafminers

Leafminers develop from egg to adult in 14 days at 95°F to 64 days at 59°F. Other species have different lower and upper limits for development, but development trends are similar – warmer temperatures result in faster development. Leafminers generally do best when plants are high in nitrogen.

Primary Liriomyza leafminer injury is from the larvae feeding within leaves, making a narrow winding trail, or mine. Both greenhouse and outdoor crops can be infested. Adult leafminer flies puncture leaves for feeding and egg-laying, and the small white spots will indicate leafminer activity. Leafminers have a very wide host plant range.

Whiteflies

Bemisia whiteflies are warm weather pests, with temperatures making a big difference in development times – 16 days at 86°F to 31 days at 68°F. A whitefly infestation will reduce a plant’s value, and high numbers can reduce plant growth or vegetable yields. Bemisia whiteflies can cause leaf spotting, white stem and bract deformation on poinsettia. Honeydew from whiteflies makes leaves and fruits sticky and is a substrate for black sooty fungus. Whiteflies can transmit many plant viruses affecting vegetable and ornamental plants.

Aphids

Common aphids on ornamental crops are the green peach aphid (Myzus persicae) and melon/cotton aphid (Aphis gossypii), but numerous other species can be found on herbaceous and woody plants. Both melon aphids and green peach aphids will infest large numbers of host plants. Although many aphids generally do better at warmer temperatures, the best temperatures for development vary with the species. For example the chrysanthemum aphid develops best at 68°F, the green peach aphid at 73°F, and the melon aphid at temperatures above 75°F. When temperatures are above 86°F and the relative humidity is above 85 percent, green peach aphid longevity and reproduction is reduced – conditions that are likely to slow (or stop) reproduction of just about anything!

Managing summer pests

Weekly scouting of crops and the use of sticky traps for pests attracted to them are the most practical methods for detecting insects and mites and keeping tabs on how the management program is going. The bottom line here is that insect and mite generations are generally shorter at warm temperatures than at cool temperatures, and your management program needs to be adjusted accordingly.

Foliar sprays will need to be applied more often when it’s warm. However, on crops where it is known that a certain insect or mite will probably appear, it is acceptable to apply pesticides preventively – especially systemic products as drenches or granules, which need time to move up into the plants.

On outdoor crops, scouting and monitoring should be done as well, and there are methods to assist the process involving so-called plant phenology charts. Just as development of insects and mites depends on temperature, so does plant development. Clever and observant folks have long associated appearance of pests with development stages of certain plants. Other clever folks have put this information into charts that help with decision-making. Phenology charts are only accurate over a limited area – maybe a state or part of a state – so growers need to use information for their area. Again, this information will help if foliar spray applications are going to be used for control.

If the goal is to use a preventative management program with soil-applied, systemic products, applications need to be made before the appearance of the pest – sometimes well before – to minimize plant injury.

Leave a Reply

Latest Stories
Weigela Czechmark (Spring Meadow Nursery)

February 22, 2018

Plant Breeders Emphasize Importance of Patent Protectio…

According to members of MarkWatch, plant patents are an important protection for plant breeders and also provide an incentive for them to invest the time and money to innovate and develop new plant varieties.

Read More
employee-reviewing-shipping-list

February 21, 2018

Four Ways to Get Your Staff to Care About Quality

It can be a challenge to convince your employees to care as much as you do about your business and the quality of products you are providing. Here are four suggestions for making this happen.

Read More
Adult Thrips feature

February 20, 2018

Thrips Causing Headaches? New Research Shows Bio-based …

Dr. Rose Buitenhuis will present practical knowledge for growers to implement immediately during Biocontrols West Conference in San Diego, March 7-9.

Read More
Sedum-Pillow-Talk

February 20, 2018

12 New Poinsettias and Succulents for Holiday Sales, Cr…

Poinsettias and succulents are both in-demand products with today’s consumers. Here’s a look at some of the newer introductions available for retail sales in 2018 and 2019.

Read More
2016 Top 100 Growers With Drone

February 20, 2018

Top 100 Growers Survey for 2018 Is Now Open!

