Bugs for Growers — Entomopathogenic nematodes

Why entomopathoegnic Heterorhabditis indica nematodes should be used to kill small hive beetles?

• They are not harmful to honeybees and honeybee brood but can kill larvae or pupae of honeybee hive insect pest called small hive beetle within 48 hours of application.
• They are commercially available and easy to apply using water cans or traditional knapsack sprayes.
• They are not harmful to children, dogs, cats and personnel involved in its application.
• Since they are exempted by EPA, no special permission need to apply them around honeybee hives against small hive beetles.

How do entomopathogenic nematodes kill small hive beetles?

When the infective juveniles of entomopathogenic nematodes are applied to the soil surface around bee hives, they start searching for their insect hosts such as larvae (grubs) or pupae of small hive beetles that are already present in the soil. Once larva and/or pupa has been located, the nematode infective juveniles penetrate into the body cavity of larva or pupa via natural openings such as mouth, anus and spiracles (breathing pores). Infective juveniles of Heterorhabditis nematodes can also enter by puncturing the inter-segmental membranes of the host cuticle. Once in the body cavity, infective juveniles of Steinernematid and Heterorhabditid nematodes release symbiotic bacteria, Xenorhabdus spp. and Photorhabdus spp., respectively from their gut in the blood of small hive beetle larva/pupae. In the blood, multiplying nematode-bacterium complex causes septicemia and kill mature larvae and/or pupae of small hive beetles usually within 48 hours after infection. Nematodes feed on multiplying bacteria, mature into adults, reproduce and then emerge as infective juveniles from the small hive beetle larval or pupal cadavers to seek new larvae small hive beetle that are already moved from bee hives in the soil for pupation.    

In my last blog post, I demonstrated the cutworms were susceptible to beneficial entomopathogenic Steinernema carpocapsae nematodes. These results are confirmed by a recent finding of Ebssa and Koppenhofer (2012), who also demonstrated that the Steinernema carpocapsae nematodes were highly effective against cutworm Agrotis ipsilon.  These researchers also demonstrated that the other species of beneficial nematodes including Heterorhabditis bacteriophora, Heterorhabditis megidis and Steinernema riobrave were effective in killing larval stages of cutworms.

Literature

Ebssa, L. and Koppenhofer, A.M. 2012. Entomopathogenic nematodes for the management of Agrotis ipsilon: effect of instar, nematode species and nematode production method.Pest Management Science 68: 947-957.

Yesterday, we harvested fresh raspberries (see photo below) from the raspberry plants that are naturally growing at the borderline of our organic garden. [caption id="attachment_312" align="aligncenter" width="300" caption="Wild raspberries picked from naturally grown plants in our organic garden"][/caption] These raspberries are delicious and can be considered 100% organic because they are grown on the border of our organic garden in which we do not apply any chemical fertilizers as a food source for our vegetable plants and chemical insecticides for the control of insect pests. In our organic vegetable garden we use only compost as a nutrient source for plants. As an alternative to chemical pesticides, we use entomopathogenic nematodes as biological control agents to manage insect pest problem in our organic garden.

