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
Cannabis Crop Protection

July 27, 2017

Keep Pests Out of Your Cannabis Facilities

Prevention of pest introduction is the most critical first step in an effective pest management program.

Read More
Nexus greenhouse construction for Knox Cannabis Facility

July 27, 2017

Ornamental Growers Will Revolutionize Cannabis Industry…

Professional growers have much to offer the emerging cannabis market, according to the co-owner of Knox Medical, one of the licensed cannabis producers in Florida.

Read More
ForwardGro

July 27, 2017

ForwardGro Receives Maryland’s First Cannabis Productio…

On May 17, the Maryland Cannabis Commission voted in favor of awarding the first full permit to grow marijuana for the state’s medical program.

Read More
cannabis-planted-in-a-greenhouse

July 27, 2017

How Cannabis Production is Becoming More High-Tech

During the National Greenhouse Manufacturers Association’s Spring Meeting, MedMen’s Damian Solomon provided an update on the transition from low-tech cultivation to more advanced indoor production.

Read More
Cannabis Grower Mistakes

July 27, 2017

5 Common Mistakes Made by New Cannabis Growers

Whether it’s overfeeding plants or failure to monitor pH in your water, here are five of the most common pitfalls you can avoid with some preparation and careful monitoring.

Read More
Emerald-Coast-Growers-Guide-Feature-Image

July 27, 2017

Emerald Coast Growers Offers Updated Guide on its Newes…

This year’s guide features new varieties while maintaining Emerald Coast’s ornamental grass program and expanding its perennial plants line.

Read More
Cannabis Structure

July 26, 2017

Greenhouse Cannabis Production Could be a Reality in Sa…

Lawmakers in San Mateo County have agreed to proceed with allowing commercial greenhouse marijuana growing in unincorporated communities.

Read More
Van Wilgens Garden Center Customer Appreciation Day

July 26, 2017

Allan Armitage: How Interacting With Your Customers Can…

Plants are our common denominator, but trust and positive interaction with our customers and each other is truly what keeps us in the plant business.

Read More
Seed Your Future feature

July 26, 2017

Seed Your Future Aims to Inspire Careers in Plants

Who will be the next generation of horticulturists? The answer lies in helping to change the perception of horticulture and using contemporary new language to tell our stories.

Read More
New Growing Media Blends

July 26, 2017

British Researchers Evaluating New Media Blends to Redu…

Research in the United Kingdom has shown that coir-free growing media has the potential to work as well as coir for strawberry crops, and these research results likely apply to greenhouse production, as well.

Read More
Workers

July 25, 2017

H-2B Gets Cap Increase – Here’s How it Impacts Ho…

Greenhouse Grower caught up with AmericanHort’s Craig Regelbrugge to find out how changes to the non-agricultural guestworker program impacts us, and what it could mean for changes to H-2A, the agricultural guestworker program.

Read More
Cultivate Town Hall 2017

July 25, 2017

Cultivate Town Hall Discussion Highlights Great Potenti…

This year’s Town Hall forum at Cultivate’17 focused on how consumable products have the potential to revolutionize the industry.

Read More
Lighting Book Light Management in Controlled Environments

July 25, 2017

Three Lucky Lighting Book Winners at Cultivate’17

Each day during Cultivate’17, the Greenhouse Grower/Meister Media Worldwide booth gave away one copy of “Light Management in Controlled Environments.”

Read More
Farwest Show Floor

July 25, 2017

Heading to Farwest 2017? Make Sure You Register by July…

July 31 is the last day to take advantage of early-bird registration discounts for the show, which includes the trade show, all education seminars and pesticide classes, and nursery country tours.

Read More
Decorative Premium Hanging Baskets (Ainong USA)

July 25, 2017

16 Products That Garden Retailers Loved at Cultivate’17

In what has become an annual tradition at Cultivate, a team of garden retailers presented awards for their picks as the best new products (both live goods and hard goods) from Cultivate’17.

Read More
Craig Regelbrugge

July 23, 2017

Horticulture Industry Insiders Offer Tips on Communicat…

With immigration in the spotlight and a national budget that could severely impact horticulture industry programs, it’s more important than ever to be vocal about how the decisions that lawmakers are implementing impact your business.

Read More

July 22, 2017

Craig Regelbrugge: Proposed Budget Cuts Could Eliminate…

President Trump’s proposed budget for the 2018 fiscal year includes significant cuts to the Agricultural Research Service, which supports the Floriculture and Nursery Research Initiative.

Read More

July 21, 2017

New Products Zone at Cultivate’17 Features Goods …

The New Products zone is always a popular exhibit at Cultivate’17. Here’s a sampling of some of the many items on display that could make growing easier than ever before.

Read More