Operations with more than 400,000 square feet of environmentally controlled production are eligible to take the survey, which provides valuable market knowledge on how the nation's largest growers are innovating, sourcing labor, keeping up with demand, and setting trends.

Read More
Pepper-Mexican-Sunset

February 19, 2018

All-America Selections Names Latest Variety Winner, Ann…

All-America Selections (AAS), the 85-year-young non-profit plant trialing organization, had a very busy month of January.

Read More

February 18, 2018

Why Biochar Might Eventually Replace Peat Moss

In a recent study, researchers from the University of California, Davis investigated biochar as an alternative to peat moss.

Read More
Gotham Greens Atrium Style Greenhouse Chicago

February 17, 2018

Gotham Greens Building Second Greenhouse in Suburban Ch…

The new $12.5 million, 105,000-square-foot greenhouse will be near the company’s first Chicago greenhouse, and will be a free-standing structure.

Read More

February 16, 2018

New England GROWS Discontinues After 25 Years

After 25 years, New England GROWS — both the annual event and the organization behind the event — are discontinuing operations.

Read More

February 15, 2018

Boxwood Blight, Seed Your Future Among Topics Receiving…

The Horticultural Research Institute recently announced the 10 research projects that will receive funding in 2018 to investigate challenges and solutions in production, pest management, environmental stewardship, and business and marketing.

Read More
Weigela Czechmark (Spring Meadow Nursery)

February 14, 2018

Spring Meadow Nursery Furthers Its Mission of Giving Ba…

The Spring Meadow-Proven Winners Endowment Fund through the Horticultural Research Institute has now topped $800,000, with more scholarships coming in 2018.

Read More
Laura Drotleff

February 13, 2018

Don’t Let Your New Year’s Resolutions Fade …

Stuff got real in 2017, and it caused many of us to stop and reflect on the current state of the world, and how we can impact change — or at least improve our own situations. Life is too short, and we work too hard, to not use the annual renewal as an opportunity to take stock of our own personal lives, businesses, and careers, and make the necessary adjustments that will allow us to work smarter and live better. Even if you have already given up on your resolutions, perhaps you can think of January as a trial month and make February the month when you really get to work on your goals. And while I know it’s a difficult month to start on some of these changes, since you’re already immersed in the busy spring season, I promise that if you take some time to evaluate your reality […]

Read More

February 12, 2018

Calling All Designers: Enter the International Plantsca…

Applications are being accepted through April 13 for AmericanHort’s International Plantscape Awards, which recognize achievements in interior plantscape design, installation, creativity, renovation, and innovation.

Read More
Jose-Milan-Bayer

February 11, 2018

Bayer Has New Turf and Ornamentals Global Market Manage…

Jose Milan will be focused on helping growers deal with regulatory issues, while promoting the environmental benefits the ornamentals industry offers.

Read More
Dr. P. Allen Hammer, Dummen Orange

February 10, 2018

Applications for Dümmen Orange’s Dr. P. Allen Hammer Sc…

Named for Dr. P. Allen Hammer in acknowledgment of the contributions he has made to the floriculture industry, the scholarship is intended to extend Dr. Hammer’s legacy by supporting the next generation of floriculture students.

Read More
Hand-Crafted Stone Mushrooms (Stone-Age Creations)

February 9, 2018

Garden Retailers at TPIE Highlight Their Favorite Produ…

A team of garden retailers once again participated in the 2018 Tropical Plants Industry Expo Cool Product Awards.

Read More
Aron Hoff feature image

February 8, 2018

Who Will Be Our 2018 Head Grower of the Year and Operat…

The deadline for submitting nominations is fast approaching, so be sure to let us know who you feel is most deserving of these awards!

Read More
Oat Grass Banker System feature

February 8, 2018

Learn the Basics of Biocontrols for Controlled Environm…

Growers producing crops in protected structures, including ornamentals, vegetable crops, and cannabis, can learn about effective sanitation, banker plants, and buying and using beneficials and predatory insects at the Biocontrols USA West Conference in San Diego, March 3-7.

Read More