Last Monday, I read an article about eastern tent caterpillars on the website of Crossville Chronicle (http://crossville-chronicle.com/features/x1221402699/PLATEAU-GARDENING-Reader-inquires-about-Eastern-tent-caterpillars) and thought that I should share the results of my small experiment that I conducted about an interaction between tent worms and [caption id="attachment_292" align="aligncenter" width="300" caption="Tent worm caterpillar- bugsforgrowers"][/caption] entomopathogenic nematodes. I hand picked four tent worms, which were crawling on my driveway and tested their susceptibility to an entomopathogenic Steinernema carpocapsae nematodes. In this experiment, I transferred 400 infective juveniles of Steinernema carpocapsae nematodes (100 juveniles/larva of tent worms) in 1 ml of water on a filter paper placed in a plastic dish (9 cm diameter) and then four tent worm larvae were transferred in the same plastic dish. [caption id="attachment_294" align="aligncenter" width="300" caption="Entomopathogenic Steinernema carpocapsae nematode infected Tent worm caterpillars"][/caption] These plates were then incubated at room temperature for 48 hours. After 48 hours of incubation, I found that all the four tent worm larvae were dead.  This means entomopathogenic Steinernema carpocapsae nematodes infected and killed tent worms within 48 hours of infection. This showed me that the tent worms were susceptible to Steinernema carpocapsae nematodes. In order to confirm the infection by entomopathogenic nematodes, tent worm cadavers were transferred in a White trap for the emergence infective juveniles of entomopathogenic Steinernema carpocapsae nematodes. [caption id="attachment_295" align="aligncenter" width="300" caption="Entomopathogenic nematode Steinernema carpocapsae infected cadavers of Tent worm caterpillars in a White trap"][/caption] After 12 days, I saw under microscope that the thousands of infective juveniles of Steinernema carpocapsae were emerged from tent worm cadavers in a White trap . Thus these results suggest that the entomopathogenic nematodes can be used to kill tent caterpillars. However, for better I believe that you have to apply nematodes when tent worms are crawling are on the ground.

Yesterday (Saturday May 12, 2012), I found a bunch of Colorado potato beetle grubs (also called as larvae) were feeding on all of my four potato plants (Photo 1) that I had planted in December of 2011. This is the first time I have planted potatoes in my organic garden but did not expect that they will be attacked by Colorado potato beetles or any other insect pests.   [caption id="attachment_273" align="aligncenter" width="300" caption="Photo 1. Potatoes were planted in a organic garden in December 2012"][/caption] I found that all the different stages of Colorado potato beetle grubs feeding at the same time on the potato leaves (Photo 2) but I did not come across the presence of their adult stages on plants. This means that these grubs are not from a same generation but they were from several different generations of beetles.   [caption id="attachment_274" align="aligncenter" width="300" caption="Photo 2. Different stages of Colorado potato beetle grubs found on organic potato plants"][/caption] I saw that all the stages of grubs were voraciously feeding (I wish, I had a video to record feeding) on the leaves as seen in photo number 3 these grubs have completely skeletonized the potato leaves.   [caption id="attachment_275" align="aligncenter" width="300" caption="Photo 3. Severe damage caused by Colorado potato beetle grubs to potato plants"][/caption] I have collected almost all the mixed stages of grubs of Colorado potato beetle with my hand from my all potato plants in a container (photo 4).   [caption id="attachment_276" align="aligncenter" width="300" caption="Photo 4. Mixed stages of Colorado potato beetle grubs are collected for exposing to entomopathogenic Steinernema carpocapsae nematode"][/caption] I am going to expose these collected larvae of Colorado potato beetle to an entomopathogenic nematode, Steinernema carpocapsae. In my next blog post, I will share results of efficacy of Steinernema carpocapsae against these Colorado potato beetle larvae. I also noticed several masses of yellow colored eggs laid by Colorado potato beetles on the under side of several different potato leaves (Photo 5).   [caption id="attachment_277" align="aligncenter" width="200" caption="Photo number 5 showing a yellow egg mass laid by Colorado potato beetle female on the underside of a leaf of potato plant"][/caption] This means when these eggs will hatch there will be a heavy infestation of Colorado potato beetles on my potato plants. Therefore, to reduce future infestation of Colorado potato beetles I need to destroy all the egg masses on the leaves. I have destroyed the eggs by plucking the leaves with eggs and crushed them. This type of mechanical control of Colorado potato beetle is possible because I have only four potato plants in my garden. However, if you have large acreage of potato crop then you cannot destroy eggs this way but you have to let grubs hatch from eggs and then use any chemical pesticides or biological control agents such as entomopathogenic nematodes to manage a high population of hatched larvae Colorado potato beetles.